Vitamin D up date 2015: from bone to general preventive healthcare

Health benefits from nutritional advices

Ligia Martini

University of São Paulo, São Paulo, Brasil

Vitamin D insufficiency is worldwide reported, even in sunnier regions. Such inadequacy could contribute to several chronic diseases beyond osteoporosis. All around the world researchers and clinicians have been investigating the risk factors and determinants, discussing the adequate requirement as well trying new approaches for it´s treatment. The objective of this presentation is to report current evidences for the health benefits of vitamin D nutritional adequacy. In 2010 the North American IOM established the current DRI for vitamin D, based on adequate skeletal development and maintenance during lifetime. The requirement of half and 97.5% of healthy individuals was defined at 400 and 600 IU, respectively. However, these values has been severely criticized since it was demonstrated that which such intake the 25(OH)D serum levels did not reach the adequate status of 30 ng/l. By considering evidences from health benefits proven by experimental, ecological, case-control, retrospective and prospective observations, the US Endocrine Society recommended that the vitamin D intake should range from 400- 1000 IU/d for babies until the first year of life, 600-1000 IU/d though 1 until 18 years old, and 1500-2000 from 18 older. Studies using supplemented vitamin D showed improvements in bone health, cardiovascular system, diabetes, immune and cancer diseases. A meta-analysis including original data on 30 011 individuals showed a statistically significant reduction of hip fractures by 30% among subjects taking 792 to 2000 IU/day; median 800 IU/day, compared to control group. In persons supplemented with lower doses, no significant reduction was detected. In addition, vitamin D could potentially exert a positive effect on muscles that can explained by a better influx of calcium into the muscle cells as well as a Vitamin D Receptor (VDR) mediated stimulation of muscle protein synthesis. This additional effect is a crucial factor for fracture reduction, since falling represents the primary risk factor for fractures. It was observed that a 34% (OR = 0.66 [0.53-0.82] p = 0.002) reduction of falling occurred with higher doses (700-1000 IU/day). In a prospective study with more than 40 000 subjects, a 25(OH)D level under 15 ng/ml when compared with levels > 30 ng/ml was associated with a significant increase in the prevalence of type 2 diabetes, hypertension, peripheral vascular diseases, myocardial infarction, as well as in the incidence of overall mortality (Anderson et al 2010). The analysis of the RECORD (Randomized Evaluation of Calcium or Vitamin D Randomized Controlled Trial) including 5292 participants the HR for cardiac failure for vitamin D supplemented group (800 IU/day) was 0.75. 95% CI 0.58-0.97). By the other hand, evidences from 36 trials (Seida et al, 2014) focusing on the associations between vitamin D on glucose homeostasis and diabetes prevention, shows no effect of vitamin D supplementation with a median dose of 3332 IU/d (IQR 1000 to 5536). Vitamin D inadequacy is common in cancer patients and seem to be correlated with diseases progression. Whilst controversial results is observed when vitamin D is given to individuals with different types and malignancy of cancer, Grober et al 2013 highlighted that vitamin D should be monitored in cancer patients, and adequate circulating levels of 25(OH)D should be maintained, especially in patients with poor nutritional status, muscular or mucocutaneous disorders, fatigue, cachexia and under use of certain drugs. Focusing on the treatment and prevention of vitamin D deficiency and insufficiency, the adopted strategies includes not only the use of supplements, but sun exposure and food sources. It has been postulated by Professor Michael Holick, that a sensible sun exposure is an inexpensive and most efficient way of obtaining and adequate amount of vitamin D Nevertheless, excessive exposure to sunlight increases the risk of melanoma and a safe exposure relies on time of the day, exposure duration, types of clothes and UV-b wavelength. Thereby increasing the intake of vitamin D from naturally rich foods and /or use of supplements can undoubtedly improve nutritional status of individuals. However, very few foods naturally contain considerable amounts of vitamin D, as such salmon, sardine, tuna, egg yolk, thus fortified foods are an important strategy to improve dietary vitamin D intake. Indeed, a systematic review on the efficacy of food fortification on serum 25(OH)D concentration, showed an improvement vitamin status in adults (O´Donnell et al, 2008) In conclusion, the improvement of vitamin D nutritional status will benefit overall health conditions of populations. A carefully designed and safe food fortification, possible including biofortification, can undeniable tackling the low intakes of vitamin D within populations.