If the nutrient content of fruits and vegetables is falling — as research suggests — it raises the question: Should everyone take nutritional supplements to make up for shortcomings?

"Absolutely," said Aileen Burford Mason, a biochemical nutritionist and a Toronto-based nutrition counsellor. "Taking a multivitamin is risk-free and could have tremendous benefit."

Dr. Burford Mason stresses that eating well is essential and that supplements are precisely that — complementing good food choices, not substituting for them.

But, as someone who has spent her career studying the importance of various micronutrients for overall health, she is also adamant that, no matter how careful people are about their diet, they need help from supplements.

"When I hear people say: 'You can get all the nutrients you need from food,' I ask them: 'Where is there a shred of evidence that is true?' They are in denial.

"No matter how well we eat, it's not possible to get adequate nutrition."

While that seems like a radical notion, it has increasing support in the nutrition community. In recent years there has been a raft of evidence about the importance of basic vitamins and minerals for long-term health.

It used to be thought that supplements were necessary only to avoid exotic diseases such as scurvy, beriberi and rickets. But today it is believed that common killers such as cardiovascular disease and cancer may have their roots in nutrient deficiencies.

Research into this area began in earnest after it was discovered that a deficiency of a seemingly innocuous nutrient, folic acid (or folate) caused the devastating birth defects spina bifida and anencephaly. A little extra folic acid may also reduce the risk of heart disease and cancer in adults, particularly if they drink alcohol (which robs the body of the nutrient).

Walter Willett, author of the seminal work Eat, Drink and Be Healthy, said the research suggests that taking supplements (in addition to eating well) "could substantially improve our long-term health."

Dr. Willett, chairman of the department of nutrition at the Harvard School of Public Health, said the Canada Food Guide should include a recommendation that supplements be included as part of a healthy diet.

He said the five nutrients that people don't get enough of in their diets are folic acid, vitamin B6, vitamin B12, vitamin D and vitamin E. These can all be found in a standard multivitamin, though he suggests that men and postmenopausal women should take an additional vitamin E supplement.

He calls a daily multivitamin a good, cheap insurance policy.

According to a survey commissioned by the Canadian Health Food Association, however, only 30 per cent of adults take a daily supplement — even though two-thirds of respondents feel that Canadians, in general, are not receiving enough nutrients from the food they eat.