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Leslie Beck: Why you need to mind your magnesium intake

If you don't pay much attention to magnesium in your diet, it's time you did: According to a large review of studies, this often-overlooked mineral defends against Type 2 diabetes, stroke and heart failure.

Magnesium is implicated in more than 300 bodily processes. It's used to make DNA and proteins, generate energy in cells, help muscles contract, transmit nerve impulses, build strong bones and regulate stress hormones, blood pressure and glucose.

Yet it's a nutrient most Canadians don't get nearly enough of.

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For the review, published last month in the journal BMC Medicine, researchers pooled the results of 40 studies, involving more than a million participants, to determine the link between dietary magnesium and the risk of cardiovascular disease, diabetes and all-cause mortality. The studies, published from 1999 through 2016, were conducted in nine countries including the Unites States, Britain, Australia, China and Japan. Study participants were followed from four to 30 years.

An extra 100 milligrams a day is protective

People who consumed the most – versus the least – magnesium from foods had a significantly lower risk of Type 2 diabetes, stroke and death from all causes. They were also less likely to develop heart failure.

(Heart failure occurs when the heart muscle weakens and can't pump enough blood fast enough to meet the needs of the body; as a result, fluid accumulates in the lungs, hands, ankles or other parts of the body.)

For every additional 100 mg of magnesium consumed a day – the amount found in 30 almonds, a quarter cup of wheat bran, two-thirds of a cup of cooked spinach or one cup of tofu – the risk of Type 2 diabetes fell by 19 per cent, stroke by 7 per cent and heart failure by 22 per cent. The risk of dying from any cause was reduced by 10 per cent.

Magnesium influences the release and activity of insulin, the hormone that removes glucose from the bloodstream.

The protective effect of magnesium on stroke risk is thought to be due to its ability to lower blood pressure.

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Higher magnesium intakes may also reduce inflammation, a risk factor for diabetes and stroke.

Study limitations

There are caveats, however. The 40 studies were observational in nature; they weren't randomized controlled trials that prove cause and effect. There is a lack of large randomized trials that investigate the relationship between increasing magnesium intake and preventing cardiovascular disease and/or Type 2 diabetes. It's also possible that lifestyle factors or other dietary components played a role in disease protection.

How much magnesium?

Women require 310 to 320 mg each day; men, 400 to 420 mg.

According to the 2012 Canadian Community Heath Study, most adults don't meet daily magnesium requirements. Earlier research revealed that many Canadian teens were also consuming too little.

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A diet that's heavy in refined grains – which are stripped of the mineral – and lacking in plant foods is largely to blame.

Green leafy vegetables, whole grains, nuts and seeds, legumes and soybeans contain the most magnesium.

Yogurt, salmon, mackerel and halibut are also decent sources.

Drugs that drain magnesium

Certain medications can deplete much-needed magnesium in the body. The most problematic are proton pump inhibitors (PPIs), which are used to treat acid reflux and ulcers by reducing stomach acid.

Several studies have observed low magnesium levels in participants taking PPIs for more than one year. PPIs include omeprazole (Losec), esomeprazole (Nexium) and lansoprazole (Prevacid).

Diuretics such as furosemide and hydrochlorothiazide cause magnesium to be lost in the urine.

If you're taking such a medication, be sure to include magnesium-rich foods in your daily diet.

In some cases, a supplement may be required.

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Boost magnesium with these five foods

Whole grains, nuts, legumes, soy and green leafy vegetables are rich sources of magnesium. Fortify your diet by eating a variety of high-magnesium foods each day, starting with these ones.

Hemp seeds

Three tablespoons deliver an impressive 210 milligrams of magnesium, two-thirds of a day's worth for women and half a day's worth for men. Sprinkle them over oatmeal, yogurt and salads or add them to smoothies.

Also eat: pumpkin seeds (191 mg a quarter cup), almonds (96 mg a quarter cup) cashews (90 mg a half cup), walnuts (45 mg a quarter cup) and sunflower seeds (43 mg a quarter cup)

Swiss chard

This leafy green contains 150 mg of magnesium a cup, cooked. Add it to soups and stir-fries or sauté it with garlic and chili flakes.

Also eat: spinach (158 mg a cup, cooked), beet greens (100 mg a cup, cooked) and kale (74 mg a cup, cooked)

Black beans

All legumes are excellent sources of magnesium, but black beans have the most, providing 90 mg a three-quarters of a cup. Add them to soups, salads, chili and tacos.

Also eat: edamame (75 mg a three-quarters of a cup), navy beans (72 mg), firm tofu (70 mg), pinto beans (65 mg), lima beans (60 mg), chickpeas (60 mg) and lentils (53 mg)

Teff

One cup of this tiny gluten-free whole grain, cooked, provides 127 mg of magnesium.

Serve it as a porridge, add it to muffin batters or mix it with other grains in salads and pilafs.

Also eat: amaranth (160 mg a cup, cooked), quinoa (118 mg), spelt (95 mg), oat bran (88 mg) and brown rice (79 mg)

Acorn squash

This winter squash serves up 88 mg of magnesium a cup, baked.

Serve it as a side dish, add cooked squash to muffin and pancake batters or blend it into smoothies.

Also eat: butternut squash (60 mg a cup, baked), baked russet potato (52 mg a medium) and sweet potato (60 mg a cup, mashed)

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.

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