Vitamin D is vital for preventing rickets and building strong bones. Despite its importance, 30-50% of Americans do not get enough. Individuals at highest risk for vitamin D deficiency are obese and dark skinned individuals.
Some studies show that low levels of vitamin D in the blood (<30ng/ml) are associated with a greater likelihood of heart failure, heart attack, high blood pressure, problems with circulation, stroke and decreased sensitivity to insulin, all conditions that are associated with inflammation and stress on cells. Vitamin D causes cells in the blood vessels and muscles to respond in a way that is beneficial to the heart.
Because vitamin D levels are easily measured and vitamin D supplements are readily available, it is tempting to take extra vitamin D in an attempt to reduce the risk of cardiovascular disease. However, caution is warranted.
Studies looking at the association between vitamin D and heart disease disappointingly do not show a clear relationship – higher levels of vitamin D do not lower the risk of heart disease. Many other factors come into play when researchers try to link diet to disease, including a person’s lifestyle, activity level, diet, and culture. Studies that attempt to control for these factors have found that the link between vitamin D and heart disease is greatly weakened and, in some cases, no longer present. It may be that low levels of vitamin D are sign of poor health rather than of a true deficiency.
Also, too much vitamin D can be harmful. Increased levels of vitamin D can in fact lead to increased absorption of calcium and subsequently cause kidney stones. The body can make vitamin D from sunlight, so the cheapest way to increase your vitamin D level is to increase your exposure to sunlight. However, too much sunlight unfortunately can lead to sunburns and skin cancer.
As with so many relationships between diet and disease, additional research is needed, and thankfully is in progress, before vitamin D can be recommended to reduce cardiovascular disease. Furthermore, we do not yet know the optimal level of vitamin D supplementation. For now, we can recommend vitamin D supplements to improve bone health but not to prevent heart disease.