Vitamin D keeps people over 65 fit

Vitamin D is not only important for your bones and the immune system, but also for the muscles. People over the age of 65 who ensure that their vitamin D levels remain at a healthy level can maintain their muscle strength and fitness.

Old textbooks stated that vitamin D is mainly important for absorbing calcium from food and transporting it to the bones. That is correct, but incomplete. Vitamin D has many more functions. Almost every cell in the body needs vitamin D in one way or another, including muscle cells.

Without sufficient vitamin D, muscle cells do not function properly. This is probably because a small amount of calcium is needed for contraction. In addition, the body must constantly replace muscle cells. Muscle tissue absorbs stem cells from the body and gradually converts them into muscle cells. Vitamin D is also needed for this process.

After the age of 30, people who do not do heavy physical work or exercise regularly lose a little muscle tissue and muscle strength every year. Initially, this happens slowly, but the pace increases as the years pass. After the age of 70, some people may have lost so much muscle that everyday activities become more difficult. Healthy vitamin D levels can slow down this process, according to a study published in 2007 by gerontologists at Wake Forest University in the United States.

The Americans used data from 976 people over the age of 65, determining not only their vitamin D concentration but also their fitness level using simple tests. For example, the researchers looked at how quickly the study participants could walk up and down a corridor and how quickly they could get up from a chair.

The Americans discovered a clear link between performance and vitamin D levels in the blood. People over 65 with less than 25 nanomoles/L of vitamin D in their blood were significantly less fit than those with higher vitamin D levels. The fittest study participants were those with vitamin D levels above 50 nanomoles/L. Not only did they score better on the tests, but they also had more muscle strength when squeezing a spring.

Most Dutch doctors use the guideline that an optimal vitamin D level for most groups should be somewhere above 50 nanomoles/L.

Dutch endocrinologists at VU University Amsterdam have more or less confirmed the results of the American study in a study similar to that of the Americans. The Dutch researchers found that people over 65 with vitamin D levels above 75 nanomoles/L performed better physically than people over 65 with vitamin D levels below 50 nanomoles/L. People over 65 with less than 25 nanomoles/L of vitamin D scored particularly poorly.

The Dutch researchers went one step further. They followed 979 study participants for three years and recorded the decline in their physical fitness during that period. After adjusting for statistical factors such as alcohol consumption, weight and chronic diseases as much as possible, they found that vitamin D levels were an important factor in the decline in fitness. People over 65 with vitamin D levels below 50 nanomoles/L declined significantly faster than those over 65 with levels above 75 nanomoles/L.

The group with vitamin D levels below 50 nanomoles/L was large. Almost half of the people aged 65 and older studied fell into that category.