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About Vitamin D

Vitamin D is commonly known as the “sunshine” vitamin, as the body can produce it from cholesterol when our skin is exposed to sunlight. Between 50-90% of vitamin D is absorbed through the skin via sunlight. Even though vitamin D can also be found in certain foods, the primary source comes from its production in the skin after exposure to sunlight.

Several forms of vitamin D influence the body in various ways and places. The forms of vitamin D include vitamin D1, vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Of these, vitamin D3 is the main active hormone humans produce through solar UVB radiation in the skin and later in the kidneys and liver.

The precursors of vitamin D, which are physiologically active at the tissue level (vitamins D2 and D3) are first hydrolyzed in the liver to form the inactive form of vitamin D storage − calcifediol (25(OH)D) (see the picture above). Next, they are hydrolyzed in the kidneys to form calcitriol (1,25(OH)2D), which binds to the vitamin D receptors (VDR) in cells. Laboratory tests usually measure calcifediol. Generally, the reference values and the efficacy of vitamin D in preventing various diseases have been evaluated in terms of the calcifediol levels in the bloodstream.

Vitamin D plays an essential role in the body. Since it improves our capacity to absorb calcium and phosphorus, it helps maintain the health of bones, teeth, cartilage, and muscles. Vitamin D also plays a crucial function in supporting our immune system to work properly. For example, it stimulates the proliferation of immune cells and regulates the synthesis of a protein that kills pathogens, including viruses and bacteria.

Adequate intake of vitamin D has been shown to reduce the likelihood of developing the following diseases:

• Osteoporosis
• Different cancers
• Diabetes (types 1 and 2)
• Cardiovascular diseases
• Different neurological disorders • Psoriasis
• Different infections
• MS
• Asthma
• Blood pressure disorders
• Arthritis
• Sarcoidosis
• Sjögren’s syndrome
• Hashimoto disease
• SLE
• Scleroderma

The following factors increase the absorption and concentration of vitamin D:


• The best sources of vitamin D are the sun and UV radiation; it is recommended to stay in the midday sun for about 15–30 minutes daily depending on the skin type (N.B. Many sunscreens prevent UV radiation from evoking efficient vitamin D production in the skin)
• Adequate vitamin A intake and its concentration in blood
• Adequate magnesium intake and its concentration in blood
• It changes the active form of vitamin D
• It helps with the transportation of vitamin D in the body
• Additional supplementation with the probiotic Lactobacillus reuteri

TOP FOODS THAT ARE HIGH IN VITAMIN D
Source: The National Food Composition Database in Finland (Fineli)


• Cod liver oil (1 tsp of 5–10 ml contains 10–20 mcg of vitamin D3)
• Eel and European river lamprey (25.6 mcg / 100 g)
• Common whitefish (22.1 mcg / 100 g)
• Canned herring (20.5 mcg / 100 g)
• Funnel chanterelle (18.9 mcg / 100 g)
• Baltic herring (17.9 mcg / 100 g)
• European perch (16.8 mcg / 100 g)
• Salmon (12.5 mcg / 100 g)
• Egg yolk (7.2 mcg / 100 g)
• Organic chicken egg (2.9 mcg / 100 g)
• Different ready spreads fortified with vitamin D (about 10 mcg / 100 g)
– For qualitative and health reasons, the authors of this book do not recommend the incorporation of ready spreads such as margarine, etc. into the diet.

Recommendations for too-high vitamin D levels

It is also possible to overdose on vitamin D. This is mainly due to individual genetic factors affecting the absorption and effectiveness of vitamin D.

Excessive amounts of vitamin D from supplements can lead to nausea, muscle weakness, neuropsychiatric disturbances, pain, loss of appetite, dehydration, excessive thirst, kidney stones, stomach pain, constipation and diarrhea. In extreme cases, an excess of vitamin D can cause renal failure, calcification of soft tissues throughout the body (including in coronary vessels and heart valves) and cardiac arrhythmia.

Biostarks references for vitamin D

  • Total Vitamin D (VitD-S): 25-80 ng/mL

Scientific references:

  • Mak, J. (2019). An Evidence-Based Review of Efficacy and Safety of Dietary, Natural Supplements and Sunlight in Vitamin D Deficiency. Vitamin D Deficiency, 95.
  • Kulie, T. & Groff, A. & Redmer, J. & Hounshell, J. & Schrager, S. (2009). Vitamin D: an evidence-based review. The Journal of the American Board of Family Medicine 22 (6): 698–706.
  • Basit, S. (2013). Vitamin D in health and disease: a literature review. British Journal of Biomedical Science 70 (4): 161–172.
  • Zittermann, A. (2013). Magnesium deficit ? Overlooked cause of low vitamin D status? BMC Medicine 11: 229.
  • Higdon, J. & Gombart, F. (2017). Vitamin D. The Linus Pauling Institute’s Micronutrient Information Center (MIC).
  • Khaw, K. & Luben, R. & Wareham, N. (2014). Serum 25-hydroxyvitamin D, mortality, and incident cardiovascular disease, respiratory disease, cancers, and fractures: a 13-y prospective population study. The American Journal of Clinical Nutrition 100 (5): 1361–1370.
  • Rooney, M. et al. (2017). Trends in use of high-dose vitamin D supplements exceeding 1000 or 4000 international units daily, 1999–2014. JAMA 317 (23): 2448–2450.
  • Higdon, J. & Gombart, F. (2017). Vitamin D. The Linus Pauling Institute’s Micronutrient Information Center (MIC).
  • Veugelers, P. & Ekwaru, J. (2014). A statistical error in the estimation of the recommended dietary allowance for vitamin D. Nutrients 6 (10): 4472–4475.
  • Papadimitriou, D. (2017). The Big Vitamin D Mistake. Journal of Preventive Medicine and Public Health 50 (4): 278–281.
  • Mangin, M. & Sinha, R. & Fincher, K. (2014). Inflammation and vitamin D: the infection connection. Inflammation Research 63 (10): 803–819.
  • Lugg, S. & Howells, P. & Thickett, D. (2015). Optimal vitamin D supplementation levels for cardiovascular disease protection. Disease markers 2015.
  • The Vitamin D Society (2021). Vitamin D Health Benefits.
  • Jones, M. & Martoni, C. & Prakash, S. (2013). Oral supplementation with probiotic L. reuteri NCIMB 30242 increases mean circulating 25-hydroxyvitamin D: a post hoc analysis of a randomized controlled trial. The Journal of Clinical Endocrinology & Metabolism 98 (7): 2944–2951.