Vitamins are organic substances required by our body in very small amounts for normal metabolism, growth and maintenance. They are not a source of energy. The importance of vitamins was first recognized by the effect of its absence.
Vitamin D which promotes bone growth has come to be regarded as a hormone rather than a vitamin because of the way it works. It is a steroid vitamin, a group of fat- soluble pro hormones, which encourages the absorption and metabolism of calcium and phosphorous. Vitamin D appears to have effects on immune function.
Several articles have concluded that woman’s risk for breast cancer. There is caution against excess amounts of vitamin D, saying that higher serum levels of vitamin D may have negative effects for women with breast cancer. Colorectal cancer risk reduction with adequate vitamin D status is well documented. Protection has also been observed for cancer at all sites, skin, prostate, and breast.
Sources of Vitamin D
Vitamin D for humans is obtained from sun exposure, food and supplements. The major source is the body itself. It is manufactured in the skin, and so it is also termed as the ‘sunshine vitamin’. Light skinned adults can obtain the necessary five micrograms of calcitriol by exposing their hand, arms and face to sunlight for 15 minutes twice a week, depending on latitude and season. Sunscreens with sun protection block the ultraviolet rays that produce vitamin D.
Calcitriol is the active form of vitamin D in the body which promotes the absorption of calcium and phosphorus from food in the gut, and re-absorption of calcium in the kidneys, rather than to excrete it in the urine. This increases the flow of calcium in the bloodstream, which is essential for the normal mineralization of bone. If your body cannot produce enough vitamin D because of insufficient sunlight exposure, you will need to obtain it from foods and perhaps supplements. Vitamin D is found in many dietary sources, such as fish, eggs, fortified milk, and cod liver oil. Many cereals are fortified with vitamins and minerals which are not normally found in grains. A food source of vitamin D is fortified milk. Fluid milk is fortified in the US but there is no mandate for other dairy products.
Vitamin D is a fat-soluble vitamin and is absorbed from the intestine like fat. It is sometimes used to monitor individuals with diseases that interfere with fat absorption, such as cystic fibrosis and Crohn’s disease. Patients who have had gastric bypass surgery may not be able to absorb enough Vitamin D.
Vitamin D Deficiency
Vitamin D deficiencies are usually the result of dietary inadequacy, impaired absorption and use, increased requirement, or increased excretion. A vitamin D deficiency can occur when usual intake is lower than recommended levels over time, exposure to sunlight is limited, the kidneys cannot convert it to its active form, or absorption of vitamin D from the digestive tract is inadequate. Vitamin D-deficient diets are associated with milk allergy, lactose intolerance and in case of strict vegetarians.
A diet deficient in vitamin D causes osteomalacia (called rickets when it occurs in children), which is a softening of the bones. Deficiency results in impaired bone mineralization and leads to bone-softening diseases. An estimated 85 per cent of people in the US are vitamin D deficient, and many scientists and researchers consider this an unrecognized global epidemic.
Research is revealing the importance of vitamin D in protecting against a host of health problems. Low blood levels of the vitamin have been associated with the following:
- Increased risk of death from cardiovascular disease
- Cognitive impairment in older adults
- Severe asthma in children
Research suggests that vitamin D could play a role in the prevention and treatment of a number of different conditions, including type 1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosis.
Vitamin D toxicity is a condition where blood serum concentration of vitamin D becomes too high, causing adverse systemic effects. The first sign of vitamin D toxicity is hypercalciuria followed by hypercalcemia. The symptoms that may be present are nausea, vomiting, poor appetite, constipation (possibly alternating with diarrhea) and weakness, to name a few. The immediate symptoms of vitamin D overdose are abdominal cramps, nausea and vomiting. More research needs to be done to determine the amount we should take and what optimal blood levels should be. Also, more is not better!