Vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 and D2.
Vitamin D obtained from sun exposure, foods, and supplements are biologically inert and must undergo two hydroxylations in the body activation. The first hydroxylation, which occurs in the liver, converts vitamin D to 25- hydroxyvitamin D also known as "Calcidiol".
Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization and to prevent hypocalcemic tetany (involuntary contraction of muscles, leading to cramps and spasms). It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts, without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D also helps protect older adults from osteoporosis.
Types:
Several forms (Vitamers) of vitamin D exist. The two major forms are vitamin D2 or ergocalciferol, and vitamin D3 or cholecalciferol. Vitamin D without a subscript refers to either D2 or D3, or both, and is known collectively as calciferol.
Vitamin D2 was chemically characterized in 1931. In 1935, the chemical structure of vitamin D3 was defined and shown to result from the ultraviolet irradiation of 7- dehydrocholesterol. A chemical nomenclature for vitamin D forms was recommended in 1981 but alternative names remain in common use.
Chemically, the various forms of vitamin D are secosteroids, that is steroids in which one of the bonds in the steroid rings is broken. the structural difference between vitamin D2 and vitamin D3 is in the side chain, which contains a double bond, between carbons 22 and 23, and a methyl group on carbon 24 in vitamin D2.
Vitamin D deficiency:
People can develop vitamin D deficiency when usual intakes are lower over time than recommended levels, exposure to sunlight is limited, the kidneys cannot 25(OH)D to its active form or absorption of vitamin D from the digestive tract is inadequate. Diets low in vitamin D are more common in people who have a milk allergy or lactose intolerance and those who consume a non-vegetarian or vegan diet.
In children, vitamin D deficiency is manifested as rickets, a disease characterized by a failure of bone tissue to become properly mineralized, resulting in soft bones and skeletal deformities. In addition to bone deformities and pain, severe rickets can cause failure to thrive, developmental delay, hypocalcemic seizures, tetanic spasm, cardiomyopathy, and dental abnormalities.
The incidence rate of rickets in children younger than 3 years in the decade beginning in 2000 was 24. 1per 100,000. Rickets occurred mainly in black children who were breastfed longer, were born with low birth weight, weighed less, and were shorter than other children. The incidence rate of rickets in infants and children are seen by 2325 pediatricians throughout Canada was 2.9 per 100,000, and almost all patients with rickets had been breastfed.
In adults and adolescents, vitamin D deficiency can lead to osteomalacia, in which existing bone is incompletely or effectively mineralized during the remodeling process, resulting in weak bones. Signs and symptoms of osteomalacia are familiar to those of rickets and include bone deformities and pain, hypocalcemic seizures, tetanic spasms, and dental abnormalities.
Screening for vitamin D status is becoming a more common part of the routine laboratory bloodwork ordered by primary-care physicians, irrespective of any indications for this practice. No studies have examined whether such screening for vitamin D deficiency results in improved health outcomes.
Symptoms:
Being sick it getting infections often:
One of vitamin D most important roles is keeping your immune system strong so you're able to fight off viruses and bacteria that cause illness. It directly interacts with the cells that are responsible for fighting infection. If you often become sick, especially with colds or the flu, low levels of vitamin D may be a contributing factor.
Fatigue and tiredness:
Feeling tired can have many causes, and vitamin D deficiency may be one of them. Unfortunately, it's often overlooked as a potential cause. case studies have shown that very low blood levels of vitamin D can cause fatigue that can have a severe negative effect on the quality of life.
Bone and back pain:
Vitamin D helps maintain bone health in a number of ways. for one, it improves your body's absorption of calcium. Bone pain and lower back pain may be signs of inadequate vitamin D levels in the blood. large observational studies have found a relationship between a deficiency and chronic lower back pain.
Bone Loss:
Vitamin D plays a crucial in calcium absorption and bone metabolism. Many older people who are diagnosed with bone loss believe they need to take more calcium. However, they may be deficient in vitamin D as well. Low bone mineral density is an indication that your bones have lost calcium and other minerals. This places older adults, especially women, at an increased risk for fractures.
Hair loss:
Hair loss is often attributed to stress, which is certainly a common cause. However, when hair loss is severe, it may be the result of disease or nutrient deficiency. Hair loss in women has been linked to low vitamin D levels, though there is very little research on this to date. In particular, research suggests that low vitamin D levels are linked to alopecia areata and may be a risk factor for developing the disease.
Muscle pain:
The causes of muscle pain are often difficult to pinpoint. There is some evidence that vitamin D deficiency may be a potential cause of muscle pain in children and adults. in one study, 71% of people with chronic pain were found to be deficient. The vitamin D receptor is present in nerve cells nociceptors, which sense pain.
Groups at risk of vitamin D inadequacy:
Obtaining sufficient vitamin D from natural food sources alone is difficult. For many people, consuming vitamin- D fortifies foods and exposing themselves to some sunlight are essential for maintaining a healthy vitamin D status.
Breastfeed Infants:
Consumption of human milk alone does not ordinarily enable infants to meet vitamin D requirements, because it provides less than 0.6 to 2.0 mcg/L. The vitamin D content of human milk is related to the mother's vitamin D status, studies suggest that the breastmilk of mothers who take daily supplements containing at least 50 mcg (2,000IU) vitamin D3 have higher levels of the nutrient.
Older Adults:
Older adults are at increased risk of developing vitamin D insufficiency, partly because the skin's ability to synthesize vitamin D decline with age. In addition, older adults are likely to spend more time than younger people indoors and might have an inadequate dietary intake of the vitamin.
People with limited sun exposure:
Homebound individuals, people who wear long robes, dresses, or head coverings for religious reasons, and people with occupations that limit sun exposure are among the groups that are unlikely to obtain adequate amounts of vitamin D from sunlight.
People with dark skin:
Greater amounts of the pigment melanin in the epidermal layer of the skin result in darker skin and reduce the skin's ability to produce vitamin D from sunlight. Black Americans, for example, typically have lower serum25(OH) D levels than white Americans. However, whether these lower levels in persons with dark skin have significant health consequences is not clear.
People with conditions that limit fat absorption:
Vitamin D is fat-soluble, its absorption depends on the Ability of dietary fat. Fat malabsorption is associated with medical conditions that include some forms of liver disease, cystic fibrosis, celiac disease, Crohn's disease, and ulcerative colitis. In addition to having an increased risk of vitamin D deficiency, people with these conditions might not eat certain foods, such as dairy products or eat only small amounts of these foods.
People who are obese or have undergone gastric bypass surgery:
Individuals with a body mass index(BMI) of 30 or more have lower serum 25(OH)D levels than nonobese individuals. Obesity does not affect the skin's capacity to synthesize vitamin D. Obese individuals who have undergone gastric bypass surgery can also become vitamin D deficient. In this procedure, part of the upper small intestine, where vitamin D is absorbed, is bypassed, and vitamin D that is mobilized into the bloodstream from fat stores might not rise 25(OH) D to adequate levels over time.
Other Conditions:
Diabetes:
A systematic review of 2014 concluded that the available studies show no evidence of vitamin D3 supplementation having an effect on glucose homeostasis or diabetes prevention. A review article of 201 reported that while there is increasing evidence that vitamin D deficiency may be a risk factor for diabetes, overall evidence regarding vitamin D levels and diabetes mellitus is contradictory, requiring future studies.
ADHD:
a meta-analysis of observational studies showed that children with ADHD have lower vitamin D levels and that there was a small association between low vitamin D levels at the time of birth and later development of ADHD. Several small randomized controlled trials of vitamin D supplementation indicated improved ADHD symptoms such as impulsivity and hyperactivity.
Depression:
Clinical trials of vitamin D supplementation for depressive symptoms have generally been of low quality and show no overall effect, although subgroup analysis showed supplementation for participants with clinically significant depressive symptoms or depressive disorder had a moderate effect.
Cognition and dementia:
A systematic review of clinical studies found an association between low vitamin D levels with cognitive impairment and a higher risk of developing Alzheimer's disease. However, lower vitamin D concentrations are also associated with poor nutrition and spending less time outdoors. Therefore, alternative explanations for the increase in cognitive impairment exist and hence the direct causal relationship between vitamin D levels and cognition could not be established.
Pregnancy:
Low levels of vitamin D in pregnancy are associated with gestational diabetes, pre-eclampsia, and small infants. Although taking vitamin D supplements during pregnancy raises blood levels of vitamin D in the mother at term, the full extent of benefits for the mother or baby is unclear.
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