Citrus fruits combat the negative nutritional side-effects of anti-nutrients that are found in vegetables.

The effects of organic acids, phytates and polyphenols on the absorption of iron from vegetables 

     Non-heme iron absorption from a variety of vegetable-based meals was investigated in Indian women to see if the chemical composition of the meals in any way affected iron absorption from their food.

     It was found that citric, ascorbic, L-malic, and tartaric acids all increased the absorption of non-heme iron by more than double in some cases when added to a basic rice meal. Oxalic and tannic acids were found to decrease iron absorption from brassicas such as cabbage and broccoli, respectively.

     After the addition of 3mg of supplemental iron in the form of ferrous sulfate to different vegetables, it was found that wheat germ, aubergine, butter beans, spinach, brown/green lentils, and beetroot greens was associated with decreased bioavailability of the iron supplement where in contrast with carrot, potato, beetroot, pumpkin, broccoli, tomato, cauliflower, cabbage, turnip and sauerkraut which were associated with moderate to good bioavailability. The later group of vegetables were found to have higher concentrations of the organic acids mentioned earlier which when added to food increase the bioavailability of non-heme iron, while the vegetables that were associated with lowered bioavailability of non-heme iron were found to have higher concentrations of phytate compounds. There was a significant inverse relationship (r 0·859, P < 0·001) between the polyphenol content of the vegetable and the absorption of iron.

     Citric and ascorbic acid are both found in high amounts in citrus fruits such limes, lemons, and oranges, but also contain L-malic and tartaric acid in lesser quantities. It can be inferred that adding citrus to your food will increase the bioavailability of non-heme iron from your diet!