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Lack of vitamin D

Lack of vitamin D in post-menopausal women linked to MetS

Postmenopausal women deserve and require more specific care, and they should seek medical advice on the need for vitamin D supplementation

There is a strong association between vitamin D deficiency and metabolic syndrome (MetS) in postmenopausal women, according to the results of a study by researchers from Brazil. Investigators at São Paulo State University's Botucatu Medical School (FMB-UNESP) detected MetS in 57.8 percent of the women analysed with vitamin D insufficiency (20-29 nanograms per milliliter of blood) or deficiency (less than 20ng/ml) and in only 39.8 percent of participants with sufficient vitamin D (30ng/ml or more).

The study, ‘Vitamin D deficiency is associated with metabolic syndrome in postmenopausal women’, published in Maturitas, included 463 women aged between 45 and 75. They were monitored for two years at FMB-UNESP's Climacteric & Menopause Outpatient Clinic. Their last menstruation occurred at least 12 months previously, and they had no existing or pre-existing heart problems.

To indicate whether or not the patient had MetS, the study adopted the typical parameters for MetS diagnosis: waist circumference above 88cm, high blood pressure (above 130/85mmHg), high blood sugar (fasting glucose above 100mg/dL), and abnormal levels of triglycerides (above 150mg/dL) and cholesterol (HDL below 50mg/dL). MetS was diagnosed if three or more of these criteria were met.

"We measured the participants' blood vitamin D levels and also analysed parameters indicating MetS,” said Eliana Aguiar Petri Nahas, a professor in FMB-UNESP's Department of Gynecology & Obstetrics and one of the authors of the study. “We found that the lower the level of blood vitamin D, the greater the occurrence of MetS. The results suggest that supplementing and maintaining adequate levels of vitamin D in postmenopausal women can reduce the risk of disease."

Previous studies described the existence of several mechanisms that might explain the effect of vitamin D on the components of MetS. According to the article, the most plausible explanation for the association is that vitamin D influences insulin secretion and sensitivity, which play a major role in MetS.

"The vitamin D receptor is expressed in insulin-secreting pancreatic beta cells and in peripheral target tissues such as skeletal muscle and adipose tissue. Vitamin D deficiency can compromise the capacity of beta cells to convert pro-insulin to insulin," wrote the researchers of the FAPESP-funded project.

According to the researchers, however, more studies are needed to confirm the link. "The objective of the study was to evaluate the association between vitamin D deficiency and risk factors for MetS in postmenopausal women," they write in the article.

In a previous study, the UNESP researchers also analysed the association between vitamin D deficiency and breast cancer in postmenopausal women. The survey involved 192 women aged 45-75 with a recent diagnosis of breast cancer and in amenorrhea for over 12 months.

Levels of vitamin D were sufficient in 33.9 percent of the patients and insufficient or deficient in 66.1 percent. A higher proportion of those with vitamin D insufficiency or deficiency had high-grade tumours or metastatic disease.

"The importance of vitamin D to bone mass is well understood, especially in helping absorb calcium into the bones," said Nahas. "Now, we're studying the extra-osseous effects of vitamin D on the cardiovascular system and on the breasts. These are the focus for our current study. In recent years, associations have been proposed between vitamin D deficiency and both inflammation and cardiometabolic diseases. However, more information is needed on the link between vitamin D and cardioinflammatory markers in the general population."

According to Nahas, aging is a key factor in vitamin D deficiency. "Exposure to the sun activates a sort of pre-vitamin D in the adipose tissue under the skin," she explained. "Aging leads not just to loss of muscle mass but also to changes in body composition, and this pre-vitamin D is lost. That's why older people produce less vitamin D even if they get plenty of sunlight."

Forthcoming research planned by the group will focus on isolated vitamin D supplementation and indicators of cardiovascular disease in postmenopausal women.

"More studies are required in order to make these important associations in terms of the effects of supplementation on cardiometabolic syndrome, the immune and inflammatory mechanisms of cardiovascular disease in postmenopausal women, and their quality of life," she added.

In her view, postmenopausal women deserve and require more specific care. They should seek medical advice on the need for vitamin D supplementation.

 "Hypovitaminosis can have repercussions, be it on breast cancer, vascular disease or metabolic syndrome," she said.

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