Vitamin D is critical in combination with calcium for bone health. Technically, vitamin D is not a vitamin at all, but a hormone. The body actually can manufacture its own vitamin D, unlike other essential vitamins such as C, and A. Vitamin D is actually a set of compounds (hormones) used by the body that can either be obtained by food or the body can synthesize it by exposing the skin to sunlight. This means that we must either ingest vitamin D through our diets or spend some time in the sun.
Vitamin D Insufficiency
Low levels of vitamin D can lead to a variety of health problems. The most well-known problem is osteoporosis and osteomalacia, which is basically a weakening of bones and bony structures. Osteoporosis is the reason why the elderly experience bone breakage when falling. Without adequate calcium and vitamin D, bones can become brittle and weak, and therefore prone to breakage. In young children, lack of vitamin D can lead to skeletal problems
Other more recent studies have shown that low levels of vitamin D can lead to susceptibility to many diseases including high blood pressure problems, Parkinson's disease, seasonal affective disorder (SAD), different types of cancer, and coronary disease, among others.
Sources of Vitamin D
The body can actually synthesize enough vitamin D through exposure of the skin to sunlight (without sunscreen). Vitamin D is often referred to as the sunshine vitamin. About 20 minutes of exposure is enough to produce the daily requirement. However, for people that live in northern climates or those that do not go outside very often, vitamin D levels can be low. These people need to supplement their diets with vitamin D rich foods. Milk is fortified with vitamin D and is a great source for this, although there is not enough vitamin D in milk to fulfill the daily requirement of a minimum of 400 IU. For those that are lactose intolerant, oily fish such as salmon, tuna, and catfish contain vitamin D. Egg yolks also contain a small amount of vitamin D. Since vitamin D is not present in many foods, manufacturers have fortified products with vitamin D. Along with milk, many cereals are fortified with vitamin D, as well as orange juice. Supplements in the form of fish oil capsules or krill can be taken as well.
How Much Vitamin D Is Needed?
The Institute of Medicine of the National Academy of Sciences has established a Recommended Daily Allowance of vitamin D to be at least 400 international units (IU) per day for most adults and 600 IU for people over the age of 60. This can be obtained through a combination of fortified foods and supplements.
While vitamin D toxicity is rare, it can happen. More than 2,000 IU per day (50 mcg) can result in hypercalcemia (too much calcium in the blood), cognitive problems, kidney stones, and high blood pressure, although recent studies have actually shown that the toxicity level may actually be much higher at 10,000 IU per day.
More and more research is being done that shows vitamin D plays an even more important role in whole-body health than anyone realized. This is an exciting field which is sure to reveal even more how important vitamin D is in the human body.
