Vitamin D is both a nutrient we eat and a hormone our bodies make. It is a fat-soluble vitamin that has been known to help the body absorb and keep calcium and phosphorus, both are needed for building bone. Also, lab studies show that vitamin D can reduce cancer cell growth, help control infections and reduce inflammation. Many of the body’s organs and tissues have receptors for vitamin D, which makes it important for roles beyond bone health, and scientists are actively looking at other possible functions.
Few foods are naturally rich in vitamin D3. The best sources are the flesh of fatty fish and fish liver oils. Smaller amounts are found in egg yolks, cheese, and beef liver. Certain mushrooms contain some vitamin D2; in addition some commercially sold mushrooms contain higher amounts of D2 due to intentionally being exposed to high amounts of ultraviolet light. Many foods and supplements are fortified with vitamin D like dairy products and cereals.
Vitamin D3 can be formed when a chemical reaction occurs in your skin, when a steroid called 7-dehydrocholesterol is broken down by the sun’s UVB light. The amount of the vitamin absorbed can vary widely. The following are conditions that decrease exposure to UVB light and therefore lessen vitamin D absorption:
- Use of sunscreen can reduce vitamin D absorption by more than 90%.
- Wearing full clothing that covers the skin.
- Spending limited time outdoors.
- Darker skin tones due to having higher amounts of the pigment melanin.
- Older ages when there is a decrease in 7-dehydrocholesterol levels and changes in skin, and a population that is likely to spend more time indoors.
Vitamin D deficiency may occur from a lack in the diet, poor absorption, or having a metabolic need for higher amounts. If you are not eating enough vitamin D and don’t receive enough ultraviolet sun exposure over longer periods, a deficiency can happen. People who cannot tolerate or do not eat milk, eggs, and fish, like those with a lactose intolerance or who follow a vegan diet, are at higher risk for deficiency. Other people at high risk of vitamin D deficiency include:
- People with inflammatory bowel disease (ulcerative colitis, Crohn’s disease) or other conditions that disrupt the normal digestion of fat. Vitamin D is a fat-soluble vitamin that depends on the gut’s ability to absorb dietary fat.
- People who are obese tend to have lower blood vitamin D levels. Vitamin D accumulates in excess fat tissues but is not easily available for use by the body when needed. Higher doses of vitamin D supplementation may be needed. Blood levels of vitamin D rise when obese people lose weight.
- People who have undergone gastric bypass surgery, which removes the upper part of the small intestine where vitamin D is absorbed.
Vitamin D may help increase muscle strength by preserving muscle fibers, which helps to prevent falls, a common problem that leads to disability and death in older people. A combined look of multiple studies found that taking 700 to 1,000 IU of vitamin D per day lowered the risk of falls by 19%, but taking 200 to 600 IU per day did not offer protection. However, the VITAL trial following healthy middle-aged men and women did not find that taking 2,000 IU of vitamin D daily compared with a placebo pill reduced the risk of falls.
We Canadians need more Vitamin D then our southern friends especially during the winter months.
Personally I take 5000 IU per day, but Im a 200 pound male who trains a lot of hours a week.
Id recommend 1-2000IU per day minimum through out the winter months.