If you want to lower your risk of stroke, there's a mineral you need to pay more attention to. According to a review of seven international studies, people who eat plenty of magnesium-rich foods – leafy greens, beans, lentils, nuts and whole grains – are significantly less likely to have a stroke.
Unfortunately, many Canadians in all age categories don't get enough magnesium. More than 50 per cent of adults, aged 51 and older, consume too little. An even greater proportion of Canadians fail to meet daily requirements after age 70, when the risk of stroke is greatest.
It's estimated there are 50,000 strokes in Canada each year, about one stroke every 10 minutes. The majority – 80 per cent – are ischemic strokes caused when a blood clot interrupts blood flow to the brain. Hemorrhagic strokes, caused by uncontrolled bleeding in the brain, account for the remaining 20 per cent.
Risk factors for stroke include high blood pressure, high cholesterol, diabetes, smoking, excess alcohol, overweight and stress. The prevalence of stroke also increases with age; after 55, the risk doubles every 10 years.
The analysis, to be published in the February issue of the American Journal of Clinical Nutrition, combined the results of seven studies published in the past 14 years in the United States, Europe and Asia. Researchers tracked how much magnesium people consumed and how many had a stroke over an 11- to 12-year period.
The average daily magnesium intake of study participants was less than recommended. (In Canada and the United States, men and women over 30 need 420 and 320 milligrams of magnesium respectively each day.) For every extra 100 milligrams of magnesium people consumed each day above the average intake (roughly 200 milligrams), the risk of having any type of stroke fell by 8 per cent.
A higher magnesium intake prevented ischemic stroke but did not significantly lower the risk of hemorrhagic stroke. Every 100 milligram increase of magnesium above the average was linked with a 9 per cent reduced risk of ischemic stroke. In other words, people who consumed 400 milligrams of magnesium a day were 16 per cent less likely to have a stroke.
Magnesium is thought to guard against stroke through its influence over risk factors. The mineral is needed to maintain healthy blood pressure. A 2006 review of 12 randomized trials showed that magnesium supplementation lowered elevated blood pressure.
Magnesium also helps regulate blood sugar (glucose) by influencing the release and activity of insulin, the hormone that clears sugar from the bloodstream. A 2010 study reported that among 4,500 adults, those who consumed the most magnesium – 400 milligrams for every 2,000 calories – were 47 per cent less likely to develop Type 2 diabetes over the 20 year follow-up compared with those whose diets provided only half as much.
Higher magnesium intakes have also been linked with lower levels of inflammation, a risk factor for diabetes and cardiovascular disease.
There's another reason to be mindful of your magnesium intake. A higher magnesium diet is also associated with a lower risk of colorectal cancer, particularly in men. Magnesium may work to ward off colon cancer by minimizing free radical damage, reducing the proliferation of colon cells and improving how the body uses insulin.
Some of the best food sources of magnesium include black beans, chickpeas, kidney beans, navy beans, soybeans, firm tofu, spinach, Swiss chard, halibut, almonds, cashews, sunflower seeds, yogurt and wheat germ.
Increase your intake of magnesium-rich foods before reaching for a supplement. These foods are also rich in fibre, folate and potassium, and low in sodium, attributes that may also play a role in keeping you healthy.
If you need to bridge the gap in your diet, supplements made from magnesium citrate are available in 100, 150, 200, 250 and 300 milligram doses. Do not take more than 350 milligrams a day from a supplement; higher intakes of supplemental magnesium can cause diarrhea.
Magnesium in foods
Men and women over 30 require 420 and 320 milligrams of magnesium respectively each day. Adults aged 19 to 30 need 400 (men) and 310 (women) milligrams daily.
The following foods each contain 100 milligrams:
Halibut, 3 1/2 oz.
Almonds, 30 nuts
Swiss chard, cooked, 2/3 cup
Cashews, 24 nuts
Soybeans, cooked, 2/3 cup
Spinach, cooked, 2/3 cup
Peanuts, 56 nuts
Tofu, firm, 1 cup
Wheat bran, raw, 1/4 cup
Wheat germ, 1/3 cup
Yogurt, plain, non-fat, 2 1/4 cups
Sunflower seeds, 2/3 cup
Baked beans, 1 1/4 cups
Brown rice, cooked, 1 1/4 cups
Black beans, cooked, 3/4 cup
Kale, cooked, 1 1/4 cups
Lentils, cooked, 1 1/2 cups
Kidney beans, cooked, 1 1/2 cups
Avocado, California, 1 1/2
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.