Vitamin D power from sunshine
Vitamin D is a fat-soluble vitamin that acts as a steroid hormone. In humans, the primary source of vitamin D is UVB-induced (sun light) conversion of 7-dehydrocholesterol to vitamin D in the skin. Vitamin D influences the bones, intestines, immune and cardiovascular systems, pancreas, muscles, brain, and the control of cell cycles.
Cancer:
Vitamin D decreases cell proliferation and increases cell differentiation, stops the growth of new blood vessels, and has significant anti-inflammatory effects. Many studies have suggested a link between low vitamin D levels and an increased risk of cancer, with the strongest evidence for colorectal cancer. In the Health Professionals Follow-up Study (HPFS), subjects with high vitamin D concentrations were half as likely to be diagnosed with colon cancer as those with low concentrations. A definitive conclusion cannot yet be made about the association between vitamin D concentration and cancer risk, but results from many studies are promising. There is some evidence linking higher vitamin D intake to a lower risk for breast cancer. The effect of menopausal status on this association is still unclear
Heart disease:
Several studies are providing evidence that the protective effect of vitamin D on the heart could be via the renin–angiotensin hormone system, through the suppression of inflammation, or directly on the cells of the heart and blood-vessel walls. In the Framingham Heart Study, patients with low vitamin D concentrations (<15 ng/mL) had a 60% higher risk of heart disease than those with higher concentrations. In another study, which followed men and women for 4 years, patients with low vitamin D concentrations (<15 ng/mL) were three times more likely to be diagnosed with hypertension than those with high concentrations (>30 ng/mL).
Hypertension:
The third National Health and Nutrition Examination Survey (NHANES-III), which is representative of the noninstitutionalized US civilian population, showed that systolic blood pressure and pulse pressure were inversely and significantly correlated with 25(OH)D levels among 12,644 participants. Age-associated increase in systolic blood pressure was significantly lower in individuals with vitamin D sufficiency. The prevalence of arterial hypertension was also associated with reduced serum 25(OH)D levels in 4030 participants of the German National Interview and Examination Survey, in 6810 participants of the 1958 British Birth Cohort, and in other study populations. The antihypertensive effects of vitamin D are mediated by renoprotective effects, suppression of the RAAS, by beneficial effects on calcium homeostasis, including the prevention of secondary hyperparathyroidism, and by vasculoprotection.
Obesity:
Low concentrations of circulating vitamin D are common with obesity and may represent a potential mechanism explaining the elevated risk of certain cancers and cardiovascular outcomes. Levels of 25(OH)D are inversely associated with BMI, waist circumference, and body fat but are positively associated with age, lean body mass, and vitamin D intake.
The prevalence of VDD is higher in black versus white children regardless of season predictors of VDD in children include black race, female sex, pre-pubertal status, and winter/spring season. Weight loss is associated with an increase in 25(OH)D levels among postmenopausal overweight or obese women.
Type 2 diabetes:
A trial of nondiabetic patients aged 65 years and older found that those who received 700 IU of vitamin D (plus calcium) had a smaller rise in fasting plasma glucose over 3 years versus those who received placebo. A correlation between vitamin D and the risk diabetes can be ruled in from the results.
Depression:
A Norwegian trial of overweight subjects showed that those receiving a high dose of vitamin D (20,000 or 40,000 IU weekly) had a significant improvement in depressive symptom scale scores after 1 year versus those receiving placebo. The result determines a correlation between vitamin D and the risk of depression.
Cognitive impairment:
In the Invecchiare in Chianti (InCHIANTI) Italian population-based study, low levels of vitamin D were associated with substantial cognitive decline in the elderly population studied during a 6-year period. Low levels of 25(OH)D may be especially harmful to executive functions, whereas memory and other cognitive domains may be relatively preserved.
Parkinson's disease:
Parkinson's disease is a major cause of disability in the elderly population. Unfortunately, risk factors for this disease are relatively unknown. Recently, it has been suggested that chronically inadequate vitamin D intake may play a significant role in the pathogenesis of Parkinson's disease. A cohort study based on the Mini-Finland Health Survey demonstrated that low vitamin D levels may predict the development of Parkinson's disease.
Fractures and falls:
Vitamin D is known to help the body absorb calcium, and it plays a role in bone health. In addition, VDRs are located on the fast-twitch muscle fibers, which are the first to respond in a fall. It is theorized that vitamin D may increase muscle strength, thereby preventing falls. Many studies have shown an association between low vitamin D concentrations and an increased risk of fractures and falls in older adults.
A combined analysis of 12 fracture-prevention trials found that supplementation with about 800 IU of vitamin D per day reduced hip and nonspinal fractures by about 20%, and that supplementation with about 400 IU per day showed no benefit. Researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University have examined the best trials of vitamin D versus placebo for falls. Their conclusion is that “fall risk reduction begins at 700 IU and increases progressively with higher doses.”
Autoimmune diseases:
VDD can contribute to autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes, rheumatoid arthritis, and autoimmune thyroid disease.
A prospective study of white subjects found that those with the highest vitamin D concentrations had a 62% lower risk of developing MS versus those with the lowest concentrations. A Finnish study that followed children from birth noted that those given vitamin D supplements during infancy had a nearly 90% lower risk of developing type 1 diabetes compared with children who did not receive supplements.
Influenza:
VDD in the winter months may be the seasonal stimulus that triggers influenza outbreaks in the winter. In a Japanese randomized, controlled trial, children given a daily vitamin D supplement of 1200 IU had a 40% lower rate of influenza type A compared with those given placebo; there was no significant difference in rates of influenza type B.
Bacterial vaginosis:
An analysis of data from the National Health and Nutrition Examination Survey showed that in pregnant women, VDD was associated with nearly a 3-fold increased risk for Bacterial Vaginosis (BV). In non-pregnant women, VDD modulated the association between smoking and BV.
Pelvic floor disorders:
The frequency of Pelvic floor disorders, including urinary and fecal incontinence, is increasing with age. Pelvic floor disorders have been linked to osteoporosis and low BMD and remain one of the most common reasons for gynaecologic surgery, with a failure rate of 30%. Subnormal levels of 25(OH)D are common among women, and lower levels are associated with a higher likelihood of pelvic floor disorders. Results from the National Health and Nutrition Examination Survey confirmed that lower 25(OH) D levels are associated with a greater risk for urinary incontinence in women older than 50 years.
Age-related macular regeneration:
High vitamin D blood levels appear to be associated with a decreased risk for the development of early age-related macular degeneration (AMD) among women younger than 75 years. Among women younger than 75 years, there is a lower risk for early AMD with higher vitamin D levels, with a threshold effect at 15.22 ng/L serum 25 (OH)D.
Vitamin D intakes recommended by the IOM and the Endocrine Practice Guidelines Committee
| Life stage group | IOM recommendations | Committee recommendations for patients at risk for vitamin D deficiency | ||||
|---|---|---|---|---|---|---|
| AI | EAR | RDA | UL | Daily requirement | UL | |
| Infants | ||||||
| 0 to 6 months | 400 IU (10 μg) | 1,000 IU (25 μg) | 400–1,000 IU | 2,000 IU | ||
| 6 to 12 months | 400 IU (10 μg) | 1,500 IU (38 μg) | 400–1,000 IU | 2,000 IU | ||
| Children | ||||||
| 1–3 yr | 400 IU (10 μg) | 600 IU (15 μg) | 2,500 IU (63 μg) | 600–1,000 IU | 4,000 IU | |
| 4–8 yr | 400 IU (10 μg) | 600 IU (15 μg) | 3,000 IU (75 μg) | 600–1,000 IU | 4,000 IU | |
| Males | ||||||
| 9–13 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 600–1,000 IU | 4,000 IU | |
| 14–18 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 600–1,000 IU | 4,000 IU | |
| 19–30 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| 31–50 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| 51–70 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| >70 yr | 400 IU (10 μg) | 800 IU (20 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| Females | ||||||
| 9–13 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 600–1,000 IU | 4,000 IU | |
| 14–18 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 600–1,000 IU | 4,000 IU | |
| 19–30 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| 31–50 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| 51–70 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| >70 yr | 400 IU (10 μg) | 800 IU (20 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| Pregnancy | ||||||
| 14–18 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 600–1,000 IU | 4,000 IU | |
| 19–30 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| 31–50 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| Lactationa | ||||||
| 14–18 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 600–1,000 IU | 4,000 IU | |
| 19–30 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
| 31–50 yr | 400 IU (10 μg) | 600 IU (15 μg) | 4,000 IU (100 μg) | 1,500–2,000 IU | 10,000 IU | |
AI, Adequate intake; EAR, estimated average requirement; UL, tolerable upper intake level.
Mother's requirement, 4,000–6,000 IU/d (mother's intake for infant's requirement if infant is not receiving 400 IU/d).
Bibliography:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356951/#ref103
https://academic.oup.com/jcem/article/96/7/1911/2833671
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