About me

My photo
Larry Newman is the Chief Operating Officer, Technical and Regulatory Affairs of Kirkman Group, Inc. (Kirkman). Contact Kirkman at 1-800-245-8282; 6400 Rosewood St., Lake Oswego, OR.

Monday, January 10, 2011

Facts About Minerals to Help You Make the Right Choices

By Larry Newman


Minerals offer more choices than any other type of dietary supplement. This wide variety of selection variables often leads to indecision and confusion on the part of consumers.
Furthermore, there is a lot of untrue information on the Internet and in the form of “old wives’ tales” that mislead the buyer. Marketing and advertising by many companies lead consumers to believe that certain forms are much better absorbed than they actually are or that you must take certain minerals in combination to get better absorption.

Decisions about mineral selection, however, really should depend upon your personal needs, taking into account all the factual information available. In this article I hope to lay out the facts on mineral types and forms to help make selection easier and to separate the facts from the fiction.


Calcium is best absorbed when taken with food. There is no argument about this fact. Among the many forms of calcium available, there is not a great difference in the absorption rate. There is controversy about this, however.

The PDR for Nutritional Supplements lists calcium absorption rates as follows:

Hydroxiapatite (Di-Calcium Phosphate)
Calcium Carbonate
Calcium Citrate

Robert Heaney, MD, of Creighton University, who is considered the best authority on calcium, did a study which pretty much parallels the values cited in the PDR. The following chart summarizes his findings. The Albion amino acid chelate on the chart equates to the bis-glycinate chelate in the PDR.
Both sets of values assume that the calcium is taken with food. Considering the individual variables in absorption rates, there is not a lot of statistical significance in these differentials other than the fact that the bis-glycinate chelate is the best absorbed. 

So, one might ask, why don’t we all just use the best absorbed form all the time, which is the amino acid bis-glycinate chelate? Well, first there isn’t enough of that form to supply everybody, plus it has an unpleasant aftertaste when used in chewables, powders, or foods. It also does not compress well into tablets. Conversely, calcium carbonate is basically tasteless, compresses into tablets well, and can be used in most products. The citrate form is also quite versatile. So each calcium salt has its place.

There are some individuals who do not produce adequate amounts of stomach acid, resulting in a condition called “achlorhydria.” If you have this condition, you should not use calcium carbonate unless taken with acidic foods or an acidic factor like vitamin C or betaine HCl. The reason for this is that calcium carbonate is a basic compound with a high pH, requiring stomach acid to be digested. If not digested properly, then gas and bloating can result.

Another “myth” that you might hear about calcium is that it must be taken with magnesium to be effectively absorbed. This is not true. A clinical trial done at the Illinois VA hospital published in the American Journal of Clinical Nutrition indicated that magnesium had little or no effect on calcium absorption at varying concentrations. This result would be expected since most individuals get a lot of their calcium from milk and milk has essentially no magnesium.

Your body can only absorb calcium so fast, so it is actually better to dose 500-600 mg. twice per day instead of the entire amount all at once. Vitamin D enhances calcium absorption, and boron may also play a role in increasing calcium levels.

Adequate calcium is important for skeletal formation, bone density, healthy teeth, and may help prevent osteoporosis.

Magnesium is a very important nutrient that is involved in over 300 metabolic reactions. It also helps regulate heart rhythm, which is the reason you don’t want to oversupplement with magnesium. A good rule of thumb for magnesium dosing is as follows:

  • Infants: 75 mg. daily 
  • Children: 80-200 mg. daily 
  • Teen girls and women: 200-350 mg. daily 
  • Adult men: 400 mg. daily 
Physicians may recommend more based on an individual's need, but you should not exceed these levels on your own.

The absorption rate of various magnesium salts is amazingly similar. A study comparing absorption rates of different magnesium sources showed that magnesium present in food was best absorbed (82%), while supplements showed magnesium amino acid chelate at 80%, magnesium oxide at 72%, and magnesium glycinate at 60%. This was a double-blinded study in which each subject received all the forms of magnesium on different days, so the results are quite convincing. The PDR for Nutritional Supplements also indicates that there is little difference in absorption rates of various magnesium salts.

Your personal needs are important to consider when selecting the type of magnesium. If you are prone to severe constipation, magnesium citrate would be the best choice as it has laxative-type effects. If you are sensitive to magnesium salts, resulting in loose stools or stomach upsets, magnesium glycinate or magnesium chelates would be a good choice. If you are able to tolerate magnesium and have no particular bowel issues, then magnesium oxide or magnesium malate would be good choices.

There are many untrue rumors saying that magnesium oxide is not a well-absorbed form of magnesium. Scientific information disputes that fact as does the fact that most magnesium prescription drug products are formulated with magnesium oxide. Drug products must go through blood studies and a dissolution testing process to ensure proper absorption. These drug products would never get to market if not absorbed. Obviously, these rumors are not factual.

Zinc is instrumental in proper growth and development and is the most important mineral for supporting a healthy immune system. Typical dosing is 25-100 mg. daily. There are many excellent forms of zinc available for supplementation. Zinc citrate is the form found in mother’s milk and is, therefore, a good source. Chelates, sulfate, and gluconate are also readily available in the marketplace and are good sources. One of the newer, highly-marketed forms is zinc picolinate. Zinc picolinate is a well-absorbed form, but one caution needs to be mentioned. Gary Evans, PhD, has researched zinc picolinate and other picolinate forms of other minerals and points out that picolinic acid, from which the picolinates are derived, is a chelator itself. He cautions against using excess picolinates because of the possibility that the picolinic acid, which is formed during digestion, could chelate unwanted metals such as lead, cadmium, antimony, etc. and introduce them into body cells. The best advice here would be to use picolinates conservatively, using one picolinate salt for one mineral (such as zinc or chromium) and other salts for other minerals.

Selenium supports immune response, detoxification, fertility, heart function and proper cell growth. It is important to supplement selenium, especially in geographic areas lacking in the mineral. Dosing ranges from 25-100 mcg. daily, though in certain situations, doctors will recommend more. There are only three recommended types of selenium for supplementation. Selenium yeast and selenomethionine are the best sources with nearly 100% absorption. Sodium selenate is an organic source which is safe and absorbed at about a 50% rate. Because of the lack of solubility of the yeast and selenomethionine sources, the selenate form is often necessary to use in liquid products.

Do not use the sodium selenite form. It is reactive and useless in the body under certain conditions.

Chromium is a necessary trace mineral which is important in carbohydrate metabolism and for type II diabetes control. Typical daily doses range from 50-200 mcg. with the recommended daily value being 120 mcg. The only safe forms of chromium for supplementation are chromium chloride, chromium yeast, chromium picolinate and chromium polynicotinate. Do not use any other form due to potential toxicity.

Molybdenum is another trace mineral which is essential for good health. The recommended daily value is 70 mcg., and normal dosages range from 50-100 mcg. per day. Molybdenum activates certain enzymes and is involved in sulfur metabolism. It may also be important in normalizing copper/zinc ratios. The only safe forms of molybdenum are molybdenum chelate, sodium molybdate, molybdenum yeast and ammonium molybdate. Don’t use any other forms

Manganese is an essential mineral in the human body, but deficiency is very rare. The recommended daily value is 2 mg., and that amount probably should not be exceeded because in large concentrations manganese becomes toxic. If you make sure that you are getting some in your multivitamin/mineral, then you should be covered.

Citrate, chelate, gluconate and sulfate are all good forms and well absorbed.


Iron is a very important mineral in human nutrition. It is involved in respiration and oxygen transport and in preventing iron deficiency anemia. It is extremely important during pregnancy. The recommended daily value is 18 mg. Most individuals get enough through food, although up to 25% of the population could be deficient. Because of its importance in pregnancy, prenatal vitamin formulations may contain up to 27 mg. per daily dosage. It is important to supplement iron only if you are deficient because iron in excess can be toxic. Blood screens at your yearly physical exam generally test for iron. Your physician should advise you if you are deficient or above recommended blood levels.

The form of iron with which you supplement is very important because iron is very hard on the gastrointestinal tract, often causing irritation, upset stomach or even bowel issues. The forms you buy in a drug store, such as ferrous sulfate or ferrous gluconate, are very harsh. Ferrous fumarate is better but still can be troublesome. Iron bis-glycinate is the gentle form recommended for sensitive individuals. It is only sold as a dietary supplement.

Iodine is vital for the proper function of the thyroid gland and has many other biochemical functions as well. The recommended daily value is 0.15 mg. (150 mcg.). If you use iodized salt and take a multivitamin, then you should need no further supplementation. Doses up to 1 mg. appear to be safe but unnecessary. In pregnancy the maximum should be 220 mcg. daily.

Potassium iodide and kelp are the only major sources of iodine outside of food. Kelp is not a good source because of the potential of heavy metal contamination. Seafood is the food highest in iodine content.