- Vitamin D National Institutes of Health, Office of Dietary Supplements
- Vitamin D, evidence Mayo Clinic
- List of foods high in vitamin D US Department of Agriculture
- Shah M et al, 2013, Long-Term Impact of Bariatric Surgery on Body Weight, Comorbidities, and Nutritional Status Endocrine Society
- Sachdev AH et al, 2013, Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance PubMed Central
- Ergocalciferol pregnancy and breastfeeding warnings Drugs.com
- Holick MF, 2007, Vitamin D Deficiency The New England Journal of Medicine
- Vitamin D Linus Pauling Institute
- 2010, Vitamin D supplementation for infants American Academy of Pediatrics
- Hatun S et al, 2005, Vitamin D Deficiency in Early Infancy The Journal of Nutrition
- Wagner CL et al, 2006, High-dose vitamin D3 supplementation in a cohort of breastfeeding mothers and their infants: a 6-month follow-up pilot study PubMed
- Balasubramanian S, 2011, Vitamin D deficiency in breastfed infants & the need for routine vitamin D supplementation PubMed Central
- Braga CB et al, 2011, Serum vitamins in adult patients with short bowel syndrome receiving intermittent parenteral nutrition PubMed
- Calcitriol injection, 1 mcg/mL Drugs.com
- Einarsdóttir K et al, 2010, Effect of a single ‘megadose’ intramuscular vitamin D (600,000 IU) injection on vitamin D concentrations and bone mineral density following biliopancreatic diversion surgery PubMed
- Vitamin D supplementation Centers of Disease Control and Prevention
- Sadat-Ali Mir et al, 2014, Topical Delivery of Vitamin D3: A Randomized Controlled Pilot Study PubMed Central
- Vitamin D Safety Mayo Clinic
- Vitamin D Evidence Mayo Clinic
- Hypervitaminosis D MedlinePlus
- Zeratsky K, What is vitamin D toxicity, and should I worry about it since I take supplements? Mayo Clinic
- Vitamin D safety Mayo Clinic
- Vitamin D interactions Mayo Clinic
Vitamin D (Ergocalciferol, Cholecalciferol)
Vitamin D Forms
Vitamin D is a fat-soluble vitamin, a conditionally essential nutrient, which means, it can be produced in your body in sufficient amounts when your skin is exposed to sun light for a certain period of time, but when it is not, you need to get additional amount from food or supplements .
Vitamin D2 or ergocalciferol in plant foods and vitamin D3 or cholecalciferol in animal foods and human skin are inactive forms of vitamin D. They are converted into calcidiol (25OHD) in your liver and, finally, mainly in your kidneys, into calcitriol (1-25OHD), which is the only active form of vitamin D in the human body .
Vitamin D Functions
Vitamin D :
- Promotes absorption of calcium and phosphate in the intestine. When blood calcium levels are low, vitamin D, stimulated by the parathyroid hormone (PTH), promotes the absorption of calcium and phosphate from the small intestine and bones. When blood calcium levels are high, vitamin D stimulates calcium incorporation into the bones and teeth and thus strengthen them. Vitamin D deficiency can result in rickets, osteomalacia or osteoporosis.
- Helps to maintain the muscle strength and normal glucose levels
- Helps to maintain immunity
Sources of Vitamin D
Skin Exposure to Sun
Ultraviolet (UV-B) rays from the sun convert dehydrocholesterol in the skin into vitamin D3 (cholecalciferol). Exposure of the face, arms, legs or back (without sunscreen) to sun for 5-30 minutes between 10 AM and 3 PM twice a week (less than 42° latitude from March to October, and less than 34° year through) results in the production of sufficient amount of vitamin D in the body in healthy people [1,8]. Cloudy weather or being in shade reduces UV exposure to about 50% . UV light does not penetrate windows so indoor exposure to sun through windows does not result in vitamin D production in the skin . Prolonged exposure to sun, visiting sunbathing saloons or using UV lamps for the purpose of increasing vitamin D is NOT recommended, since they can increase the risk of skin cancer, but it does not lead to vitamin D toxicity .
Recommended Daily Intake
According to the Institute of Medicine of the National Academics in the US, the Recommended Dietary Allowance (RDA) for vitamin D for adults between 19-50 years is 15 mcg or 600 IU (International Units)/day, for 71+ years 20 mcg (800 IU)/day and for pregnant and breastfeeding women 15 mcg (600 IU)/day .
Recommended Intake for Infants
Human breast milk contains about 0.5-1 mcg (25-40 IU) of vitamin D per liter [3,7,10], which is much less than the Recommended Dietary Allowance (RDA) for vitamin D for 0-12 old infants is 10 mcg (400 IU)/day, so American Academy of Pediatrics recommends that infants should get 400 IU/day by supplements–available as nonprescription multivitamin drops–from the first days on . To increase the concentration of vitamin D in the breast milk to meet the infants needs, mothers would need to take supplements in large doses, but for now this is generally not recommended [11,12].
1 liter of vitamin D fortified formula or fortified cow’s milk should provide enough vitamin D to meet the infants’ needs .
Foods High in Vitamin D
Vitamin D can be mainly found in oily fish and liver and in smaller amounts in meat and dairy. In the US, Canada and some other countries, milk and, often, soy milk, margarine, ready-to-eat cereals, rice and orange juice are fortified with vitamin D (D2 or D3). Plant foods (fruits, vegetables, nuts, legumes, cereals) do not naturally contain vitamin D.
Picture 1. Examples of foods high in vitamin D
Chart 1. Foods High in Vitamin D
Vitamin D (IU)
|Salmon, swordfish, trout (3 oz, 85 g)||300-730|
|Fish oil, cod liver (1 tsp, 5 g)||450|
|Halibut, mackerel, sturgeon (3 oz, 85 g)||200-450|
|Flatfish, herring, rockfish, sardines, tilapia (3 oz, 85 g)||120-150|
|Buttermilk, eggnog (1 cup, 237 mL)||130|
|Anchovies, tuna (3 oz, 85 g)||40-70|
|Egg (50 g); all vitamin D is in the yolk||40|
|Cod, haddock, pollock (3 oz, 85 g)||20-40|
|Pork, veal (3 oz, 85 g)||20-50|
|Beef liver (3 oz, 85 g)||30-40|
|Fat: chicken, turkey (1 tbsp, 13 g)||25|
|Beef, duck, lamb, turkey (3 oz, 85 g)||5-20|
|Cheese (2 oz, 57 g)||10-15|
|Lard (1 tbsp, 13 g)||13|
|Butter (1 tbsp, 15 g)||10|
|Chicken (3 oz, 85 g)||5|
|Tofu (90 g)||40|
|Mushrooms, shiitake (100 g)||30|
|Mushrooms, white (100 g)||8|
|Mushrooms, portabella, exposed to UV light (100 g)||525|
|Fortified beverages (1 cup, 237 mL)||80-325|
|Milk, plain or chocolate, soymilk (1 cup, 237 mL)||100-130|
|Formulated bars (80 g)||60-120|
|Cereals ready-to-eat (30 g dry = 1 cup prepared)||30-100|
|Yogurt (6 oz, 170 g)||80-90|
|Margarine (1 tbsp, 15 g)||60|
|Cheese, American, pasteurized (2 oz, 57 g)||60|
References: USDA.gov 
Vitamin D Absorption
Vitamin D is absorbed in the small intestine. Absorption can occur only in the presence of fats from the food, and bile acids.
Blood Tests, Normal Blood Levels Range
The most commonly measured form of vitamin D in the blood is calcidiol (25OHD), which reflects the recent production of the vitamin in your body and the vitamin intake, but not the body vitamin stores . Calcitriol (1-25OHD) levels decrease only in severe deficiency so they are not a good indicator of the body vitamin D status .
Normal blood levels of vitamin D (calcidiol, 25 OHD) are 50-125 nmol/L (20-50 ng/mL).
Abnormal levels :
- Levels below 30 nmol/L are associated with rickets in infants and osteomalacia in adults.
- Levels 30-50 nmol/L are considered inadequate for bone and general health.
- Levels above 125 nmol/L can cause side effects.
Vitamin D Deficiency: Causes, Symptoms
- Low production of vitamin D in the skin, which may be due to a low exposure to sunlight, skin completely covered with clothes, dark skin color, using sunscreen (a sun-protecting factor 8 reduces vitamin D production by 95%), living at altitudes greater than 42°, old age
- Low vitamin D intake combined with a low exposure to sunlight in exclusively breastfed infants  and strict vegetarians
- Fat malabsorption in celiac disease, Crohn’s disease, liver cirrhosis, obstruction of the bile duct by gallstones, chronic pancreatitis, cystic fibrosis, gastric bypass (bariatric surgery) , short bowel syndrome (after surgical removal of a large part of the small intestine) , small intestinal bacterial overgrowth (SIBO) 
- Obesity–vitamin D is diluted in body fat
- Chronic kidney disorders resulting in impaired synthesis of the active form of vitamin D (calcitriol)
- Magnesium deficiency 
- Interactions with medications (corticosteroids, orlistat, cholestiramine, phenytoin, phenobarbital)
- Reference: 
Vitamin D deficiency can cause hypocalcemia with numbness and tingling in the fingers, toes and around the mouth (paresthesia), lightheadedness, excessive bleeding, leg cramps or muscle twitching, constipation, seizures or abnormal heart rhythm (arrhythmia). Chronic hypocalcemia can cause dry and itchy skin.
Vitamin D deficiency results in poor mineralization of bones causing rickets in children, and osteomalacia (soft bones) and osteoporosis (when calcium is also deficient) in adults. Symptoms include deformed, fragile bones, teeth defects, muscle pain and weakness and bone pain.
Picture 1. Rahitis: X-Ray: deformed leg bones in a child
Diagnosis. Vitamin D deficiency is estimated from the level of calcidiol (25OHD) in the blood. Calcitriol (1-25OHD) levels are lowered only in severe cases. Treatment is by vitamin D supplements.
Vitamin D Supplements
Without prescription (over-the-counter):
- Vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) in usual doses (400 IU) are considered equally effective, but in large doses, vitamin D3 is more effective .
- Vitamin D is included in some multivitamin and calcium supplements and in prenatal vitamins.
- Available forms: tablets, chewables, capsules, liquid (drops), powder, sublingual tablets, cream 
- Intravenous injection of calcitriol–the active form of vitamin D–for example, to prevent hypocalcemia in individuals undergoing hemodialysis 
- Intramuscular injection of cholecalciferol (vitamin D3) in megadoses, for example 600,000 IU after bariatric surgery for weigh loss (biliopancreatic diversion)
Possible Vitamin D Benefits
Vitamin D is EFFECTIVE in [2,19]:
- Treatment of vitamin D deficiency, osteomalacia, rickets
- Correction of low blood phosphate levels in familial hypophosphatemia and Fanconi syndrome
- Correction of low blood calcium levels due to low parathyroid hormone (PTH) levels (hypoparathyroidism)
- Reduction of bone loss during treatment with corticosteroids
Vitamin D is POSSIBLY EFFECTIVE in:
- Prevention of hip fractures due to osteoporosis (800 IU in combination with calcium supplements) [7,19]
- Treatment of renal osteodystrophy – a bone disorder caused by kidney failure 
Vitamin D is POSSIBLY INEFFECTIVE in prevention of breast cancer, high blood pressure, improving muscle strength in older adults, preventing bone loss after kidney transplantation .
There is INSUFFICIENT EVIDENCE about vitamin D effectiveness in prevention or treatment of asthma, bronchitis, cancer (breast, colon), chronic obstructive pulmonary disease, depression, diabetes type 1 or 2, fibromyalgia, flu, gum disease, high blood pressure, HIV/AIDS, inflammatory bowel disease (Crohn’s disease) , chronic kidney disease, low birth weight in infants, metabolic syndrome, mood disorders, multiple sclerosis, muscle weakness, muscle pain caused by statins, myelodysplastic syndrome, osteoarthritis, premenstrual syndrome (PMS), proximal myopathy or warts, rheumatoid arthritis, seasonal affective disorder (SAD), stroke, tooth loss in old people or in promoting immunity, vitiligo, weight gain or loss [2,19].
Vitamin D is POSSIBLY INEFFECTIVE in prevention or treatment of eczema, heart disease or high cholesterol .
Vitamin D Supplements Safety: Side Effects, Toxicity
Institute Of Medicine in the US has set the Tolerable Upper Intake Level (UL)–the amount of oral vitamin D supplements that should not be toxic–at 100 mcg (4,000 IU) per day for adults, but even doses up to 250 mcg (10,000 IU)/day for up to 5 months are not known to cause any toxicity [7,8]. According to Mayo Clinic, intramuscular injections of vitamin D in doses up to 300,000 IU 3 times a year are probably safe .
Vitamin D supplements may increase the risk of high blood pressure during pregnancy (preeclampsia) .
Vitamin D in doses greater than Recommended Dietary Allowance (15 mcg or 600 IU/day) is a pregnancy category C drug, which means harmful effects in fetuses have not been observed so far but cannot be excluded because insufficient studies have been done . Intramuscular injections in doses up to 60,000 IU monthly for 3 months are probably safe . If you intend to use vitamin D supplements during pregnancy or breastfeeding, speak with your doctor.
Allergic reactions to vitamin D are possible .
Long-term side effects (complications) of vitamin D in high doses can include kidney stones, bone loss, accumulation of calcium in the arteries (arteriosclerosis), heart, kidneys and other organs and increase the risk of urinary tract infections, respiratory infections [1,18,22].
Overdose (Hypervitaminosis D)
Large oral doses of vitamin D–over 10,000 IU, but probably only over 50,000 IU for several months–may cause hypercalcemia with weakness, fatigue, sleepiness, headache, dry mouth, metallic taste, excessive thirst, loss of appetite, nausea, vomiting, abdominal cramps, constipation, diarrhea, excessive urination and weight loss [7,20,21]. High amounts of vitamin D from foods, or sun exposure do not cause hypervitaminosis D .
Who may need to use vitamin D supplements with caution?
In individuals with tuberculosis, sarcoidosis, primary hyperparathyroidism, histoplasmosis and lymphoma, even usual doses of vitamin D supplements increase the risk of hypercalcemia [1,22].
Vitamin D Supplements Interactions With Drugs
- Drugs that can decrease vitamin D (25OHD) blood levels: phenytoin, fosphenytoin, phenobarbital, carbamazepine, rifampin, steroids, chemotherapeutics and antiretrovirals (for HIV/AIDS)
- Drugs that can affect vitamin D absorption when taken together with vitamin D
- Vitamin D increases the absorption of aluminum from aluminum antacids, possibly resulting in excessive aluminum levels in the body, especially in people with kidney disease.
- When taken together, vitamin D may decrease the effectiveness of atorvastatin, clarithromycin, cyclosporine, diltiazem, lovastatin, estrogens, indinavir, triazolam, verapamil, or increase side effects of calcipotriene, digoxin.
- Vitamin D taken along with diuretics (chlorothiazide, hydrochlorothiazide, indapamide, metolazone, chlorthalidone) may cause hypercalcemia.
- Vitamin D can raise the level of magnesium in people who have low magnesium and low vitamin D levels.
- References: [8,23]
- Vitamin A - Retinol and retinal
- Vitamin B1 - Thiamine
- Vitamin B2 - Riboflavin
- Vitamin B3 - Niacin
- Vitamin B5 - Pantothenic acid
- Vitamin B6 - Pyridoxine
- Vitamin B7 - Biotin
- Vitamin B9 - Folic acid
- Vitamin B12 - Cobalamin
- Vitamin C - Ascorbic acid
- Vitamin D - Ergocalciferol and cholecalciferol
- Vitamin E - Tocopherol
- Vitamin K - Phylloquinone
- Hydrogenated starch hydrolysates (HSH)
- Fructo-oligosaccharides (FOS)
- Galacto-oligosaccharides (GOS)
- Human milk oligosaccharides (HMO)
- Isomalto-oligosaccharides (IMO)
- Mannan oligosaccharides (MOS)
- Raffinose, stachyose, verbascose
- SOLUBLE FIBER:
- Acacia (arabic) gum
- Beta mannan
- Carageenan gum
- Carob or locust bean gum
- Fenugreek gum
- Gellan gum
- Glucomannan or konjac gum
- Guar gum
- Karaya gum
- Psyllium husk mucilage
- Resistant starches
- Tara gum
- Tragacanth gum
- Xanthan gum
- INSOLUBLE FIBER:
- Chitin and chitosan
- Aspartic acid
- Glutamic acid
- FATTY ACIDS
- Alpha-linolenic acid (ALA)
- Eicosapentaenoic (EPA) and Docosahexaenoic acid (DHA)
- Arachidonic acid (AA)
- Linoleic acid
- Conjugated linoleic acid (CLA)
- Short-chain fatty acids (SCFAs)
- Medium-chain fatty acids (MCFAs)
- Long-chain fatty acids (LCFAs)
- Very long-chain fatty acids (VLCFAs)
- Flavanols: Proanthocyanidins
- Flavanones: Hesperidin
- Flavonols: Quercetin
- Flavones: Diosmin, Luteolin
- Isoflavones: daidzein, genistein
- Caffeic acid
- Chlorogenic acid
- Tannic acid
- Alcohol chemical and physical properties
- Alcoholic beverages types (beer, wine, spirits)
- Denatured alcohol
- Alcohol absorption, metabolism, elimination
- Alcohol and body temperature
- Alcohol and the skin
- Alcohol, appetite and digestion
- Neurological effects of alcohol
- Alcohol, hormones and neurotransmitters
- Alcohol and pain
- Alcohol, blood pressure, heart disease and stroke
- Women, pregnancy, children and alcohol
- Alcohol tolerance
- Alcohol, blood glucose and diabetes
- Alcohol intolerance, allergy and headache
- Alcohol and psychological disorders
- Alcohol and vitamin, mineral and protein deficiency
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- Alcoholic liver disease
- Long-term effects of excessive alcohol drinking
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