Vitamin Poisoning

Are you taking too many vitamins? Do you know the harmful effects of consuming excessive vitamin and mineral supplements?

Vitamin deficiency syndromes are uncommon in Western countries. Overeating is more prevalent than starvation.

Then why 30 per cent of the population consumes over-the-counter vitamin and mineral supplements?

The answer is simple. They hope to improve their health and prevent disease. For healthy individuals, experts recommend the following vitamin supplements:

1. folic acid (400 ug/day) – reduces the risk of heart disease, colon and breast cancer and birth defects during pregnancy,
2. vitamin B6 (2 mg/day) – keeps homocystein levels down and reduces the risk of heart disease,
3. vitamin B12 (6 ug/day), – same as B6 plus reduces the risk of cancer,
4. vitamin D (400 IU/day) – minimizes risk of osteoporosis and fractures,
5. omega-3 fatty acids (1000 mg/day or eat fish two to three times a week) – reduces the risk of sudden heart attack by 50 to 80 per cent, and
6. a multivitamin will ensure an adequate intake of other vitamins for which the evidence of benefit is indirect.

Regular use of vitamin E and C remains controversial.

Recently, the UK Food Standards Agency reviewed 36 vitamins and minerals and discussed the potential harms that can come from consuming such supplements. This information is summarized in the Canadian Medical Association Journal by Dr. Eric Wooltorton.

If a person consumes high doses of some vitamins, especially taking them on a regular basis, may suffer from side effects. The side effects generally involve the liver, stomach and bowel. Such as: nausea, vomiting, diarrhea, liver damage, visual problems, nerve damage etc.

The CMAJ article says that minerals taken as supplements can also be toxic. For example:
-magnesium can cause diarrhea at doses above 400 mg/d;
-phosphorus can cause diarrhea at doses above 750 mg/d, and mild nausea and vomiting at lower doses;
-iron can cause constipation, nausea and vomiting, reduced zinc uptake, and iron overload;
-zinc can cause nausea and vomiting, immunosuppression and impaired copper uptake; and
-selenium at doses above 0.91 mg/d can cause brittle hair and nails, peripheral neuropathies and gastrointestinal upset.

Is it possible to prevent vitamin and mineral toxicity?

Yes, regular screening enquiries about the use and dose of vitamin and mineral supplements may help to optimize a patient’s nutrient intake and avoid potential harm from inappropriate use of supplements (e.g., intake of beta carotene by smokers may increase the risk of lung cancer), says CMAJ article.

The article says that the European Union recently moved to adopt strict labeling standards for vitamin and mineral supplements, including having manufacturers list the percentage of a person’s daily intake that is represented by one dose of the product, as well as toxicity warnings when they are appropriate.

Will Canada adopt similar standards? asks Dr. Wooltorton. Only time will tell. In the mean time, do not over dose yourself with vitamins and minerals. Eat a healthy diet, eat lots of fruits and vegetables, exercise regularly and take vitamins as described above.

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