Men who consume the recommended amount of vitamin D are less likely to suffer a heart attack or stroke than those who consume little of the vitamin, a new large U.S. study suggests.
The researchers followed nearly 119,000 adults for two decades. After accounting for a range of factors -- age, weight, exercise levels, diet habits, etc. - the research team found that men who got at least 600 IU of vitamin D from food and supplements had a 16 percent lower risk of heart attack and stroke compared to men who got less than 100 IU of vitamin D per day.
There was no such pattern among women, however. One possibility is that women may have less active vitamin D circulating in the blood. Also vitamin D is stored in fat, and women typically have a higher percentage of body fat than men do.
Last year, the Institute of Medicine (IOM), a scientific advisory panel to the U.S. government, bumped up the recommended dose to 600 IU for most people. Adults older than 70 are advised to get 800 IU per day. A safe upper daily limit of 4000 IU was also established.
The jurt is still out whether vitamin D actually cuts heart disease and stroke risk.
More answers should come from an ongoing randomized clinical trial that is looking at whether 2000 IU vitamin D per day can cut the risk of heart disease, stroke and other chronic diseases.
Numerous studies in recent years have linked higher vitamin D intake to lower risks of everything from diabetes, to severe asthma, heart disease, certain cancers and depression.
Those studies - like the current study - were "observational". In this type of study researchers looked at people's vitamin D intake, or their blood levels of the vitamin, and whether they developed a given health condition. Observational studies cannot prove cause-and-effect.
Randomized clinical trials, in which people are randomly assigned to a treatment or a placebo, are considered the "gold standard" of scientific evidence.
In theory, vitamin D could help ward off heart disease and stroke. Lab research suggests that the vitamin may help maintain healthy blood vessel function and blood pressure levels, reduce inflammation in the blood vessels, and aid blood sugar control.
Sun is the major natural source of vitamin D since sunlight triggers vitamin D synthesis in the body. Food sources are relatively few and include fatty fish like salmon and mackerel and fortified dairy products. To obtain an adequate vitamin D intake in the fall and winter months, a supplement is necessary for people who live north of 37 degrees latitude.
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