Supplements: How Much is Too Much? - Part 3

The recommended daily standard for specific nutrients isn’t necessarily appropriate for every body, and most experts agree that the values are too low to meet our nutritional needs. That should not imply, however, that taking more supplements or larger doses is better. Deficiencies and excesses of specific nutrients may cause symptoms or imbalances, and certain nutrients, particularly minerals, can displace other nutrients. We conclude this topic with a look at three popular supplements: vitamin C, iron, and zinc.

Vitamin C (ascorbic acid)

Since the body doesn't produce or store vitamin C, it's important to include this invaluable antioxidant daily. An excess of water-soluble vitamin C is excreted via urine, so there shouldn’t be much concern about taking large doses, especially considering the broad spectrum of uses. Vitamin C, also known as ascorbic acid, makes anti-aging collagen, boosts immunity, fights stress, may shorten the duration of colds, and contributes to the prevention of heart disease and cancer.

Taking more vitamin C than your body needs will cause diarrhea and there is some evidence that long-term use may contribute to kidney stones, although this has largely been refuted. Because it’s a weak acid, regular, long-term use of ascorbic acid can potentially lead to acid reflux, tooth erosion and gastrointestinal obstruction. These conditions are easily prevented by using buffered vitamin C supplements.

Peculiarly, large doses of vitamin C may not be recommended during pregnancy. A bizarre condition called rebound scurvy may occur with regular intake of large doses. During pregnancy, the fetus becomes accustomed to unnaturally high levels of vitamin C passed through the placenta. When the baby is born, unless the breastfeeding mother continues to take the same dose, the baby’s vitamin C level drops down, the newborn may become deficient in vitamin C and may even develop some of the symptoms of scurvy, the end-state of vitamin C deficiency.

Amounts of vitamin C can be adjusted as needed. For daily use, a minimum of 1,000 mg taken in divided doses is appropriate (for example, 500 mg with breakfast and 500 mg with dinner). Up to 10,000 mg a day can be taken to battle a cold or flu or to boost immunity.

Iron

Excess iron levels have been linked to serious medical concerns, including an increased risk of colon cancer.

The body has no means of excreting excess iron, therefore excessive intake can lead to iron overload in susceptible subjects, especially men. About one million Americans (mostly males, particularly of northern European descent) have a rare hereditary disorder called hemochromatosis. The condition predisposes males and some non-menstruating females to accumulate too much iron (usually measured as ferritin). Though typically asymptomatic, if there are symptoms, they may include weakness, headaches, darkening of skin, sexual dysfunction, and joint pain. If left untreated, hemochromatosis may lead to diabetes, arthritis, liver disease, or heart failure. Those diagnosed with or with a family history of hemochromatosis must avoid iron supplements (including multivitamin/multimineral supplements containing iron) and have blood removed often (by donation, for example) to lower their iron levels. A simple blood test can help diagnose the condition.

Since the 1980s, studies have been conducted to find a link between excess iron levels in the body and heart attacks and stroke. So far, however, the results have yielded contradictory results and are inconclusive.

To explain the possible link (nicknamed the “iron-heart” hypothesis), some experts suggest that high amounts of iron contribute to oxidation – the harmful process by which LDL (“bad”) cholesterol becomes fatty plaque in the arteries. The link between high iron levels and heart disease is strengthened by the fact that women are at a lower risk of heart disease before menopause, when they are having regular menstrual cycles. Post-menopause, a woman’s risk of heart disease increases along with the levels of iron in the bloodstream. Some scientists suggest, however, that the increased risk of heart disease following menopause has more to do with a decrease in estrogen (which is thought to protect the body against heart disease) than an increase in iron levels.

Other experts believe that high iron levels contribute to the production of oxygen free radicals, which promote the buildup of plaque in the arteries. Because antioxidants such as vitamins A, C, E and selenium counteract both oxidation and oxygen free radicals, it has been further proposed that taking supplements that contain antioxidants may counter this potentially harmful effect of iron.

Clearly, further research is needed to identify association between iron levels, heart attack and stroke.(1) Until then, it is recommended that men and non-menstruating women avoid taking large doses of iron supplements.

Iron excess can also interfere with zinc absorption. Watch for white spots on your fingernails as an indicator of low zinc.

If iron supplementation is required, an organic form of iron such as ferrous fumerate or ferrous gluconate is best. The supplementation range is 10-18 mg daily.

Zinc

Zinc is the most touted nutrient for the prostate. It’s been well-documented that a deficiency results in prostate enlargement, but research has found that a daily intake above 100 mg from supplements can more than double the risk of prostate cancer compared with those who take less than 25 mg (2). This is a classic case of “more is not better.” Doses between 15 to 25 mg are beneficial for the prostate, whereas larger doses taken regularly may exacerbate prostate issues, interfere with immunity, and inhibit the absorption of copper.

Nutritional supplements significantly contribute to a healthy lifestyle, but they will not compensate for a poor diet and are not intended to replace natural food. Use caution and do your research before taking large doses of supplements long-term.

References

1. www.sciencedaily.com/releases/2007/02/070213175520.htm

2. Leitzmann et al., “Zinc Supplement Use and Risk of Prostate Cancer” Journal of the National Cancer Institute, 2003, 95.