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Is taking a multivitamin or mineral supplement worthwhile?

Globe and Mail columnist Leslie Beck.

I want to start the year off right with my nutrition. Should I take a multivitamin? Do I need to take a special one for women? Does my age matter?

Some experts contend that multivitamin and mineral supplements are a useless waste of money. I disagree. There are a number of reasons why adding a one-a-day to your nutrition regime may be beneficial.

That said, there is universal agreement that a multivitamin – or any nutrition supplement for that matter – cannot replace a healthy diet. Maintaining good health is related far more to the types, amounts and variety of foods you eat than to the amounts of certain vitamins or minerals you consume.

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Vegetables, fruit, beans, nuts and whole grains, for example, also supply fibre and hundreds of disease-fighting phytochemicals. It's thought that vitamins and minerals work in concert with other components in food to exert health benefits.

Not surprisingly, studies that have investigated the effect of multivitamins on cardiovascular disease and cancer risk have turned up disappointing results. Taking a multivitamin was found to offer no protection from heart attack, stroke, cardiovascular death or cognitive decline in well-nourished people.

Yet, preventing chronic disease has never been my rationale for recommending a multivitamin to a client. It's about filling nutrient gaps that, if not covered, could lead to a nutrient deficiency.

Who should take a multivitamin/mineral?

While it's ideal to try to meet your daily vitamin and mineral requirements from food alone, for some people, this isn't always easy to do.

Women of childbearing age who could become pregnant or who are pregnant, should take a multivitamin that provides 0.4 to 1.0 milligrams of folic acid, a B vitamin that reduces the risk of neural tube defects – birth defects that affect the brain and spinal cord.

A daily multivitamin/mineral can also benefit menstruating women who require 18 mg of iron a day (vegan females need 32 mg), an amount that's challenging to get from diet alone.

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Vegans who avoid animal foods need supplemental iodine, a mineral that's found in seafood and dairy and is needed to make thyroid hormones.

Adults over 50 are advised to get most of their daily vitamin B12 – a nutrient that maintains nerve function, keeps red blood cells healthy and repairs DNA – from fortified foods and/or a vitamin supplement. That's because aging reduces a person's ability to absorb B12 from foods.

I also recommend a multivitamin for people who take medications that reduce the body's absorption of vitamin 12, such as anti-reflux and ulcer drugs (e.g., Nexium, Dexilant, Zantac) and metformin, a drug that helps control blood sugar.

And if you're a low-calorie dieter or someone who frequently skips meals, a daily multivitamin and mineral supplement can help make up for dietary shortfalls.

What about those who are 50-plus?

A basic adult multivitamin/mineral supplement combines all or most vitamins and minerals, with the majority in amounts close to daily recommended amounts.

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Because nutrient needs differ for women and men, and they change as you get older, multivitamins are also formulated to more closely match the needs of your age and sex.

Since women in the childbearing years have higher iron requirements than do men and older women, and need to ensure they're taking folic acid, products tailored for women contain more iron (18 mg) and folic acid (0.6 to 1 mg).

Multiples designed for men under 50 include less iron (men need 8 mg a day) and folic acid. They may also contain higher amounts of B vitamins, vitamin C, magnesium, zinc and sometimes vitamin E and selenium.

As we age, our bodies absorb certain nutrients less efficiently. Calcium and vitamin D needs increase, too. And after menopause, women need less iron, 8 mg a day.

For these reasons, multivitamin/minerals for adults over 50 have a smaller dose of iron, or none at all, and are typically higher in vitamins B12, C and D as well as calcium and magnesium.

Read labels

The formula for multivitamins will vary from brand to brand; read labels to see what you're getting.

Menstruating women should look for a product with 10 to 18 mg of iron. Postmenopausal women and men should take a multi with no more than 8 mg.

Be mindful of calcium, too. Some multivitamins for women 50-plus have 300 to 500 mg of the mineral. Consider these a calcium supplement, too, which you may not need.

Get your daily calcium from food sources, preferably. Older women need 1,200 mg of calcium a day; men require 1,000 mg to the age of 70 and 1,200 mg over 70.

While not conclusive, some studies have raised concerns that excess calcium from supplements may increase the risk of heart problems among women and possibly men, too.

Leslie Beck, a Toronto-based private practice dietitian, is Director of Food and Nutrition at Medcan.

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