Absorption of Minerals
Although minerals are essential for all aspects of health, they tend to be poorly absorbed. Thus, when supplementing minerals, it is necessary to bind the mineral to a substance that enhances its absorption. The binding substance, called a chelate, is usually an acid – preferably an amino acid or an organic acid. Examples of organic acids to which minerals can be bound include citric acid/citrate, malic acid/malate, or picolinic acid/picolinate.
Some dietary supplement manufacturers utilize minerals they refer to as "amino acid chelates." An amino acid chelate, however, is usually a mineral that is mixed with a protein source, such as soy, and is not a true amino acid or organic acid. Enzymes break down the soy protein into various smaller pieces, some as small as individual amino acids, but most of the soy protein is only broken down into short strings of amino acids, called peptides. The minerals then bind to a variety of these smaller protein peptide segments. Thus, an amino acid-chelated mineral may contain fragments of residual, allergenic soy protein and cannot be considered to be truly hypoallergenic. Only when individual minerals are bound to individual amino acids or organic acids can the resultant chelate be considered hypoallergenic. To ensure superior absorption, a consumer of a mineral dietary supplement should always be aware of the source of the product's chelating material.
What Are Some Well-absorbed Forms of Calcium and Magnesium?
Calcium is a substance that is necessary for healthy bones.* Dairy products are one of the best sources of dietary calcium. In fact, the American diet depends on dairy products for about 75 percent of its calcium. Unfortunately, a significant number of people are lactose intolerant (they do not have enough of the enzyme lactase to digest the milk sugar lactose) or they are allergic to dairy products. Therefore, the best way of getting a consistent amount of calcium daily may be to take it as a calcium supplement.*
Calcium supplements, however, are not created equal, with some forms being much better absorbed than others. For instance, the most common (and cheap) form of calcium – calcium carbonate (found in oyster shells) – is not as well absorbed as other forms, such as calcium citrate or calcium citrate-malate. The better its solubility in water (i.e., how fast it dissolves in water), the better it will be absorbed in the body. Calcium carbonate has poor water solubility and needs a rather acidic environment to dissolve, such as in stomach acid. Unfortunately, elderly people, those who probably have the greatest need for calcium, tend to have decreased stomach acid.
Numerous studies have compared the rates of absorption of various forms of calcium. In one study, more calcium was absorbed after a 500-mg dose of calcium citrate than after a 2,000-mg dose of calcium carbonate. One reason calcium citrate is well absorbed is because three molecules of calcium can bind to one molecule of citrate. Calcium citrate-malate is an even better absorbed form of calcium; it dissolves six times better than either calcium citrate or calcium malate. And, when calcium dissolves better, it is absorbed better.
Like calcium, magnesium citrate or magnesium citrate-malate is also better absorbed than less expensive forms, such as magnesium oxide, the form of magnesium typically found in inexpensive dietary supplements. Absorption studies have found much better absorption of magnesium citrate compared to magnesium oxide.
Importance of Taking a Well-absorbed Form of Iron
Conventional iron supplementation, including forms such as ferrous sulfate, often causes GI side effects, such as nausea, vomiting, constipation, diarrhea, or dark-colored stools. That is because these forms are poorly absorbed; therefore, most of the iron remains in the intestines and is eliminated. Taking a well-absorbed form of iron, such as iron citrate or iron picolinate (see below), not only increases the amount of iron taken into the body but decreases the risk of constipation or other GI side effects associated with poorly absorbed forms of iron.
Absorption of Trace Minerals Enhanced by Picolinic Acid
Trace mineral absorption can also be enhanced by binding to certain natural chelates. For instance, picolinic acid can provide superior absorption of certain trace minerals compared to other chelates. Picolinic acid is a natural organic acid produced in the body from the conversion of the amino acid tryptophan. It is naturally produced in the pancreas and binds to minerals to facilitate their absorption. Found in high concentrations in breast milk, picolinic acid promotes mineral absorption in infants. Studies indicate mineral picolinates provide superior absorption when compared to other mineral chelates. For example, in one study, zinc picolinate was more effective in reversing a zinc deficiency than other forms of zinc.
Consult with a health-care practitioner to help you determine which minerals you need to supplement, in what form, and in what amounts.