February 18, 2025, 4:50 pm | Read time: 5 minutes
Vitamin D is involved in numerous processes in the body — and is apparently also of great importance for muscle function. This was revealed by studies that have investigated the effect of a vitamin D deficiency on muscle strength.
As women and men get older, the production of sex hormones decreases, which is accompanied by a reduction in bone density and muscle mass, among other things. A protein-rich diet and sufficient exercise, i.e., moderate sport, are considered important to counteract this development. A possible vitamin D deficiency also appears to play a role in maintaining muscle strength, as studies have shown.
Overview
Studies Show That Muscle Strength Decreases with Vitamin D Deficiency
If you want to maintain your strength and performance for as long as possible, you should avoid a vitamin D deficiency. This is the conclusion of a study conducted by Trinity College in Dublin in 2019. A team of researchers led by Professor Maria O’Sullivan used data from the English Longitudinal Study of Aging (ELSA for short, a multidisciplinary longitudinal study with data from the British population) for their investigation and examined the data of 4,157 over-60s with regard to their muscle function.1
The results showed that “vitamin D deficiency was associated with impaired muscle strength” in the majority of the study subjects. More specifically, people with low vitamin D levels were almost twice as likely to experience muscle wasting as those with adequate levels. In terms of muscle performance, a third of those with low vitamin D levels performed significantly worse than those with normal levels.2
Muscle Maintenance for a Healthy Aging Process
The scientists issued a statement about their study on the faculty’s website. “Maintaining muscle function is incredibly important for healthy aging and is often overlooked,” commented Prof. O’Sullivan.3 Vitamin D could play an important role here. This is not the only reason why a deficiency should be prevented. “In the food policy of some countries, e.g., Finland, vitamin D fortification has already been successfully implemented, and vitamin D deficiency has been virtually eliminated in the population there,” said co-author Dr. Eamon Laird.
A study in 2022 with 3200 subjects aged 50 years or older also found a similar correlation. Using blood tests to determine vitamin D levels and measure grip strength, the scientists were able to draw a clear picture. People who suffered from vitamin D deficiency were 70 percent more likely to lose muscle strength than subjects who were not deficient.4
How Do You Get Vitamin D?
Strictly speaking, vitamin D is not a vitamin, as the body can produce it itself. It is produced in the skin cells and the liver when we are exposed to UVB rays from the sun. In the darker months, this does not happen (or at least much less), and in summer, UV protection inhibits synthesis. Vitamin D can also be obtained from foods such as oily fish. However, you would need around 200 grams of salmon to cover your daily requirement. Some people, therefore, turn to dietary supplements.
More Vitamin D for Better Performance in Sport?
However, the fact that vitamin D deficiency has a negative effect on muscles does not automatically mean that an increase in levels must be accompanied by a positive change in muscle strength. This was emphasized by the scientists at Trinity College, who were responsible for the first study mentioned in 2019.
In this regard, a study from 2023 came to exciting conclusions. It showed that an increase in vitamin D levels did not lead to an increase in muscle strength. The study examined 65- to 89-year-old people who already had reduced physical performance. The researchers wanted to find out whether taking vitamin D3 for a year would improve muscle strength (leg and grip strength), leg performance (lower limb performance), and general mobility. In addition, biopsies examined the muscle structure of a subgroup of participants to analyze potential changes at the cellular level.5
The result: although vitamin D supplementation led to a significant increase in vitamin D levels, this had no effect on the functional parameters examined. Unfortunately, increasing vitamin D levels does not appear to be able to increase muscle strength and mobility — at least not in people with already reduced physical performance. The extent to which an increase in vitamin D levels affects performance and muscle strength in people with, as yet, unimpaired physical abilities was not revealed by the 2023 study.
Avoid Vitamin D Deficiency, Not Just for Muscles
Even if more vitamin D does not necessarily mean a boost in muscle strength, vitamin D deficiency should be avoided — for muscle strength and for health in general.
Vitamin D not only plays an important role in the calcium and phosphate metabolism of bones, it is also associated with the formation of haemoglobin. This is the blood pigment in red blood cells that binds and transports oxygen in the blood. A vitamin D deficiency can, therefore, also be a cause of anemia and lead to a corresponding reduction in performance and fatigue. In older people, in particular, who spend less time in sunlight, anemia is often the cause of weakness. Therefore, in addition to iron levels, vitamin D levels should always be checked.
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A deficiency of the “sun vitamin” can — even before the age of 50 or 60 — lead to reduced performance, tiredness, listlessness, and even depressive moods. The immune system is also said to depend on vitamin D status. Anyone who would also like to maintain their muscle strength for as long as possible should also make sure that they do not go through life with a vitamin D deficiency for a long time. According to the German Nutrition Society (DGE), around 60 percent of Germans are deficient in vitamin D or have a deficiency. Vitamin D deficiency is particularly common in the winter months when there is little sunshine.6