Are Common Chemicals Feeding Obesity Epidemic?

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Are Common Chemicals Feeding Obesity Epidemic?

 

*By Amanda Gardner*

/HealthDay Reporter/ /Thu Mar 15, 7:01 PM ET/

 

THURSDAY, March 15 (HealthDay News) -- Exposure to a class of chemicals

commonly found in soap and plastics could be fueling the obesity

epidemic by contributing to abdominal obesity and insulin resistance in

men, a new study suggests.

 

The chemicals, known as phthalates, have already been implicated in male

reproductive problems including low sperm counts and low testosterone

levels. However, it's too soon to know whether they are actually causing

these health problems, cautioned the researchers and others.

 

" It's premature for folks to be alarmed, " said study author Dr. Richard

Stahlhut, a resident in preventive medicine at the University of

Rochester School of Medicine & Dentistry in New York.. " What is more

alarming is the reason we are doing studies like this. Another study

showed that testosterone levels had dropped about 22 percent in men, and

that sperm counts had dropped to levels that are considered subfertile

or infertile. "

 

" It's an important observation that chemical exposures could be

contributing to obesity and diabetes in the general population, " added

Dr. Ted Schettler, science director for the Science and Environmental

Health Network. " This is one more example of a family of chemicals that

may be contributing to this problem, but this study has obvious limits

that the authors acknowledge in great detail. "

 

The study was published in the March 14 online edition of /Environmental

Health Perspectives/.

 

Phthalates have been widely used for more than half a century in

everything from paint to time-released medicines, but only recently have

they become a topic of concern. Animal studies show that phthalates

decrease testosterone levels while human studies have found that

phthalates are associated with poor sperm quality in men.

 

This study follows up on other studies that correlated abnormal sperm

counts and low testosterone levels with phthalates. Men with low

testosterone levels develop abdominal obesity and insulin resistance, so

these authors speculated that phthalates might be behind the depressed

testosterone levels.

 

" That's the missing link, testosterone as a [possible] link between

phthalates and obesity, " Stahlhut said.

 

Stahlhut and his team analyzed urine, blood samples and other data

collected for the National Health and Nutritional Examination Survey

(NHANES), a large government survey, from 1999 to 2002.

 

Of the adult men available, 1,451 had data on phthalate exposures,

obesity and waist circumference. Of these, 651 also had data on fasting

glucose and insulin levels needed to calculate insulin resistance.

 

According to the analysis, more than 75 percent of the U.S. population

has measurable levels of several phthalates detectable in their urine.

 

Men with the highest levels of phthalates in their urine had more belly

fat and insulin resistance, even after adjusting for other factors.

 

One drawback of the data, and therefore of the study, is that no

information on hormone levels was available, nor was there any long-term

data.

 

In any event, phthalates are unlikely to be the whole story. The

chemicals have been shown, in animal studies, to have an effect on

thyroid hormone, which could also be a pathway to increased obesity.

 

" This is just part of the search for answers, " Stahlhut said. " The thing

we're certain of is not that phthalates are doing this, but that

phthalates require very careful scrutiny. I'm certain that the declines

in testosterone and sperm production require urgent investigation, and

I'm certain that phthalates are on the list of chemicals that could be

part of the issue. "

 

" It's a complex, multi-factorial problem, " Schettler added. " What the

authors are suggesting is that a chemical exposure may be one among many

factors. The study is certainly hypothesis-generating. It clearly makes

a case that this potential link ought to be studied in more detail in

more systematic ways. "

 

*More information*

 

Visit the American Diabetes Association

<http://www.diabetes.org/type-2-diabetes.jsp> for more on type 2 diabetes.