Winters coming - Get your Vitamin D

Vitamin D is absolutely essential for optimal health.

Unfortunately, only a handful of foods contain significant amounts of this vitamin, and deficiency is extremely common.

Vitamin D is one of the fat-soluble vitamins (A, D, E and K), meaning that it dissolves in fat/oil and can be stored in the body for a long time.

It is crucial for a number of bodily processes as well as supporting our quest to become awesome at CrossFit! Going into the winter months when sunlight is at a premium, ensuring our vitamin D levels are adequate is crucial.

Functions of Vitamin D

It is well known that vitamin D regulates calcium metabolism and affects various cells related to bone health. But research has now found it to be involved in all sorts of other processes, including -

  • Immune function

  • Increased skeletal muscle function

  • Decreased recovery time from training

  • Increase both force and power production

  • Increase testosterone production

  • May help prevent seasonal affective disorder (winter blues)

Small amounts of vitamin D can be obtained through the diet in things like mushrooms, eggs, salmon, cod liver oil and fortified milk products. The majority of vitamin D made in the body occurs with exposure to adequate sunlight.


Signs of deficiency

  • Muscle weakness

  • Excessive sweating

  • Depression

  • Joint pain

  • Backache

  • Regular illness

  • Tooth decay

  • Hair loss.

Your skin makes vitamin D when it is exposed to a dose of sunlight. How much vitamin D you make depends on your age, how much skin is uncovered, and your skin tone. Without sunblock and with arms and legs exposed, your skin will make 10,000 to 15,000 units of vitamin D in one pinking sun exposure, on average. (Sunblock with an SPF of more than 15 blocks 100% of vitamin D production in the skin.)


Everyone should have his or her vitamin D level checked at least once a year (infants through the elderly). Below are conditions that have been associated with vitamin D levels:

10 ng/mL Severely deficient

15 ng/mL Risk of rickets

20 ng/mL 75% greater risk of colon cancer

30 ng/mL Deficient

  • Increased calcium loss from bones, osteoporosis

  • Poor wound healing

  • Increased muscle pain

  • Increased joint and back pain

  • Greater risk of depression

  • Increased diabetes

  • Increased migraines

  • Increased autoimmune disease (lupus, scleroderma)

  • Increased allergies

  • Increased inflammation

30–50 ng/mL Suboptimal levels

  • 34 ng/mL Twice the risk of heart attack

  • 36 ng/mL Increased high blood pressure

  • 40 ng/mL Three times the risk of multiple sclerosis

50–80 ng/mL Optimal levels

  • 50 ng/mL 50% reduction in breast cancer, decreased risk of all solid cancers

  • 80–100 ng/mL Slowing of cancer growth in patients with cancer

  • 150 ng/mL+ Increased risk of toxic symptoms (hypercalcemia)

Vitamin D Supplementation Doses

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Vitamin D

Normal dosing of vitamin D depends on your blood levels. Treatment doses for blood level ranges are:

  • 10 ng/mL – 10,000 units per day

  • 10–20 ng/mL – 10,000 units per day

  • 20–30 ng/mL – 8,000 units per day

  • 30–40 ng/mL – 5,000 units per day

  • 40–50 ng/mL – 2,000 units per day

If you are taking a vitamin D supplement, adequate calcium and magnesium intake are also required. Vitamin D works well with vitamin K and magnesium both of which are required to assist bone mineral density.

It is very difficult to get too much vitamin D. People can take up to 10,000 units per day for 6 months and not have adverse effects.

Checking Your Vitamin D Level

It is recommended that you recheck your vitamin D level within 2 months after starting supplementation, depending on your medical and health condition.


We use Medichecks to test our clients Vitamin D. Check them out here.

Vitamin D test is £39 and can be done via a finger prick test at home.


  1. – overview

  2. - Overall health

  3. vitamin D and athletes review

  4. – vitamin D and performance

  5. – review effect on athletes

  6. – potential role on muscle performance