PSA for vegetarians and vegans: Beware of tea and coffee
I'll preface by saying that, as far as I know, this doesn't concern iron from animal sources.
I'm a vegetarian. I have been carefully adjusting my diet for a year now in order to up my iron intake, yet I hardly reaped any benefits. Some days I'd feel a lot better, but most of the time I wouldn't notice much of a difference from before I changed my diet.
Then last week I randomly stumbled upon a little fun fact: the polyphenols contained in coffee (and tea) bind to non-heme iron in your digestive tract, creating an insoluble molecule that the body cannot easily adsorb. As a result, it is recommended to consume such beverages at least 2 hours before or after an iron rich meal.
Thinking back on it I never quite followed this rule. It now makes sense why the effects of the increased iron intake were random: the iron from my breakfast and lunch was pretty much nullified, as I always drink my coffee at the same time as those meals. That only leaves dinner. Whenever I had an especially iron rich dinner I did feel fine the next day...obviously, however, not all my dinners contain such high amounts of iron, so there would be days in which I was simply starving my body of the mineral.
For a couple days now I have been drinking coffee strictly 2 hours after breakfast and lunch, and the difference is downright massive. I feel as energetic as when I was taking supplements.
Give it a try if you're a vegan or a vegetarian and didn't know of the coffee thing.