- Sunlight may reduce blood pressure in part through releasing nitric oxide from compounds under the skin, in part through producing vitamin D.
- Vitamin D may reduce blood pressure and the risk of hypertension, but vitamin D supplementation studies have found limited reductions.
Hypertension (high blood pressure) is an important risk factor for serious illnesses. These include chronic kidney disease and cardiovascular disease.
Several important risk factors raise blood pressure:
- Alcohol (drinking a large amount)
- Salt and sugar intake
Blood pressure can be lowered by eating foods high in potassium. This includes fruits, vegetables, fish, and nuts.
Sunlight exposure and hypertension risk
Several studies reported increases in blood pressure in people who lived in higher latitudes. There is less ultraviolet-B (UVB) light and vitamin D production further from the equator, as latitude increases.
Blood pressure also varies with the seasons. Blood pressure is often higher in winter. The temperature is cooler and vitamin D production is lower. Vitamin D may affect the seasonal changes of blood pressure.
Long-wave UV (UVA) also lowers blood pressure. This occurs because UVA releases nitric oxide from compounds under the skin.
Vitamin D and hypertension
Vitamin D may reduce the risk of hypertension and lower blood pressure.
In studies, lower vitamin D levels are associated with the risk of high blood pressure. For example, in a Harvard study of nurses, women with low vitamin D levels (17 ng/m [42 nmol/L]) had a 67% increased risk of developing hypertension.
However, in 10 other studies, there is little evidence that vitamin D reduces blood pressure. In general, there is only 1-3 mm difference in systolic and diastolic blood pressure between those with low and high vitamin D blood levels.
Thus, those with high blood pressure and low vitamin D levels may benefit from increasing vitamin D.
How vitamin D works
Vitamin D may lower blood pressure by:
- Altering renin: This enzyme constricts blood vessels and raises blood pressure.
- Increasing insulin sensitivity: Insulin resistance is a risk factor for high blood pressure.
- Reducing arterial calcification: Hardening of the arteries may contribute to high blood pressure. Vitamin D regulates calcium absorption and metabolism. Higher vitamin D levels help direct calcium to the bones and teeth rather than the soft tissues such as the arteries.
Further work is needed to fully understand how UV light and vitamin D may affect blood pressure.
Keeping vitamin D blood levels above 30-40 ng/ml (75-100 nmol/l) may help reduce blood pressure and risk of developing hypertension.
Vitamin D may be beneficial for high blood pressure, but more studies are needed.
In addition to taking vitamin D, people with high blood pressure should consider the Dietary Approaches to Stop Hypertension (DASH) diet. This diet is rich in fruits, vegetables, and low-fat dairy products. It is low in fats and cholesterol, salt, and sugar. DASH also recommends no smoking, reduced alcohol intake, increased potassium through diet or supplements, and acetyl-L-carnitine. Acetyl-L-carnitine can be produced in the body by the liver and kidneys if enough carnitine is in the diet. The primary sources of carnitine are red meat, dairy products, but other foods such as nuts and seeds, beans, vegetables, and grains also contain carnitine.
Find out more…
Do you want to find out more and see the research upon which this summary is based? Read our detailed evidence summary on Hypertension.
Page last edited: 17 May 2011