What is the Most Effective Vitamin D Supplement?

Vitamin D is known as the sunshine vitamin because it is produced by your skin when it’s exposed to sunlight. However, if you spend a lot of time indoors or have dark skin, it’s easy to get deficient in vitamin D. This can lead to a variety of health problems, including bone weakness and osteomalacia (soft bones), muscle weakness and rickets in children, and depression and anxiety in adults.

Deficiency can occur when your dietary intake is low over time, if you don’t get enough exposure to the sun or if your kidneys aren’t able to convert vitamin D to its active form in the body. There are also a number of other factors that can decrease your dietary intake of vitamin D, including being lactose intolerant or consuming an ovo-vegetarian or vegan diet [1,2,6,7].

Serum concentrations of 25-hydroxyvitamin D (25(OH)D) are the best indication of a person’s vitamin D status. The serum concentrations of 25(OH)D are based on the amount of the chemical that is produced endogenously by your skin when it’s exposed to UVB rays from the sun and that you’re able to absorb from the food you eat. In a healthy body, serum 25(OH)D levels between 30 and 49 nanomol/L (nmol/L) are sufficient for normal function. Levels above 125 nmol/L (50 ng/mL) are associated with adverse effects and can cause kidney damage, calcification of soft tissues, heart disease, thrombosis (blood clots), and stroke.

Clinical trials have shown that taking vitamin D supplements (typically 10 to 50 mcg/day) for 2 months can lower systolic blood pressure, but they don’t appear to improve diastolic blood pressure or prevent cardiovascular events. Similarly, a 3-year trial in New Zealand randomized 5,110 adults to a single dose of 5,000 mcg (200,000 IU) vitamin D3 followed by 2,500 mcg (100,000 IU) each month or a placebo for a median of 3.3 years and did not show a reduction in the incidence of cardiovascular disease or CVD mortality.

The results of these trials are not entirely clear because of a lack of long-term followup and the limited number of studies. However, a meta-analysis of 20 clinical trials in 2,703 people from around the world found that taking vitamin D supplements for 2-6 months reduced insulin resistance to a small but significant degree.

Vitamin D supplementation has been linked to a lower risk of breast cancer, colorectal cancer, lung cancer, and pancreatic cancer. In one study, women who took a daily supplement of vitamin D3 and calcium (1000 IU) for 5 years had no increase in the rate of breast cancer. A second study of women with a family history of breast cancer found that those who took calcium and vitamin D had a 30% lower rate of breast cancer than those who took a placebo.

In addition to lowering the risk of cancer, vitamin D is known to have anti-inflammatory properties and may be protective against osteoarthritis, rheumatoid arthritis, and asthma. It also may reduce the symptoms of inflammatory bowel diseases and improve quality of life in patients with irritable bowel syndrome. There are also studies that suggest that vitamin D can improve the symptoms of Crohn’s disease and fibromyalgia.