I have been checking vitamin D levels on my patients the last year or so, due to an abundance of data showing the benefits of vitamin D. I have been amazed how many women are low, even though we live in “Sunny San Diego”. Vitamin D is known as the “sunshine” vitamin. The body makes vitamin D from cholesterol through a process triggered by the action of the sun’s ultraviolet B rays on the skin. Factors such as skin color, age, amount and time of sun exposure, and geographic location affect how much vitamin D the body makes.
An estimated 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency. This is mostly attributable to people getting less sun exposure because of climate, lifestyle, and concerns about skin cancer. Current studies suggest that we may need more vitamin D than presently recommended to prevent chronic disease. For many years, researchers have studied the numerous benefits of vitamin D. It is well known that vitamin D plays an important role in the skeletal development of children and maintenance in adults. Numerous studies have shown that people who live at higher latitudes have an increased risk for many chronic conditions, including cardiovascular disease (CVD), diabetes, and common cancers such as breast, colon, and prostate. For those of us living in the Southern US, with the use of sunscreen, our risks have risen as well.
Cardiovascular Disease - Recent evidence suggests that vitamin D deficiency may adversely affect cardiovascular health and predispose patients to hypertension, coronary artery disease, congestive heart failure and diabetes mellitus. Epidemiologic studies have shown that living at higher latitudes and inadequate vitamin D and calcium levels are associated with coronary risk factors and increased risk for adverse cardiovascular events. The Framingham Offspring Study found that men and women with serum vitamin D levels less that 15 ng/ml have a 60% to 80% increased risk for CVD than those with higher levels. Furthermore, a recent meta-analysis found a 74% prevalence of vitamin D deficiency among patients with coronary artery disease and congestive heart failure. The Women’s Health Initiative trial combined 400 IU/d of vitamin D with 1000 mg/d of calcium. They found no effect. However, 400 IU/d is a very low dose of vitamin D and might not have been enough to show a difference.
Neuromuscular Function - Several studies have shown that vitamin D insufficiency contributes not only to increased risk for fractures but also to muscle weakness and subsequent falls in older persons. Also, vitamin D deficient patients have decreased hip muscle strength that affects gait stability and predisposes the elderly to falls. A recent 3-year randomized controlled trial showed an even more protective effect of vitamin D plus calcium supplementation. Two hundred forty-six women 65 or older were randomly assigned to receive 700 IU vitamin D plus 500 mg calcium or placebo. The risk of falling in women who received supplementation was reduced by 46%.
Breast Cancer –Vitamin D has been reported to assist in the regulation of cell growth and prevention of cancer progression by increasing cell differentiation and disintegration of cancer cells. Ecologic studies reveal that women residing in areas of low exposure to sunlight have a higher risk for breast cancer and increased breast cancer morbidity and mortality rates. In a large meta-analysis women were divided into quintiles based on 25(OH) D levels. In patients with levels > 52 ng/ml, there was a 50% reduction in breast cancer risk when compared with those women with levels lower than 10 ng/ml. Another meta-analysis of 11 studies showed a 45% decrease in breast cancer in patients with vitamin D levels of 30-50 ng/ml.
Autoimmune diseases and Influenza – Since vitamin D has a role in regulating the immune system and a strong anti-inflammatory effect, it has been theorized that vitamin D deficiency could contribute to autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes, rheumatoid arthritis, and autoimmune thyroid disease. A Finnish study that followed children from birth noted that those given vitamin D supplements during infancy, had a nearly 90% lower risk of developing type 1 diabetes compared with children who did not receive supplements. Scientists have suggested that vitamin D deficiency in the winter months may be the seasonal stimulus that triggers influenza outbreaks in the winter.
Should you be taking vitamin D? - Although research into vitamin D’s possible roles in diseases is conflicting, the risk for vitamin D toxicity is minimal when intake is 2,000 IU or less, while the benefit may be substantial. The upper limit that is recommended by the IOM (The Institute of Medicine) is 4000 IU/day. If your levels are low, your health care provider may recommend a higher dose for a short period of time. I normally repeat the blood test after 3 months. If you have a low level, it probably means you should take 1-2000 IU long-term to maintain the health benefits. Do you know your vitamin D level? If not, ask your health care provider. It normally costs $20-30 and insurance usually covers the test. Dollars well spent.