Depression, Diabetes, Age related illnesses, General | October 5, 2014 | Author: The Super Pharmacist
Vitamin D is a term referring to a type of steroid (derived from cholesterol) molecule found in the body and in food associated with a variety of biological mechanisms involved in maintaining life and health. There is more than one subtype of Vitamin D, but cholecalciferol, also known as Vitamin D3, tends to be most relevant to human physiology. Cholecalciferol is involved in the regulation of growth and development, cell functions, natural immunity and mineral absorption.
Deficiency in Vitamin D3 is linked to many diseases and conditions. Although human skin cells can synthesise the vitamin in response to sunlight exposure, some researchers conclude that a chronic lack of sunlight, experienced by many large regions of the Earth for extensive parts of the year, are responsible for the prevalence of many illnesses. Therefore, it is hypothesised that increased vitamin D intake, through diet or supplements, may reduce the risks of these disorders and conditions.
Vitamin D is popularly associated with benefits to many areas of health and wellbeing, several of which are discussed below.
Bones are made up of specific matrices of the element calcium. Therefore, calcium is an important mineral or inorganic component of an individual’s diet. Vitamin D plays an essential role in absorbing calcium from the gut into the rest of the body, so that bone cells can take it up and continue to develop or maintain bone integrity. In addition, vitamin D may play a role in muscle cell growth and development, which also contributes to skeletal health.
Rickets. Vitamin D deficiency can cause a disease in childhood, rickets, in which bones do not form properly, and may take on a 'bowed' appearance.
Children in countries at latitudes allowing for relatively high and consistent sunlight exposure may still develop rickets due to vitamin D-deficient diets.
Osteomalacia is the adult form of rickets, which may cause spinal abnormalities and chronic musculoskeletal pain.
Osteoporosis. People with osteoporosis, a condition in which bone density decreases, and is strongly associated with post-menopausal women, may also benefit from maintaining optimal vitamin D levels through diet or supplements.
It can be difficult to separate the effects of vitamin D on bone health from those of calcium, as both are so intrinsically linked in bone formation. Many studies have found moderate benefits of vitamin D on bone health and density.
Optimal Vitamin D intake is often linked to cardiovascular health, as the vitamin contributes to the health of cells that make up the linings of artery walls. These cells are often at particular risk of damage in diabetic patients, which increases the risk of cardiovascular disorders in this population.
A 12-week trial comparing vascular function in 50 diabetic patients receiving 5000 IU of vitamin D supplements daily with 50 receiving a placebo daily found no effect of supplementation on this or other biological markers of cardiovascular damage. A European study including 1006 adolescents demonstrated an association between low vitamin D levels and reduced cardiovascular fitness. In addition, obesity or high body fat is associated with vitamin D deficiency. (It appears from this study that reduced fitness and increased body fat are causative factors of reduced vitamin D, not the other way around.) A recent analysis of 9 trials (approximately 48,000 subjects) found no effect of vitamin D supplementation on heart attack or heart disease. Similar analysis of 8 trials (over 46,000 subjects) found no effect of this on the risk of stroke.
Vitamin D has been found to play a role in the control of the immune system and its cells. It is often linked to the prevention or treatment of autoimmune disorders.
Deficiencies in the vitamin, or abnormalities in its receptor on immune cells, may play a role in disorders in which inflammation is a factor(also controlled by the immune system), such as diabetes, inflammatory bowel disease, and rheumatoid arthritis.
In a study comparing patients with inflammatory bowel disease and healthy control subjects, reduced vitamin D was correlated with increased intestinal inflammation. A similar study comparing 181 people with rheumatoid arthritis with 186 controls showed that vitamin D levels were significantly lower in the arthritis patients. Disease activity (i.e. incidences of pain or other symptoms) was not associated with vitamin D deficiency, however. A study of vitamin D-deficient diabetics randomised 118 patients to either 50000 IU vitamin D per week, 1000mg calcium a day, a combination of the two or placebo, for 8 weeks.
Inflammatory biological markers (interleukin-6 and TNF-alpha) were significantly reduced for the calcium, vitamin D and combination groups compared to placebo. Therefore, supplementation in some immune system disorders may be beneficial, but more research into the efficacy of this may be necessary.
Neurological studies have found that the vitamin D receptor is found in many areas of the brain involved in cognition. Defects in the vitamin D receptor are also associated with Alzheimer's disease and Parkinson's disease.
An analysis of 7 trials including just under 7,700 subjects indicated a significant association between mild cognitive impairment (a condition in which cognitive deficit is greater than the normal age-related changes but not severe enough to fulfil the criteria of dementia) and reduced vitamin D intake. Another review of 4 studies of Alzheimer's disease indicated that patients had reduced vitamin D concentrations in comparison to healthy controls. This indicates the need for placebo-controlled trials of the effects of supplementation on conditions in which cognitive faculties are affected.
Vitamin D deficiency may impact on both the mother and foetus in the course of pregnancy. A review of 31 studies indicated its association with a higher risk of pre-eclampsia, low birth weight and diabetes during pregnancy.
Advancing age is associated with the decreased capacity of skin cells to produce a precursor of vitamin D, thus reducing the availability of cholecalciferol from skin. Therefore, supplementation is often recommended to combat the effects of potential bone and muscle loss, which may increase the risk of death or disability in the elderly. A review of 38 trials involving approximately 81,000 subjects on the effects of vitamin D supplementation on mortality was inconclusive.
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