Vitamin D is one of the vitamins essential for good health and necessary for the absorption of calcium to build strong bones and teeth. It is often called the "sunshine" vitamin because the body makes vitamin D when the skin is directly exposed to the sun.
Gilad Shalit, the Israeli soldier, who was released after more than five years in captivity, was found to be deficient in vitamin D. This is an extreme case of vitamin D deficiency caused by years without access to sunlight. Surprisingly, many of us in sunny Israel do not have the recommended level of vitamin D.
In adults, lack of vitamin D can lead to malformed bones and osteoporosis. In children, vitamin D deficiency once caused rickets, a bone disease rarely seen now that vitamin D drops are given to infants. Newer studies suggest that vitamin D may also protect against heart disease and cancer.
Who's at Risk for "D" Deficiency?
Though vitamin D deficiency was thought to be rare in sunny countries, studies show that vitamin D deficiency is unexpectedly high in Israel among the elderly, young mothers and their newborn infants.
Up to 35% of elderly people in Israel are vitamin D deficient. This is mainly because the elderly spend more time indoors and are less exposed to sunlight than younger people. Aging decreases the capacity of human skin to produce vitamin D, and the elderly cannot absorb the fat-soluble vitamin D from food as well as younger people.
A survey conducted at Rambam Medical Center found that there is a severe shortage of vitamin D in the ultra-Orthodox community due to their modest dress, shielding them from the sun's rays. And young high-tech workers have a vitamin D deficiency due to the many hours spent working in offices during daylight hours.
A Kupat Holim health maintenance organization checked vitamin D levels in teenagers and found an average of only two-thirds of the recommended level.
How do we get vitamin D?
The required level of vitamin D can be obtained by exposure to the sun for 10-15 minutes three times weekly. But because exposure to sunlight is a risk factor for skin cancer, a sunscreen should always be used after a short period in the sun even though it blocks vitamin D production. Food can supply 5-10 percent of total vitamin D requirements. Good sources are oily fish - salmon, sardines, mackerel, cod, tuna - , egg yolks, cod liver oil, beef liver, margarine and cheeses, milk and cereals that have been fortified with vitamin D.
There are usually no symptoms of vitamin D deficiency. Since it is difficult to get enough vitamin D from food alone, some people may need to take a supplement in the form of drops, capsules or sublingual tablets. Though these are available without a prescription, it is important to check with your health care professional before taking vitamin D on your own.
The health benefits of vitamin D
Vitamin D is known to help the body absorb calcium and it plays a role in bone health. Vitamin D also increases muscle strength, lowering the risk of fractures and falls in older adults.
Many studies have indicated that vitamin D may protect against both heart disease and many forms of cancer, including colon cancer. More research is needed to determine how vitamin D works in these disease processes but the evidence so far is positive.
Lack of vitamin D has also been linked with diabetes, depression and autoimmune diseases such as multiple sclerosis (MS), but much more research is needed to determine if and how vitamin D is involved in these diseases.
How much vitamin D do we need?
How much vitamin D a person needs is very individual and depends on age and gender. Other factors, such as pregnancy and health, are also important and some medicines may affect the absorption of vitamin D. In general, people over age 50 need higher amounts of vitamin D than younger people.
For babies, Tipat Halav (well baby) clinics advise on the daily supplement of vitamin D starting after birth and continuing till the baby is weaned. Older children usually get all the vitamin D they need through foods including fortified milks and cereals.
There is a simple blood test available to check the level of vitamin D and your doctor can order it through the health funds. For adults, it is advisable to have this blood test at least once to determine whether you lack the vitamin. Current guidelines indicate that you are getting enough vitamin D to keep your bones healthy when your blood level is at least 20 nanograms per milliliter (ng/mL).
How Much Is Too Much?
Be aware there is an upper limit to how much vitamin D you can safely take. Taking too much can cause symptoms of nausea, vomiting and weakness and raise blood calcium levels that can lead to kidney and tissue damage. The best approach is to check with your health care provider before taking vitamin D supplements.
Remember, vitamin D is one of the essential vitamins for maintaining good health. Adequate levels can be achieved by a short time spent in the sun (only spend minutes before applying sun screen) and from food sources like oily fish, fortified milk and cereals. Supplements should only be taken on medical advice when there is a deficiency, bone disease or other approved indication.
Disclaimer: The information given in this article is for general purposes only and is not a substitute for the care provided by licensed healthcare practitioners. Patients are urged to consult with their healthcare practitioner in all instances.
More on Vitamin D
By Dr Menachem Shapiro
Adverse effects of excess Vitamin D: The first measurable evidence of vitamin D toxicity is elevated levels of calcium in blood and urine found when Vitamin D levels are above 88 ng/mL.
Symptoms of acute Vitamin D poisoning include confusion, excess urination and fluid intake, loss of appetite, vomiting and muscle weakness. Chronic intoxication may cause bone demineralization and bone pain. Many patients, especially the elderly, take vitamin and mineral supplements that contain Vitamin D. If Vitamin D supplements are prescribed in addition, the patient may be at risk for Vitamin D poisoning.
Relationship of Vitamin D and Calcium: Vitamin D increases the absorption of calcium. If there is inadequate calcium intake, the effectiveness of Vitamin D is diminished. In general, the daily requirement of calcium for adults, aged 19 through 70, is 1000 mg. However, women, aged 51 through 70, as well as all adults above 71 years of age should increase their daily intake to 1200 mg.
Testing for Vitamin D Deficiency and Therapy: The approach to testing and treatment for Vitamin D deficiency is based upon an initial assessment of a patient’s risk for having a low Vitamin D level. High risk patients include, among others, the homebound or institutionalized elderly, those with limited sun exposure, the obese, the dark skinned, and those with osteoporosis and diseases of the gastrointestinal tract. Those taking antiepileptic agents are also at risk.
Measurement of vitamin D in the above patients is especially important. The replacement dose of vitamin D, when needed, should be individualized, based on the patient and his condition. The daily required maintenance dose will then be determined by the physician with periodic measurement of vitamin D levels.
Prof. Menachem S. Shapiro, (retired) Sackler School of Medicine, Tel Aviv, Medical consultant in the KAMAR unit - Kupat Cholim Clalit. Former Head of the Endocrine Unit at Meir Hospital, Sapir Medical Center, Kfar Saba.