Vitamin D is essential for strong bones, because it helps the body use calcium from the diet. Traditionally, vitamin D deficiency has been associated with rickets, a disease in which the bone tissue doesn't properly mineralize, leading to soft bones and skeletal deformities. But increasingly, research is revealing the importance of vitamin D in protecting against a host of health problems.
The amount of vitamin D you need each day depends on your age. The recommended amounts, in international units (IU), are
Birth to 12 months: 400 IU
Children 1-13 years: 600 IU
Teens 14-18 years: 600 IU
Adults 19-70 years: 600 IU
Adults 71 years and older: 800 IU
Pregnant and breastfeeding women: 600 IU
People at high risk of vitamin D deficiency may need more.
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects. In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol).
The major natural source of the vitamin is synthesis of cholecalciferol in the lower layers of epidermis skin through a chemical reaction that is dependent on sun exposure (specifically UVB radiation). Cholecalciferol and ergocalciferol can be ingested from the diet and from supplements. Only a few foods, such as the flesh of fatty fish, contain significant amounts of vitamin D, and fish does not contain enough vitamin D to achieve optimal Vitamin D status without sunlight or supplements. Dietary recommendations typically assume that all of a person's vitamin D is taken by mouth, as sun exposure in the population is variable and recommendations about the amount of sun exposure that is safe are uncertain in view of the skin cancer risk.
Vitamin D from the diet, or from skin synthesis, is biologically inactive. A protein enzyme must hydroxylate it to convert it to the active form. This is done in the liver and in the kidneys. As vitamin D can be synthesized in adequate amounts by most mammals exposed to sufficient sunlight, it is not an essential dietary factor, and so not technically a vitamin. Instead it could be considered a hormone, with activation of the vitamin D pro-hormone resulting in the active form, calcitriol, which then produces effects via a nuclear receptor in multiple locations.
Symptoms and Health Risks of Vitamin D Deficiency
Symptoms of bone pain and muscle weakness can mean you have a vitamin D deficiency. However, for many people, the symptoms are subtle. Yet, even without symptoms, too little vitamin D can pose health risks. 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 type1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosis.
Causes of Vitamin D Deficiency
Vitamin D deficiency can occur for a number of reasons:
You don't consume the recommended levels of the vitamin over time. This is likely if you follow a strict vegan diet, because most of the natural sources are animal-based, including fish and fish oils, egg yolks, fortified milk, and beef liver.
Your exposure to sunlight is limited. Because the body makes vitamin D when your skin is exposed to sunlight, you may be at risk of deficiency if you are homebound, live in northern latitudes, wear long robes or head coverings for religious reasons, or have an occupation that prevents sun exposure.
You have dark skin. The pigment melanin reduces the skin's ability to make vitamin D in response to sunlight exposure. Some studies show that older adults with darker skin are at high risk of vitamin D deficiency.
Your kidneys cannot convert vitamin D to its active form. As people age, their kidneys are less able to convert vitamin D to its active form, thus increasing their risk of vitamin D deficiency.
Your digestive tract cannot adequately absorb vitamin D. Certain medical problems, including Crohn's disease, cystic fibrosis, and celiac disease, can affect your intestine's ability to absorb vitamin D from the food you eat.
You are obese. Vitamin D is extracted from the blood by fat cells, altering its release into the circulation. People with a body mass index of 30 or greater often have low blood levels of vitamin D.
Who is at risk of vitamin D deficiency?
Some people are at higher risk of vitamin D deficiency:
Talk with your health care provider if you are at risk for vitamin D deficiency. There is a blood test which can measure how much vitamin D is in your body.
Can too much vitamin D be harmful?
Getting too much vitamin D (known as vitamin D toxicity) can be harmful. Signs of toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. Excess vitamin D can also damage the kidneys. Too much vitamin D also raises the level of calcium in your blood. High levels of blood calcium (hypercalcemia) can cause confusion, disorientation, and problems with heart rhythm.
Most cases of vitamin D toxicity happen when someone overuses vitamin D supplements. Excessive sun exposure doesn't cause vitamin D poisoning because the body limits the amount of this vitamin it produces.
By Mehdiyeva B.