Mixed Findings on Vitamin D and Metabolic Syndrome

Mixed Findings on Vitamin D and Metabolic Syndrome

MedPage Today
Published: May 18, 2010

PRAGUE -- Suggestions that vitamin D insufficiency may account for at least some cases of metabolic syndrome received support from a small study reported here but were refuted in a much larger study.

Action Points

* Explain to interested patients that low vitamin D levels have been reported to be associated with metabolic syndrome and some of its components, but it remains to be confirmed in large, rigorous analyses.

* Explain that such associations do not necessary mean that low vitamin D actually causes these conditions, although it is possible, nor do they suggest that vitamin D supplements will prevent them.

* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.

Individuals with relatively severe vitamin D deficits, as measured by serum 25-hydroxyvitamin D (25-OH-D), were at significantly increased risk for components of metabolic syndrome in a 92-patient study, according to Viliam Mojto, MD, PhD, of Derer's University Hospital in Bratislava, Slovakia, and colleagues.

But Natielen J. Schuch and colleagues at the University of Saõ Paolo in Brazil found no relationship between vitamin D insufficiency and metabolic syndrome in a study of 405 people -- perhaps because some 85% of the entire sample had low levels of the vitamin.
Both studies were reported here at the World Congress on Controversies to Consensus in Diabetes, Obesity, and Hypertension.

Metabolic syndrome is a condition characterized by a constellation of major risk factors for both cardiovascular disease and type 2 diabetes: obesity, dyslipidemia, impaired glucose tolerance, or insulin insensitivity, and high blood pressure.

The Slovakian researchers measured serum 25-OH-D levels in 92 adults, ages 25 to 92 years, treated as inpatients or outpatients at Derer's University Hospital.

Prevalences of individual components of metabolic syndrome or related overt diseases in the entire sample were as follows:

* Dyslipidemia: 4.1%
* Hypertension: 21.8%
* Impaired glucose tolerance: <2%
* Diabetes mellitus: 9.5%
* Atherosclerosis: 7.3%
* Ischemic heart disease: 20.6%
* Renal insufficiency: 12.7%

Mojto and colleagues found that the median level of 25-OH-D was about 16 ng/mL, well below the 30-ng/mL level regarded as insufficiency, and near the 15-ng/mL standard for serious deficiency.

For men as well as women, analyzed separately, diagnoses of hypertension, diabetes, ischemic heart disease, and renal insufficiency were all more common in those with 25-OH-D levels below 16 ng/mL.

In women, the excesses in diagnoses, compared with participants having higher 25-OH-D levels, ranged from 19% for hypertension to 160% for diabetes. Excess diagnoses in men ranged from 40% for diabetes to 67% for ischemic heart disease (P not reported).

These associations persisted after adjusting for age and sex, Mojto and colleagues indicated.

But they were not confirmed in the much larger Brazilian study.

About 46% of the 405 people enrolled in the University of Saõ Paolo study qualified for a diagnosis of metabolic syndrome, according to criteria developed by the U.S.-based National Cholesterol Education Program, according to Schuch and colleagues.

The mean 25-OH-D level in the 187 individuals who fit the criteria for metabolic syndrome was 24.4 ng/mL (SD 7.2), compared with a mean of 21.2 ng/mL (SD 6.4) among the 218 participants without the full syndrome (P<0.05).

In other words, 78% of those with metabolic syndrome met the 30-ng/mL standard for vitamin D insufficiency, compared with 92% of those without the syndrome.

The researchers didn't report on the possible relationships between vitamin D and individual components of metabolic syndrome.