A diet rich in magnesium might have health benefits for smokers
Publication Date:11/03/2008
A diet rich in magnesium could slightly reduce the risk of a common type of stroke for male smokers, according to a new study. The study doesn't tell us if the same benefit applies to women or non-smokers. And the reduction in risk from a magnesium-rich diet is very small compared with the extra risk of a stroke that comes from smoking in the first place.
What do we know already?
Magnesium is a mineral that you get from eating leafy vegetables, such as spinach. You also get magnesium from nuts, bread, wholegrain cereal products, fish, meat and dairy foods. It helps your body turn food into energy, and may also play a part in keeping your blood pressure low.
A study has now looked at more than 26,000 Finnish men, who all smoked. They were aged between 50 and 69. Researchers looked at the kinds of food the men ate, and the amounts of magnesium and other minerals they got from their diet. The aim was to find out whether a diet high in minerals could lower men's risk of a stroke.
What does the new study say?
Men who ate a diet high in magnesium had a slightly lower risk of a common type of stroke, compared with men who ate a diet low in magnesium. Other minerals, such as calcium, potassium and sodium (salt), didn't seem to make any difference to people's risk of a stroke.
In men with the lowest magnesium intake, 11 in 100 had a stroke caused by a blood clot, while in men with the highest magnesium intake, 9 in 100 had this type of stroke. The researchers think that magnesium might help to lower blood pressure or cholesterol, which could play a part in preventing strokes. However the risk of having a stroke if you are a smoker in the first place is much higher than this slight drop in risk with a diet high in magnesium.
To put the drop in risk in perspective, someone who smokes has double the stroke risk of a non-smoker. The risks are even higher for heavy smokers.
Magnesium made no difference to the risk of a less common type of stroke, caused by bleeding from a burst blood vessel in the brain.
Where does the study come from?
The researchers were based at several universities and research organisations, including the Karolinska Institutet, a medical university in Stockholm, Sweden, and the National Public Health Institute in Helsinki, Finland.
How reliable are the findings?
The study looked at a large number of people, which helps to make it more reliable, but there are some problems with the way it was done.
At the start of the study, the men filled in a questionnaire about what they ate. This was used to work out how much magnesium they got from their diet. But the study lasted for nearly 20 years, and the men were never asked again about their diet. So, changes to what the men ate over time could make the study less reliable.
Also, a diet high in magnesium may be healthy in other ways too. For example, it would probably include lots of vegetables. And people who eat a healthy diet may also be more likely to exercise. So, it's hard to know whether magnesium really has a benefit, or whether people who ate lots of it just had a healthier lifestyle in general.
What does this mean for me?
The study only looked at male smokers, so it doesn't tell us much about magnesium and the risk of stroke for women or non-smokers. However, foods that are high in magnesium include leafy green vegetables, like spinach, and wholegrain foods, like wholemeal bread. A diet with lots of these foods is likely to be good for you.
What should I do now?
If you smoke and want to cut your risk of a stroke, the best thing you can do is stop smoking. Keeping your blood pressure and your cholesterol under control also play an important part in preventing strokes.
According to the Food Standards Agency, the government food safety watchdog, you can get all the magnesium you need from a healthy, balanced diet. The recommended amounts are 300 milligrams (mg) a day for men, and 270 mg a day for women. However, the men in the study with a lower risk of stroke were eating an average of 575 mg a day.
The study didn't look at magnesium supplements. So, it's impossible to say whether taking supplements would offer the same benefits as getting magnesium from food. High doses of magnesium can give you diarrhoea, but the Food Standards Agency says it's safe to take supplements containing up to 400 mg of magnesium per day.
From:
Larsson SC, Virtanen MJ, Mars M, et al. Magnesium, calcium, potassium, and sodium intakes and risk of stroke in male smokers. Archives of Internal Medicine. 2008; 168: 459-465.
To read more, see our information on stroke prevention and on giving up smoking.
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