Making sure you have the right amounts of all the necessary minerals.

Minerals play a vital role in many of our major bodily functions, and deficiencies can lead to health issues. Despite this, mineral deficiencies are still very common, with 61% of Americans 19 and older having dietary intakes of magnesium lower than the estimated average requirement and 49% having intakes below the estimated average requirement for calcium (1). A lack of mineral consumption in the diet is the biggest culprit for mineral deficiencies, but there are other factors to consider such as medical problems that cause mineral loss or poor mineral absorption like Crohn’s disease, excessive vomiting or severe diarrhea. Many people trying to bolster their levels of important minerals turn to dietary supplements, but it’s important to do so with care. When dealing with minerals, maintaining balance is key.

Calcium: The Bodily Building Block
Calcium is the body’s most abundant mineral, serving as a major structural component in bones and teeth. Calcium is similar to a fat-soluble vitamin like vitamin A or D in that it requires a carrier to be absorbed in the body, which takes more time than water-soluble vitamins and minerals (2). Vitamins D and K2 are just two of the nutrients required for calcium to be properly absorbed, but the presence of high levels of other minerals can also interfere with calcium absorption, one of which is sodium.

While sodium plays a role in several vital bodily processes, the amount of it required for survival is relatively low. However, many people ingest far more sodium in their diet than what is needed. This affects calcium due to the combination of calcium not immediately being absorbed when consumed as well as the fact that excess sodium and calcium bind in the body. Excess sodium is excreted in urine, so bound calcium is often lost before it can be absorbed. In adult women, each extra gram of sodium consumed per day can be projected to increase the rate of bone loss by 1% per year if all of the calcium loss comes from the skeleton (3). Phosphorous is another mineral traditionally found in very protein-rich foods that can also increase the amount of calcium expelled in urine, particularly in people already suffering from calcium deficiency.

Because of the amount of calcium present in the body as well as the fact that many are deficient in it, calcium supplementation is relatively common, particularly in women trying to minimize risk of osteoporosis and similar conditions. However, overabundance of calcium from supplements can interfere with the mineral balance of the body just as much as low levels. Probably the most important impact involves magnesium. These two minerals are heavily linked, with the body’s demand for calcium tied to its demand for magnesium, so people who supplement heavily with calcium may be depleting their magnesium stores without even knowing it (4). In addition, magnesium plays a role in the absorption and utilization of calcium, so not only does the excess calcium create another deficiency, but it also won’t even be properly utilized. It is commonly recommended that calcium supplements be taken along with magnesium supplements at a 2:1 ratio, with a 1:1 ratio also recommended in the case of certain medical conditions or an extremely calcium-heavy diet. Excess phosphorous can also hamper the body’s ability to absorb magnesium.

Magnesium: The Perfect Partner
While magnesium is certainly deeply linked with calcium, this mineral is also involved in over 300 essential metabolic reactions, such as energy production and synthesis of essential molecules. Having proper levels of magnesium is also believed to play a strong role in heart health, as well as maintaining a healthy metabolism and low stress levels (5). Despite its importance, a recent U.S. survey showed that the average daily magnesium intake is about 350 mg for men and about 260 mg for women—significantly below the current recommended amount (6).

Just as calcium can negatively affect magnesium absorption, so too might high levels of supplemental zinc. One study reported that daily zinc supplements of 142 mg given to a group of healthy adult males significantly decreased magnesium absorption and disrupted magnesium balance (7). Large increases in dietary fiber and protein have also been shown to affect magnesium levels in studies, but the extent of this change in people with balanced diets has yet to be determined (3).

The strongest dietary sources of magnesium are leafy green vegetables, along with whole grains and nuts, but poor soil quality may be negatively impacting the magnesium content of even these foods. Drinking water regularly can also account for as much as 10–20% of your daily magnesium requirement, but this varies from source to source. So for consumers concerned about getting enough, supplementation is their best bet.

Iron: The Blood Booster
Iron is extremely important due to the roles it plays in our body’s daily function, including transporting oxygen in the blood. At the same time, iron deficiency is the number one nutritional disorder in the world, with up to 80% of the world’s population being iron deficient and 30% at risk of developing iron deficiency anemia (8). Pregnant women, young women during their reproductive years and children tend to be at the highest risk of iron deficiency, which most commonly manifests as fatigue, but can also lead to other conditions like impaired immune function, pregnancy complications and impaired development in children. The majority of these deficiencies stem from diets low in protein sources, but some other minerals do interact with iron absorption.

Adequate levels of copper in the body are believed to be an important factor in the absorption of iron, with anemia being a sign of both iron and copper deficiency (9). This is corroborated by several animal studies. One study demonstrated the role of copper in iron absorption, and another noted that copper-deficient animals tended to accumulate iron in their livers, suggesting that copper may play a role in transporting iron to the bone marrow for red blood cell formation (9). Another study has also shown that when consumed together in a single meal, calcium decreased iron absorption. While this effect isn’t as pronounced as some of the previously mentioned examples, it is still a good idea to avoid taking calcium and iron supplements at the same time.

At the other end of the spectrum, high amounts of iron can interfere with other minerals in the body, such as lowering the absorption of zinc supplements. Curiously, this is strictly the case when taking iron and zinc supplements on an empty stomach, as supplemental iron taken with food had no effect on zinc absorption, nor did iron-fortified foods. There also may be a relationship between iron and manganese, but the exact nature of it requires more study to be determined. Animal studies suggest that iron deficiency can increase absorption of manganese, and that the opposite is also true. Studies of children with iron deficiency have also shown elevated levels of manganese in the blood, though the exact link has yet to be determined (10).

Zinc: An Unsung Mineral
As a cofactor to over 300 enzymes, zinc has applications ranging from immune support to skin health to reproductive health in men. While the body doesn’t necessarily need huge amounts of zinc to function, zinc deficiency is still somewhat common in the developing world, as the best dietary sources of this mineral are red meat, chicken and oysters, especially (11). The reasons why people may turn to zinc supplements extend beyond standard nutrition, as zinc supplementation has been studied for possible effects on the common cold, age-related macular degeneration, diabetes and HIV/AIDS (12).

High levels of iron can inhibit zinc absorption, but animal tests have also shown that high levels of dietary calcium can also affect zinc. Human trials have been done to test this also, but results have been inconclusive, with one study of post-menopausal women showing calcium from milk to lower zinc absorption and balance, but other studies involving adolescent girls and women aged 21–47 showing no relationship between the two (12). One hypothesis behind this is that calcium combined with phytic acid or phytate may be responsible for lowering zinc levels. Large quantities of zinc (50 mg/day or more) have also been proven to interfere with copper absorption, though such levels would generally only come from supplements, not dietary intake of zinc. High copper levels also do not appear to have any effects on zinc, so some physicians recommend taking a copper supplement alongside zinc, be it for health issues or mineral deficiency (12).

Selenium: The Next Immune Supporter?
Selenium is unique among this group of minerals in that while there may not be as many instances of selenium deficiency, there is still a great deal of demand for selenium supplements. This trace element is a constituent of over two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis and protection from oxidative damage and infection (13). Organ meats and seafood are two of the strongest dietary sources of selenium, though the exact amounts can vary due to selenium concentration in soil that animals eat. In general, though, animals still maintain tissue concentrations of selenium, while plant sources vary far more widely based on geographic location. Most cases of selenium deficiency occur in regions where there is little selenium in the soil and people live on diets consisting primarily of vegetables (13).

One major reason people are interested in selenium supplementation even though they may be at proper levels is due to possible applications for immune support, particularly cancer. Several studies have shown selenium deficiency to have an association with impaired immune function and increased progression of viral infections, though the mineral cannot be said to treat any disease. One study also showed increased immune response in people supplemented with selenium who were not selenium deficient. In the case of cancer, while the exact relationship has not been discovered, several animal trials have shown reduced levels of tumor incidence among selenium supplemented populations. It is believed that methylated forms of selenium specifically may be the ones causing this effect. In humans, the effects are not as clear, but several studies show that long-term selenium deficiency can factor into increased cancer risk (14). For more clarity on the differences between various forms of selenium, read the December Vitamin Connection column on “Taking the Confusion Out of ‘Selenium.’”

The effects of selenium on other nutrients are minimal, but it is believed that selenium deficiency can exacerbate the effects of iodine deficiency. Extremely high selenium intake can also be harmful, but it is very unlikely to reach such a point from diet alone, and heavy supplementation would be needed. The current Tolerable Upper Intake Level for selenium is 400 mcg a day (13). WF

1. Environmental Working Group, “How Much is Too Much? Appendix B: Vitamin and Mineral Deficiencies in the U.S.,”, accessed Dec. 3, 2014.
2., “Vitamins and Minerals: Are You Getting What You Need?”, accessed Dec. 3, 2014.
3. Linus Pauling Institute, Micronutrient Information Center, “Calcium,” “Magnesium,”, accessed Dec. 8, 2014.
4. C. Dean, The Magnesium Miracle  (New York, NY, Ballantine Books, 2007).
5. M.S. Seeling and A. Rosanoff, The Magnesium Factor (New York, NY, Avery, 2003).
6. A. Moshfegh et al., “What We Eat in America, NHANES 2005-2006: Usual Nutrient Intakes from Food and Water Compared to 1997 Dietary Reference Intakes for Vitamin D, Calcium, Phosphorus, and Magnesium. U.S. Department of Agriculture, Agricultural Research Service.”
7. H. Spencer, C. Norris and D. Williams, “Inhibitory Effects of Zinc on Magnesium Balance and Magnesium Absorption in Man,” J. Amer. Coll. Nutr. (5), 479–484 (1994).
8. University Of Maryland Medical Center, “Iron,”, accessed Dec. 15, 2014.
9 . Linus Pauling Institute, Micronutrient Information Center, “Iron,”, accessed Dec. 15, 2014.
10., “Manganese,”, accessed Dec. 15, 2014.
11., “Zinc,”, accessed Dec. 15, 2014.
12. Linus Pauling Institute, Micronutrient Information Center, “Zinc,”, accessed Dec. 15, 2014.
13. National Institutes of Health, “Selenium Dietary Supplement Fact Sheet,”, accessed Dec. 15, 2014.
14. Linus Pauling Institute, Micronutrient Information Center, “Selenium,”, accessed Dec. 15, 2014.


Published in WholeFoods Magazine, February 2015