Vitamin D used to be a nutrient that was believed to be important for bone health and little else. But in recent years, it has grown to be associated with an increasing number of conditions including cardiovascular disease, cancer, multiple sclerosis, improved mood and enhanced immunity. New research suggests that another condition that might be influenced by vitamin D is metabolic syndrome. This condition, characterised by a range of potential issues including excess weight around the midriff, high blood pressure, raised blood sugar and raised levels of blood fats known as triglycerides. Metabolic syndrome is a precursor of type 2 diabetes, and is also associated with an increased risk of cardiovascular disease.
The research in question assessed the relationship between vitamin D levels and metabolic syndrome in Chinese adults aged 50-70. Compared to those with the highest levels of vitamin D, those with the lowest levels were found to be at a 52 per cent increased risk of metabolic syndrome. Also, lower levels of vitamin D were found to be associated with higher insulin levels, higher measures of insulin resistance, and higher levels of HbA1c (a measure of blood sugar levels over the preceding 2-3 months). All of these things taken together would suggest higher levels of vitamin D is associated with improved blood sugar and insulin regulation and a reduced risk of type 2 diabetes.
Another thing that was interesting about this study was just how prevalent suboptimal levels of vitamin D were in this population. Individuals were adjudged to be vitamin D insufficient or deficient if their vitamin D levels were 50-<75 and <50 mmol/L respectively (20-<30 and and <30 ng/ml). Prevalence of insufficiency and deficiency was about 70 and 25 per cent respectively.
This study is epidemiological in nature and cannot be used to conclude that vitamin D protects against metabolic syndrome and associated issues. However, it does, yet again, link higher vitamin D levels with distinct benefits for health.
As an addendum, I’d like to add that I was particularly interested in this study because I have quite a strong family history of type 2 diabetes. And, I recently had my vitamin D levels checked for the first time too. I had these assesedat the end of our winter in the UK because I wanted to check my levels at their likely low point in the year. Having said this, I think I get a LOT of sunshine exposure throughout the year one way or another and have not used sunscreen for about 20 years. My levels came back at a crashingly low 15 ng/ml, which puts me in the firmly vitamin D deficient category. It was a bit of a shock, I can tell you. I am currently supplementing with vitamin D (3000 IU per day, currently) and plan to re-check my levels at the end of the summer. I’m hoping to have at least doubled my vitamin D levels by then.
Lu L, et al. Plasma 25-hydroxyvitamin D Concentration and Metabolic Syndrome among Middle-aged and Elderly Chinese. Diabetes Care Epub ahead of print publication on 14th April 2009 DOI: 10.2337/dc09-0209