number of minerals are essential to human health and therefore must be provided by the diet. Minerals play an important role in human physiology and can be enzyme co-factors, used in structural components such as bone, or play a role in nerve impulses. Ingestion of adequate mineral containing foods is therefore an important part of human nutrition, the traditional source of which is plants. Plants are a good source of minerals because they can absorb inorganic material from the soil and store it in their tissues. When animals eat the plants they absorb the minerals required and use them for physiological purposes. The minerals from plants are generally well absorbed because they are present as colloids which increases the absorption across the gut lining. However, because of poor quality soils, plants are increasingly becoming devoid of minerals and so many individuals turn to supplements to attain optimal nutrition.
However, some forms of minerals are not well absorbed and so it is important to choose supplements that have been demonstrated to have adequate intestinal absorption in humans. Calcium is one popular supplement that is available in many forms. Generally these can be inorganic, as might be found in rock, or organic whereby the mineral is bonded to an organic molecule. Organic bonding of minerals tends to increase absorption rates and although they are more expensive than inorganic forms, they may be more cost effective. For example, researchers1 have compared the bioavailability of calcium citrate and calcium hydrogen phosphate in 8 normal healthy subjects. Participants in the subject ingested either 750 mg of organic calcium citrate or inorganic calcium hydrogen phosphate tagged with a 47Ca tracer. The results showed that calcium was absorbed at least twice as well from citrate compared with hydrogen phosphate.
These results support other studies in that they show superior absorption from organically bound minerals. Other studies have shown that calcium citrate is more readily absorbed than calcium carbonate. Binding to an organic molecule such as citrate, ascorbate, picolinate or an amino acid increases the absorption of minerals because the organic molecule is recognised by intestinal transporters and the mineral absorbed through active transport mechanisms. Inorganic minerals may or may not be absorbed actively, but if absorbed passively require a suitable charge to allow adequate absorption. The differences in absorption between mineral forms should be taken into account when supplementation is undertaken in order to achieve the desired result. It is also worth noting that not all organic versions of minerals are superior in absorption. For example, magnesium appears to be very well absorbed in the oxide form, and so the extra expense of organically bound forms of magnesium are not worth considering.
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