It's estimated that 40 per cent of Canadians take vitamin and mineral supplements each day. Yet according to a report in the December issue of the Journal of the American Dietetic Association, the formula for optimal health isn't in the supplement aisle of a health-food store.
Instead, the best strategy for staying healthy and lowering your risk for heart disease, diabetes and certain cancers is to eat a wide variety of nutrient-rich foods – a practice that for many people is not a habit.
Still, the report recognizes that some people do require vitamin and mineral supplements. Knowing which ones to take – and how much – can be confusing.
The fact is, the maintenance of good health is related more to the types and amounts of foods you eat than to the amount of certain vitamins or minerals you consume. When obtained from foods, certain nutrients have been demonstrated to guard against a number of health conditions. But studies investigating the effect of supplements on health outcomes have turned up disappointing results.
Foods are complex, providing more than just a single vitamin or mineral. Plant foods such as fruits, vegetables, legumes, nuts and whole grains also contain fibre, along with hundreds of disease-fighting compounds called phytochemicals. It's thought that vitamins and minerals work in concert with other components of food to exert health benefits.
You've heard it over and over: Choose mainly whole grains, get seven to 10 daily servings of fruit and vegetables, eat beans and lentils more often, and so on. Yet a very small percentage of Canadians lives by Canada's Food Guide.
According to national survey data, Canadians of all ages don't get enough magnesium, folate or potassium from their diet. Most adults don't get enough calcium from foods. And women under 50 consume too little iron.
While it's ideal to try to meet your daily nutrient requirements from food, for some people this is hard to do. Pregnant women, nursing mothers, strict vegetarians, people with food intolerances and allergies, and elderly adults often need to fill dietary gaps with a multivitamin and mineral pill.
People with certain health conditions, or who take medications that alter their need for some vitamins or minerals, may also need to rely on supplements. And older adults, people with dark skin and those with inadequate sun exposure require extra vitamin 
If you fall into one of the following categories, consider taking certain supplements in addition to eating plenty of nutrient-rich foods.
Women of childbearing age
Women who may become pregnant should take a multivitamin supplement that provides 0.4 to 1 milligram of folic acid, a B vitamin that reduces the risk of neural tube defects – birth defects that affect the brain and spinal cord.
Menstruating women also need 18 milligrams of iron per day, an amount that's challenging – if not impossible – to get from foods alone. Look for a multivitamin with 10 to 18 milligrams of iron. (Vegetarians need an extra 14 milligrams to account for reduced iron absorption from plant foods.)
Pregnant women
During pregnancy, women need 0.6 milligrams of folic acid from a daily supplement in addition to food sources of folate. Natural sources include spinach, lentils, asparagus, broccoli, avocados and oranges.
Pregnant women also need 27 milligrams of supplemental iron each day (vegetarian women 48 milligrams). Choose a prenatal multivitamin supplement with 0.6 to 1 milligram of folic acid and 27 milligrams of iron.
Older adults
The U.S.-based Institute of Medicine advises that people over 50 get 2.4 micrograms of vitamin B12 each day in the form found in fortified foods and supplements. That's because aging reduces ability to digest B12 from food.
Vitamin B12 helps maintain nerve function, keeps red blood cells healthy and is needed to make DNA. Evidence also suggests it may guard against heart disease and maintain cognitive function.
To get your B12, choose a multivitamin and mineral supplement. If you prefer, take a B-complex supplement that contains all eight B vitamins.
Choose a product that provides no more than 0.4 milligram of folic acid, the recommended daily intake. Recently, there's concern that higher doses may accelerate the growth of pre-cancerous cells or early cancer growths.
In healthy cells, folic acid ensures that DNA replicates normally. But cancer and pre-cancer cells synthesize new copies of DNA faster than normal cells and need folic acid to multiply.
There's no evidence that the B vitamin in foods is harmful. In fact, the evidence shows that a diet rich in natural sources of folate is good for you.
At 50, calcium requirements increase to 1,500 milligrams daily. In most cases, people need to rely on calcium supplements in addition to diet to meet daily needs.
More vitamin D
Evidence suggests that optimal vitamin-D status helps prevent certain cancers, heart attacks, multiple sclerosis, diabetes, osteoporosis and rheumatoid arthritis.
The fact that Canadians don't produce enough vitamin D in their skin from sunlight between October and March prompted the Canadian Cancer Society in June, 2007, to recommend that adults take 1,000 international units (IU ) of the vitamin daily in fall and winter.
Older adults, people with dark skin, those who don't go outdoors often, and those who wear clothing that covers most of their skin should take the supplement year-round.
Before you buy, figure out how much vitamin D you're already getting from multivitamin and calcium supplements. Choose a supplement than contains D3 instead of D2, which is less potent.
Haphazard eaters, dieters
If you don't eat well despite your best intentions, or you consume less than 1,600 calories per day, a multivitamin and mineral supplement can help make up for shortfalls. But keep in mind that supplements can't replicate the nutritional and health benefits of whole foods.
Speak to your dietitian or doctor about which supplements and what doses might be appropriate for you. If you take medications, ask about possible interactions.
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