Σχετικοί σύνδεσμοι και επιστημονικές μελέτες για τη Βιταμίνη D - Scientific studies and surveys about Vitamin D
Σχετικοί σύνδεσμοι - Related websites & resources
Analyzing data on more than 10,000 patients, University of Kansas researchers found that 70 percent were deficient in vitamin D and they were at significantly higher risk for a variety of heart diseases.
A prospective study in which 1739 participants without prior cardiovascular disease were followed-up for 5 years showed that individuals with hypertension and 25(OH) vitamin D levels <15 ng/ml had a 2-fold risk of cardiovascular events compared to those with levels >15 ng/ml.
An analysis of 454 men, who were free of diagnosed cardiovascular disease at baseline and developed myocardial infarction or coronary heart disease during 10 years of follow-up, and 900 controls indicated that the risk of myocardial infarction was double for individuals with insufficient levels of 25(OH) vitamin D (<15 ng/ml) compared to sufficient levels (>30 ng/ml).
A 7-year follow-up study of 3258 patients referred for coronary angiography showed that decreasing 25(OH) vitamin D levels were associated with increasing risk for all-cause and cardiovascular
Low 25-hydroxyvitamin D levels have been associated with the cardiovascular disease risk factors of hypertension, obesity, diabetes mellitus and the metabolic syndrome, as well as cardiovascular disease events including stroke and congestive heart failure. Studies suggest vitamin D deficiency may be a contributor to the development of cardiovascular disease potentially through associations with diabetes or hypertension.
Researchers found that patients with very low levels of Vitamin D were 77 percent more likely to die, 45 percent more likely to develop coronary artery disease, and 78 percent were more likely to have a stroke than patients with normal levels. Patients with very low levels of Vitamin D were also twice more likely to develop heart failure than those with normal Vitamin D levels.
The results add to evidence that lack of vitamin D can lead to impaired vascular health, contributing to high blood pressure and the risk of cardiovascular disease. Study participants who increased their vitamin D levels were able to improve vascular health and lower their blood pressure.
Women with breast cancer should be given high doses of vitamin D because a majority of them are likely to have low levels of vitamin D, which could contribute to decreased bone mass and greater risk of fractures, according to scientists at the University of Rochester Medical Center.
Vitamin D and its analogues exhibit potent antitumor effects in many tissues, including the pancreas. We examined associations between dietary intake of vitamin D, calcium, and retinol and subsequent risk for pancreatic cancer. After adjusting for vitamin D intake, calcium and retinol intakes were not associated with pancreatic cancer risk. In two U.S. cohorts, higher intakes of vitamin D were associated with lower risks for pancreatic cancer. Our results point to a potential role for vitamin D in the pathogenesis and prevention of pancreatic cancer.
Abundant experimental studies and epidemiological data, as well as several human clinical trials suggest a protective effect of Vitamin D against colon carcinogenesis. Hypercalcemia, a side effect of natural Vitamin D, has currently restricted its therapeutic use; however, the development of new synthetic analogs with reduced hypercalcemic activity is promising for cancer therapy and prevention. Extensive research to elucidate the mechanisms underlying the anti-cancer action of Vitamin D is being undertaken. Understanding the complex molecular and cellular networks induced by Vitamin D or its analogs will improve the use of these compounds for the prevention and treatment of colorectal cancer.
A pooled analysis of two studies with 880 cases of breast cancer and 880 controls demonstrated that individuals with serum 25(OH) vitamin D of approximately 52 ng/ml had 50% lower risk of breast cancer than those with levels <13 ng/ml.
An analysis of 1394 post-menopausal breast cancer cases and 1365 controls suggested that serum 25(OH) vitamin D concentration was significantly inversely associated with breast cancer risk, particularly at levels <20 ng/ml.
A 4-year trial including 1179 healthy women supplemented with placebo, calcium or calcium and vitamin D showed that vitamin D supplementation reduced by 77% the relative risk of developing cancer.
The study was conducted within the EPIC study, a cohort of more than 520000 participants from 10 western European countries, to examine the association between pre-diagnostic circulating vitamin D concentration, dietary intake of vitamin D and calcium, and the risk of colorectal cancer in European populations.
The results of this large observational study indicate a strong inverse association between levels of pre-diagnostic vitamin D concentration and risk of colorectal cancer in western European populations.
As early as 1941, it was observed that people living at higher latitude were at higher risk of dying of cancer. In the 1980’s and the 1990’s, several reports surfaced revealed that living at higher latitude and being at higher risk of vitamin D deficiency increased risk of developing and dying of cancers of the colon, rectum, prostate, breast, ovary. More recently, vitamin D deficiency has been associated with increased risk of developing many other cancers including cancer of the esophagus, pancreas and leukemia.
Women in the Women’s Health Initiative that evaluated the effect of calcium and vitamin D on risk of developing colorectal cancer revealed that women who were vitamin D deficient and followed for eight years had a 253% increase risk of developing colorectal cancer. These data are also supported by a recent observation by Lappe et al who reported that women ingesting 1,100 IU of vitamin D and 1,200 milligrams of calcium a day reduced overall risk of developing cancer by almost 70%.
Black Americans diagnosed with cancer generally have lower survival rates than white Americans, even after adjustment for stage of cancer at time of discovery and level of treatment received. The hypothesis developed in this work is that these lower cancer survival rates may be due to lower serum 25-hydroxyvitamin D for black Americans attributed to lower production rates of vitamin D from solar ultraviolet-B (UVB) irradiance due to darker skin. Black Americans generally have 50-75% as much serum vitamin D as white Americans, and vitamin D is now thought to reduce the risk of incidence and mortality for 18 types of cancer.
Previous studies, such as the Women’s Health Initiative, have shown that a low dose of vitamin D did not protect against colorectal cancer, yet a meta-analysis indicates that a higher dose may reduce its incidence. Five studies of serum vitamin D in association with colorectal cancer risk were identified using PubMed. The results of all five serum studies were combined using standard methods for pooled analysis. The evidence to date suggests that daily intake of 1000-2000 IU/day of vitamin D could reduce the incidence of colorectal with minimal risk.
The purpose of this analysis was to determine the efficacy of calcium alone and calcium plus vitamin D in reducing incident cancer risk of all types.
Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women.
Among whites (148 cases, 296 controls), the risk of multiple sclerosis significantly decreased with increasing levels of vitamin D. The inverse relation with multiple sclerosis risk was particularly strong for vitamin D levels measured before age 20 years. Among blacks and Hispanics (109 cases, 218 controls), who had lower vitamin D levels than whites, no significant associations between vitamin D and multiple sclerosis risk were found. The results of our study suggest that high circulating levels of vitamin D are associated with a lower risk of multiple sclerosis.
Multiple sclerosis (MS) is a chronic inflammatory disease with an as yet not fully understood etiological background. The geographical distribution of MS is striking with a prevalence that increases with latitude. For this reason, vitamin D deficiency is considered a possible pathogenic co-factor in MS.
Our data suggest that higher circulating levels of vitamin D are associated with a lower incidence of MS and MS-related disability in women. This may imply clues to the pathogenesis of the sex difference in risk and to the nature of the environmental factors involved in MS.
To date, the evidence includes observational studies supporting a beneficial role of vitamin D in reducing the risk of diseases linked to dementia such as vascular and metabolic diseases, as well as an understanding of the role of vitamin D in reducing the risk of several mechanisms that lead to dementia.
It is known that if you are born above 35° latitude at approximately Atlanta, Georgia, and live at this latitude for the first ten years of your life that you have a 100% increase risk of developing multiple sclerosis. Recent studies have suggested that women and men who increase their vitamin D intake above 400 IU of vitamin D a day reduce risk of developing multiple sclerosis by approximately 40%.
A relationship between vitamin D and several diseases, including multiple sclerosis (MS), has recently received interest in the scientific community. Vitamin D appears to have important actions beyond endocrine function, particularly for the immune system. Risk of development of MS, as well as disease severity, has been associated with vitamin D in a variety of studies. There remains a need for prospective studies to further establish this relationship. Given the current evidence of the potential benefits of vitamin D, it appears to be reasonable and safe to consider vitamin D supplementation at dosing adequate to achieve normal levels in patients with MS and clinically isolated syndrome.
This review examines the epidemiological evidence that suggests ultraviolet radiation (UVR) may play a protective role in three autoimmune diseases: multiple sclerosis, insulin-dependent diabetes mellitus and rheumatoid arthritis. To date, most of the information has accumulated from population studies that have studied the relationship between geography or climate and autoimmune disease prevalence. An interesting gradient of increasing prevalence with increasing latitude has been observed for at least two of the three diseases. This is most evident for multiple sclerosis, but a similar gradient has been shown for insulin-dependent diabetes mellitus in Europe and North America. Seasonal influences on both disease incidence and clinical course and, more recently, analytical studies at the individual level have provided further support for a possible protective role for UVR in some of these diseases but the data are not conclusive.
Bone disorders (Osteoporosis)
During the past decade, major advances have been made in vitamin D research that transcend the simple concept that vitamin D is Important for the prevention of rickets in children and has little physiologic relevance for adults. Inadequate vitamin D, in addition to causing rickets, prevents children from attaining their genetically programmed peak bone mass, contributes to and exacerbates osteoporosis in adults, and causes the often painful bone disease osteomalacia. Adequate vitamin D is also important for proper muscle functioning, and controversial evidence suggests it may help prevent type 1 diabetes mellitus, hypertension, and many common cancers. Vitamin D inadequacy has been reported in approximately 36% of otherwise healthy young adults and up to 57% of general medicine inpatients in the United States and in even higher percentages in Europe. Recent epidemiological data document the high prevalence of vitamin D inadequacy among elderly patients and especially among patients with osteoporosis.
Recent studies have revealed that women who ingest more than 400 IU of vitamin D a day reduce their risk of developing rheumatoid arthritis by as much as 42%.
Vitamin D deficiency has been associated with an increased risk of developing osteoarthritis.
In addition to its role in calcium hemostasis and bone metabolism, vitamin D also appears to be an important regulator of immune function. However, its role in modulating RA disease activity has not been studied. Here, Patel et al explore the effects of serum vitamin D levels on clinical response in patients with early inflammatory polyarthritis.
Vitamin D deficiency causes a defect in the ability of the body to deposit calcium into the collagen jello-like matrix in the bone. As a result, the covering on the bone which contains pain sensing nerves is easily deformed resulting in throbbing aching bone pain. Patients with osteomalacia often complain of achiness in their muscles and bones. These non-specific aches and pains in the bones and muscles are often misdiagnoses as fibromyalgia or chronic fatigue syndrome. There have been several studies demonstrating that patients with severe bone and muscle pain and muscle weakness associated with osteomalacia have dramatic improvement in their symptoms when vitamin D deficiency is corrected. It takes months to years to develop osteomalacia and associated symptoms and it takes three to six months before significant improvement in symptoms results from correcting vitamin D deficiency.
Hypovitaminosis D and a low calcium intake contribute to increased parathyroid function in elderly persons. Calcium and vitamin D supplements reduce this secondary hyperparathyroidism, but whether such supplements reduce the risk of hip fractures among elderly people is not known.
Supplementation with vitamin D3 and calcium reduces the risk of hip fractures and other nonvertebral fractures among elderly women.
Vitamin D deficiency has again become an epidemic in children and rickets has become a global health issue. In addition to vitamin D deficiency, calcium deficiency and acquired and inherited disorders of vitamin D, calcium, and phosphorus metabolism cause rickets.
Rickets is a disorder of mineralization of newly synthesized organic matrix, leading to improper bone formation. Deficiencies in vitamin D, calcium, phosphorous or inadequate exposure to sunlight are the major causes of rickets. Skeletal deformities develop in growing children who remain untreated for extended periods. Tibial involvement produces bowing of the legs. A rachitic rosary develops at the costochondral margin from the overgrowth of cartilage.
Diabetes is a leading cause of cardiovascular disease. Persons with diabetes are at greater risk for early cardiac mortality, and for repeat events if they survive their first cardiac event. Recently, low serum concentrations of vitamin D have been associated with increased risk for cardiac events. Evidence indicates that persons with diabetes have lower serum concentrations of vitamin D. In addition, persons at risk for diabetes or metabolic syndrome have inadequate serum concentrations of vitamin D. Effective detection and treatment of inadequate vitamin D concentrations in persons with diabetes or those at risk for diabetes may be an easy and cost-effective therapy which could improve their long-term health outcomes as well as their quality of life.
This commentary reviews the current state of knowledge regarding the role of vitamin D in the pathogenesis of diabetes mellitus. In type 1 diabetes mellitus or in adult onset latent autoimmune diabetes (LADA), vitamin D exhibits immunomodulatory actions, influencing the activity of lymphocytes and interleukins. In type 2 diabetes mellitus vitamin D appears to act through different mechanisms, affecting insulin secretion and insulin sensitivity through its effects on the beta cells, mediators of inflammation and parathyroid hormone.
Prevention, or at least delay in onset of type 2 diabetes is possible by intensive lifestyle intervention. This is costly and labor intensive and alternative methods of preventing diabetes have been sought. Vitamin D has important physiological effects aside from its effects on bone metabolism, including an important role in glucose homeostasis, insulin release and response. Observational data strongly support the role of vitamin D deficiency in the pathogenesis of type 2 diabetes. The time is ripe for a well conducted randomized controlled trial of vitamin D in high risk individuals to test the hypothesis that vitamin D delays the onset of type 2 diabetes.
Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes. Ensuring adequate vitamin D supplementation for infants could help to reverse the increasing trend in the incidence of type 1 diabetes.
Vitamin D supplementation in early childhood may offer protection against the development of type 1 diabetes. The evidence for this is based on observational studies.
This prospective study reports inverse associations between baseline serum vitamin D and future glycemia and insulin resistance. These associations are potentially important in understanding the etiology of abnormal glucose metabolism and warrant investigation in larger, specifically designed prospective studies and randomized controlled trials of supplementation.
This study is supported by the observation in Finland where children in the 1960’s routinely received 2,000 IU of vitamin D a day during their first year of life. When these children were followed for the next 31 years, it was observed that these children had a reduced risk of developing type I diabetes by 78%. Children who were vitamin D deficient at the same time and also followed for 31 years had an almost 300% increased risk of developing type I diabetes.
It has long been recognized that patients with tuberculous do better when treated with vitamin D or exposed to sunlight. It was recently recognized that the immune cell known as the macrophage needs vitamin D in order to produce a peptide which is responsible for killing infectious agents such as tuberculous. It has been speculated that one of the reasons that influenza occurs in the winter time in tepid climates is because the sun is unable to produce vitamin D, and the resulting vitamin D insufficiency may promote and enhance the infectivity of the influenza virus.
Obesity is associated with vitamin D deficiency. The reason is that the vitamin D is trapped within the fat and cannot easily exit. As a result, obese patients need at least twice as much vitamin D as a normal weighted individual in order to maintain a normal vitamin D status between 30-60 ng/ml.
Obesity in children and adolescents has reached epidemic proportions, with a prevalence of 16.4 percent among 10 to 17 year olds as of 2007. The increased prevalence of obesity may lead to increased risk of diabetes, hypertension, and cardiovascular disease, as well as to an increased risk of cancer. Some of these health consequences of obesity have also been associated with vitamin D deficiency or insufficiency. In addition, vitamin D status is significantly associated with muscle power/force, and therefore, a deficiency may interfere with the obese adolescent’s ability to increase physical activity.
Serum 25(OH)D levels are inversely associated with recent upper respiratory tract infections (URTI). This association may be stronger in those with respiratory tract diseases. Randomized controlled trials are warranted to explore the effects of vitamin D supplementation on RTI.