
This always happens. I want to blog about something, I take too much time and, all of a sudden, my topic is in the news! This time, the topic is vitamin and mineral supplementation. It’s the cover story in this month’s Nutrition Action and Maclean’s magazine.
I’ve never been a fan of vitamin and mineral supplementation, despite the fact that nutrition experts like Dr. Walter Willett recommend a multivitamin a day for “health insurance”, as do many doctors. Well, it makes me happy that the use of a daily multivitamin is being questioned- finally!
According to Stats Canada, nearly half of Canadian adults have taken a multivitamin in the last month (as did more than one in three kids). The supplement industry is huge and works hard to convince you your diet is deficient.
According to the Centre for Science in the Public Interest, there is very, very little evidence that there is any benefit to taking a multivitamin. However, the evidence that there is harm to taking one is not consistent. A handful of studies have found that people taking a multivitamin have a slightly higher risk of cancer and other “negative human consequences”.
Food is abundant in North America and most of us get more than enough vitamins and minerals in our diet, with no risk of overdosing on them. As a result, if you’re healthy and eat a variety of foods, there’s no need to supplement your diet. In fact, you might be better off!
If you insist on taking a multivitamin, here are some of the nutrients you need to be aware of:
Folic acid: High intakes- 1000 mcg (1mg) or more- of folic acid has recently been linked to increased risk of colon and breast cancer. The daily recommended intake is 400 mcg. Women in their childbearing years should continue to take a multivitamin that contains 400 mcg folic acid daily to reduce the risk of birth defects. For men and post-menopausal women that insist on taking a multivitamin, choose one with less than 400 mcg folic acid. If your multivitamin has 400 mcg folic acid, don’t take it every day.
Selenium: The daily recommended intake of selenium is 55mcg/day. Some studies have shown that more than 200mcg selenium a day may increase the risk of skin cancer and diabetes. Choose a supplement with less than 100mcg.
Vitamin C: The daily recommendation for Vitamin C is 75mg for a woman and 90mg for a man (btw, 1 cup orange juice contains 128mg). 250-500mg saturates the body’s tissues so more than that is excreted. However, high doses of 1000mg or more can cause diarrhea, interfere with iron metabolism and contribute to kidney stones.
Vitamin A: The recommendation is 3000 IU a day. Too much retinol (vitamin A palmitate or acetate) can increase your risk of hip fractures, liver problems and birth defects. If you take a supplement, it shouldn’t contain more than 4000 IU retinol or more than 6000 IU beta-carotene.
Vitamin D: Vitamin D helps with the absorption of calcium and recent research has shown that it can help reduce the risk of cancer and diabetes. The current recommendation is 200IU per day but 400IU for people over the age of 50 and 600 IU for people over the age of 70. However, many experts recommend an intake of 1000IU a day for everyone (including the amount that comes from the sun and from food- fish and added in margarine, milk and cereal). Most multivitamins contain 400IU.
Vitamin E: 33IU/day is recommended daily. Research has shown that more than 400IU of vitamin E increased the risk of death. As a result, aim for less than 100IU a day.
Calcium: The recommendation is 1000mg a day for men and women below the age of 50 and 1200mg/day for women above 50. Men who consume more than 1500mg a day are at greater risk for prostate cancer so your multivitamin should contain less than 200mg.
Sources:
Liebman B, Schardt D, Cohen D et al. Multi Complex: Picking a multivitamin gets tricky. Nutrition Action Health Letter. Centre for Science in the Public Interest, June 2008.
Gulli C. How vitamins can be hazardous to your health. Maclean's, Apr 21 2008.
Nestle M. What to eat. NY: North Point Press. 2006