As reported in our news section: Liverpool FC Vitamin D Levels, a group of researchers led by Dr. James P. Morton measured vitamin D levels in 20 English Premier League (EPL) players. This study is important because of the sun exposure the soccer players received during the summer time and their resultant blood levels.
Morton JP, Iqbal Z, Drust B, Burgess D, Close GL, Brukner PD. Seasonal variation in vitamin D status in professional soccer players of the English Premier League. Appl Physiol Nutr Metab. 2012 May 4. [Epub ahead of print]
The players competed for Liverpool FC, one of the world’s most famous soccer teams. They measured the levels in late August just at season’s start and then again 4 months later, in late December.
In the summer prior to the EPL season, 10 of the 20 players took part in the 2010 World Cup in South Africa (between 22° and 35°S) in June and July. After the tournament, they vacationed for 2-3 weeks in the Mediterranean (in July). For the other 10 who did not partake in the World Cup, they vacationed in the Mediterranean for the month of June, and then trained outdoors in the UK and Switzerland for the month of July.
All players reported back to Liverpool 3-4 weeks prior to collecting the first blood sample. During this period, players typically trained outdoors for 90 minutes between 10:30am and noon Monday through Friday in Liverpool, UK (53°N). No players traveled to any southern destinations during this time.
The mean blood levels in late August were 41.6 ng/ml, with a range between 27.2 and 60.4 ng/ml. The two dark skinned players had the lowest levels at 27.2 and 28 ng/ml.
In the fall and early winter, the players then continued their routine of training for 90 minutes before noon Monday through Friday, with game days typically taking place in the afternoon on Saturdays or Sundays. When blood levels were drawn again in late December, they had fallen significantly. This time, the mean level was 21.1 ng/ml, with a range between 8.8 and 33.6 ng/ml. Once again, the two dark skinned players had the lowest levels, with levels of 8.8 and 15.6 ng/ml.
A Vitamin D Council sponsor, Bio-Tech Pharmacal, supplies the English soccer clubs West Ham United, Arsenal, Bolton Wanderers, and Manchester United with vitamin D supplements. These are some of the most historic and successful clubs in the history of English football!
Surprisingly, there are relatively few studies that examine the vitamin D levels of people who live true outdoor lifestyles. Earlier this year, we reported that semi-nomadic tribes in equatorial Africa had mean levels of 45 ng/ml. In this study, the investigators report that soccer players achieve levels of 41.6 ng/ml after training and vacationing under the Mediterranean sun for a summer.
These levels show the influence of consistent sun exposure. The investigators said that no player was taking a supplement. We can presume that the players used more clothing than the semi-nomadic tribes did. Still, these players were able to achieve similar blood levels. This study can be added to the small list of studies that have examined blood levels in populations with outdoor lifestyles.
This study also highlights the challenges in maintaining vitamin D levels in the wintertime, and the likely need to supplement if you live at high latitudes. Reinhold Vieth has theorized that dropping vitamin D levels are adverse because fluctuating levels compromise the general equilibrium of the vitamin D “system.” If about 40 ng/ml is the physiologic level outdoor athletes achieve, then it may be in their best interest to maintain these kinds of levels year round.
Beyond these common sense principals, we need more controlled trials to understand the difference between summer and winter levels on athletic performance (though we generally know that better vitamin D levels are associated with better muscle function). Still, we have controlled trials using doses that achieve levels of 40 ng/ml or higher, which show increase in bone density, reduction in influenza A incidence, and improved mood and well-being during the winter time; findings that are useful to the professional athlete trying to grind through the season.
The English Premier League runs August through May, so players have to play through rough British winters and stay healthy, skilled, and fit. After the past few seasons, any Liverpool FC fan will tell you that they need all the help they can get!u