Fish oil, and other omega-3-rich sources have previously been shown to decrease body fat in rodents, but the mechanism behind such observations and whether doses smaller than those usually found in humans could also exert an effect of the development of fat cells, and therefore play a potential role in weight management.
The retail market for weight management products was estimated by Euromonitor International to be worth US$0.93bn (€0.73) in Europe in 2005 and $3.93bn in the US, indicating that call to slim down or face the health consequences is being heeded by a slice of the overweight population at least.
The new research, published in the new issue of the Journal of Nutrition (Vol. 136, pp. 2965-2969), looked at the effects of DHA on cell growth, differentiation, cell death (apoptosis), and fat breakdown in cultured fat (3T3-L1) cells.
Hye-Kyeong Kim and co-workers from the University of Georgia state that the concentrations used in their study were based on physiological levels of free fatty acids (FFA).
"It was reported that plasma FFA levels were 0.5-2.3 millimoles per litre (mmol/L) in rats and 0.25-0.73 mmol/L in humans," said Kim. "We selected 25-200 micromoles per litre as the experimental doses in our in vitro study."
The Georgia-based researchers report that when added to a culture of preadipocytes (cells that can be stimulated to develop into fully-fledged fat cells, adipocytes) all the concentrations studied (25, 50, and 200 umol/L) resulted in a reduction in the number of viable cells. This was due, said the researchers, to an effect of DHA on adoptosis (programmed cell death).
They also report that DHA significantly decreased the accumulation of fat in the preadipocytes in a dose-dependent manner and the development (differentiation) of mature adipocytes in culture.
"These results demonstrate that DHA may exert its anti-obesity effect by inhibiting differentiation to adipocytes," said the researchers.
"Therefore, it could mediate a reduction in body fat."
Further studies are clearly needed to determine whether dietary and supplemental DHA could play a role in weight management in vivo.
The study adds to an ever-growing list of potential health benefits from the omega-3 polyunsaturated fatty acids, identified as one of the super-nutrients taking the food and supplements industry by storm. Much of its healthy reputation that is seeping into consumer consciousness is based largely on evidence that it can aid cognitive function, may help protect the heart against cardiovascular disease, and could reduce the risk of certain cancers.
Such reports have seen the number of omega-3 enriched or fortified products on the market increase.
However, fears about dwindling fish stocks and the presence of pollutants, such as methyl mercury, dioxins, and polychlorinated biphenols (PCBs), have pushed some academia and industry to start producing omega-3s from alternative sources, such as algae extraction or transgenic plant sources. Most extracted fish oils are molecularly distilled and steam deodorised to remove contaminants.
According to Frost and Sullivan, the European omega-3 market was worth around €160m (£108m) in 2004, and is expected to grow at rates of 8 per cent on average to 2010.