This article is part of a series by the Ismaili Nutrition Centre that examines evidence-based studies published in scientific journals, and distills what they mean to our readers.

Whole grain cereals can be a great source of magnesium. Look for those that are also low in salt and sugar. Vanessa Courtier

Magnesium is essential for good health, and magnesium minerals are the fourth most abundant minerals in the human body. Approximately 50 – 60 per cent is found in bone and teeth, while the rest is in body tissues and organs like the heart and brain. In addition to keeping the heart beating at a steady rhythm, our body uses magnesium in over 300 chemical reactions to help our nerves function, support our immune system, and keep our bones and teeth strong.

Researchers at Harvard University studied 88 375 women over 26 years to find out if magnesium protects the heart from sudden rhythm failures, and published their results in 2010 in the American Journal of Clinical Nutrition. This is an important issue because more than half of deaths related to heart disease occur from sudden heart rhythm failures, accounting for over 400 000 deaths each year in the United States alone.

The study found that women who ate enough magnesium were 34 per cent less likely to die from sudden heart rhythm failures than women who only ate 80 per cent or less of the recommended amount of magnesium. The same effect has been shown in men in other studies.

Sudden heart rhythm failures cause the heart to stop beating suddenly. People usually need to be resuscitated with electric shock to survive. Magnesium is involved in keeping the heart's rhythm steady, and healthy magnesium levels over the long-term help avoid these problems.

What this means for you

This study does not prove that magnesium can prevent sudden heart related deaths, but getting more of it may help lower your risk. Make sure that you include magnesium-rich foods as part of your daily intake to reach the Canadian and American recommended amounts of 320 milligrams for women and 420 milligrams for men each day, or the European Union recommendation of 375 milligrams per day for men and women.

The richest sources of magnesium are green leafy vegetables like spinach, whole grains, beans and nuts. Fish, meats and dairy foods are also good sources. If you take a multivitamin, look for one that has around 100 – 200 milligrams of magnesium. Taking more than 350 milligrams from supplements may be harmful and can cause diarrhea, so don't overdo it.

For those who are healthy and can eat a full diet, it is generally better to meet nutritional needs by eating a varied diet than to depend on supplements. Most people get enough magnesium from a healthy, balanced diet, and we therefore recommend keeping a balanced diet with green vegetables and the other foods above.

See the table below for some of the foods that are richest in magnesium.