Health Benefits of Vitamin D and Sunlight - Metabolic Syndrome

High levels of vitamin D in older people can reduce heart disease and diabetes

Middle aged and elderly people with high levels of vitamin D could reduce their chances of developing heart disease or diabetes by 43%, according to researchers at the University of Warwick.

A team of researchers at Warwick Medical School carried out a systematic literature review of studies examining vitamin D and cardiometabolic disorders. Cardiometabolic disorders include cardiovascular disease, type 2 diabetes mellitus and metabolic syndrome.

Vitamin D is a fat-soluble vitamin that is naturally present in some foods and is also produced when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Fish such as salmon, tuna and mackerel are good sources of vitamin D, and it is also available as a dietary supplement.

Researchers looked at 28 studies including 99,745 participants across a variety of ethnic groups including men and women. The studies revealed a significant association between high levels of vitamin D and a decreased risk of developing cardiovascular disease (33% compared to low levels of vitamin D), type 2 diabetes (55% reduction) and metabolic syndrome (51% reduction).

The literature review, published in the journal Maturitas, was led by Johanna Parker and Dr Oscar Franco, Assistant Professor in Public Health at Warwick Medical School.

Dr Franco said: “We found that high levels of vitamin D among middle age and elderly populations are associated with a substantial decrease in cardiovascular disease, type 2 diabetes and metabolic syndrome.

“Targeting vitamin D deficiency in adult populations could potentially slow the current epidemics of cardiometabolic disorders.”

All studies included were published between 1990 and 2009 with the majority published between 2004 and 2009. Half of the studies were conducted in the United States, eight were European, two studies were from Iran, three from Australasia and one from India.

Low vitamin D level is linked to metabolic syndrome, which increases the risk of heart disease and Type 2 diabetes.

A new study presents more evidence of a possible link between low vitamin D levels and a higher risk of Type 2 diabetes and heart disease. The results were presented at The Endocrine Society's 94th Annual Meeting (2012) in Houston.

The study found an inverse relationship between the level of vitamin D in the blood and the presence of the metabolic syndrome, which is a group of risk factors that increases the risk of heart disease and Type 2 diabetes. People with the highest blood levels of vitamin D had a 48 percent lower risk of having the metabolic syndrome than did those with the lowest vitamin D levels, the authors reported.

"This association has been documented before, but our study expands the association to people of diverse racial and ethnic backgrounds," said the lead author, Joanna Mitri, MD, a research fellow at Tufts Medical Center in Boston. "These include minority groups that are already at higher risk of diabetes."

Furthermore, all study participants were at risk of developing diabetes because they had prediabetes, abnormally high blood sugar levels that are not yet high enough to be classified as diabetes. Prediabetes affects an estimated 79 million Americans ages 20 or older, according to 2010 statistics from the Centers for Disease Control and Prevention.

Mitri and her co-investigators conducted the study using data from participants of the Diabetes Prevention Program, a large, now-completed study funded by the National Institutes of Health. They divided study subjects into three groups based on plasma 25-hydroxyvitamin D level, which is the most common way used to measure vitamin D status in the body, according to Mitri. The Institute of Medicine recommends a 25-hydroxyvitamin D level of 20 to 30 ng/mL as adequate for healthy people.

In the new study, the group with the highest levels of vitamin D had a median vitamin D concentration of 30.6 nanograms per milliliter, or ng/mL, and those in the lowest group had a median vitamin D concentration of 12.1 ng/mL. The risk of having the metabolic syndrome with a high vitamin D level was about one half the risk with a low vitamin D level, Mitri said.

The researchers also found an association between vitamin D status and some of the individual components of the metabolic syndrome, which includes a large waist size, low HDL ("good") cholesterol, high triglycerides (fats in the blood), high blood pressure and high blood glucose (sugar). Study participants with the best vitamin D status had a smaller waist circumference, higher HDL cholesterol and lower blood sugar.

Mitri cautioned that their research does not prove that vitamin D deficiency causes Type 2 diabetes, or even that there is a link between the two conditions.

"However, the metabolic syndrome is common, and progression to Type 2 diabetes is high," she said. "If a causal relationship can be established in ongoing and planned studies of vitamin D, this link will be of public health importance, because vitamin D supplementation is easy and inexpensive."

Low vitamin D linked to the metabolic syndrome in elderly people

A new study adds to the mounting evidence that older adults commonly have low vitamin D levels and that vitamin D inadequacy may be a risk factor for the metabolic syndrome, a condition that affects one in four adults. The results were presented at The Endocrine Society's 92nd Annual Meeting (2010) in San Diego.

"Because the metabolic syndrome increases the risk of diabetes and cardiovascular disease, an adequate vitamin D level in the body might be important in the prevention of these diseases," said study co-author Marelise Eekhoff, MD, PhD, of VU University Medical Center, Amsterdam.

The researchers found a 48 percent prevalence of vitamin D deficiency. The study consisted of a representative sample of the older Dutch population: nearly 1,300 white men and women ages 65 and older.

Nearly 37 percent of the total sample had the metabolic syndrome, a clustering of high blood pressure, abdominal obesity, abnormal cholesterol profile and high blood sugar.

Subjects with blood levels of vitamin D (serum 25-hydroxyvitamin D) lower than 50 nanomoles per liter, considered vitamin D insufficiency, were likelier to have the metabolic syndrome than those whose vitamin D levels exceeded 50. That increased risk especially stemmed from the presence of two risk factors for the metabolic syndrome: low HDL, or "good" cholesterol, and a large waistline.

There was no difference in risk between men and women, the authors noted.

The study included subjects who were participating in the Longitudinal Aging Study Amsterdam. Although the data were from 1995 and 1996, Eekhoff said they expect that vitamin D inadequacy remains prevalent among whites in the Netherlands.

Using follow-up data from 2009, the researchers plan to study how many of the subjects with low vitamin D levels developed diabetes.

"It is important to investigate the exact role of vitamin D in diabetes to find new and maybe easy ways to prevent it and cardiovascular disease," Eekhoff said.