Low levels of “sunshine and seafood” vitamin correlate with risk of heart attack, hypertension, heart failure, and stroke
by Craig Weatherby
During the last decade, researchers have made a number of startling discoveries about vitamin D.
These include evidence that increasing dietary intake of the “sunshine and seafood” vitamin above average American levels may help prevent high blood pressure, fibromyalgia, diabetes, and multiple sclerosis and common cancers.
Low levels of vitamin D correlate with greater calcification of coronary arteries (Watson KE et al. 1997) and increased risk of high blood pressure (Forman JP et al. 2007).
And when it came to protecting cholesterol from oxidation—a key goal of preventive heart health—vitamin D was found more effective than vitamin E in an animal experiment (Sardar S et al. 1997).
As we reported last month, researchers who examined diet and blood sample data collected from 15,088 Americans found that those with the lowest blood vitamin D levels had dramatically higher rates of four key heart-risk factors (Martins D et al. 2007; see “Vitamin D Linked to Lower Rates of Diabetes, Obesity, Heart Risks, and Death”).
Correlations between low levels of vitamin D and increased heart risks appear again in a new analysis of data from participants in the Framingham Offspring Study: an offshoot of the landmark Framingham Heart Study.
Results link low vitamin D levels to higher heart risks
The new analysis was conducted by a team of doctors and statisticians from Massachusetts General Hospital, Harvard Medical School, Boston University, and the USDA Aging Research Center at Tufts University (Wang TJ et al. 2008).
The volunteers' average age was 59, a little more than half of the 1,739 participants were women, and all were Caucasians. None of the volunteers had any heart problems at the start of the five-year study and the researchers used blood samples to measure blood levels of vitamin D.
Average adult vitamin D blood levels in America range from 20-56 ng/mL, but levels above 30 ng/mL are considered the minimum for bone health, and experts recommend a target of 80 ng/mL to ensure optimal health.
Only 10 percent of the participants in the Framingham Offspring Study had vitamin D blood levels above 30 ng/mL, while 28 percent had levels lower than 15 ng/mL.
Over the five year course of the study, 120 participants suffered an adverse cardiovascular event (heart attack, stroke, etc.), and participants with vitamin D levels below 15 ng/mL were 62 percent more likely to experience these life-threatening events, compared with people with vitamin D levels above 15 ng/mL.
And people with low vitamin D levels and high blood pressure (hypertension) were 113 percent more likely to suffer an adverse heart event than those with normal blood pressure and higher vitamin D levels.
As lead author Thomas Wang M.D., noted, “Vitamin D receptors have a broad tissue distribution that includes vascular smooth muscle and endothelium, the inner lining of the body's vessels. Our data raise the possibility that treating vitamin D deficiency, via supplementation or lifestyle measures, could reduce cardiovascular risk.”
Dr. Wang went on to make an important point: “What hasn't been proven yet is that vitamin D deficiency actually causes increased risk of cardiovascular disease. This would require a large randomized trial to show whether correcting the vitamin D deficiency would result in a reduction in cardiovascular risk.”
However, his team's report noted several compelling correlations found in previous investigations (Wang TJ et al. 2008):
- “Administration of dietary vitamin D or UV-B treatment has been shown to lower blood pressure, restore insulin sensitivity and lower cholesterol.”
- “Research suggests that low levels of vitamin D may contribute to or be a cause of syndrome X with associated hypertension, obesity, diabetes and heart disease. Vitamin D regulates vitamin-D-binding proteins and some calcium-binding proteins, which are responsible for carrying calcium to the ‘right location' and protecting cells from damage by free calcium. Thus, high dietary levels of calcium, when D is insufficient, may contribute to calcification of the arteries, joints, kidney and perhaps even the brain.”
- “Many researchers have postulated that vitamin D deficiency leads to the deposition of calcium in the arteries and hence atherosclerosis, noting that northern countries have higher levels of cardiovascular disease and that more heart attacks occur in winter months.”
- [Vitamin D is required for metabolism of calcium.] “Scottish researchers found that calcium levels in the hair inversely correlated with arterial calcium—the more calcium or plaque in the arteries, the less calcium in the hair. Ninety percent of men experiencing myocardial infarction [heart attack] had low hair calcium. When vitamin D was administered, the amount of calcium in the beard went up and this rise continued as long as vitamin D was consumed. Almost immediately after stopping supplementation, however, beard calcium fell to pre-supplement levels.”
Vitamin D insufficiency is the norm in northern regions
Researchers have been pressing the Institute of Medicine to raise the recommended daily allowance (RDA) for vitamin D based on fast-growing evidence that higher intakes could protect against osteoporosis and certain cancers.
Wintertime sunshine levels in northern regions are so weak that the body makes no vitamin D at all, leading to estimates that more than half of the population in northerly temperate zones—as in the states above the Mason-Dixon line—have chronically deficient levels of the vitamin.
In addition, more and more people have indoor jobs and get little sun exposure even during warmer months.
Having darker skin also reduces the amount of UVB radiation that penetrates skin to trigger manufacture of vitamin D, and darker skinned people are more at risk of vitamin D deficiencies.
The researchers' conclusions seem like the proverbial no-brainer: “The findings [of the new study] may have potentially broad public health implications, given the high prevalence of vitamin D deficiency in developed countries, the contribution of lifestyle and geography to vitamin D status, and the ease, safety, and low cost of treating vitamin D deficiency.”
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