Persistent organic pollutants (POPs) are organic compounds, they are resistant to environmental degradation - they do not break down easily, so they persist and build up in the environment. POPs can bioaccumulate (build up) in human and animal tissue, as well as food chains. POPs have potential significant impacts on human health, as well as the environment. A considerable number of persistent organic pollutants used to be used as pesticides; some were used in industrial processes, such as the production of solvents, pharmaceuticals and polyvinyl chloride. Some POPs come from natural sources, but the majority were manmade in industrial processes, either deliberately or as byproducts. POP exposure can disrupt the endocrine, reproductive and immune systems. They have also been linked to neurobehavioral disorders and some types of cancers if exposure is high enough. Experts say that POP exposure can occur through diet, accidents or the environment.
Study leader, Dr. Duk-Hee Lee, Department of Medicine, Kyungpook National University, Daegu, South Korea, explains that POP compounds are usually stored in fatty tissues (adipose tissues). However, when fat breaks down during weight loss they are released into the bloodstream.
As soon as these POPs get into the bloodstream they can then reach essential body organs, such as the brain or heart, the authors explained.
The researchers wrote that there have been very few population-based studies on the effects long-term weight loss can have on blood concentrations of POPs.
Dr. Lee and team examined data on 1,099 American individuals; they were looking out for blood concentrations of seven POP compounds.
The investigators found that the highest concentrations of POP compounds were found in those who had lost the most weight over ten years, when compared to individuals whose weight had remained steady or people who had gained weight over the same period.
Dr. Lee said there is increasingly compelling evidence that POPs are linked to health problems and illnesses, such as hypertension, type 2 diabetes, coronary heart disease, dental diseases and rheumatoid arthritis.
These findings may help explain why some individuals appear to have a higher risk of dementia, heart disease and some other illnesses after losing weight (not proven).
The team believes further studies are required which may measure the benefits of weight loss against the risks of higher POP blood levels. Also, further studies will have to determine whether the POPs are to blame, or whether the health risks were caused by obesity-related health consequences which were already there before weight loss began, and persisted after the individual lost weight.
The authors wrote:
Although both beneficial health effects after weight loss and harmful health effects after weight gain are generally expected, changes in serum concentrations of POPs in relation to weight change may act on health in directions opposite to what we expect with weight change.
"Inverse associations between long-term weight change and serum concentrations of persistent organic pollutants"
J S Lim1,2, H-K Son1,3, S-K Park1, D R Jacobs Jr4,5 and D-H Lee
International Journal of Obesity advance online publication 7 September 2010; doi: 10.1038/ijo.2010.188