Can supplements be harmful?

Some vitamins and minerals taken in high doses can be toxic. The fat soluble vitamins A and D, vitamin B6, as well as several minerals, can be stored in organs and fatty tissues (e.g. the liver, adipose tissuetand, therefore, accumulate over time).

Excess vitamin A can cause nausea, skin changes such as flakiness, liver damage and birth defects in unborn babies. Pregnant women are advised to avoid vitamin A supplements, fish liver oils and concentrated food sources of vitamin A such as liver and liver pate. Too much vitamin D from supplements can cause high blood pressure and kidney stones. Excessive doses of vitamin B6 may lead to numbness, persistent pins and needles and unsteadiness (a type of neuropathy). High doses of iron can cause constipation and discomfort through an upset or bloated stomach.

Vitamin C and the B vitamins are water soluble and are therefore not stored in the body. Excessive intakes are excreted from the body in the urine, although extremely high intakes from supplements may have minor adverse effects.

Vitamin E, on the other hand, is a fat soluble vitamin which appears to be safe even at doses 10-100 times the recommended intake. There is evidence that supplements of up to 80 mg/day may be beneficial in preventing heart disease.

Except perhaps in the case of liver (owing to modern animal feeding practices), it is almost impossible to overdose on vitamins and minerals from food. Problems are more likely to arise from the indiscriminate use of supplements, so always follow the guidelines on the label or the advice of a nutritionist, and never take more than 10 times the RDA of any of the fat soluble vitamins and minerals.

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