How do you know if a vitamin or nutritional supplement is safe?

Insider Health Information

Vitamins and minerals: What to check for when buying a nutritional supplement.

You need to consider the safety of a nutritional product in conjunction with the importance of quality manufacturing in nutritional products. The two go hand in hand and are important as each other when selecting a vitamin and nutritional products for your own consumption.

Compare supplements to modern medicine

A favourable comparison of the safety of vitamins and supplements is to compare deaths due to supplementation with deaths due to modern medicine.

An article in the April 15th, 1998 issue of the Journal of the American Medical Association by Dr Bruce Pomeranz stated that prescribed medications cause over 100,000 deaths a year. By comparison deaths from nutritional supplementation are extremely rare. Those very rare cases have usually involved massive doses.

Vitamin A

The vitamin that requires most caution is vitamin A (Retinol). Toxicity from vitamin A can occur in adults who take excess supplementation over a period of time. This is further complicated by the individual variances for tolerances of vitamin A. There is a great variance in individuals particularly those with existing liver defects.

Signs of vitamin A toxicity can include nausea, headache, fatigue and dry skin amongst other symptoms. Women should be extremely cautious of vitamin A supplementation when pregnant, or avoid it completely - it has been known to cause birth defects.

The easiest way to avoid this danger is to take a supplement that does not have vitamin A but has beta-carotene in appropriate levels. The body can convert beta-carotene into vitamin A as it needs. An additional benefit of beta carotene is that it a greater antioxidant than retinol.

Vitamin C

Vitamin C has been proven to be safe in relatively high doses. Some people do find at a certain level excess vitamin C supplementation may cause diarrhoea.

There have been studies in the past claiming that vitamin C destroys vitamin B12. This was as a result of a report by Dr Victor Herbert in 1974 and backed up by a report in 1975 by Dr JD Hines. Errors in the reports of measuring B12 in the blood serum has been criticized buy a number of independent laboratories. (Refs 1,2)

There have also been claims that Vitamin C may cause kidney stones because it degrades to oxalate. Oxalate is the basis of many stones. However, even with high doses of vitamin C the body keeps oxalate levels from rising too high. (3)


As discussed throughout this site oxidative stress is the underlying cause of degenerative disease.

There is some concern that iron supplementation may increase oxidative stress. There are two types of iron; the first is Heme-iron, the type found in meat. This type of iron is absorbed easily and used by the body.

The second type is elemental iron which is usually used in the cheaper type of nutritional supplement which could potentially increase oxidative stress. The best way to supplement iron is through your diet – lean red meat, whole grain cereals, beans and leafy green vegetables. Any Iron supplementation beyond this is best considered in consultation with your own health care provider.

Vitamin B6

When taken in large amounts for months or years vitamin B6 is one of the water soluble vitamins where there is a risk of toxicity.

This toxicity can lead to nerve damage if taken in large doses between 500 mg to 5 grams over an extended period of time.

Supplements as part of a lifelong process

Preventive health is a lifelong process. Regularly taking a nutritional supplement is part of that process. The potential risk of cumulative toxicity in relation to vitamins A, Iron and B6 should be dealt with due caution.

When choosing a nutritional supplement you need make sure that it is of high quality. Additionally you should spend time educating yourself about the correct use of a particular nutritional supplement or vitamin product at appropriate levels.

Most nutrients in supplementation when used in the correct amounts with the right potency, purity, consistency and biovailability have a high degree of safety and should form part of a lifelong nutrition programme to assist in preventing chronic degenerative diseases.


For medical references click on 1,2,3

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