Author: Joanna Pike, First Tri Physio

Sunlight. A rare sighting for many of us within the UK at this time of year. However, have you ever thought about how the lack of sunlight may be affecting your bones and muscles? Commonly known as the sunshine vitamin, lack of sun exposure during autumn and winter can leave us susceptible to low levels of vitamin D. But how would a low level of vitamin D affect your musculoskeletal health?

One of the most well-known functions of vitamin D within the body is maintaining the balance of two important minerals – calcium and phosphate. Both these minerals have several vital functions, with their absorption from the gut stimulated by vitamin D. Our bones act as a reservoir for the storage of both calcium and phosphate which in turn provides the hardness and rigidity necessary for the skeleton. Any slight reduction of calcium within the blood stimulates the removal of both calcium and phosphate from the bones, directly affecting bone strength and reducing the skeletons ability to adapt to daily physical stresses. Additionally, evidence is also suggesting that vitamin D can influence muscle strength which is especially important for older adults.

A balanced diet alone is not enough to provide the daily recommendation of vitamin D and protect our musculoskeletal system. Naturally occurring within very few foods, vitamin D is unique in that 80% of its source arises from UVB radiation stimulating production within our skin. In the UK, UVB radiation is virtually non-existent during the winter months leaving us to rely on the very limited sources within our diet and the stores we build during the summer months. So, for us to continue meeting the daily recommendation throughout the year, Public Health England recommends that everyone over the age of 4 should consider taking a daily supplement containing 10 µg (400IU) of vitamin D during autumn and winter.

Vitamin D supplements are readily available, but it can be confusing which strength to buy. Expert recommendations are based on the differing guidance provided by The Institute of Medicine and The Endocrine Society. Different population groups such as older adults and athletes may also require different strengths of vitamin D. What does need to be borne in mind is that too much can be a bad thing and may lead to vitamin D toxicity. Therefore, as a health professional I would recommend following Public Health England’s guidance of 10µg (400IU) per day and do not exceed 100µg (4000IU) per day.

Although there is an upper limit to how much vitamin D you should take, there is no limit on the amount of sun exposure, as our bodies will only make what is needed. Factors such as season, time of day, latitude, altitude, cloud cover, air pollution, clothing use, sunscreen use, and your age all influence your skins ability to produce vitamin D. For many of us, our occupations will also determine our sun exposure. It is also important to stay sun safe, therefore 20 minutes of direct sun exposure between the hours of 11am and 3pm to your arms/legs/body prior to applying sunscreen is thought to be adequate.

So, in order to keep your musculoskeletal system healthy, take into consideration the recommendations by Public Health England and how your diet and sun exposure are influencing your vitamin D levels so that you can make the decision whether vitamin D supplements are right for you.

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