With Thanksgiving over and winter on its way, it is a great time to discuss vitamin D. Many of you likely know vitamin D as the sunshine vitamin, since it can be obtained from sunlight. It is more difficult to obtain vitamin D this way during the winter for a few reasons. The first reason is that colder temperatures require us to wear long sleeves and other layers to keep us warm. This prevents sunlight from reaching our skin to start the activation process of vitamin D. The second reason is that the sun itself is further away during winter. Combine that with less time being spent outside due to the cold weather, it is likely that deficiencies can occur. A research study titled “25(OH)D Status of Elite Athletes with Spinal Cord Injury Relative to Lifestyle Factors” by Kelly Pritchett PhD, RDN, CSSD et al was published last year. She happens to be another registered dietitian I know. So I reached out to her for my first guest blog post!
Vitamin D: Do athletes with a spinal cord injury need to supplement?
Guest post by Kelly Pritchett PhD, RDN, CSSD
Vitamin D is a fat-soluble vitamin that functions like a hormone in the body playing various roles in in the body including immunity, bone health and muscle function. It can be obtained from sunlight and vitamin D containing foods, however it’s difficult to meet your needs from food alone. Vitamin D containing foods (containing ~25-1000 IU depending on the source) include: wild salmon, mushrooms, tuna, fortified milk, orange juice, fortified cereal, and egg yolks . To put it into perspective, the skin can synthesize about 15,000 IU of vitamin D from the sun in less than 30 minutes.
Individuals with spinal cord injuries (SCI) are at an increased risk of vitamin D insufficiency/ deficiency due to decreased sun exposure, poor diet/absorption, and medication use. Our lab at Central Washington University in collaboration with the United States Paralympic teams has conducted trials to examine vitamin D status in elite athletes with a SCI. Findings from our lab suggest that a substantial proportion (41%–51%) of elite athletes with SCI in the population we examined have insufficient vitamin D status in the winter, and autumn (Pritchett et al 2016).
These findings led us to investigate whether a sliding scale vitamin D supplementation protocol would improve vitamin D status and performance measures in athletes with SCI. Thirty-four members of the US Olympic Committee Paralympic program, and the Canadian Wheelchair Sports Association from outdoor and indoor sports participated. Serum 25(OH)D concentrations, lifestyle and dietary factors were assessed during the Winter and Spring. Participants were assigned to a 16-week sliding scale vitamin D3 (cholecalciferol) (KleanAthlete Brand) supplementation protocol based on initial 25(OH)D levels. Participants with deficient 25(OH)D (<20ng/mL-1) status received 50,000 IU/wk for 8 wks, and participants with insufficient status (20-30 ng/mL-1) received 35,000 IU/week for 4 weeks followed by a maintenance dosage of 15,000 IU/wk. Participants with sufficient status (>30ng/mL-1) received the maintenance dosage of 15,000 IU/wk. Findings from this study suggested that 26% of athletes had sufficient 25(OH)D concentrations prior to supplementation, and 94% had sufficient concentrations post supplementation. In the current study, 60% of participants improved handgrip strength post supplementation. However, no change in wheelchair sprint performance time was observed.
Athletes with SCI exemplify a fascinating group to examine due to the diversity of physical impairment resulting in a variety of physiological abilities. Muscle wasting below the level of the lesion (which reflects both level and completeness of injury) may hinder the demonstration of any possible relationship between 25(OH)D levels and muscle strength tests. We can only speculate that the ability to detect a change in performance measures may be limited given that the subjects in the current study are highly trained, elite athletes with SCI. Finally, research is warranted to appropriately identify serum 25(OH)D goal levels in athletes with SCI and routine screening and supplementation protocols need to be instituted to prevent vitamin D insufficiencies.
A lack of consensus exists regarding optimal vitamin D supplementation doses. The current study suggests that a moderate dosage, 16-week sliding supplementation protocol that is based on initial 25(OH)D levels is effective for achieving sufficient vitamin D concentrations during the winter months in elite athletes with SCI. Results of our investigation will support the current literature suggesting that a higher intake of vitamin D through dietary sources and supplementation may be necessary to optimize vitamin D levels. Finally, if you are concerned about your vitamin D status, have your levels assessed annually especially during the winter months. A registered sports dietitian or physician can help determine whether supplementation is necessary based on your vitamin D level.
Here are some tips to boost vitamin D levels:
• Consume vitamin D rich fish, like wild salmon, 2 to 3 times per week
• Add fortified milk, yogurt or orange juice to smoothies
• Consume 1 hard-boiled egg with fortified cereal at breakfast
• Add mushrooms, and cheese to your rice bowl for dinner