It used to be simple: just get a “healthy” tan and your body will make all the vitamin D it needs. Desk jobs and sunscreen have changed all that, just as research is underlining the importance of vitamin D and suggesting its possible role in preventing many health problems.
- Vitamins play a crucial role in our body’s metabolism, but only tiny amounts are needed to fill that role. Vitamin D is one of the 13 vitamins discovered in the early 20th century by doctors studying nutritional deficiency diseases.
- Vitamin D breaks the other rules for vitamins because it’s produced in the human body, it’s absent from all natural foods except fish and egg yolks, and even when it’s obtained from foods, it must be transformed by the body before it can do any good.
- Emerging research supports the possible role of vitamin D in protecting against cancer, heart disease, fractures and falls, autoimmune diseases, influenza, type 2 diabetes, and depression.
- Vitamin D influences the bones, intestines, immune and cardiovascular systems, pancreas, muscles, brain, and the control of cell cycles.
- As our habits change, most of us cannot rely on our bodies to produce vitamin D the old-fashioned way. Instead, we increasingly depend on artificially fortified foods and pills to provide this vital nutrient.
Metabolism of Vitamin D
- Vitamin D is not one chemical but many. The natural type is produced in the skin from a universally present form of cholesterol, 7-dehydrocholesterol. Sunlight is the key: Its ultraviolet B (UVB) energy converts the precursor to vitamin D3 – Cholecalciferol.
- The first stop is in the liver, where vitamin D picks up extra oxygen and hydrogen molecules to become 25-hydroxyvitamin D, or 25(OH)D – Calcidiol. This is the chemical that doctors usually measure to diagnose vitamin D deficiencies.
- In Kidney it acquires a final pair of oxygen and hydrogen molecules to become 1,25 dihydroxyvitamin D– active form of the vitamin as 1,25(OH)2D, or Calcitriol.
Maintaining Vitamin D levels in our body
- You can make your vitamin D the old-fashioned way, by exposing your skin to UVB radiation in sunlight. However, it has to be done in moderation depending on the geographical location and ethnicity or else one could increasing their risk of malignant melanomas and other skin cancers, as well as wrinkles and premature skin aging
- Diet can help, but it’s very hard to approach the new goals with food alone. Fish and shellfish provide natural vitamin D (oily fish are best), but you’ll have to eat about 200 grams of salmon, 200 grams of halibut, 850 grams of cod, or nearly 250 grams tuna to get just 400 IU. An egg yolk will provide about 20 IU. Other foods like mushrooms, fortified milk, yogurt, cheese have even lesser vitamin D.
- Most people require supplements to get the vitamin D they need. It’s the main benefit of a daily multivitamin; most provide 400 IU.
- Cod liver oil supplements have vitamin D but it also come with good amounts of vitamin A. High cod liver oil intake is not recommended.
- So the solution is eating fish and whole eggs, time under sun whenever possible, along with judicious doses of vitamin D supplements would keep vitamin D level good.
- Even though dosages up to 10,000 IU daily do not cause toxicity, it generally is not recommended to take more than 2,000 IU daily in supplement form without the advice of a health care provider.
- Individuals at high risk for deficiency should have a vitamin D blood test first; a dosage of up to 3,000 to 5,000 IU may be required to restore blood concentrations.
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References:
https://www.uspharmacist.com/article/vitamin-d-supplementation-an-update