VITAMIN D: “The Sun Vitamin”
Nicholas H.E. Mezitis MD and Despina Komninou MD, PhD, CNS
Did you know that vitamin D, as a hormone, has an important role in metabolic harmony?
Recent studies have shown that vitamin D in its active form is vital for bone health, since it ensures dietary calcium absorption, and helps prevent heart disease, cancer (breast, prostate, lung and colon ), as well as many other illnesses such as diabetes mellitus, rheumatoid arthritis, psoriasis, multiple sclerosis and tuberculosis.
Vitamin D regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestinal tract and by limiting the excretion of calcium by the kidneys. It influences the cells involved in remodeling bone (osteoclasts and osteoblasts) and it inhibits the secretion of parathyroid hormone, which signals calcium release from bone matrix. Importantly, it has a role to stimulate the immune system, promoting phagocytosis and anti-tumor activity among other functions.
The body produces vitamin D when bare skin is exposed to the sun, hence the term �sun vitamin�. Exposure to sunlight for at least 15 minutes two to three times a week produces adequate quantities of this vitamin for the body�s needs. It is estimated that the body can produce more than 20000 IU (international units) of vitamin D with just 20 minutes of sun exposure.. Once adequate amounts of vitamin D have been formed the body, excess amounts formed are rapidly degraded to protect from overload, in the event of prolonged exposure to the sun. However, conditions such as cloudy skies, northern climates, and atmospheric pollution, limit solar ultraviolet radiation exposure and restrict our ability to replete vitamin D stores.
Vitamin D can also be obtained from dietary sources. It is lipid-soluble and is therefore stored in fat. That is why we find it in fatty fish (like salmon and tuna), eggs, cod-liver oil and fortified milk. In our daily diet, 3 servings of milk (about 250 ml) provide us with approximately 900 mg of calcium and 300 IU of vitamin D.
The recommended daily intake (RDI) of vitamin D is 200 IU for infants, youths and adults up to the age of 50 years. The requirement increases to 400 IU for adults ages 51 to 70 and to 600 IU for people older than 70 years. The RDI and the normal reference values for vitamin D in the blood, are based on levels reported to the prevent rickets and osteomalacia, the two main diseases attributed to lack of this vitamin. Rickets is a childhood disease characterized by poor growth and bone weakness, while osteomalacia is the clinical expression of vitamin D deficiency in adults and is characterized by demineralized bones, fractures, bone pain and generalized weakness. Osteoporosis represents abnormal weakening of bone structure with demineralization of the skeleton, and may also be associated with low levels of vitamin D.
Recent studies confirm that optimal vitamin D status is achieved when the 25- OH vitamin D level in the blood is more than 30 ng/ml. Levels between 10-30 ng / ml represent vitamin D insufficiency (hypovitaminosis D) which can either be moderate (21-30 ng/ml) or severe (10-20 ng/ml). Vitamin D levels below 10 ng/ml are considered vitamin D deficiency and have serious consequences. We now know that long before the full clinical presentation of painful osteomalacia, hypovitaminosis D may cause non-specific symptoms such as persistent musculoskeletal pain regardless of age, gender and ethnic origin.
It is worth noting, that a significant proportion of the population has insufficient levels of vitamin D, mainly due to lack of sun exposure, especially during the winter months, which is not compensated by the usual diet. Indeed, today many of us work in buildings with sealed and tinted glass windows and drive everywhere with very few opportunities to walk in the sunlight. During our limited sun exposure opportunities we frequently use a sun screen lotion further obstructing the beneficial effects of sunlight. In areas above 40˚ latitude (e.g. New York, Northern California), sunshine adequate for vitamin D synthesis in the skin is restricted to the months from May through September. Therefore, a large proportion of the population in the United States is at increased risk for vitamin D deficiency
The prevention of hypovitaminosis D has important public health implications. Millions of health care dollars are spent in dealing with the illnesses and complications associated with this problem and additional funds are lost due to curtailed productivity on a societal level. Since sun exposure has its limitations, the diet is our primary source for this vitamin to ensure an intake of at least 1000 IU daily.
The proper diet must be rich in fatty fish such as salmon, mackerel and sardines, mushrooms (Shitake, sun dried, provide 1600 international units per 100 grams), free-range eggs and fortified milk products. Supplementation of vitamin D and calcium is advisable, especially for children and the elderly. Finally, regular, weight-bearing exercise ensures that calcium absorbed through the activity of vitamin D is used to mineralize the skeleton. Similar to a musical composition, health is ensured through harmony in diet and exercise.
More on the maintenance of metabolic harmony will be discussed in our next article *.
* This article is part of medical communication produced by the MEZITIS EDUCATION AND RESEARCH INSTITUTE for the print media, television and radio programs(Cosmos FM “����� ��� ���” every Saturday at 12:30 pm on 91.5 FM and the internet, live streaming, at gaepis.org) focusing on topics in general health, metabolism and nutrition.
Tags: adequate quantities, atmospheric pollution, bone matrix, calcium absorption, calcium release, cancer breast, cod liver oil, dietary calcium, dietary sources, excess amounts, fatty fish, heart disease cancer, md phd, northern climates, osteoblasts, osteoclasts, phosphorus levels, rheumatoid arthritis, solar ultraviolet radiation, ultraviolet radiation exposure