A diet that contains a lot of fat is known to be a poor choice for good heath in part because it can cause metabolic syndrome, symptoms that collectively has been identified as risk factors for the development of diabetes and heart disease. Researchers have now found that a necessary component of metabolic disease progression in mice is deficiency of vitamin D, happening in conjunction with dysfunction in the bacterial population in the mouse gut. While these findings have to be replicated in humans, if that happens it’s possible that simple treatments like getting enough sun and taking vitamin supplements could help patients with metabolic syndrome.
"Based on this study, we believe that keeping vitamin D levels high, either through sun exposure, diet or supplementation, is beneficial for prevention and treatment of metabolic syndrome," said Professor Stephen Pandol of Cedars-Sinai Medical Center, who collaborated with the research group of Yuan-Ping Han at Sichuan University, China in the study.
Metabolic syndrome affects nearly a quarter of the world's adult population, and it is defined by a group of risk factors that put you on the road to diabetes and heart disease. The characteristic symptoms include obesity around the waistline and at least two of the following: high blood sugar levels, high blood pressure or high cholesterol. Sufferers usually also have excess fat in their liver.
It’s likely that a primary cause of metabolic syndrome is a diet that is high in fats or carbohydrates. The syndrome impacts around a quarter of adults globally, setting them up for future bouts with heart disease and diabetes. Hallmarks are two of the following three symptoms: high blood sugar, high blood pressure, and high cholesterol, along with waistline obesity. Another common characteristic is a fatty liver.
Previous studies have also identified a link between metabolic syndrome and vitamin D deficiency, a common health issue affecting from 30 to 60 percent of the global population.
In this work, published in Frontiers in Physiology, the researchers have demonstrated that there a likely causative role for vitamin D deficiency in the development of this syndrome. "A sufficient dietary vitamin D supplement can partially but significantly antagonize metabolic syndrome caused by high fat diet in mice," explained Pandol. "These are amounts equivalent to the dietary recommendations for humans.
They research team has found that high consumption of fats can alter the balance of good and bad gut microbes. A slight increase in blood sugar and mild induction of fatty liver is subsequently seen in mice. Interestingly, if the supply of vitamin D is impaired, the gut flora imbalance is aggravated, further encouraging the development of a fatty liver and metabolic syndrome.
Defensins are anti-microbial molecules that are critical to the maintenance of healthy gut flora, and the production of those molecules decreases with a reduction in vitamin D. Synthetic defensin taken orally can restore balance to the gut bacterial population, and subsequently improves fatty liver and reduces blood sugar levels.
The researchers suggest that a high fat diet is not enough to cause metabolic syndrome on its own, but vitamin D deficiency will tip the scale into disorder. They also found that supplementation with vitamin D can help treat metabolic syndrome in mice. Next, they have to check out how this works in humans.
"Few studies have indicated that vitamin D supplementation may not improve metabolic disorders in humans. However, these studies are largely based on long-term surveys, which may be hampered by poor compliance and insufficient dosage," said Hans. "We are planning a clinical study to confirm the link of vitamin D deficiency with gut bacteria disruption, and its association with metabolic syndrome,” Han concluded.
The following talk from Robert Lustig, MD of UCSF discusses metabolic syndrome, and its impact on children.
Sources: AAAS/Eurekalert! via Frontiers Blog, Frontiers in Physiology