DOI

https://doi.org/10.1007/s00394-026-04068-7

Association between fish-related metabolites and metabolic syndrome risk factors in Japan: INTERLIPID metabolome -wide association study

Abstract

This cross-sectional INTERLIPID analysis asked whether fish intake and fish-related metabolites line up with metabolic syndrome risk factors in a high seafood-consuming Japanese population. That gap matters because most prior work treated fish as one broad exposure, relied heavily on self-report, and came from populations with much lower seafood intake. The cohort included 1,047 Japanese men and women aged 40 to 59 years, with four multiple-pass 24 h dietary recalls, two timed 24 h urine collections, anthropometrics, questionnaires, and blood sampling, plus urinary and serum profiling by 1H NMR spectroscopy.

Urinary TMAO and taurine, and serum creatine and threonine, correlated with fish intake, while homarine tracked with shellfish intake, all at p < 0.01. Total fish intake was inversely associated with triglycerides, with the clearest signal for low omega-3 fish, and fish intake also tracked with lipoprotein shifts across VLDL, IDL, LDL, and HDL subclasses. On the metabolic syndrome side, urinary TMAO and taurine were linked to lower triglycerides (-3.47 mg/dL, p = 0.01 and -3.88 mg/dL, p < 0.01), urinary taurine to lower systolic BP (-0.73 mmHg per 2 SD, p = 0.03), serum threonine to lower BMI (-0.18 kg/m2 per 2 SD, p < 0.01) and lower diastolic BP (-0.29 mmHg per 2 SD, p = 0.05), and serum threonine to higher HDL-c (0.98 mg/dL per 2 SD, p < 0.01). Urinary TMAO also linked to higher HDL-c (0.47 mg/dL per 2 SD, p = 0.04), while serum creatine linked to higher triglycerides (2.78 mg/dL, p = 0.01). Serum threonine was inversely associated with overall MetS risk (OR 0.84, p < 0.01).

Study Design and Methodology

• Design: Cross-sectional metabolome-wide association study
• Sample size: N = 1,047
• Population: Japanese men and women aged 40 to 59 years
• Study period: Participants surveyed during 1996 to 1998
• Diet assessment: Four in-depth multiple-pass 24 h dietary recalls
• Biological samples: Two timed 24 h urine collections and non-fasting blood
• Metabolomics: 1H NMR spectroscopy for urine and serum
• Lipoprotein profiling: Bruker B.I.-LISA and BI-QUANT-PS
• Statistical adjustment: age, sex, study center; then extensive multivariable models including lifestyle, medication, diet, urinary sodium, and BMI
• Metabolic ward: No
• Blinding: No
• Washout period: No, not applicable to this observational design

Key Findings

• Mean fish intake was 47.0 g per 1000 kcal.
• Urinary TMAO, urinary taurine, serum creatine, and serum threonine correlated with fish intake; homarine correlated with shellfish intake.
• TMAO had the strongest urine biomarker performance for high vs low fish intake, with AUC 0.802.
• TMAO to creatinine ratio had AUC 0.798.
• Taurine had AUC 0.74, and taurine to creatinine ratio had AUC 0.72.
• Homarine was a weaker shellfish biomarker, with AUC 0.64.
• Serum creatine and threonine were weaker discriminators of fish intake than the urinary markers, with AUC 0.58 and 0.57.
• Total fish intake was inversely associated with triglycerides: -2.44 mg/dL, p = 0.02.
• Low omega-3 fish showed the clearest triglyceride association: -2.73 mg/dL, p < 0.01.
• Total fish intake tracked with lower triglycerides in VLDL, IDL, and HDL-4, plus shifts in LDL subclass patterns.
• Raw fish showed stronger metabolomic correlations than fried fish; fried fish often showed weak or null links.
• Urinary TMAO was inversely associated with triglycerides: -3.47 mg/dL, p = 0.01 and positively associated with HDL-c: 0.47 mg/dL, p = 0.04.
• Urinary taurine was inversely associated with triglycerides: -3.88 mg/dL, p < 0.01 and systolic BP: -0.73 mmHg per 2 SD, p = 0.03.
• Serum threonine was inversely associated with triglycerides: -9.53 mg/dL, p < 0.01, BMI: -0.18 kg/m2 per 2 SD, p < 0.01, and diastolic BP: -0.29 mmHg per 2 SD, p = 0.05.
• Serum threonine was positively associated with HDL-c: 0.98 mg/dL per 2 SD, p < 0.01.
• Serum threonine was inversely associated with overall MetS risk: OR 0.84, p < 0.01.
• Serum creatine was positively associated with triglycerides: 2.78 mg/dL, p = 0.01.
• In this cohort, the fish-related metabolites lined up with a more favorable cardiometabolic profile overall, especially taurine and threonine.

Limitations

• Cross-sectional design prevents causal inference.
• Single-country cohort limits generalizability.
• Age range was narrow: 40 to 59 years.
• Non-fasting blood draw can influence lipid and glucose measures.
• One-time biomarker measurement limits repeatability checks.
• Residual confounding remains possible despite broad adjustment.
• This was not an intervention study, so there was no blinding and no washout.

Discussion and Implications

This paper strengthens the case that fish intake in a habitual seafood-eating population lines up with a favorable metabolic profile, and it does so using objective biomarkers rather than diet recall alone. The most interesting part is the metabolite pattern: taurine and threonine looked especially favorable, with lower triglycerides and lower blood pressure, while TMAO behaved like a seafood exposure marker rather than a simple danger signal in this setting.

That matters because it pushes back against the oversimplified “TMAO equals risk” framing. In this cohort, fish-derived TMAO, taurine, and threonine sat alongside lower triglycerides, higher HDL-c, and lower blood pressure, which is exactly why context matters in nutritional epidemiology. The study doesn’t prove causality, but it does show that the source of TMAO matters, and that fish intake, especially certain fish types, maps onto a metabolomic pattern associated with better cardiometabolic status.

Fish intake in this Japanese cohort lined up with lower triglycerides, lower blood pressure, and a better overall metabolic profile.

Taurine and threonine were the clearest favorable metabolites, while TMAO acted as a seafood-linked biomarker rather than a simple harm signal.

This doesn’t settle the TMAO debate, but it does show why fish, taurine, and other seafood metabolites can’t be interpreted through a one-size-fits-all anti-animal-food lens.

DOI: https://doi.org/10.3390/nu18183072

Late-Life Dietary Patterns and Subsequent Survival Among Adults Aged 90 Years or Older in the Sardinian Blue Zone

This prospective cohort study asked a narrower question than most longevity papers: not what people ate across life to reach extreme old age, but whether diet measured after age 90 related to survival from that point forward. The authors enrolled 200 Sardinian Blue Zone residents aged 90 to 106 years and followed them for up to 7 years to address a gap in the longevity literature, which has leaned heavily on ecological and cross-sectional data. Baseline diet was captured with a qualitative food-frequency questionnaire covering 17 foods or food groups, and participants were grouped using principal component analysis into empirical dietary patterns.

The main signal was a dairy–traditional-fat pattern built around milk, cheese, and lard, with lower olive oil and coffee. Higher adherence to that pattern tracked with longer survival: per 1-SD increase, mortality hazard fell to HR = 0.839 (95% CI: 0.727 to 0.969, p = 0.017), but that pattern-level result did not survive false-discovery-rate correction (q = 0.066). In tertile analyses, the highest versus lowest tertile showed HR = 0.682 (95% CI: 0.480 to 0.969), and median survival rose from 2.3 years in the lowest tertile to 4.3 years in the highest. Of the individual foods, milk (HR = 0.735, q = 0.0014), cheese (HR = 0.775, q = 0.0077), and chicken (HR = 0.811, q = 0.0275) were linked to lower mortality, while wine was linked to higher mortality (HR = 1.336, q = 0.0022). None of the other dietary patterns, including red-meat, chicken–carbohydrate, or plant–starchy food, showed a significant association with survival.

Study design and methodology

• Design: prospective cohort study
• Sample size: N = 200
• Population: Sardinian Blue Zone residents aged 90 to 106 years
• Follow-up: up to 7 years; mean follow-up 3.27 ± 1.81 years
• Outcome: all-cause mortality
• Diet assessment: face-to-face qualitative FFQ with 17 foods or food groups
• Pattern derivation: principal component analysis with Varimax rotation
• Covariate adjustment: age, sex, and comorbidity burden using a CIRS-derived count; sensitivity models also included MMSE, BADL, calf circumference, physical activity, and recruitment wave
• Controls used: no separate control group, this was an observational cohort
• Metabolic ward: no
• Blinding: no
• Washout period: no

Key findings

• Four dietary patterns emerged:
  • Dairy–traditional-fat
  • Red-meat
  • Chicken–carbohydrate
  • Plant–starchy food
• The dairy–traditional-fat pattern was the only one consistently linked to lower mortality.
  • Continuous score: HR = 0.839 (95% CI: 0.727 to 0.969, p = 0.017)
  • Highest vs lowest tertile: HR = 0.682 (95% CI: 0.480 to 0.969)
  • Median survival: 4.3 years vs 2.3 years in the highest vs lowest tertile
• The association with the dairy pattern did not meet the study’s FDR threshold:
  • q = 0.066
• No significant mortality association appeared for the other patterns:
  • Red-meat: HR = 1.043, p = 0.566
  • Chicken–carbohydrate: HR = 0.984, p = 0.821
  • Plant–starchy food: HR = 0.993, p = 0.928
• In mutually adjusted models, the dairy pattern stayed associated with lower mortality:
  • HR = 0.832
  • 95% CI: 0.718 to 0.964
  • p = 0.014
• In sensitivity analyses, the dairy-pattern result stayed broadly similar after extra adjustment for cognitive status, function, body size, physical activity, and recruitment wave:
  • Example: HR = 0.832, p = 0.012 with physical activity and recruitment wave included
• Excluding early deaths did not erase the signal, though it weakened:
  • Excluding deaths within 6 months: HR = 0.852, p = 0.031
  • Excluding deaths within 1 year: HR = 0.865, p = 0.063
• Food-level analysis showed:
  • Milk: HR = 0.735, q = 0.0014
  • Cheese: HR = 0.775, q = 0.0077
  • Chicken: HR = 0.811, q = 0.0275
  • Wine: HR = 1.336, q = 0.0022

Limitations

• Small sample size: N = 200
• Observational design, so causality can’t be inferred
• Diet was measured only at baseline
• Qualitative FFQ, so no portion sizes or total energy intake
• Residual confounding is a real issue, especially from frailty, appetite loss, swallowing problems, and functional decline
• Reverse causation is plausible in this age group
• No blinded design, no intervention, no washout
• No metabolic ward, so intake wasn’t tightly controlled
• Participants were highly selected survivors who had already reached age 90 or older
• Attrition wasn’t the issue here, since all participants died by the end of follow-up, but follow-up timing still varied

Discussion and implications

This paper adds an important distinction that longevity research often blurs: diet linked to reaching old age is not the same as diet linked to surviving after age 90. In this cohort, a dairy-heavy late-life pattern tracked with lower mortality, and the food-specific results lined up with that pattern, especially for milk and cheese.

The wine finding also matters because it cuts against the common habit of treating alcohol, especially traditional wine intake, as automatically beneficial in very old age. The authors are careful not to overclaim causality, and that caution is warranted. Still, the consistency of the dairy signal across the main, categorical, and sensitivity analyses gives the result real weight, even if multiple-testing correction weakens the formal significance.

This study points toward dairy foods, especially milk and cheese, as markers of better late-life survival in a very old Sardinian cohort. It does not prove dairy extends life, but it does show that diet still matters after age 90, and the pattern is worth following up in larger prospective studies.

DOI: https://pmc.ncbi.nlm.nih.gov/articles/PMC13626808/

Effect of a walnut-based low carbohydrate diet on fat redistribution and visceral fat accumulation in people with central obesity: A randomized controlled trial

Abstract

Central obesity remains a major cardiometabolic risk state, with excess abdominal and visceral adiposity linked more strongly to diabetes and cardiovascular outcomes than overall adiposity. This 12-week randomized controlled trial tested whether replacing staple carbohydrates with walnuts within a structured diet could improve fat distribution and reduce visceral fat accumulation in adults with central obesity in China. The trial recruited participants aged 18 to 60 years who met Chinese central obesity criteria, defined by waist circumference at least 90 cm in men and at least 85 cm in women, with BMI between 24 kg/m2 and 32.5 kg/m2. Participants were assigned to a walnut-based low carbohydrate diet or a high-carbohydrate low-fat diet after a one-week nut washout period.

The primary between-group signal came from the time course of fat distribution and visceral fat change, not endpoint separation at 12 weeks. The Group × Time interaction was significant for TLR, eta squared = 0.071, p = 0.039, VFA, eta squared = 0.093, p = 0.014, and BMI, eta squared = 0.168, p = 0.001, while WHR showed a near-significant interaction, eta squared = 0.052, p = 0.072. Within the walnut group, TLR fell with a large effect, eta squared = 0.174, p = 0.001, VFA fell with a large effect, eta squared = 0.393, p < 0.001, and BMI fell with a large effect, eta squared = 0.399, p < 0.001. At 12 weeks, GLP-1 was higher in the walnut group, 2.10 pmol/L [1.84, 2.69] vs 1.59 pmol/L [0.86, 2.14], Z = -2.343, p = 0.019, PYY was higher, 33.1 ± 5.50 pg/mL vs 26.8 ± 5.93 pg/mL, t = 3.663, p = 0.001, and C-peptide was lower, 1.11 [0.73, 1.29] ng/mL vs 1.61 [1.01, 3.64] ng/mL, Z = -2.242, p = 0.025.

Study Design and Methodology

• Design: 12-week prospective randomized controlled trial
• Population: 80 adults with central obesity randomized 1:1, 40 to w-LCD and 40 to HCD
• Final analyzed sample: 35 in w-LCD, 29 in HCD
• Duration: 12 weeks
• Recruitment period: December 2022 to October 2023
• Allocation: computer-generated random number table, concealed by a non-principal researcher
• Blinding: allocation concealment was described, participant and dietary blinding was not reported
• Washout: 1-week purge period avoiding all nut supplementation before intervention
• Diet control: structured meal plan based on 2021 Chinese Medical Nutrition Therapy guidance
• Intervention contrast: HCD used the guideline-based low-fat, high-carb regimen, w-LCD replaced 150 g/day of staple food with walnuts
• Measurements: InBody720 bioelectrical impedance for TLR, VFA, BMI, BF%, and trunk and leg fat; tape-measured WC and HC for WHR; fasting GLP-1, PYY, and C-peptide by ELISA; 3-day diet records; IPAQ for physical activity
• Follow-ups: baseline, 1 week, 4 weeks, 8 weeks, 12 weeks
• Statistics: repeated-measures ANOVA, t tests, Mann-Whitney tests, chi-square tests, ITT with LOCF

Key Findings

• TLR improved over time in w-LCD, with a significant Group × Time interaction, eta squared = 0.071, p = 0.039
• VFA improved over time in w-LCD, with a significant Group × Time interaction, eta squared = 0.093, p = 0.014
• BMI improved over time in w-LCD, with a significant Group × Time interaction, eta squared = 0.168, p = 0.001
• WHR trended lower, interaction eta squared = 0.052, p = 0.072
• Within w-LCD, TLR fell from 1.80 ± 0.19 to 1.74 ± 0.20, eta squared = 0.174, p = 0.001
• Within w-LCD, VFA fell from 113 ± 33.4 cm2 to 97.4 ± 31.7 cm2, eta squared = 0.393, p < 0.001
• Within w-LCD, BMI fell from 27.6 ± 2.49 to 26.1 ± 2.63 kg/m2, eta squared = 0.399, p < 0.001
• Between-group comparison at 12 weeks did not separate significantly for TLR, VFA, or BMI, despite the stronger trajectory in w-LCD
• GLP-1 was higher in w-LCD at 12 weeks, p = 0.019
• PYY was higher in w-LCD at 12 weeks, p = 0.001
• C-peptide was lower in w-LCD at 12 weeks, p = 0.025
• Dietary adherence showed the macronutrient shift was achieved: w-LCD maintained roughly 39% carbohydrate and 42% fat, HCD maintained roughly 57% carbohydrate and 24% fat
• Energy intake fell in both groups over time, from 1746 ± 412 to 1162 ± 224 kcal/day in w-LCD and from 1892 ± 512 to 1211 ± 326 kcal/day in HCD
• Group effect for carbohydrate intake was significant, eta squared = 0.184, p = 0.001
• Group effect for fat intake was significant, eta squared = 0.155, p = 0.002
• Fat intake had a strong Group × Time interaction, eta squared = 0.290, p < 0.001
• Within w-LCD, fat intake rose from 52.1 ± 18.5 to 55.2 ± 11.2 g/day, while HCD fell from 54.7 ± 21.3 to 31.3 ± 11.3 g/day

Limitations

• Small sample size with substantial attrition, 35 vs 29 completed
• Unequal dropout, higher in HCD than w-LCD
• Short duration, only 12 weeks
• Self-reported dietary records introduce reporting bias
• No strict isocaloric control, so energy matching was imperfect
• No baseline C-peptide
• No dynamic postprandial hormone testing
• No insulin resistance or inflammatory biomarkers
• No stratified subgroup analysis by sex, baseline obesity severity, or lipid profile
• Walnut exposure was partially self-funded, which can affect adherence and external validity

Discussion and Implications

This trial shifts the nutrition conversation from “low-fat versus low-carb” toward carbohydrate quality and macronutrient substitution. Replacing staple carbohydrate with walnuts produced a stronger reduction trajectory for trunk fat distribution and visceral adiposity than the comparator diet, while also shifting fasting GLP-1, PYY, and C-peptide in the expected direction. The data support walnut inclusion as a practical food-based strategy inside a carbohydrate-restricted framework, not as a simple calorie addition.

Conclusion

Overall, the study found that swapping some staple carbs for walnuts led to better reductions in belly fat patterning and visceral fat over 12 weeks, while also shifting appetite-related hormones in a favorable direction. The results are promising, but this is still a small, short trial, so it needs larger and longer follow-up before anyone treats it as settled practice.

DOI: 10.3390/nu18183098

L-Theanine Prevents Autophagy Impairment to Counteract Cadmium-Induced Hepatic Mitochondrial Dysfunction, Ferroptosis, and Glucolipid Dysmetabolism in Mice - PMC

Abstract

Cadmium exposure disrupts hepatic autophagy, mitochondrial homeostasis, and glucolipid metabolism, yet the role of L-theanine in reversing these injuries has remained unclear. This study tested whether L-theanine could protect mice from acute cadmium lethality and subchronic cadmium-induced liver dysfunction, using male 3-week-old Kunming mice. The acute arm examined survival after cadmium injection, while the longer experiment assessed hepatic injury, Cd bioaccumulation, autophagy-linked signaling, ferroptosis, mitochondrial function, and metabolic readouts under controlled dietary conditions.

L-theanine extended median survival from 4 h to 16 h, reduced acute cadmium mortality from 100% to 60%, and lowered the 4 h mortality rate from 60% to 30% and the 8 h mortality rate from 100% to 50%. In subchronic exposure, cadmium increased liver and serum Cd, but L-theanine did not alter Cd accumulation or MT1/MT2 expression. Cadmium increased serum TG to 2.0439 ± 0.5785 mmol/L versus 1.2062 ± 0.3808 in controls, lowered serum HDL-C to 3.7716 ± 0.6370 versus 5.0740 ± 0.8310, raised liver TC to 0.3175 ± 0.0520 versus 0.2119 ± 0.0348, and reduced liver HDL-C to 0.0049 ± 0.0008 versus 0.0061 ± 0.0010. It also elevated Fe2+ in serum and liver, increased MDA, depleted GSH, suppressed COX and SDH, downregulated SIRT1, PGC-1α, Parkin, NRF1, TFAM, PI3K/AKT, AMPK, and p-AMPK, and increased DPP-4, p-mTOR, p-p70S6K, ACSL4, and ubiquitin. L-theanine reversed these changes, restored AMPK-linked autophagy signaling, raised p-ACC(Ser79), stabilized GPX4 and FSP1, improved fatty acid oxidation markers, reduced lipogenesis markers, and normalized liver histology, fibrosis, and glycogen-lipid accumulation, with significance reported across multiple endpoints at p < 0.05, p < 0.01, and p < 0.001.

Study Design and Methodology

• Population: Male, 3-week-old Kunming mice
• Acute arm: N = 24 total, 8 per group
  • Ctrl
  • CdCl2, 8 mg/kg i.p.
  • LT + CdCl2, 200 mg/kg LT i.g. for 3 days before Cd
• Subchronic arm: N = 36 total, 9 per group
  • Ctrl
  • CdCl2, 2.5 mg/kg i.g.
  • Low LT, 1 mg/mL in drinking water
  • High LT, 2 mg/mL in drinking water
• Duration: Acute survival tracked over hours, subchronic exposure lasted 10 weeks
• Controls and handling: Random allocation, cage positions cyclically shifted every 3 days, daily gavage/weighing between 10:00 and 12:00 a.m.
• Blinding: No blinding
• Washout: None reported
• Measurement tools: H&E, PAS, Oil Red O, Masson staining, ICP-MS for Cd, RT-qPCR, Western blot, enzyme assays for COX, SDH, DPP-4, MDA, GSH, CAT, TG, TC, HDL-C, AKP, Fe2+
• Primary outcome: Prespecified hepatic autophagy prior to data collection
• Stats: One-way ANOVA, t-tests, Welch’s t-test, Kruskal-Wallis with post hoc testing, significance threshold p < 0.05

Key Findings

• Acute survival improved sharply
  • Median survival time increased from 4 h to 16 h
  • Mortality dropped from 100% to 60%
  • At 4 h, mortality fell from 60% to 30%
  • At 8 h, mortality fell from 100% to 50%
  • Survival benefit reported at p < 0.05
• Cadmium caused clear hepatic injury and dysmetabolism
  • Liver hypertrophy, fatty infiltration, amyloidosis, collagen accumulation, and glycogen loading increased
  • Serum AKP and liver AKP increased significantly
  • Serum TG rose to 2.0439 ± 0.5785 mmol/L from 1.2062 ± 0.3808
  • Serum HDL-C fell to 3.7716 ± 0.6370 mmol/L from 5.0740 ± 0.8310
  • Liver TC increased to 0.3175 ± 0.0520 mmol/g prot from 0.2119 ± 0.0348
  • Liver HDL-C declined to 0.0049 ± 0.0008 mmol/g prot from 0.0061 ± 0.0010
  • Several endpoints reached p < 0.05, p < 0.01, or p < 0.001
• Cd disrupted mitochondrial function
  • COX and SDH declined significantly
  • SIRT1, PGC-1α, Parkin, NRF1, TFAM, and Nrf2 fell
  • Fibrosis markers rose, including α-SMA, TGF-β1, and Col1a1
  • Insulin signaling dropped, including p-PI3Kp85 and p-AKT(Ser473)
• Cd promoted ferroptosis
  • Serum and liver Fe2+ increased
  • Hepatic MDA rose
  • GSH decreased
  • GPX4, FSP1, and membrane FSP1 decreased
  • ACSL4 increased
  • Ubiquitin increased, with reduced GPX4 protein consistent with ubiquitin-mediated degradation
• Cd suppressed AMPK-linked autophagy
  • DPP-4 increased
  • p-AMPK(Thr172) decreased
  • p-mTOR(Ser2481) and p-p70S6K increased
  • LC3B mRNA rose
  • p-ACC(Ser79) declined
  • CPT1α, PPARα, ACOX1, and GLUT2 declined
  • SREBP1, FASN, PPARγ, and TXNIP increased
• L-theanine reversed the entire injury cascade
  • Lowered DPP-4
  • Increased SIRT1
  • Restored AMPK phosphorylation
  • Reduced mTOR activation
  • Increased p-ACC(Ser79)
  • Improved fatty acid oxidation and reduced lipogenesis
  • Restored GPX4 and FSP1
  • Reduced lipid peroxidation and ferroptosis markers
  • Preserved mitochondrial function through PGC-1α/NRFs/TFAM signaling
  • Improved liver histology, fibrosis, and glycogen-lipid accumulation
  • Did not change Cd burden in liver, serum, feces, or MT1/MT2 expression

Limitations

• Small animal sample sizes, especially for protein-level analyses
• No blinding
• No washout period
• Rodent model only, so external validity is limited
• Acute Cd exposure used intraperitoneal dosing, which does not mimic dietary exposure
• The autophagy readout did not include direct flux testing
• Self-reporting was not applicable
• Residual confounders related to housing and handling remain possible despite cage rotation

Discussion and Implications

This paper shifts the field away from a narrow detoxification model and toward a signaling-centered model of Cd injury. L-theanine did not lower cadmium burden, so its protective effect comes from intracellular repair rather than metal removal. The critical mechanism runs through DPP-4, SIRT1, AMPK, and mTOR, with downstream correction of autophagy-linked mitochondrial failure, ferroptosis, and glucolipid dysmetabolism.

For nutrition science, this matters because it positions L-theanine as a cytoprotective dietary compound with mechanistic relevance beyond general antioxidant claims. In a cadmium-exposed context, the practical value lies in preserving hepatic energetics, limiting lipid peroxidation, and maintaining metabolic stability, even when cadmium remains in the system.

Conclusion

L-theanine produced a strong hepatoprotective signal in cadmium-exposed mice, with benefits tied to restored AMPK-linked autophagy signaling, mitochondrial function, and metabolic control. For a nutrition professional, the practical takeaway is that L-theanine has translational potential as an adjunctive dietary strategy in heavy-metal stress, not as a chelator, but as a cellular resilience modulator.

Circulating imidazole propionate and coronary heart disease risk: interplay between histidine intake, fiber, and gut microbiome

DOI: https://doi.org/10.1186/s12916-026-05012-6

Abstract

Microbial metabolism of dietary histidine produces imidazole propionate (ImP), a metabolite previously linked to insulin resistance and type 2 diabetes. While histidine intake itself often correlates with positive health outcomes, the prospective relationship between its microbial byproduct, ImP, and coronary heart disease (CHD) risk remained unquantified. This research sought to bridge that gap by evaluating the longitudinal association between plasma ImP and incident CHD, identifying the specific gut microbial species responsible for ImP production, and determining how dietary fiber intake modulates this metabolic axis. The study utilized data from 7,432 participants across the Nurses’ Health Study (NHS), NHSII, and Health Professionals Follow-up Study, alongside detailed metagenomic and dietary record analysis from the Men’s Lifestyle Validation Study (MLVS) and Mind-Body Study (MBS).

Elevated plasma ImP concentrations demonstrated a robust positive association with CHD risk, yielding a hazard ratio of 1.82 (95 percent CI 1.17 to 2.81, p-trend = 0.002) when comparing extreme quintiles. Histidine intake showed a non-significant inverse association with CHD, emphasizing that the metabolite, not the precursor, drives cardiovascular risk. Metagenomic analysis identified 17 ImP-predicting species, including Ruminococcus gnavus and Clostridium symbiosum, with the microbial model outperforming diet and demographics in predicting ImP levels (Spearman r = 0.71). A critical three-way interaction was observed between histidine intake, microbial capacity, and pectin (p = 0.01). High histidine intake only predicted increased ImP when pectin intake was low. Total fiber (p = 0.09) and soluble fiber (p = 0.09) showed similar but non-significant trends.

Study Design and Methodology

This prospective investigation tracked 7,432 healthy participants from the NHS, NHSII, and HPFS cohorts for up to 31 years. Researchers identified 225 incident CHD cases through medical record review and the National Death Index. Plasma ImP and urocanic acid were measured via liquid chromatography-tandem mass spectrometry. Dietary data were captured using validated semi-quantitative food frequency questionnaires (FFQ) administered every 4 years. The mechanistic component utilized the MLVS (N = 296) and MBS (N = 205), employing two sets of 7-day diet records (7DDR) and shotgun metagenomic sequencing of 1,684 stool samples. Statistical models adjusted for age, BMI, physical activity, alcohol, smoking, and total energy intake. Batch effects were corrected, and microbial taxa were normalized using centered log-ratio (CLR) transformation.

Key Findings

• High plasma ImP levels correlate with a 1.82-fold increase in CHD risk (p-trend = 0.002).
• Joint analysis shows participants with low histidine and high ImP have the highest risk (HR = 3.40, 95 percent CI 1.71 to 6.73).
• Pectin intake is the strongest negative dietary predictor of plasma ImP (beta = -0.21, 95 percent CI -0.35 to -0.07).
• Metagenomic modeling of species and enzymes predicts ImP concentrations with high accuracy (Spearman r = 0.71).
• Thirteen species, including Clostridium scindens and Hungatella hathewayi, positively predict ImP (FDR q < 0.1).
• Presence of the microbial urocanate reductase gene (urdA) is associated with higher ImP (beta = 0.51, 95 percent CI 0.13 to 0.89) and lower HDL-C (beta = -0.12, p < 0.05).
• The interaction between histidine intake and microbial score on ImP levels is significant only under low pectin intake (p for 3-way interaction = 0.01).
• Plasma ImP is positively associated with hs-CRP (p < 0.05) and negatively associated with HDL-C (p < 0.05).

Limitations

The observational nature of the cohorts prevents definitive causal inference. Self-reported dietary data, even when using 7DDR, contains inherent measurement error. The study population consists primarily of white health professionals, which limits generalizability to more diverse ethnic or socioeconomic groups. While the microbial findings were replicated in the MBS, the correlation between the microbial score and circulating ImP was modest (Spearman r = 0.15), suggesting other unmeasured factors influence metabolite levels.

Discussion and Implications

These data redefine the relationship between dietary protein and cardiovascular health by identifying the gut microbiome as the primary gatekeeper of histidine metabolism. The divergent outcomes between histidine intake and its metabolite ImP prove that dietary precursors aren't inherently pathogenic. Instead, the pathogenicity depends on microbial shunting. The discovery that pectin and other fibers can block the production of ImP even in the presence of high histidine intake and ImP-producing bacteria provides a clear metabolic mechanism for the cardioprotective effects of the Mediterranean and DASH diets. This study shifts the focus from simple nutrient intake to the complex interplay of substrate availability and microbial enzymatic capacity.

Conclusion

Circulating imidazole propionate is a significant prospective biomarker for coronary heart disease risk, driven by specific gut bacteria like Ruminococcus gnavus. Dietary fiber, particularly pectin, acts as a metabolic buffer that prevents the microbial conversion of histidine into this harmful metabolite. Clinicians should prioritize fiber co-ingestion with protein to mitigate the cardiovascular risks associated with microbial histidine metabolism.

Effects of breakfast macronutrient composition on postprandial glycemic control in patients with diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials

https://doi.org/10.3389/fendo.2026.1859725

Postprandial hyperglycemia is an independent risk factor for cardiovascular complications and all-cause mortality, yet clinical consensus on the ideal breakfast macronutrient ratio remains elusive. Breakfast serves as the primary metabolic signal for resetting the circadian clock and managing the "dawn phenomenon," making its composition critical for daily glucose stability. This systematic review and network meta-analysis synthesized evidence from 37 randomized controlled trials involving 1,030 participants with Type 1, Type 2, and Gestational Diabetes to evaluate how varying ratios of carbohydrates, proteins, fats, and fibers influence metabolic outcomes.

Adjusting breakfast macronutrient composition significantly reduced 2-hour postprandial blood glucose by a mean difference of -1.90 mmol/L (95% CI: -2.46 to -1.34; p < 0.001) and lowered HbA1c by a mean difference of -0.52% (95% CI: -0.59% to -0.45%; p < 0.001). The area under the postprandial glucose curve (iAUC) showed a significant reduction with a standardized mean difference of -1.24 (95% CI: -2.45 to -0.03; p = 0.045). Subgroup analyses identified legume-based breakfasts as the most effective for acute 2-hour glucose control (85.7% SUCRA), while whey protein supplementation was superior for long-term HbA1c reduction, yielding a pooled MD of -0.50% (95% CI: -0.56 to -0.44; p < 0.001).

Study Design and Methodology

The researchers conducted a systematic search of PubMed, Web of Science, and Cochrane CENTRAL through March 2026, identifying 37 RCTs (N = 1,030). The majority of trials (86.5%) utilized isocaloric designs to control for total energy intake. Intervention durations ranged from acute single-meal challenges to 140-day trials. Outcomes were measured via continuous glucose monitoring (CGM), 2-hour postprandial testing, and HbA1c assays. The Cochrane RoB 2.0 tool was used for quality assessment, with most studies categorized as having "some concerns" due to the nature of dietary intervention blinding.

Key Findings

• High-protein breakfasts (whey or eggs) achieved a pooled HbA1c reduction of -0.50% (95% CI: -0.56 to -0.44), surpassing the clinical significance threshold for diabetes management.
• Legume-based breakfasts (black beans, adzuki, or speckled beans) lowered 2-hour postprandial glucose by -2.10 to -2.46 mmol/L.
• Low-carbohydrate breakfast interventions (10% to 16% of energy) resulted in a pooled reduction of -0.62 mmol/L (95% CI: -0.88 to -0.36; p < 0.001).
• Specific low-carb trials reported extreme acute improvements, including an 86.9% reduction in iAUC.
• High-fiber interventions (> 10g soluble fiber) demonstrated a mean difference of -0.78 mmol/L (95% CI: -1.04 to -0.52) in postprandial glucose.
• Egg-based breakfasts were found to improve inflammatory markers compared to oatmeal-based controls (Ballesteros, 2015).

Limitations

High statistical heterogeneity (I2 = 93.7%) was observed across primary analyses, likely due to variations in baseline patient characteristics and insulin use. Egger’s test (p = 0.026) indicated potential publication bias, suggesting a lack of published small-scale null findings. The star-like network meta-analysis structure limited the ability to perform formal inconsistency testing between direct and indirect evidence loops.

Discussion and Implications

This evidence necessitates a clinical shift away from high-carbohydrate "balanced" breakfasts toward protein and fiber-dense morning meals. High-protein breakfasts, particularly those utilizing whey protein or eggs, provide a potent second-meal effect that improves insulin sensitivity throughout the day. Legumes offer a dual benefit by providing high-viscosity soluble fiber that slows glucose absorption and plant-based protein that supports satiety. While low-GI grains show some benefit, they don't match the 0.5% HbA1c reduction seen with high-protein loading. Practitioners should prioritize the morning meal as a therapeutic window to mitigate the dawn phenomenon and reduce cardiovascular risk via tighter postprandial control.

Optimizing breakfast by prioritizing high protein (20-35g) and viscous fiber from legumes significantly improves both acute postprandial spikes and long-term HbA1c levels. Nutrition professionals should recommend replacing refined grains with eggs, whey protein, or beans to achieve a clinically meaningful 0.5% reduction in HbA1c and up to an 86% reduction in post-meal glucose surges.

Effect of Intake of Lycopene-Containing Products on Vascular Endothelial Function in Healthy Adults: A Systematic Review with Meta-Analysis

DOI: https://doi.org/10.3390/nu18152505

Abstract

Vascular endothelial dysfunction serves as a critical early indicator for the progression of atherosclerosis and cardiovascular disease (CVD). While previous research highlighted the antioxidant properties of lycopene (a red carotenoid found in tomatoes and watermelon), existing meta-analyses suffered from narrow inclusion criteria, outdated search dates, and limited outcome measures. This systematic review addressed these gaps by evaluating the impact of oral lycopene intake from diverse food sources on vascular endothelial function specifically in healthy adults. The researchers targeted a population of healthy individuals to determine if lycopene functions as an effective early-stage intervention for those with low baseline CVD risk.

Analysis of four continuous intake studies (at least 7 days) involving 182 participants demonstrated a significant increase in flow-mediated dilation (FMD) compared to control groups. The pooled data yielded a mean difference (MD) of 1.36 percent (95 percent CI: 0.20, 2.51, p = 0.02). Heterogeneity remained low at I2 = 24 percent. One specific study utilizing 15 mg of lycopene for 8 weeks reported a significant increase in the reactive hyperemia peripheral arterial tonometry (RH-PAT) index (p < 0.05). While a single-intake study (27.8 mg) failed to reach significance (p = 0.18), the cumulative data from multi-week interventions confirm improvements in endothelial dynamics.

Study Design and Methodology

This systematic review and meta-analysis followed PRISMA 2020 guidelines and was registered under UMIN000058348. The authors searched four databases (PubMed, Cochrane, Ichushi-Web, Global Index Medicus) and three registries through June 2026. The final analysis included six studies (four RCT-C and two RCT-P designs) conducted across the USA, Germany, Greece, Japan, and Korea. Total participants in the meta-analysis reached N = 182. Intervention durations ranged from a single dose to 12 weeks, with lycopene dosages spanning 6 mg to 46.2 mg per day. Controls received placebos, no intervention, or extremely low-lycopene alternatives. Risk of bias was assessed using a 13-item checklist and the RoB2 tool, with five studies rated as moderate risk and one as low risk.

Key Findings

• Continuous lycopene intake significantly improves FMD with a pooled MD of 1.36 percent (p = 0.02).
• Daily consumption of 15 mg and 26.7 mg of tomato juice for 12 weeks both resulted in significant FMD increases (p < 0.001).
• Lycopene supplementation at 15 mg for 8 weeks significantly boosted the RH-PAT index (p < 0.05), whereas 6 mg did not (p > 0.05).
• Tomato paste providing 33.3 mg of lycopene for 15 days produced a significant improvement in endothelial dynamics (p = 0.03).
• Standardized effect sizes for lycopene on FMD (1.36 percent) are comparable to other potent nutrients like CoQ10 (1.45 percent) and resveratrol (1.43 percent).
• Leave-one-out sensitivity analysis showed that the exclusion of the largest, lowest-bias study (Yoshida et al.) rendered the FMD results non-significant.

Limitations

The small number of included studies (n = 6) limits the ability to perform robust subgroup analyses on ethnicity or specific food matrices. Relying on endpoint values rather than change-from-baseline data in three studies may introduce variance. The meta-analysis results rely heavily on a single high-quality study, and the lack of paired data for crossover trials necessitated treating them as parallel groups, which potentially ignores within-participant correlations.

Discussion and Implications

These results shift the focus of lycopene research from general antioxidant support to specific vascular protective mechanisms. Lycopene enhances nitric oxide (NO) bioavailability by quenching reactive oxygen species and increasing NO synthase activity. The data suggest that 15 mg per day is the minimum threshold required to elicit measurable improvements in endothelial function over a period of 8 to 12 weeks. Because these improvements occur in healthy populations, lycopene-rich diets act as a primary preventative tool against the initiation of the atherosclerotic cascade. The findings validate the use of diverse sources (watermelon, tomato juice, and concentrates) rather than just isolated supplements.

Conclusion

Continuous intake of at least 15 mg of lycopene daily significantly improves vascular endothelial function in healthy adults as measured by FMD and RH-PAT. Nutrition professionals should recommend regular consumption of processed tomato products or watermelon to enhance nitric oxide bioavailability and reduce early cardiovascular risk.

Clinical and mechanistic evidence on metabolic effects of oat β-glucan, rice bran, and unripe banana flour: a systematic review with mechanism-informed synthesis

DOI: https://doi.org/10.1017/jns.2026.10127

Abstract

Metabolic syndrome (MetS) remains a critical global health burden characterized by central obesity, dyslipidemia, and impaired glucose regulation. While dietary fiber is recognized as a primary modulator of metabolic health, comparative evidence across distinct fiber sources like oat β-glucan, rice bran, and unripe banana flour (UBF) hasn't been adequately synthesized. This systematic review addresses the research gap by evaluating 15 studies (indexed 2014 to 2025) to determine how differences in fiber structure, viscosity, and fermentability influence glycemic and lipid outcomes in adults with at least one MetS component.

Oat β-glucan demonstrated a dose-dependent reduction in postprandial glucose AUC, where each gram of fiber reduced glucose AUC by 4.35 percent and peak glucose by 6.57 percent (p values not specified for all individual markers but consistent across trials). Rice bran oil (RBO) interventions yielded significant lipid improvements, specifically reductions in total cholesterol (TC) and LDL-C (p < 0.05) alongside increases in HDL-C. Unripe banana flour (UBF) resistant starch was associated with reductions in fasting glucose, HOMA-IR, and body weight, though these findings stem from smaller trials with durations between 3 days and 12 weeks.

Study Design and Methodology

This systematic review followed PRISMA 2020 guidelines, screening 602 records and including 15 studies (14 RCTs and 1 non-randomized intervention). The total sample sizes across individual trials ranged from N = 10 to N = 154. Intervention durations spanned 3 days to 12 weeks. Measurement tools included standardized glycemic markers (HbA1c, HOMA-IR), lipid profiles (LDL-C, TC, TG), and mechanistic biomarkers like SCFA profiles and gut hormone response (PYY, GLP-1). Risk of bias was rigorously evaluated using the RoB 2.0 tool for randomized trials and the Newcastle-Ottawa Scale for the non-randomized study.

Key Findings

• Oat β-glucan intake of 0.9 to 5.3 g showed a linear dose-response for glycemic control.
• Rice bran oil significantly decreased LDL-C and TC while increasing HDL-C (p < 0.05).
• Defatted rice bran supplementation over 12 weeks resulted in significant reductions in HbA1c and blood pressure.
• Unripe banana flour consumption improved insulin sensitivity and reduced ghrelin AUC while increasing PYY levels.
• Oat bran supplementation (40 g/day) in one trial showed no additional benefit over a low-calorie diet alone, with a recorded reduction in HDL-C.
• Microbiota modulation was observed with oat bran, specifically increasing Bifidobacterium and Spirillum species.

Limitations

Heterogeneity in dosing and food formulations limits the ability to perform a formal meta-analysis. Several trials featured small sample sizes and short durations (under 4 weeks). Mechanistic assessments like SCFA profiles and bile acid signaling were inconsistently reported across the included literature.

Discussion and Implications

The evidence confirms that fiber isn't a monolithic category. Metabolic responses are dictated by the specific physicochemical properties of the fiber source. Viscosity-driven mechanisms (oat β-glucan) provide predictable postprandial glucose control. Phytochemical-mediated pathways (rice bran) target lipid oxidation and antioxidant status. Fermentation-driven pathways (resistant starch in UBF) influence long-term insulin sensitivity and satiety through incretin modulation. Clinical practice should transition from general fiber recommendations toward targeted, mechanism-based interventions that match a patient's specific metabolic phenotype.

Oat β-glucan, rice bran, and unripe banana flour provide distinct but complementary metabolic benefits through viscosity, phytochemical, and fermentation pathways. Practitioners should utilize oat β-glucan for acute postprandial glucose management and rice bran or unripe banana flour for long-term lipid and insulin sensitivity improvements.

DOI: https://doi.org/10.3389/fnut.2026.1782327

Title: Planetary health diet index and low muscle mass in adults aged 20–60 years: exploratory evaluation of a dairy-upweighted outcome-specific adaptation

Abstract

The EAT-Lancet Planetary Health Diet (PHD) framework prioritizes environmental sustainability by restricting animal-sourced proteins, yet this restriction potentially conflicts with the anabolic requirements necessary to maintain muscle mass across the life course. Investigators identified a critical research gap regarding whether the standard Planetary Health Diet Index for the United States (PHDI-US) supports muscle preservation or if the restriction of dairy creates a nutritional deficit for aging populations. This study evaluated the association between PHDI-US adherence and low muscle mass (LMM) in a representative sample of 10,329 U.S. adults aged 20 to 60 years, while exploring a machine learning-derived adaptation that upweights dairy intake to better align with physiological needs.

Analysis of the fully adjusted models demonstrated that higher PHDI-US scores were associated with lower odds of LMM, specifically for the highest versus lowest quartile (OR = 0.73, 95% CI: 0.57 to 0.95, p = 0.02). The exploratory dairy-upweighted index (PHDI-Dairy) yielded a significantly more robust inverse association, with the top quartile showing a 32% reduction in LMM risk (OR = 0.68, 95% CI: 0.55 to 0.84, p < 0.01). Validation in an independent Southern Chinese cohort (n = 218) confirmed that the highest dairy intake quartile was associated with a 74% lower risk of LMM (OR = 0.26, 95% CI: 0.11 to 0.61, p < 0.01). Stratified analyses revealed these protective effects were most pronounced in women aged 46 to 60 years (p for overall < 0.05), suggesting that the high leucine density of dairy is critical as anabolic resistance emerges in midlife.

Study Design and Methodology

This research utilized a cross-sectional design based on five cycles of NHANES data (2005 to 2006 and 2011 to 2018) involving 10,329 participants. Appendicular lean mass was measured via dual-energy X-ray absorptiometry (DXA), with LMM defined as less than 7.0 kg/m2 for men and 5.5 kg/m2 for women. Dietary intake was captured through two-day 24-hour recalls. A random forest model with recursive feature elimination identified dairy as the most influential component for muscle mass prediction. Investigators then constructed the PHDI-Dairy score by multiplying the original PHDI-US total by observed dairy intake. The study adjusted for age, sex, race, poverty-income ratio, BMI, smoking, hypertension, and diabetes, with internal 5-fold cross-validation used to assess model stability.

Key Findings

• PHDI-US adherence correlates with lower LMM risk in the highest quartile (OR = 0.73, p = 0.02).
• Dairy-upweighted PHDI-Dairy scores show superior predictive strength (OR = 0.68, p < 0.01) and a significant trend (p for trend < 0.01).
• The Southern Chinese cohort analysis found a massive risk reduction in the highest dairy quartile (OR = 0.26, p < 0.01).
• Machine learning identified dairy as the number one predictor of muscle mass among all 16 Planetary Health Diet components.
• The study identifies a critical anabolic threshold of 14 to 40g of milk protein daily to significantly improve appendicular muscle mass.
• Effective muscle protein synthesis requires approximately 2.5 to 3g of leucine per meal, a density easily achieved via dairy but difficult under strict EAT-Lancet plant-protein limits.
• Restricted cubic spline analysis for PHDI-Dairy indicates a continuously decreasing dose-response curve without a plateau.

Limitations

The cross-sectional nature of the NHANES data precludes any causal inferences regarding dietary changes and muscle mass retention. Self-reported 24-hour dietary recalls are subject to recall bias and may not reflect long-term habitual intake. Confounding variables such as precise physical activity levels and resistance training frequency were not fully controlled. The Southern Chinese cohort was hospital-based and small (n = 218), limiting its generalizability as a formal external validation of the full composite index.

Discussion and Implications

This study challenges the strict animal-protein limitations of the original EAT-Lancet framework by demonstrating that dairy is the single most important dietary component for maintaining muscle mass in adults. The data suggest that physiological sustainability must be balanced with ecological goals, as the restriction of dairy may accelerate the progression toward sarcopenia. While red meat restriction remains viable for environmental reasons, dairy provides a necessary anabolic stimulus due to its superior leucine content and complete amino acid profile. These findings indicate that nutritional guidelines for aging populations should prioritize high-quality dairy protein (targeting 14 to 40g of protein daily) to mitigate the effects of anabolic resistance that begin as early as the fifth decade of life.

Conclusion

Standard Planetary Health Diet adherence is modestly protective against low muscle mass, but recalibrating the index to prioritize dairy intake significantly enhances its clinical relevance. For adults aged 46 to 60, particularly women, higher dairy consumption is a primary dietary determinant for preserving muscle mass and preventing early-stage sarcopenic phenotypes.

Title: Association between composite dietary antioxidant index and risk of ischemic heart disease and stroke: a prospective cohort study from the UK Biobank

DOI: Link

Abstract

Oxidative stress represents a critical driver in the pathogenesis of cardiovascular diseases, yet the cumulative impact of multiple dietary antioxidants remains poorly defined. This study addressed the research gap regarding whether a synergistic combination of antioxidants, rather than isolated nutrients, influences long term vascular outcomes. Researchers utilized data from the UK Biobank, focusing on a large cohort of middle aged and older adults. The primary objective was to evaluate the association between the Composite Dietary Antioxidant Index (CDAI), a weighted score of vitamins A, C, E, selenium, zinc, and carotenoids, and the incidence of ischemic heart disease (IHD) and stroke.

The analysis revealed a non linear, L shaped relationship between antioxidant intake and vascular events. Participants in the highest quartile of CDAI scores experienced a 10 percent reduction in IHD risk (HR 0.90, 95 percent CI 0.85 to 0.95, p < 0.001) and an 18 percent reduction in stroke risk (HR 0.82, 95 percent CI 0.74 to 0.91, p < 0.001) compared to the lowest quartile. Restricted cubic spline analysis identified a significant threshold at a CDAI score of -0.30, beyond which the risk reduction for IHD reached a plateau. These findings were consistent across multiple sensitivity analyses, confirming that higher composite antioxidant intake significantly correlates with lower cardiovascular morbidity in a general population.

Study Design and Methodology

This prospective cohort study utilized a massive sample size of 164,177 participants from the UK Biobank. The median follow up duration reached 12.1 years, providing robust longitudinal data. Dietary intake was assessed using the Oxford WebQ, a validated 24 hour dietary recall tool administered at least twice to ensure representativeness. The CDAI was calculated by standardizing the intake of six key nutrients (vitamin A, C, E, zinc, selenium, and carotenoids) into Z scores. Researchers controlled for a comprehensive suite of covariates including age, sex, ethnicity, Townsend Deprivation Index, BMI, smoking status, alcohol consumption, physical activity (IPAQ scores), and comorbidities like hypertension and diabetes. The study excluded participants with baseline cardiovascular disease to minimize reverse causality.

Key Findings

• Ischemic Heart Disease: The risk decreased significantly as CDAI scores moved from the lowest to the third quartile (HR 0.89, 95 percent CI 0.85 to 0.94).
• Stroke Incidence: The highest antioxidant intake group (Q4) demonstrated the most profound protection with an 18 percent lower risk (p < 0.001).
• Threshold Effect: An inflection point for IHD risk was identified at a CDAI of -0.30 (p for non-linearity < 0.001).
• Inflammatory Markers: Higher CDAI scores correlated with lower C-reactive protein (CRP) levels, with Q1 at 1.34 mg/L versus Q4 at 1.16 mg/L.
• Fiber Correlation: High CDAI scores strongly tracked with fiber intake, where Q4 participants averaged 25.29g per day compared to 11.58g in Q1.
• Subgroup Stability: The inverse association remained significant across different age groups, sexes, and BMI categories.

Limitations

The use of self reported 24 hour recalls introduces potential recall bias and underreporting of specific food items. While the CDAI captures six major antioxidants, it does not account for thousands of other phytochemicals and polyphenols that contribute to total antioxidant capacity. The UK Biobank population exhibits a "healthy volunteer" bias, potentially limiting the generalizability of these findings to more diverse or high risk global populations. Observational designs cannot definitively establish causality despite rigorous adjustment for known confounders.

Discussion and Implications

This research shifts the focus from individual "magic bullet" nutrients to the importance of a comprehensive dietary pattern. The L shaped curve suggests that while correcting low antioxidant intake is vital for vascular protection, there is a clear point of diminishing returns. The data indicates that once a certain nutritional threshold is met, further increases in antioxidant intake do not yield proportional benefits. The strong correlation between high CDAI scores and fiber intake implies that the protective effects are likely driven by the whole food matrix rather than isolated chemical compounds. Clinicians should prioritize the cumulative intake of antioxidant rich whole foods to reach the identified protective threshold of -0.30 on the CDAI scale.

Conclusion

Vascular risk reduction is maximized when dietary antioxidant intake reaches a specific composite threshold, after which the protective benefits for ischemic heart disease plateau. Achieving this level typically requires a high fiber, plant rich diet that provides a synergistic blend of vitamins and minerals rather than isolated supplementation.