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Low vitamin D levels may increase metabolic syndrome risk

By Stephen Daniells
17/07/2007- Low blood levels of vitamin D may increase the risk of developing metabolic syndrome among obese people, suggests a new study from Spain.

The research, published online in the journal Clinical Nutrition, adds to an ever-growing body of science linking vitamin D deficiency to increased risk of certain diseases, including certain cancers, type-2 diabetes and osteoporosis.

It is not clear from the study however if supplementation with the vitamin could prevent the development of metabolic syndrome among obese patients and more research is necessary to explore the potential benefits of the vitamin for at-risk populations.

"Our results may be of special interest, given that our patients with and without vitamin D deficiency had similar BMI and waist circumference, so the differences in metabolic syndrome prevalence and lipid levels may indeed reflect a true association between vitamin D status and the metabolic syndrome, irrespective of adiposity," wrote lead author Jose Botella-Carretero, from Hospital Ramon y Cajal in Madrid.

Metabolic syndrome (MetS) is a condition characterised by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type-2 diabetes and CVD.

Fifteen per cent of adult Europeans are estimated to be affected by MetS, while the US statistic is estimated to be a whopping 32 per cent.

Botella-Carretero and co-workers recruited 73 morbidly obese patients (BMI 40 kg per sq. m) and diagnosed 37 with vitamin D deficiency. Forty-six of the patients also had MetS.

Over 60 per cent of those with MetS were vitamin D deficient, compared to only 33 per cent of those without the syndrome.

It was also observed that blood levels of HDL-cholesterol were lower (37. mg/dl vs. 44.9 mg/dl), and triglycerides levels were higher (163.3 mg/dl vs. 95.1 mg/dl) in the vitamin D-deficient group compared to the vitamin S-sufficient group.

"The most relevant finding in our study was the association of vitamin D concentrations with lipid levels. Our results are in concordance with the concept that vitamin D appears to be necessary to maintain adequate apolipoprotein A-I concentrations, the main component of HDL cholesterol," stated the researchers.

"Vitamin D deficiency is associated with the metabolic syndrome in morbidly obese patients," they added.

The researchers stated that vitamin D deficiency has previously been linked to impaired insulin secretion in animals and humans, and has also been linked to insulin resistance in healthy, glucose-tolerant subjects. However, Botella-Carretero and co-workers said that these links could be confirmed by their study.

Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet, from consumption of foods such as oily fish, egg yolk and liver.

Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body

Source: Clinical Nutrition (Elsevier)
Published on-line ahead of print, doi :
"Vitamin D deficiency is associated with the metabolic syndrome in morbid obesity"
Authors: J.I. Botella-Carretero, F. Alvarez-Blasco, J.J. Villafruela, J.A. Balsa, C. Vazquez and H.F. Escobar-Morreale