Vitamin D — is not actually a vitamin because we can synthesize it in adequate amounts with sufficient sunlight exposure. Vitamin D can be considered a hormone.
- Purpose?
- Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of important chemicals such as calcium, magnesium, and phosphate. Calcium is essential for the development, growth, and maintenance of bone. Magnesium helps keep blood pressure normal, bones strong, and the heart rhythm steady. Phosphate is necessary for the formation of bone and teeth. Phosphate is also used as a building block for several important substances, including those used by the cell for energy, cell membranes, and DNA (deoxyribonucleic acid). Bone contains about 85% of the body’s phosphate.
- Why supplement?
- For many people, indoor lifestyles and outdoor use of sunscreen limits sun exposure. Vitamin D can be increased through increased UVB sun exposure, fortified foods or supplements.
- Severe deficiency impacts bone health and may cause rickets.
- 2018 research linked low vitamin D blood levels to higher risk of diseases ranging from diabetes to breast cancer. See this chart for significant impact in disease reduction.
- Surprisingly, the darker the skin, the greater the probability of a vitamin D deficiency, perhaps because melatonin blocks sunlight. Even in southern climates, 55% of African Americans and 22% of Caucasians are deficient. A light skinned person, wearing a bathing suit and no sunscreen, will make about 15,000 IU of vitamin D in 15-20 minutes in July at midday. Darker-skinned individuals can do the same, but it will take twice as long.
- Dosage?
- Leading Vitamin D scientists recommend keeping Vitamin D serum levels within 40-60ng/ml and not to exceed 125 ng/ml which has been linked to adverse side effects, such as nausea, constipation, weight loss, heart rhythm problems and kidney damage.
- Medical institutes differ on vitamin D dosage and provide dosage guidance assuming no sun exposure. In practice, daily dosage should vary with the weather and sun exposure. When wearing minimal clothing, an average person can produce adequate amounts from 10 to 15 minutes in the sun, three times a week.
- According to the National Institutes of Health, the current recommended average daily amount is 400 IU for children up to 1 year; 600 IU for ages 1 to 70 years (less for pregnant or breastfeeding women) and 800 IU for persons over 70,
- According to the latest Institute of Medicine (IOM) report, 2010, indicates 10,000 IU/day is considered the NOAEL (no observed adverse effect level). 4000 IU/day can be considered a safe upper intake level for adults aged 19 and older.
- From Grassroots Health, a non-profit organization of leading Vitamin D scientists, an average adult body needs at least 4000 IU/day in order to maintain a healthy concentration of 25(OH)D in the blood. Because most of us don’t get enough sun exposure, the little vitamin D we get that way, plus food and fortified food sources, totals no more than about 2000 IU/day. Thus in order to meet the body’s need for about 4000 IU/day, most adults should take supplements providing 1000-3000 IU daily.
- A 2015 study in the American Journal of Medicine indicated
- Vitamin D intakes and serum 25(OH)D must be very high—perhaps 200-400 ng/mL—to cause the classic toxicity of marked hypercalcemia and kidney and liver damage.
- Emerging observational data suggest that adverse outcomes may occur at much lower levels, such as in the 50-75 ng/mL range. These suspected adverse outcomes appear to include increases in all-cause mortality and increases in the rate of heart disease and some cancers. Limited evidence suggests that African Americans may be more susceptible to these adverse effects.
- There is little concern about vitamin D excess at doses between 400 and 1000 IU per day. Concerns have been raised about supplementation in the range of 10,000-50,000 IU per day, which may be excessive.
- Clinical Trials
- Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital in Boston led several trials of over 20,000 adults. 2022 VITAL trial results showed that vitamin D was no more effective than placebo in preventing or reducing cancer, bone fractures, diabetes, heart attacks, chronic kidney disease, atrial fibrillation and cardiovascular death.
- Potential adverse drug interactions?
- See Drugs.com for Vitamin D3 interactions. There are 161 of them with 7 major ones.
- Data sources