Immunity Series: Vitamin D
What is it?
Vitamin D is a fat-soluble vitamin that supports bone health, immune function and cell growth and development.
What does Vitamin D do?
Vitamin D helps us to maintain calcium and phosphorus balance.
Vitamin D, sometimes referred to as the “sunshine vitamin” because upon sun exposure it can be made in the skin in addition to consuming it from dietary sources.
In our immune system, Vitamin D expresses more antibacterial proteins and plays a protective role by reducing the risk of autoimmune disease.
Vitamin D is essential for proper absorption of calcium and phosphorus in the intestine.
Vitamin D and Athletic Performance
Most of the general population is at risk for a Vitamin D insufficiency. A common symptom of a lack of Vitamin D is muscle weakness. For athletes who constantly rely on their muscles to perform their sport this raises concern.
Because Vitamin D is essential in bone growth and mass, an insufficiency could cause bone injury. When Vitamin D is low, the body responds by increasing bone breakdown to transfer calcium from bone tissue to blood in order to meet the body’s yearning for calcium. Low Vitamin D increases the risk for bone injuries like stress fractures. Recent studies examining Finnish military recruits reported Vitamin D to be an important determinant of maximum bone mass. In this group, levels of VItamin D below 30ng/mL increased the risk for stress fractures.
Studies are not conclusive on performance enhancing qualities of Vitamin D, but the research has demonstrated the support of Vitamin D on reducing the risk of chronic disease. Optimal Vitamin D intake supports the prevention of stress fractures and serious muscle injuries. Vitamin D has been found to be a key factor in optimizing bone health, which is of great importance for athletes.
What foods contain Vitamin D?
- Fatty fish (salmon, tuna, mackerel),
- Egg yolks and cheese (small amounts)
- Hard boiled eggs
- Fortified plant based milk
- Low-fat milk fortified with Vitamin D
- Canned tuna
- Cereal/oatmeal fortified with Vitamin D
- Mushrooms
Should I supplement and how much should I take?
Vitamin D is often hard to obtain from food sources alone.
The recommended dietary allowance (RDA) of Vitamin D for adults is 600 IU or 15mcg. Supplementation may be considered if you consistently consume less than the recommended amount. The tolerable upper intake level for adults is 4000 IU or 100 mcg. In supplements and fortified foods, Vitamin D is present as Vitamin D2 or Vitamin D3. Most steps in the metabolism process of D2 and D3 are identical. Both sources have been proven effective in curing deficiency, but in high amounts, Vitamin D2 is less potent. Most people need at least some of their Vitamin D through sunlight exposure to UV rays.
Those who suffer from milk allergies, lactose intolerance and those who follow a vegan diet are specifically at risk for Vitamin D deficiency. Those who have undergone bariatric surgery, are obese or struggle with inflammatory bowel disease and other malabsorption conditions are most likely to be in need of Vitamin D supplementation to meet the recommended intake.
Vitamin D deficiency presents challenges to bone health and development. In children, rickets, causing soft bones and skeletal malformation is a result of deficiency. In adults, Vitamin D deficiency can cause osteomalacia which weakens bones. Symptoms for possible deficiency can include bone pain, muscle weakness or fatigue.
How safe is it?
In appropriate amounts, Vitamin D supplementation is generally regarded as safe. However, excessive consumption through supplementation of Vitamin D may result in Vitamin D toxicity which can raise blood levels of calcium. Heightened levels of calcium can contribute to damage to the heart, blood vessels and kidneys.
Vitamin D supplements may interfere with prescription or over the counter medications. Prednisone, often prescribed to treat inflammation, can reduce the absorption of calcium and the metabolism of Vitamin D which can contribute to causes of osteoporosis in the long term.
Consultation with your healthcare provider is recommended if you are taking a medication that may interfere with Vitamin D absorption.
Bottom Line:
In appropriate amounts, Vitamin D supplementation is generally regarded as safe. However, excessive consumption through supplementation of Vitamin D may result in Vitamin D toxicity which can raise blood levels of calcium. Heightened levels of calcium can contribute to damage to the heart, blood vessels and kidneys. Vitamin D supplements may interfere with prescription or over the counter medications. Prednisone, often prescribed to treat inflammation, can reduce the absorption of calcium and the metabolism of Vitamin D which can contribute to causes of osteoporosis in the long term. Consultation with your healthcare provider is recommended if you are taking a medication that may interfere with Vitamin D absorption.
Want to learn more about your individual micronutrient status and nutrition needs?
Check out our nutrition programs here.
References:
https://lpi.oregonstate.edu/mic/health-disease/immunity-in-brief
https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3725481/
