Vitamin D is important to maintain serum calcium in the human body via the action of parathyroid hormone. It increases calcium absorption in the small intestines, store increases re-absorption from urine (kidney) and leads to increased bone mineralization. Vitamin D deficiency affects bone health and causes rickets in children, information pills osteomalacia, osteopenia and osteoporosis in adolescents/adults and increases risk of fractures. Vitamin D deficiency causes secondary hyperparathyroidism leading to a reduction in mineralized bone volume. Osteoporosis affects many of the elderly and is a debilitating disease with the hallmark of fragility fractures. It is urgent to tackle this problem with nutritional approaches and policy making for prevention and treatment.
PREVENTITIVE effects of Vitamin D on various illnesses
Preventative effects have been seen with cancer, infectious disease, heart diseases and stroke, type 1 and 2 diabetes, muscle strength, MS, rheumatoid arthritis and Chron´s. Beneficial effects on preventing mental illnesses i.e. depression, schizophrenia, Alzheimer´s, seasonal affective disorders and dementia are known and vitamin D increases general feeling of well-being.,, Vitamin D has some affinity with sleep duration.
VITAMIN D requirements
Institute of Medicine
The new DRI from the IOM, published 2010, are 15 mcg (600 IU) per day for 0-64 years old, male and female. For 65 and over it is 20 mcg per day (800 IU).
Department of Health
The DOH has still got the same RNIs. DRV for vitamin D were reviewed by the Department of Health Nutrition and Bone Health report in 1998 and later by the SACN in 2007 no changes were made. RNI is set at 8.5 mcg for 0-6 months (340 IU) and 7 mcg (280 IU) for 7 months – 3 years old. For pregnant and breastfeeding women it is 10 mcg a day and for breasted babies it is 7-8.5 mcg daily from 6 moths (earlier with increased risk of deficiency, i.e. low maternal status). For 4 -64 years of age, the RNI is 0 mcg.
These DRV are set for dietary amount required to prevent serum 25-hydroxyvitamin D to fall below 20nmol/l, which is the amount needed to prevent osteomalacia., Current RNI for the 4-64 years old population is based on the assumption that individuals get enough UVB exposure for vitamin D manufacture.
VITAMIN D status in the UK
Result from NDNS report 2008-2010 reveal low levels of vitamin D in adults and older children of both sexes, which have implications for bone health, especially increased risk of osteomalacia and rickets. Combined results from NDNS, year 1,2 and 3, key findings on vitamin D show evidence of low 25-OHD concentrations in all age groups; 18% in 19-64 years old and 20% in 11-18 years old, implicating risk of bone health problems. In the NDNS report for 65 years and over, the blood levels of 25-OH was low in 37% of the participants. Low bone mineral mass is the main factor underlying osteoporotic fracture. Preventing loss of bone in later life and good bone developing in early life, are the two major preventing factors for osteoporosis. According to the report from the HQIP are injurious falls the leading cause of accident-related mortality in older people. Estimation of annually hip fractures alone, are over 70,000 and with aging population the problem is still rising. The importance to take action to counteract this is extreme as the healthcare cost is estimated at 2 billion pounds.
Who are at Risk?
People at risk of vitamin D deficiency are those who are living in high latitude, people with darker skin, those who are spending little time outdoors, the elderly, exclusively breast-fed infants and those who are veiling. In the D-FINES study, vitamin D intake was low in Caucasian and Asian women; especially with in the pre-menopausal Caucasian group in comparison with the post-menopausal Caucasian group.
Vitamin D Sources
Vitamin D intake is via the skin (endogenous) and diet (exogenous). Seasonal variations are seen with vitamin D status in the UK, plasma concentrations of 25(OH)D to be the highest in July-September and lowest in January-March. To maintain vitamin D status the population relies on body stores and dietary vitamin D.8 The latitude about 52°N and above does not provide ultraviolet light of appropriate wavelength for the skin to synthesize vitamin D. Appropriate wavelength (UVB 290-315 nm) is essential for maintaining adequate vitamin D status. In the UK, the mainland is between 50°-60°N and therefore the UK population is at risk, especially during the winter months. Evidence on vitamin D and health can be found in the 1958 British Cohort Study. The relative significance of both dietary sources and sunlight is not known in relation to vitamin D status. Dietary vitamin D is found in oily fish, cod liver, eggs, milk and butter, margarine and fortified cereals as well as supplements. It seems likely that the British population is neither getting enough vitamin D from sunshine nor from diet.
PREVENTION of Deficienc
A significant proportion of the population in the UK has plasma 25-hydroxy vitamin D concentration lower than 25nmol/l with the increased risk of deficiency and therefore a specific recommendation on vitamin D dietary supplements are committed. This applies for vulnerable groups, i.e. pregnant and lactating women, infants, the elderly and minority groups like black people or other ethnic groups, and those who are not able to get sufficient cutaneous exposure to sunlight. Food fortification has been voluntary for margarine since 1925. Infant formula is fortified with vitamin D in the UK, between 1 and 2.5 mcg/100 kcal.
Vitamin D is important to maintain serum calcium in the human body. Vitamin D deficiency affects bone health and causes rickets in children, osteomalacia, osteopenia and osteoporosis in adolescents/adults and increases risk of fractures. Deficiency leads to reduction in mineralized bone volume. The DOH has still got the same RNIs. DRV for vitamin D were last reviewed in 2007 but no changes were made and there is still no RNIs set for 4 -64 years of age. This is interesting as the UK population does not get sufficient amount of cutaneous exposure to sun during the winter months and people are getting limited amount of vitamin D from the diet. This needs further investigation and preventative measures e.g. policymaking and nutritional approaches should be focused on.
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