I am a science fanatic, but one of the curses that the scientific age has brought upon us is a tidal wave of chemicas, many extremely common in every day life, that can pull the rug right out from under your hormonal hindquarters. Read the list of chemicals below and you'll be ready to hide under the mattress (instead of doing something constructive on top of it) in order to save your precious testosterone. Maybe the Amish were right after all!
The good news is that, for the most part, these chemicals can be avoided with a few simple lifestyle changes:
1) Excitotoxins. Animal studies show that fetal exposure to excitotoxins, such as MSG in food and aspartame in diet drinks, can lead to reproductive and hormonal abnormalities in puberty and beyond. Read more about Testosterone and Excitotoxins and find out more. SOLUTION: Buy nothing in it with MSG, aspartame, monosodium glutamate, autolyzed yeast extract, Equal or any of the other ingredients I list in Testosterone and Excitotoxins.
2) Mercury. Mercury, specifically methylmercury, is a testosterone (and other hormone) killer. See my link on How to Protect Your Testosterone From Mercury for more details.
3) Pesticides. The FDA has gotten rid of some of the worst testosterone-whacking pesticides, such as DDT, but many still remain. Read about Testosterone and Pesticides for some of the sobering details. SOLUTION: Avoid the dirty dozen fruits and vegetables mentioned in Testosterone and Pesticides for being particularly overly sprayed. You may even want to buy organic when possible.
4) Drugs and Pharmaceuticals. Yes, there are some drugs that lower testosterone. Read more about Statins for one of the most common examples. SOLUTION: Check all of your medications (with your pharmacist and doctor) for testosterone lowering properties.
5) Phthalates. I hope you didn't sound like you were coughing up a fur ball trying to say this one, but it's actually quite easy: just don't say the "ph". That's right - phonetically these are "thal-its" and they are just as nasty to your testosterone as they are to say. These are potent endocrine disruptors that every hormone-luvin' male should avoid like the plague. One study examined dosages of 100, 80, 60, 40, 20, 10, 5, or 0% of the mixture.on fetal rates and found a dose-dependent decrease in testosterone, meaning the more phthalates, the less the testosterone.  Low testosterone can be just as devastating for a male infant. Researchers have found evidence that phthalates, a common family of chemicals used in air fresheners and to soften plastics that lower testosterone  are linked to effeminizing behavior in boys. See number 10 in my link on Child IQ for more details. Animal studies have shown nasty effects from phthalates as well, including permanent reproductive disorders  and a recent human study showed lowered sperm counts as verification. In other words, the damage seems to be permanent. SOLUTION: Use only glass and stainless steel for cooking and don't let anyone freshen your air.
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6) Bisphenol-A. The chemical, used (in America) in almost every canned good, is a proven endocrine disruptor. Read more about Bisphenol-A to find out how the levels that we are commonly exposed to are enough to have a clinically negative effect. SOLUTION: Avoid canned goods.
7) Lead. China is by now means the only source of lead in our environment but has been implicated frequently in a number of recent studies and exposes. Our children are particularly exposed to the onslaught of this chemical we once thought we had purged from our environment. Lead is a known testosterone-lowerer. One study, for example, found that lead exposed and poisoned men, who had complained of lowered libido and intercourse, had reduced Leutinizing Hormone and, therefore, testosterone levels.  This is just the beginning, however, as lead attacks many systems in the body, including the brain and kidneys. Since we've eliminated lead in our gasoline and paints, we're safe, right? Read this Consumer Report's article on the many products they found with lead. SOLUTION: This is the toughest one as there is no inexpensive, easy way to detect and avoid lead products.
1) Toxicological Sciences, 2008, 105(1):153-165, "A Mixture of Five Phthalate Esters Inhibits Fetal Testicular Testosterone Production in the Sprague-Dawley Rat in a Cumulative, Dose-Additive Manner"
2) Toxicology, 1 June 2006,223(1-2):144-155, "Mechanisms underlying the anti-androgenic effects of diethylhexyl phthalate in fetal rat testis"
3) Food Chem Toxicology, 2008, 46:270-279
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".
5) Infertility, 1978, 1(1):33-51, "Hypogonadism in chronically lead-poisoned men"