Who is at risk of low Vitamin D?
Lack of sunlight is the number one risk factor for low Vitamin D. Ultraviolet (UV) radiation is involved in production of Vitamin D in the skin. So if you spend a lot of your daylight hours indoors your risk is increased. I work with a number of athletes who train predominantly indoors, so they have an increased risk of being low in Vitamin D. Athletes may also have increased physiological demands for Vitamin D, compared to general population.
Others at higher risk include:
- If your lifestyle requires you to be predominantly indoors during daylight hours eg. work, study
- If you cover your skin for religious reasons
- If you have naturally very dark skin
- If you avoid the sun for cosmetic reasons or skin cancer protection
- Specific medical conditions
Why is Vitamin D important?
Vitamin D is a pretty clever little vitamin and plays an important role in many of our body systems.
Bones - Vitamin D controls calcium levels in the blood and is required for the absorption of calcium from the gut, which in turn is important for bones. Low Vitamin D can increase the risk of musculoskeletal problems, including longer term conditions such as osteopenia and osteoporosis. For athletes, an increase in bone turnover with low Vitamin D can increase the risk of bone injuries such as stress fractures. Sufficient Vitamin D may help to prevent this.
Immune System - Vitamin D is thought to have a role in maintaining a healthy immune system, and some studies suggest that Vitamin D deficiency may increase the risk of viral respiratory tract infections. Winter is often when Vitamin D levels decrease, so if you are prone to getting sick in the cooler months make sure your Vitamin D levels are kept up throughout.
Mental health – There seems to be a link between Vitamin D and mental health, including moods and even depression.
Muscle strength – Vitamin D may have a particularly important role for improving muscle strength in athletes. A study in athletes showed a positive impact on muscle function with Vitamin D supplementation if levels are low.
Injury prevention - Low Vitamin D may increase the risk for inflammatory-related injuries.
Performance - Few studies have looked at Vitamin D and its direct effect on performance in young adults, however multiple performance studies in older adults have related low vitamin D levels to decreased reaction time and poor balance.
Strategies to increase Vitamin D levels
- It's difficult to obtain enough Vitamin D just from foods. Only 5-10% of our Vitamin D may come from food. Foods that are rich in Vitamin D include– salmon, dark-flesh fish, egg yolks, fortified foods (like milk), UV mushrooms.
- Expose skin to the sun uncovered for short periods of time. Find a sensible balance between sun exposure for vitamin D and protection against skin cancer. The amount of time required for exposure will vary depending on where you live. Check the SunSmart website for more details on exposure times in Australia.
- Many people don’t like to risk going out in the sun without sunscreen and this is where a supplement may be useful. Vitamin D supplementation may be required for certain individuals. Speak with your health professional about appropriate dosages if you have been found to have low Vitamin D levels
Summary: For athletes, there is limited evidence to support vitamin D as a direct performance enhancer, however optimal Vitamin D is important for immune function and reduced risk of bone injuries such as stress fractures, and muscle injury.
Although Vitamin D is not shown to have a direct performance effect, the indirect impact could make a significant difference to performance and health/injury outcomes. Further research is required to determine the magnitude of effect of vitamin D on performance, in particular the areas of strength, power, reaction time and balance.
Ogan,D. & Pritchett, K. Vitamin D and the Athlete: Risks, Recommendations, and Benefits. Nutrients 2013, 5:1856-1868
Von Hurst, P.R. & Beck, K.L. Vitamin D and skeletal muscle function in athletes. Curr Opin Clin Nutr Metab Care 2014 Nov;17(6):539-45
SDA Fact Sheet – Vitamin D and AIS Fact Sheet – Vitamin D
Lisa Middleton is one of Australia’s most experienced Sports Dietitians. Lisa has spent over 15 years advising some of the nation’s most elite athletes and teams across a range of sports including VIS athletes, the Essendon, Hawthorn and St Kilda AFL Football clubs, Melbourne Vixens Netball, Melbourne Storm Rugby League and Melbourne Victory Football clubs throughout grand final and premiership years.