வைட்டமின்கள் மற்றும் தாதுக்கள்

The role of vitamin D in calcium homeostasis and its impact on bone is well characterized and validated; however, the role vitamin D plays in non-bone physiology is less concrete. The Vitamin D Receptor (VDR) is expressed throughout the body and regulates many cellular processes. This discovery has led to vigorous research of vitamin D and the role it plays in many illnesses, especially those of high prevalence in the United States. Vitamin D deficiency has been implicated in numerous health conditions and thus is an intriguing target for therapeutic intervention. Studies examining the therapeutic effects of vitamin D in chronic disease and disease prevention have yielded conflicting results. Additionally, many publications on vitamin D result from studies in which vitamin D was not the primary focus. Given the increasing interest in the non-bone effects of vitamin D, we will review and summarize the recent literature related to older adults, a group with significantly increased risk of vitamin D deficiency. Older adults have substantial morbidity and mortality due to dementia, cancer and heart disease, all of which have been linked to vitamin D deficiency. We will explore current evidence of the expression of VDR and the effects of exposure to vitamin D that might impact these illnesses among older adults. We will review the most recent research on cognitive function and depression as a result of vitamin D deficiency. Through this work we aim to summarize the current data that sheds light on the possibility of clinical application of vitamin D therapy.

In this perspective we present the advances in the study of the metabolism of folate, B-12 vitamin and selenium, whose deficiency is closely linked to the metabolic bone disease. However, the genetic variations of both mutation and polymorphism in genes are related to the metabolism of these nutrients and also lead to the development of monogenic and complex diseases. The challenge in the post-genomic era is to establish the genetic profiles related to megalin and selenoproteins in relation to serum levels of these vitamins in order to be analyzed as factors for the prediction and response to treatment of associated diseases. Governments should specifically consider the investment in this area, since the consumption of these vitamin and minerals are very common in food supplements.

The obesity epidemic in the US has continued for over two decades as the proportion of overweight and obese adults in the population continues to rise. Also, obesity has been linked with the risk of development of various diseases such as diabetes, cardiovascular disease and certain types of cancers. There are conflicting reports about the effects of obesity on serum vitamin D levels in human and animal models. We hypothesize that obesity will affect the serum levels of vitamin D metabolites. Therefore, the objective of this study was to investigate the influence of obesity on the serum concentrations of two metabolites of vitamin D [25-(OH)-D and 1,25-(OH)₂-D] in rats. Sixteen 5-week-old female Zucker rats (8 obese fa/fa and 8 lean) were acclimated for one week, and at the age of 42 days, the rats were housed 2 per cage with ad libitum access to water and AIN-93G diet. Rats were weighed twice weekly. At the end of the experiment (8 weeks), all rats were sacrificed and serum was collected and stored at −20°C. Serum concentrations of 25-OH-D and 1,25-(OH)₂-D were measured using HPLC-UV. Data were analyzed using Excel software and presented as mean ± SD. Obese rats had significant weight gain (P<0.001). Serum concentration of 25-(OH)-D metabolite in obese rats was significantly (P<0.05) lower compared to lean rats. At the same time, serum concentration of 1,25-(OH)₂-D metabolite in obese rats was only 8% lower and did not significantly (P<0.3) change compared to the lean group. The serum ratio of 1,25-(OH)₂-D:25-(OH)-D was approximately 10% higher (P<0.3) in obese rats compared to the lean group. In summary, lower serum concentration of 25-OH-D (hormonally inactive form of vitamin D) metabolite is consistent with higher body mass in rats, but obesity did not affect the serum concentration of 1,25-(OH)₂-D. Our results show that the obese Zucker rat can be a good model for assessing vitamin D status.

With the abundance of dietary advice coming from different sources and origins, it is important to identify those coming from the official government or other legitimate non-profit organizations which have been accepted and approved by the USA government. This review gives a brief history of dietary recommendations and their evolvement over time, as well as the description of the current official recommendations in the USA.