CLA continues to promise benefits for diabetics
insulin action, and decreasing circulating glucose levels, with rat
and human studies both reporting significant benefits.
Professor Jack Vanden Heuvel, co-director of Penn State's Center of Excellence in Nutrigenomics, has suggested that incorporating CLA as a dietary supplement or from enriched foods, in addition to a balanced diet, could be a suitable way of helping diabetics control their blood glucose and insulin levels.
CLA are found predominantly in dairy products such as milk, cheese and meat, and are formed by bacteria in ruminants that take linoleic acids - fatty acids from plants - and convert them into conjugated linoleic acids, or CLA.
The benefits of CLA supplementation for diabetics is not new, with studies with the rat model for diabetes, called the Zucker fatty rat, producing a 50 per cent reduction in glucose and insulin.
Despite human intervention trials producing mixed results, said Vanden Heuvel, generally eight weeks of CLA supplementation in type-2 diabetics can lead to improvements.
An estimated 19m people are affected by diabetes in the EU 25, equal to four per cent of the total population. This figure is projected to increase to 26m by 2030.
In the US, there are over 20m people with diabetes, equal to seven per cent of the population. The total costs are thought to be as much as $132bn, with $92bn being direct costs from medication, according to 2002 American Diabetes Association figures.
"The eight-week number that was quoted actually comes from examining the review articles on the human studies. By eight-weeks of CLA [suuplementation] you see a reduction in body fat (in most studies); since body fat is causally related to diabetes, I interpret this to mean that there is an improvement in diabetes," Vanden Heuvel told NutraIngredients.com.
Prof. Vanden Heuvel said however that no studies have shown a decrease in glucose utilization in humans given CLA supplements, highlighting a need for a large, long-term clinical study to examine the effects of CLA supplements on human health.
The mechanism behind these benefits is said to be similar to anti-diabetic drugs, said Vanden Heuvel, and works by triggering a set of nuclear receptors called PPAR, with the biological purpose to sense fatty acids and fatty acid metabolites within the cell, and increase the tissues' sensitivity to insulin.
"Anti-diabetes drugs act the same way. They mimic the natural activators of the receptors by getting into the cell and interacting with the PPARs to regulate glucose and fat metabolism," said Vanden Heuvel.
"And compared to the synthetic drugs used to treated this disease, CLA does not cause weight gain and may in fact decrease overall body fat," said Vanden Heuvel.
Despite such promising results, several challenges remain, said Prof. Vanden Heuvel. "[Firstly], showing that there is true, clinical efficacy of CLA in treating diabetes. Rat models are great for testing a hypothesis, but they may not reflect what happens in humans. [Secondly], there are more than one "CLA". This term refers to a lot of isomers and each isomer may have a different biology. Some of the studies done on diabetes were performed using a purified isomer whereas others use a mixture of CLA isomers. This makes interpretation difficult.
"[Finally], how can we incorporate this information into a healthy lifestyle? Should we encourage consumption of dairy products or are we talking about a dietary supplement? We need more research to address all of these issues."
Prof. Vanden Heuvel told NutraIngredients.com that his work has generated interest from industry, with CLA supplement makers, Pharmanutrients and Natural said to be keen, while the National Cattlemen's Beef Association were said to have funded some of the initial research.
