Is organic food just for girly men? Actually, it might be just the opposite: recent studies are showing strong evidence that some pesticides may make a guy a little too light in the loafers. A recent issue of Epidemiology found a correlation between exposure to the pesticide chlorpyrifos and a decline in testosterone.  The researchers examined males undergoing fertility treatment and found "multiple linear regression models showed an inverse association between TCPY [a metabolite of chlorpyrifos] and testosterone concentration". Simply put, that means the more the chlorpyrifos, the less the testosterone.
Testosterone and Pesticides
The Tour De France is a little over 2,000 miles and your food typically has to travel about that on average to get to your local supermarket. Your fruits, vegetables and grains travel an average of between 1,500 and 2,500 miles and increasingly from foreign countries including China.  This means - you guessed it - more pesticides and chemicals have to go on your food to get it to survive the typical megatrek to your plate.
What does that mean to all of you concentrating on your fitness and health? It means that as you do the right thing and eat your fruits and green stuff, Old MacDonald is trying to shrink your nuts to the size of a fruit fly! Am I exagerrating? Well, a little bit. But the study found that men with the most pesticide byproducts in their systems typically had 10% less testosterone than men with the least pesticide by products. That’s quite a hit for just one pesticide, especially for those on the low testosterone side in the first place. I should also mention that previous research has found this pesticide widely present in the general population: in other words, you'll be extremely unlikely to escape ingesting it under normal circumstances. (Before I go on, please, please read this section on Excitotoxins: these have the potential to be much more deadly to your testosterone than even pesticides.)
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The researchers also found that two additional pesticides, carbaryl and naphthalene, were also correlated with lower testosterone in subjects. Imagine what the other forty pesticides you’re eating are doing to your precious testosterone. The concern over pesticides actually came over decades of observations as to what they (and other chemicals such as those used in plastics) are doing to the animal kingdom. Florida gators next to pesticide manufacturing plants have a drastically increased mortality and many of the adult males have ovaries instead of testes. Not good.
Atrazine is another example. In America 60 million pounds of this are sprayed on annually on sugar cane, corn and other crops where, of course, it washes into rivers, streams and various water supplies. Unfortunately, researchers found that it caused sexual abnormalities in frogs! In Europe it is banned but not in the good ol’ U.S. of A! NOTE: The National Resources Defense Council just found Much Higher Levels of Atrazine than previously estimated by the EPA.
Why do these chemicals cause so many problems? The trouble is that many of them are endocrine disruptors. Some of them, for example, mimic estrogen or testosterone and take over receptor sites. Others interfere with the chemical pathways responsible for formation or delivery of testosterone or estrogen. In the case of chlorpyrifos, researchers believe it effects luetinizing hormone, which signals production of testosterone in males.
I should mention that pesticides and herbicides don't just do their damage by modifying hormone levels. Pesticides and herbicides can do damage throughout the body without ever touching your hormones! See this link on How Pesticides and Herbicides Can Lead to ADHD and Parkinson's.
One example of this is dieldrin, a DDT alternative, which has proven to be more toxic to vertebrates than insects. One study showed it increases oxidative stress, lowers dopamine levels and is likely a cause of Parkinson's Disease.  Furthermore, it has induced liver and hepatocellular cancers.  Even worse, it is not biodegradable. It has been banned for decades yet still persists in our food supply like radioactive waste. How could they use a non-biodegradable pesticide in our food supply? Is it possible to be more irresponsible?
Previous data from the National Academy of Sciences has shown that Agent Orange and other herbicides do not just damage the brain but can induce hypertension, as shown by examination of Vietnam Vets with significant exposure.  Dioxins and other chemicals cause proteins to accumlate in and around the organs which can cause significant issues including lymphomas and cancers as well. They stated that "the committee based its conclusion on the fact that AL amyloidosis shares many biological and pathological similarities with multiple myeloma and certain B-cell lymphomas, which have been found to be associated with exposure to herbicides". Nasty!
NOTE: Dioxins are so deadly that they were used in 2005 to poison Victor Yushchenko, a well-known opposition Ukranian leader.
So how do you avoid these T-killing compounds? If you want to shop at a regular supermarket, it will be tough. About the only thing that researchers can tell us at this point is which fruits and vegetables have the greatest incidence and total amount of pesticides. Here's a link that gives such a list: http://www.ewg.org/news/story.php?id=2076.
This EWG states that among the worst offenders, which they call the Dirty Dozen, are "apples, bell peppers, celery, cherries, imported grapes, nectarines, peaches, pears, potatoes, red raspberries, spinach and strawberries".
The Latex Glove Award: Apples are particularly known for being the "most sprayed". The problem is that apples are usually grafted and therefore not very pest resistant. Farmers spray more to compensate and that's why organic is probably a good idea in this case.
The Latex Glove Runner Up: Probably the second most chemical-ridden item out of a farm is the potato. Because they're a root vegetable, they get treated with fungicides and then are sprayed with an herbicide to get rid of the "little string roots" that come out of potatoes. After they are harvested, they get another dose making for one scary vegetable.
The least contaminated produce found was "asparagus, avocados, bananas, broccoli, cauliflower, corn, kiwi, mangoes, onions, papayas, pineapples and sweet peas".
At least science has provided us with a way that you can try to avoid pesticides: by limiting yourself to those on the least contaminated list. Realistically, though, the only real way to avoid pesticdes is to buy organic. Studies have shown that children who eat organic vegetables and fruit only dramatically lose pesticide residues in their body tissues and then regain them upon returning to regular produce.
Keep in mind that the knowledge about the effects of pesticides on humans is still in its infancy. Making the task even more difficult is the fact that there are about 87,000 different chemicals currently in use making it impossible to test even a small percentage of the total. My opinion, though, is "better safe than sorry".
News Flash #1: Pesticides and fungicides are increasingly being correlated with thyroid disease as well. One 2009 study based in Nebraska found that women exposed to the most of organochlorine pesticides and fungicides were much (40%) more likely to develop hypothyroidism, which results often in weight gain, loss of libido and other serious medical conditions. 
News Flash #2: Recent research has found that Triclocarban, a chemical that is widespread in our water supply and various home care products such as antibacterial soaps, can actually increase testosterone. But before you try to transform yourself into Barry Bonds by washing your hands twenty times a day, I only relayed this story to show that we are not researching the products we put onto and into our bodies nearly enough. Who knows what else triclocarban does to you? Messing with your testosterone may be just the beginning.
Mercury: Although not really a pesticide, I want to mention that Methyl Mercury will definitely lower testosterone.  Sadly, one of nature's most healthy foods, fish, is often contaminated with Mercury and so extreme care is warranted. Most recommend fish only once or twice per week because of it. Researchers just announced that mercury contamination is extremely common in high fructose corn syrup: 50% of products tested by researchers were contaminated!  The issue apparently is that there are no standards for mercury residue in hydrochloric acid and hydrochloric acid is used to make high fructose corn syrup.
Other Articles You May Be Interested In:
2) Food Chem Toxicology, 2008, 46:270-279
3) 4) J Environmental Health, Jan 2009, 8:2"Mercury from chlor-alkali plants: measured concentrations in food product sugar", Renee Dufault, et al; Institute for Agriculture and Trade Policy, Jan 26 2009, "Much High Fructose Corn Syrup Contaminated with Mercury New Study Finds: Brand Name Food Products Also Discovered to Contain Mercury".
4) National Acad of Sciences, July 24 2009, "LIMITED DATA SUGGEST POSSIBLE ASSOCIATION BETWEEN AGENT ORANGE EXPOSURE AND ISCHEMIC HEART DISEASE AND PARKINSON'S DISEASE IN VIETNAM VETERANS", http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=12662
5) National Academy of Sciences, July 27 2007, http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=11906, "Data Suggest a Possible Association Between Agent Orange Exposure and Hypertension, But the Evidence Is Limited"
7) Brian Halweil, Nov 2002, Worldwatch Institute on November 1, 2002, "Worldwatch Paper #163: Home Grown: The Case For Local Food In A Global Market"
8) Exp Neurol, Apr 2007, 204(2): 619–630, "Dieldrin exposure induces oxidative damage in the mouse nigrostriatal dopamine system"
9) Hayes WJ jr. and Laws ET jr. eds. (1991) Handbook of Pesticide Toxicology, Academic Press Inc., San Diego, 732-735, 741, 828, 832, 836-840
10) American Journal of Epidemiology, 2010, 171(4):455-464, "Pesticide Use and Thyroid Disease Among Women in the Agricultural Health Study"