The researchers linked this apparent deterrent effect to magnesium’s potential power to help stabilize blood pressure and improve key risk factors for diabetes.
Ischemic (i-skee-mik) strokes are the most common kind by far. They occur when blood vessels narrow in the brain, causing a clot that deprives the brain of blood and oxygen.
Artery narrowing is associated with the arterial plaque buildup known as atherosclerosis, which can also lead to heart failure, heart attack, or sudden cardiac death.
Dietary factors—including low intake of omega-3 and high intake of omega-6 fats—affect the risk of ischemic stroke, and the strongest association is with between high sodium intake, which also raises blood pressure, a key risk factor for stroke.
In contrast, diets high in magnesium, potassium, and calcium appear to lower the risk of developing high blood pressure (Lee S et al. 2009).
Top magnesium sources
According to USDA data, the top food sources of magnesium include these, in descending order of magnesium content:
Other major food sources include bran, seaweed, leafy green vegetables, meats, grains, and milk.
What about supplements? Conventional wisdom calls for taking about one part magnesium to two parts calcium.
But other researchers argue, persuasively, that a one-to-one ratio is healthier, given the overload of calcium in most Americans' diets, and the lack of magnesium.
Also, prehistoric diets seem to have provided the minerals in a one-to-one ratio, suggesting that this ratio is what humans evolved in response to.
Finally, magnesium aids calcium absorption into bones, but the opposite is not true, with excess calcium impeding magnesium uptake.
Unfortunately, many people—especially African-Americans—fall well short of reaching the recommended daily allowance (RDA) for magnesium.] which is 320 mg for women and 420 mg for men (NIH/ODS 2009).
U.S. study links magnesium to stroke protection
Researchers from the University of Minnesota’s School of Public Health analyzed data collected from 14,221 men and women aged 45 to 64 years, who’d participated in the 15-year-long Atherosclerosis Risk in Communities Study.
The incidence of stroke among the volunteers, and their blood chemistry, was obtained from hospital records.
At the end of the study, those who had higher blood magnesium levels 15 years earlier had a 25 percent lower risk of stroke.
The risk of stroke was highest among those diagnosed with diabetes or hypertension (high blood pressure).
After the results were adjusted to account for having hypertension or diabetes, the link between higher magnesium intake and reduced stroke risk fell below the level of statistical significance.
The researchers said this finding means that magnesium probably lowers the risk of ischemic stroke by discouraging development of hypertension and diabetes... the very same effects seen in other recent studies (Lee S et al.; Guerrero-Romero F et al.; Larsson SC, Wolk A. 2007; Schulze MB et al. 2007; Song Y et al. 2006; Jee SH et al. 2002).
As the Minnesota team put it, "Low serum [blood] magnesium levels could be associated with increased risk of ischemic stroke, in part, via [the mineral’s deterrent] effects on hypertension and diabetes” (Ohira T et al 2009).
Magnesium vs. diabetes
Analysis of seven epidemiological (prospective cohort) studies by researchers at Stockholm’s Karolinska Institute showed that for every 100 milligram increase in magnesium intake, the risk of developing type-2 diabetes decreased by 15 percent.
As co-authors Susanna Larsson and Alicia Wolk wrote, "This finding suggests that increased consumption of magnesium-rich foods such as whole grains, beans, nuts, and green leafy vegetables may reduce the risk of type 2 diabetes” (Larsson SC, Wolk A 2007).
In terms of reducing risk factors for developing diabetes, higher magnesium intake seems helpful, whether you get the mineral from foods, supplements, or both (Jee SH et al. 2002; Guerrero-Romero F et al. 2004; Song Y et al. 2006; Schulze MB et al. 2007; Lee S et al. 2009).
Best magnesium sources: "Mediterranean” foods rank high
Drs. Larsson and Wolk cited whole grains, beans, nuts, and green leafy vegetables—foods at the heart of the healthful "Mediterranean” diet—as top magnesium sources.
They, like many researchers, failed to mention the high amounts of magnesium found in ocean fish and seafood (Ocean fish are also rich in health-protective selenium).
Fish plays a prominent role in that proven-healthful eating model, and fish was emphasized further in an updated version of the Mediterranean Diet Pyramid, issued recently by the Oldways Foundation… which, along with the Weston A. Price Foundation, champions it and other traditional diets.
Read the article in this issue to learn more about this recent update of the Mediterranean Diet Pyramid.
Magnesium-rich foods: Amounts per serving
The recommended daily allowance (RDA) for adults aged 31 or older is 320 mg for women and 420 mg for men (NIH/ODS 2009).
- Foods offered by Vital Choice are highlighted in bold
- Milligrams per 3.5 oz cooked portion, except as noted
Sablefish (black cod)
Almonds, 1 ounce roasted
Cashews,1 ounce roasted
Spinach, 1 cup
Oatmeal, 1 cup
Potato, baked w/ skin, 1 medium
Yogurt, skim milk, 1 cup
Brown rice, 1 cup
Beans or lentils, 1 cup
Albacore Tuna, canned
Banana, 1 medium
Whole milk, 1 cup
- Burnett-Hartman AN et al. Supplement use contributes to meeting recommended dietary intakes for calcium, magnesium, and vitamin C in four ethnicities of middle-aged and older Americans: the Multi-Ethnic Study of Atherosclerosis. J Am Diet Assoc. 2009 Mar;109(3):422-9.
- Gao SK et al. Suboptimal nutritional intake for hypertension control in 4 ethnic groups. Arch Intern Med. 2009 Apr 13;169(7):702-7.
- Guerrero-Romero F et al. Oral magnesium supplementation improves insulin sensitivity in non-diabetic subjects with insulin resistance. A double-blind placebo-controlled randomized trial. Diabetes Metab. 2004 Jun;30(3):253-8.
- Jee SH et al. The effect of magnesium supplementation on blood pressure: a meta-analysis of randomized clinical trials. Am J Hypertens. 2002 Aug;15(8):691-6.
- Larsson SC, Wolk A. Magnesium intake and risk of type 2 diabetes: a meta-analysis. J Intern Med. 2007 Aug;262(2):208-14. Review.
- Lee S et al. Effects of oral magnesium supplementation on insulin sensitivity and blood pressure in normo-magnesemic nondiabetic overweight Korean adults. Nutr Metab Cardiovasc Dis. 2009 Apr 7. [Epub ahead of print]
- National Institutes of Health/Office of Dietary Supplements (NIH/ODS). Magnesium. Accessed online June 6, 2009 at http://ods.od.nih.gov/factsheets/magnesium.asp
- Ohira T et al. Serum and Dietary Magnesium and Risk of Ischemic Stroke: The Atherosclerosis Risk in Communities Study. Am J Epidemiol. 2009 Apr 16. [Epub ahead of print]
- Schulze MB et al. Fiber and magnesium intake and incidence of type 2 diabetes: a prospective study and meta-analysis. Arch Intern Med. 2007 May 14;167(9):956-65.
- Song Y et al. Effects of oral magnesium supplementation on glycaemic control in Type 2 diabetes: a meta-analysis of randomized double-blind controlled trials. Diabet Med. 2006 Oct;23(10):1050-6.