Animals fed a high-fat diet and supplemented with 0.015 per cent capsaicin lowered blood sugar insulin, and leptin levels, according to findings published in Obesity.
“Our data suggest that dietary capsaicin may reduce obesity-induced glucose intolerance by not only suppressing inflammatory responses but also enhancing fatty acid oxidation in adipose tissue and/or liver, both of which are important peripheral tissues affecting insulin resistance,” wrote the researchers, led by Rina Yu from The University of Ulsan in South Korea.
If the results can be replicated in further studies, the results could see a strengthening of capsaicin in the weight management supplements market, currently estimated by Euromonitor International to be worth US$0.93bn (€0.73) in Europe in 2005 and $3.93bn in the US.
Over 300m adults are obese worldwide, according to latest statistics from the WHO and the International Obesity Task Force. About one-quarter of the US adult population is said to be obese, with rates in Western Europe on the rise although not yet at similar levels.
Inflammation related to obesity is known to contribute to the development of a range of disorders, including type-2 diabetes, heart disease, insulin resistance, and fatty liver disease.
The South Korean researchers fed male C57BL/6 obese mice a high-fat diet for 10 weeks and the separated them into two groups: Both continued to eat the high-fat diet for a further ten weeks, but one group received supplemental capsaicin.
“Dietary capsaicin lowered fasting glucose, insulin, leptin levels, and markedly reduced the impairment of glucose tolerance in obese mice,” they reported.
Markers of inflammation such as tumour necrosis factor-alpha (TNF-alpha), monocyte chemoattractant protein-1 (MCP-1), and interleukin (IL)-6 fell significantly following capsaicin supplementation, in both fat tissue and the liver.
These decreases occurred with a simultaneous increase in levels of adiponectin, a hormone that regulates a number of metabolic processes. Furthermore, the researchers noted changes in the gene-expression of peroxisome-proliferator-activated receptor-alpha (PPAR-alpha), which controls enzymes linked to fatty-acid-oxidation, they said.
Additional studies are needed to examine if such effects could be repeated in humans.
Capsaicin has been used in folk medicine as a remedy for rheumatism. The humble red chilli pepper has also been in the news recently with research linking the spice to inhibiting the growth of pancreatic cancer cells, as well as a growing body of studies suggesting it may cut fat and energy intake when added to the diet.
Some experts recommend caution, however, as high intake of hot chillies has been linked with increased risk of stomach cancers in the populations of India and Mexico.
Published online ahead of print, 1 October 2009, doi:10.1038/oby.2009.301
“Dietary Capsaicin Reduces Obesity-induced Insulin Resistance and Hepatic Steatosis in Obese Mice Fed a High-fat Diet”
Authors: J-H Kang, G. Tsuyoshi, I-S Han, T. Kawada, Y.M. Kim, R. Yu