If you have low levels of vitamin D, replacing it is important. Studies have shown that it may be effective in a wide swath of chronic diseases, both in prevention and as part of a treatment paradigm. However, many questions remain.
There still is no consensus on the ideal blood level for vitamin D. For adults, the Institute of Medicine recommends between 20 ng/ml and 50 ng/ml, and The Endocrine Society recommends at least 30 ng/ml.
At the 70th annual American Academy of Dermatology meeting in 2012, Dr. Richard Gallo, who was involved with the Institute of Medicine recommendations, spoke about how, in most geographic locations, sun exposure will not correct vitamin D deficiencies.
Interestingly, he emphasized getting more vitamin D from nutrition. Dietary sources include cold-water fatty fish and fortified foods.
We know its importance for bone health; however, we have only encouraging — but not yet definitive — data for other diseases. These include cardiovascular and autoimmune diseases and cancer.
Cardiovascular mixed results
Several observational studies have shown benefits of vitamin D supplements with cardiovascular disease. For example, the Framingham Offspring Study showed that those patients with deficient levels were at increased risk of cardiovascular disease.
However, a small randomized control trial (RCT) questioned its cardioprotective effects. This study of postmenopausal women, using biomarkers such as endothelial function, inflammation or vascular stiffness, showed no difference between vitamin D treatment and placebo.
The treatment group was given 2,500 IUs. The authors concluded there is no reason to give vitamin D for cardiovascular disease prevention.
Most vitamin D trials are observational, which provides associations, but not links. However, the VITAL study was a large, five-year RCT looking at the effects of vitamin D and omega-3s on cardiovascular disease and cancer.
Study results were disappointing, finding that daily vitamin D3 supplementation at 2000 IUs did not reduce the incidence of cancers (prostate, breast or colorectal) or of major cardiovascular events.
In a meta-analysis of eight studies, vitamin D with calcium reduced the mortality rate in the elderly, while vitamin D alone did not. The difference between the groups was statistically important, but clinically small: 9 percent reduction with vitamin D plus calcium and 7 percent with vitamin D alone.
One of the analysis’ weaknesses was that vitamin D in two of the studies was given in large amounts of 300,000 to 500,000 IUs once a year, which has different effects.
There is good news on the weight front. Vitamin D may play a role in reducing weight gain in women 65 years and older when blood levels are more than 30 ng/ml, according to the Study of Osteoporotic Fractures.
This association held true at baseline and after 4.5 years of observation. If the women dropped below 30 ng/ml, they were more likely to gain more weight, and they gained less if they kept levels above the target. Unfortunately, vitamin D did not show statistical significance with weight loss.
The U.S. Preventive Services Task Force recommends against giving “healthy” postmenopausal women vitamin D, calcium or the combination of vitamin D 400 IUs plus calcium 1,000 mg to prevent bone fractures, and it found inadequate evidence of fracture prevention at higher levels.
The supplement combination also increases the kidney stone risk.
When to supplement?
It is important to supplement to optimal levels, especially since many of us in the Northeast have low levels. While vitamin D may not be a cure-all, it may play an integral role with many disorders. But it is also important not to raise levels too high.
I tell my patients to target between 32 and 50 ng/ml, depending on their health circumstances.