Vitamin D’s Crucial Role in Cardiovascular ProtectionSeptember 2007
By William Davis, MD
Health-conscious adults regularly monitor their cardiovascular risk factors—such as cholesterol, glucose, and homocysteine—in order to reduce their risk of debilitating cardiovascular disease. Now, intriguing new research suggests that vitamin D may play an essential yet overlooked role in staving off heart disease. Vitamin D deficiency may eventually be added to the list of causative factors that contribute to cardiovascular disorders.
A growing body of research indicates that vitamin D deficiency contributes to a broad spectrum of conditions such as high blood pressure, poor insulin sensitivity, inflammation, and other fundamental processes that underlie heart disease.
Alarmingly, vitamin D deficiency is extremely common throughout the population—affecting more than half of adults and the majority of the elderly.1
In this article, we’ll explore the epidemic of vitamin D deficiency, its detrimental effects on cardiovascular and whole-body health, and how you can protect yourself by maintaining healthy blood levels of vitamin D.
If you look up “coronary risk factor” in any standard medical textbook, you’ll find a list that includes high cholesterol, diabetes, smoking, sedentary lifestyle, obesity, and hypertension. However, vitamin D status is not listed. Perhaps you’ll find vitamin D in the list of risks for childhood rickets and osteoporosis in females. But a coronary risk factor? You’ll not see it.
New data, however, are suggesting a whole new panel of health effects previously unsuspected for this underappreciated vitamin. It may, in fact, be a crucial nutrient that plays a central role in coronary heart disease prevention.
“Vitamin D deficiency and its consequences are extremely subtle, but have enormous implicationsfor human health and disease. It is for this reason that vitamin D deficiency continues to go unrecognized by a majority of health care professionals.”
—Dr. Michael Holick, University of Boston
Vitamin D Deficiency: A Modern Epidemic
Poor diet, sedentary lifestyles, and stressful schedules have contributed to today’s epidemic of cardiovascular disease. Interestingly, dietary and lifestyle factors are also linked with another potentially dangerous and possibly related epidemic—that of vitamin D deficiency.
Human skin is rich with latent pre-vitamin D, which is activated by sunlight. Humans are meant to obtain vitamin D through sunlight exposure. Vitamin D is not contained to any significant degree in food, nor was it meant to be obtained through oral intake. But over the centuries, people have migrated to colder, sun-deprived climates, work indoors in offices or factories, travel by car, exercise in gyms rather than outdoors, and wear clothes that cover all but 5% of body surface area. In fact, even adults living in sunny Miami are likely to be deficient in vitamin D for at least part of the year.2 Oral intake of vitamin D has become necessary as humans developed lifestyles involving less and less sun exposure. Add to this the sun phobia fostered by dermatologists advising us that sun exposure causes skin cancer, and most of us are terribly sun-deprived and thereby unable to activate vitamin D.
There are few dietary sources of vitamin D. An eight ounce glass of milk contains 100 IU, although this is often inconsistent.3,4 Other dairy products, like cheese and yogurt, tend to have little or no vitamin D added. Oily fish like salmon, mackerel, and sardines contain 200–360 IU vitamin D per 3.5 ounce serving. Many breakfast cereals contain 40–100 IU per serving.1 Despite this, many people fail to obtain even the modest “adequate” intake every day. Strict vegetarians and lactose intolerant individuals are especially likely to be substantially vitamin D deficient.5 Other people at high risk for vitamin D deficiency include: the elderly, who convert less vitamin D with sunlight exposure compared to younger people; the obese; and dark-skinned individuals, due to high melanin skin content.4,6
Vitamin D Recommendations Based on Fiction, Not Facts
In 1963, when the Institute of Medicine drafted the Recommended Daily Allowance (RDA) for vitamin D, there were literally no scientific data available to help determine requirements for optimal health. It was clear, however, that vitamin D was a necessary ingredient for health, since children who failed to receive at least 300–400 IU per day, usually supplemented as cod liver oil, developed “bow legs,” or rickets, due to abnormal bone maturation in the legs. But the vitamin D dose recommended for adults was purely—and admittedly—fabrication. It was based on a disease model—that is, the amount thought to prevent rickets, rather than the amount needed to promote optimal health, which may be far greater.
“The basis for adult vitamin D recommendations [was] arbitrary. Thirty-six years ago, an expert committee on vitamin D could provide only anecdotal support for what it referred to as ‘the hypothesis of a small requirement’ for vitamin D in adults and it recommended one-half the infant dose, just to ensure that adults obtain some from the diet.”
—Dr. Reinhold Vieth University of Toronto
In the 1960s, the only known consequence of vitamin D deficiency in adults was osteomalacia, a form of bone softening. Administration of 200 IU per day of vitamin D was just enough to prevent osteomalacia. More recent vitamin D research, however, has uncovered the fact that exposure to just 10–20 minutes of sunlight yielded the blood-level equivalent of 10,000 units of vitamin D taken orally.7 Why would the naturally-intended source of vitamin D yield levels far beyond that specified by the RDA?
Speculation grew that the true vitamin D requirement for health was far more than the RDA in the absence of substantial sunlight exposure. A study conducted during the winter months in Omaha, Nebraska, in healthy adult men showed that the participants utilized 3000–5000 international units of vitamin D per day to maintain a steady vitamin D blood level. The researchers concluded that the current RDA was inadequate to meet these requirements.8 Low government-issued vitamin D intake recommendations, along with deprivation of sunlight, has therefore resulted in a nation that is frightfully deficient in a crucial nutrient.
Further investigation using blood levels of vitamin D have uncovered the extraordinary prevalence of deficiency. A study of 1500 women receiving treatment for osteoporosis showed that 52% of participants were deficient (<30 ng/mL 25-hydroxyvitamin D); and 18% were severely deficient (<20 ng/mL 25-hydroxyvitamin D).9 The likelihood of vitamin D deficiency ranges from a low of 36% in healthy adults 18–29 years old, to 57% of a general adult population in the US, to as much as 100% in the elderly.1 North of 37 degrees latitude (approximately a line drawn horizontally connecting Norfolk, Virginia, to San Francisco, California), sunlight is insufficient to trigger vitamin D conversion in the winter months.10 Living in a southern climate is no guarantee that deficiency won’t occur. A study conducted in Miami, Florida showed that approximately 40% of 212 adults were deficient in winter, with a modest improvement in summer.2
Sunlight, Vitamin D, and Heart Attack
The farther north you live, the more likely you will suffer a heart attack.11 That curious observation led to the suspicion that vitamin D may somehow be related to the development of heart disease. It suggests that sunlight exposure may somehow provide a protective effect, perhaps through vitamin D. The notable exception to this pattern is the Eskimos, who eat large quantities of oily fish, a rich source of vitamin D and omega-3 fatty acids.
An early hint that deficiency of vitamin D might be behind heart disease came from a New Zealand study of 179 people presenting with heart attacks. Heart attack sufferers proved to have lower vitamin D blood levels (25-hydroxyvitamin D) compared to people without heart attacks.12
A corroborating observation emerged from analysis of the enormous database of 259,891 heart attacks maintained by the National Registry of Myocardial Infarction. In this nationwide tabulation, heart attacks surged by 53% during sun-deprived winter months compared to summer.13 Further corroboration came from observations in sub-tropical climates, where intense sun shines year-round and seasonal variation in heart attack rates doesn’t occur.14 Unlike the large ranges in cold or hot weather found in temperate regions, the warm climate of a subtropical region does not affect the frequency of heart attacks.
If vitamin D is indeed related to heart disease risk, then we would also expect to see fewer heart attacks in sunny climates and more heart attacks in cooler climates. Indeed, an exhaustive study performed by Dr. David Grimes and colleagues at the Blackburn Royal Infirmary in England demonstrated a consistent worldwide relationship between sunlight exposure and heart disease: the farther north in latitude, the more heart attacks occurred.11 Dr. Grimes and others have suggested that the vitamin D activated by sunlight is behind the reduced risk of heart disease.
Vitamin D: Essential for Heart Health
Abundant evidence now points to the numerous cardioprotective functions of vitamin D. Restoring vitamin D to normal levels has been found to help reduce inflammation, normalize blood pressure, and improve insulin sensitivity—all factors that reduce heart disease risk.15-18
Vitamin D deficiency has been shown to diminish contractile function of heart muscle cells, contribute to endothelial dysfunction, distort heart muscle structure (triggering hypertrophy, or abnormal heart muscle growth), and increase smooth muscle growth in the coronary artery wall—a process that leads to atherosclerotic plaque formation.19,20 Low levels of serum 25-hydroxyvitamin D have been linked with congestive heart failure, a condition in which the heart is unable to keep up with the body’s demands for blood and oxygen.21 A recent analysis showed that individuals with low serum levels of vitamin D had higher rates of high blood pressure, diabetes, and elevated triglycerides than those with higher vitamin D levels.22
Longstanding vitamin D deficiency is a major contributor to osteoporosis, and scientists have long known that women with osteoporosis are more likely to have coronary heart disease. The correlation between osteoporosis and heart disease may reflect common risk factors and mechanisms, such as estrogen and vitamin D.23 A study in 2,500 postmenopausal women showed a four-fold greater risk of heart attack in women with osteoporosis.24 A University of Illinois study showed that the computed tomography (CT) heart scan score (a measure of coronary atherosclerotic plaque) in women with osteoporosis averaged 222 (optimal is zero), while women with normal bone density had far lower average scores of 42.25 Similar findings have shown that higher levels of coronary calcification are found in those with lower levels of vitamin D.26,27
Vitamin D deficiency may extend to vascular disease beyond the coronary arteries. A recent Italian study determined that the greater the vitamin D deficiency, the more carotid atherosclerotic plaque was present, as assessed by carotid ultrasound. The authors concluded that low vitamin D blood levels were an independent and strong predictor of atherosclerosis. Diabetics were also twice as likely as non-diabetics to be severely vitamin D deficient.28
Some authorities have proposed that inadequate vitamin D is part of the reason for the extremely high incidence of cardiovascular disease in people with abnormal kidney function.29 People with little or no kidney function often have very low levels of vitamin D, since the kidney is required for its activation.30 A Japanese study in 240 people on dialysis for severe kidney disease suggested that treatment to correct vitamin D deficiency resulted in a dramatic reduction in heart attack and death from heart disease.31 Emerging science argues strongly in favor of vitamin D as an important risk factor for cardiovascular disease. Optimizing vitamin D status holds tremendous potential to safely, inexpensively, and dramatically reduce cardiovascular risk.
“… there is a striking similarity between the benefits of vitamin D and the benefits of statin therapy. I believe that the unexpected and unexplained beneficial effects of statin therapy might be mediated by activation of vitamin D receptors by this group of drugs.”
—Dr. David S. Grimes Blackburn Royal Infirmary, Lancashire, UK