Metabolic syndrome is a collection of conditions that may increase your risk of developing cardiovascular disease, stroke or diabetes. Other names for metabolic syndrome are syndrome X and insulin resistance syndrome. It is estimated that upwards of one-third of Americans have metabolic syndrome. The Mayo Clinic states that metabolic syndrome is possibly linked to insulin resistance, a potential precursor to type 2 diabetes. Research shows that vitamin D may help improve insulin resistance.
Metabolic Syndrome Risk Factors
The presence of any three of the following metabolic disorders can lead to a metabolic syndrome X diagnosis: consistent high blood pressure readings greater than 130/85 mmgHg; abdominal obesity with a waist measurement more than 35 inches for women and 40 inches for men, normally accompanied by an apple-shaped, rather than a pear-shaped, midriff; triglyceride levels greater than 150 mg/dL; HDL cholesterol, or "good" cholesterol, levels less than 50 mg/dL in women and 40 mg/dL in men; and a diagnosis of insulin resistance, or glucose intolerance, with a fasting blood sugar of more than 100 mg/dL.
Vitamin D is essential for the metabolism of calcium. It is fat-soluble, and cannot be used by your body on its own. Vitamin D may be acquired from food, supplements or synthesized by your skin from sunlight. Once vitamin D is in your bloodstream, the liver processes it and converts it to 25-hydroxyvitamin D. From here, it goes to the kidneys where it is once again converted to an even more potent form called 1,25-hydroxyvitamin D, or calcitrol. Vitamin D is now ready to link up with your cells' vitamin D receptors, or VDRs.
Insulin resistance may play a key role in metabolic syndrome. Insulin resistant cells are unable to adequately utilize your body's insulin to allow glucose to cross from your bloodstream to your cells to be used for energy. This results in fat storage, particularly around your waist, and difficulty maintaining a healthy weight. The University of Washington lists three causes for insulin resistance: increased abdominal fat, changes in the hormone secretions of fat cells and increased chronic, low-level inflammation in the cells.
Vitamin D and Metabolic Syndrome
A study cited in the journal "Diabetes Care" involving over 3,000 Chinese men and women between the ages of 50 and 70 concludes that vitamin D deficiency is associated with insulin resistance and metabolic syndrome. Another review in the "Journal of Clinical Endocrinology & Metabolism" concludes that vitamin D supplementation in metabolic syndrome may improve glucose metabolism, or insulin resistance. The mechanism by which vitamin D works to improve insulin resistance is yet unknown, but researchers at Rockefeller University, as of 2011, are conducting a study to delve into it. The study hopes to prove that vitamin D sensitizes muscle cells to insulin. As insulin sensitivity improves, the conditions that make up metabolic syndrome may improve as well.