An introduction to cardiovascular diseases Patient friendly summary

  • CVD is more common in winter, when there is less UVB light and lower vitamin D levels.
  • CVD occurs less often in summer, when there is more UVB light and more vitamin D production.
  • Vitamin D levels above 40 ng/ml (100 nmol/l) may provide moderate protection against CVD.
  • Vitamin D level increases after diagnosis of CVD may increase the rate of survival and reduce the risk of a second CVD.

Cardiovascular disease (CVD) includes a number of diseases:

  • Atherosclerosis (fatty build-up or plaque and thicker arterial walls)
  • Congestive heart failure
  • Coronary heart disease (blockage of blood flow to the heart)
  • Peripheral artery disease
  • Stroke
  • Thrombosis (blood clots)

Plaque build-up can block blood flow. This causes coronary heart disease, peripheral artery disease, and thrombosis. Strokes are caused by either a blocked artery (due either to a plaque or clot) or a ruptured blood vessel in the brain.

Risk factors

The most important risk factors for CVD are:

  • Diet: An unhealthy diet, including too much sugar and some types of fat, can clog arteries.
  • Smoking: Smoking increases blood pressure and clotting of the blood. Both of these effects contribute to CVD.
  • Alcohol: Drinking too much alcohol may increase fat content in the blood and blood pressure.
  • Genetics: The “thrifty gene” (alipoprotein E epsilon 4) increases body cholesterol levels. People carrying this gene are at risk for CVD and Alzheimer’s disease.

Other risk factors include:

  • Diabetes: People with diabetes are two to four times more likely to have CVD.
  • Chronic kidney disease: This disorder reduces concentrations of the active form of vitamin D, thereby increasing the risk of CVD.
  • Low temperature: Cold weather tends to raise blood pressure, which contributes to CVD.

Sunlight exposure and CVD risk

According to studies, there are seasonal variations in CVD illness and death:

  • CVD is more common in winter, when there is less solar UVB light, especially in areas farther from the equator. Vitamin D production rates are also at their lowest in winter.
  • CVD occurs less often in summer, when there is more UVB light and more vitamin D production.

In some studies, living at higher altitude is associated with reduced risk of CVD. Solar UVB doses increase by 15-20% for each kilometer (25-30% per mile) increase in altitude, so vitamin D production rates are higher than at lower altitudes.

Vitamin D and CVD

A number of observational studies have found that low vitamin D levels in the blood are associated with increased risk of CVD. There is increasing evidence that vitamin D reduces the risk of coronary heart disease, peripheral vascular disease, and stroke.

Vitamin D levels

There have been about ten observational studies investigating risk of CVD incidence or death as a function of vitamin D blood levels before diagnosis. Risk drops rapidly for vitamin D increases at low starting levels, then more slowly at higher levels. Risk of CVD drops by about 40% for levels above 40 ng/ml (100 nmol/l) compared to 20 ng/ml (50 nmol/l).

How vitamin D works

There are a number of ways vitamin D might protect against CVD. Vitamin D regulates calcium. By helping calcium move to the bones and teeth rather than the soft tissues, vitamin D may assist the cardiovascular system.

In addition, vitamin D has been shown to:

  • Reduce inflammation
  • Increase muscle strength and maintain muscle function, which reduces the risk of heart failure.


The evidence that vitamin D reduces the risk of CVD is primarily from observational studies finding that those with higher vitamin D levels have lower risk of developing or dying from CVD.

However, there have not yet been any randomized controlled trials showing that higher vitamin D intake or levels result in lower rates of CVD.


There have not been any studies of treating those with CVD with vitamin D. Certainly conventional and other alternative approaches such as switching to a low-fat all vegetable product diet as pioneered by Dean Ornish should be considered the primary mode of treatment when CVD is diagnosed. Increasing vitamin D levels after diagnosis may help reduce the risk of death or a second CVD.

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 An Introduction to Cardiovascular Diseases.

Page last edited: 17 May 2011