Low vitamin D linked to death from heart and circulation problems
Publication Date:25/06/2008
Scientists have long known that a lack of vitamin D can weaken our bones. A new study shows that low levels of this nutrient may also be linked to a higher chance of dying early from heart and circulation problems, as well as other causes.
What do we know already?
Vitamin D helps our bodies absorb calcium, which our bones need to grow and stay healthy. You can get some vitamin D from certain foods, but the main source of this nutrient is our skin, which makes vitamin D when exposed to sunlight.
Unfortunately, many of us don't get enough vitamin D. Experts say that up to 6 in 10 older people have low amounts, and many younger people are also thought to have low levels. The reasons for this aren’t clear, but possible causes include air pollution, which blocks some sunlight (this is called ‘global dimming’), and less time spent outdoors.
Low levels of vitamin D can lead to weakened bones and breaks, as well as malformed bones in children (a condition called rickets). But the health problems probably go beyond our bones. Previous research has suggested that a lack of vitamin D also increases the chance of getting problems with our immune system, certain cancers, and problems with our heart and circulation, which can cause heart attacks and strokes.
Now researchers have looked at whether low levels of vitamin D might affect the chances of dying early from any condition, and from heart and circulation problems in particular.
What does the new study say?
The study included more than 3,200 men and women who'd been referred to hospital for chest pain or another symptom suggesting a problem with their heart or circulation. All the people in this study were white and ranged in age from 55 to 73 (the average age was 62).
For more than seven years, they had regular blood tests to track levels of vitamin D Researchers put the men and women into one of four groups, depending on their levels of this vitamin. At the end of the study, people in the two groups with the lowest levels of vitamin D were most likely to have died, whether from heart and circulation problems or from another condition. In fact, 37 percent of the group with the lowest amount of one form of vitamin D had died, compared with 13 percent in the group with the highest amount.
The researchers can't say for sure why low levels of vitamin D might be linked to people dying earlier than expected. One theory is that vitamin D helps prevent blood vessels called arteries from becoming narrower (a condition called atherosclerosis, which is also called 'hardening of the arteries'). Narrow arteries make it more difficult for blood to supply the heart.
People with more vitamin D were also less likely to die of causes not related to their heart and blood vessels.
Where does the study come from?
The study was done by researchers in Austria and Germany. It was funded by several drug companies. This doesn't necessarily affect the quality of its findings, as studies often receive funding from drug manufacturers. It was published in the Archives of Internal Medicine, which is a journal produced by the American Medical Association.
How reliable are the findings?
This was a large study and it was reasonably well done. But it had a few problems.
- This type of study (called a cohort study) can't prove that low vitamin D caused some people to die earlier than expected. It can show only that there may be a link. And researchers can't be 100 percent certain about this link. Perhaps there was something else about people with low vitamin D that made them more likely to die during the study. When working out the results, the researchers tried to take into account other factors (such as older age, lack of exercise and serious heart disease), but they might have missed something.
- Most of the people in the study had gone to their doctor for chest pain or another symptom suggesting a heart or circulation problem. So we don't know if the study's results apply to people who haven't had this type of symptom. Also, all the people in the study were white, so the findings might not apply to other racial groups.
- Finally, vitamin D is difficult to measure in the body. We can't be sure the study's measurements were entirely accurate.
What does this mean for me?
Bear in mind that this study looked at older people who already had symptoms related to their heart or circulation. We don't know whether its findings about low levels of vitamin D apply to younger people, or people without heart or circulation problems.
However, we already know that people of all ages, including children, need enough vitamin D, to keep the bones strong or to help strong bones develop. This study suggests that vitamin D may also be important to health for other reasons, although we need more research to say for sure.
What should I do now?
It's hard to know how much vitamin D you're getting, since much of it may come from time spent in the sun. Some experts say as little as 10 minutes of sun a day provides many people with all they need. People with dark skin, however, may need longer, as dark skin doesn't readily absorb the rays that produce this nutrient.
Another thing you need to consider is that sunscreen is thought to block out rays that help the skin make this vitamin, but wearing sunscreen is important to protect against skin cancer. Staying in the sun for 10 minutes without sunscreen is likely to be safe, but it can be difficult to get the balance right.
It's possible to get some vitamin D from what you eat and drink. Vitamin D isn't plentiful in many foods, but fish and fish oils are good sources, and margarine, cereals and powdered milk often have this vitamin added.
Some people are more likely than others to have low vitamin D and may need to take supplements. These include older people, nursing mothers, and people who wear cultural dress that covers their skin. It’s a good idea to talk to your GP if you have questions about your level of vitamin D, to find out how you can make sure you get enough.
From:
Dobnig H, Pilz S, Scharnagl H, et al. Archives of Internal Medicine. 2008; 168: 1340-1349.
To learn more about problems that can affect your heart and circulation, see our information on stroke prevention, heart attacks, heart failure, stable angina and unstable angina.
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This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
