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leslie beck's food for thought

Most of us don't pay much attention to magnesium, a mineral found in leafy greens, nuts and legumes. Yet it's been shown to guard against high blood pressure, heart disease, Type 2 diabetes, migraines and osteoporosis.

Now, a study to be published in the April issue of the Journal of Nutrition suggests that the health benefits of magnesium extend even further.

According to data from Japan, if you're male, boosting your intake of the mineral can help significantly reduce the risk of colon cancer.

Previous research in animals demonstrated the ability of magnesium supplements to reduce experimentally induced colon tumours.

The current study followed 87,117 Japanese men and women, aged 45 to 74, for eight years to determine whether dietary magnesium could help prevent colon cancer.

Among men, those who consumed at least 327 milligrams of magnesium a day were 52 per cent less likely to develop colon cancer, compared to those whose daily diets provided less than 238 milligrams.

Magnesium intake was not associated with the risk of colon cancer in women, a finding that differed from earlier research conducted among Swedish and American women.

The 2005 Iowa Women's Health Study followed 41,386 postmenopausal women for 17 years and determined that a daily magnesium intake greater than 351 milligrams - versus less than 245 milligrams - reduced the risk of colon cancer by 23 per cent.

The Swedish Mammography Cohort, also conducted in 2005, studied 61,433 women, aged 40 to 75 years, for nearly 15 years and found that women whose daily diets provided at least 255 milligrams of magnesium were 40 per cent less likely to be diagnosed with colorectal cancer compared to their peers who consumed less than 209 milligrams each day.

Magnesium is implicated in more than 300 biochemical reactions in the body. It's needed to monitor and repair DNA and plays a critical role regulating cell growth and division. The mineral also helps cells fight harmful free radicals by maintaining their antioxidant status.

A greater magnesium intake may protect against colon cancer by minimizing free radical damage, reducing the proliferation of colon cells, and improving how the body uses insulin.

Insulin resistance, a condition in which the body produces the hormone insulin but does not use it properly, is considered a risk factor for colon cancer. Insulin is thought to stimulate the growth of colon cancer cells. Genetics, excess weight and physical inactivity all contribute to insulin resistance.

The new finding that a higher magnesium intake did not alter the risk of colon cancer in Japanese women, may be due to the fact that women in this study were leaner, more active and less likely to have diabetes than their male counterparts.

As well, alcohol intake was much higher for men than women. Since alcohol can interfere with DNA repair, men in this study were more likely to benefit more from magnesium.

In 2009, an estimated 22,000 Canadians were diagnosed with colorectal cancer, the second leading cause of cancer death for men and women combined. The following nutrition strategies may help lower your risk of developing the cancer.

Increase magnesium: Men and women, aged 19 to 30, require 400 and 310 milligrams of magnesium per day, respectively. After age 30, daily requirements increase to 420 milligrams for men and 320 milligrams for women.

Get your magnesium from foods, since they also provide other nutrients linked to colon health such as fibre, antioxidants and folate.

Add dairy: Many studies have found that a greater intake of calcium from dairy products and supplements is associated with a lower risk of colorectal cancer. It's thought that once calcium is ingested, the mineral binds with bile acids in the intestinal tract, thereby preventing them from entering colon cells. (Certain bile acids, which are used to digest fat, are toxic to colon cells.)

Adults, aged 19 to 50, need 1,000 milligrams of calcium a day; older adults require 1,500 milligrams a day.

One cup (250 ml) of milk or yogurt delivers roughly 300 milligrams of calcium as does 1.5 ounces (45 grams) of hard cheese. Calcium-enriched beverages such as soy, rice and orange juice also provide about 300 milligrams a serving. Supplements can also help increase your calcium intake.

Take vitamin D: A number of studies have supported the notion that higher levels of vitamin D in the body help guard against colorectal cancer. Research even suggests that sufficient vitamin D blood levels at the time of diagnosis and treatment may improve survival from colorectal cancer.

The fact that very few foods contain vitamin D, and our skin doesn't produce the vitamin from sunlight in the fall and winter, makes it necessary to take a supplement. The Canadian Cancer Society recommends adults take 1,000 IU (international units) of vitamin D each day in the 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.

Limit red and processed meat: The evidence is convincing that a high intake of red meat and processed meat increases the risk of colorectal cancer. Cooking meat at a high temperature forms heterocyclic amines, compounds linked to precancerous colon polyps in humans. It's also thought that nitrites, used as colour additives and preservatives, in processed meats may form cancer-causing compounds.

Limit your intake of red meat (beef, veal, pork, lamb, goat) to less than 18 ounces (500 g) per week. Choose fish, chicken, turkey, legumes, tofu and soy foods more often than red meat. Eat very little, if any, processed meats, including ham, bacon, pastrami, salami, bologna, hot dogs and sausages. On sandwiches, enjoy tuna, salmon or fresh-cooked chicken and turkey.

Reduce alcohol: Alcohol is thought to increase colon cancer risk by stimulating the growth of colon cancer cells, activating cancer-causing substances and helping transform of polyps into cancer. Alcohol also interferes with the body's use of folate, a B vitamin needed for the repair of DNA in cells.

If you do drink, limit alcohol intake to seven drinks a week for women and nine a week for men, and increase your intake of folate-rich foods such spinach, lentils, asparagus, avocado and oranges.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is