Does alcohol help or hurt your testosterone? That's a question every guy should ask himself. Alcohol is currently a much-loved chemical in the health media and blogging worlds. After all, it is manly, helps with heart disease and is often ground zero of our social universe.
However, for those of us who want to optimize our hormonal and testosterone levels, alcohol, or ethanol as it is known scientifically, is certainly no friend. Animal studies, for example, found that alcohol lowered testosterone levels in rats by about 40%.  We also know that heavy drinkers (without liver disease) have significantly lowered sperm counts, sperm motility and free testosterone.  By the way, alcohol does not just affect testosterone but growth hormone levels as well. 
The short term reason for this is that acetylaldehyde, the primary breakdown product of ethanol (alcohol), acts on the Leydig Cells directly to reduce testosterone production. Even small dosage levels affect testosterone production in isolated rat Leydig cells, a very bad sign indeed.  The drop in testosterone can even be more severe in those with depleted Vitamin E levels. Researchers found drops in testosterone of 50% in one study!  And consider this: rats fed a 5% ethanol diet lose 50% of the weight of their testicles.  Ouch!
NOTE: Researchers at the National Institute of Health believe that alcohol lowers testosterone through four key mechanisms: 1) an increase in the opiod beta-endorphin, 2) a reduction in testicular nitric oxide, 3) oxidative damage, 4) cell damage (from increased oxidation).  All of these pathways will lower testosterone and explain why alcohol is such a potent testosterone lowerer, especially in those who drink more than moderately.
Okay, so alcohol is hard on rats and dogs - so what about humans? Sorry, but alcohol has been found to be just as tough on human testosterone. One study found that (a heavy dose) of alcohol on 8 adult males lowered testosterone (and raised cortisol) for 24 hours afterward!  A more recent study, almost twenty five years later, verified that drinkers in the armed forces had lower free and total testosterone (and higher estrogen levels). 
What if you don't overdrink? The results are a little less noxious according to one study out of the Netherlands. These researchers found that moderate drinking lowered testosterone by 7% (but did raise HDL by 12%). 
Alcohol is also a notorious estrogen-increaser. It does this by affecting the liver's P450 enzyme subsystem in a negative way. Basically, it slows down your body's ability to process estrogen, allowing it to build up in your blood stream. That means, as good Peak Testosterone readers know, that testosterone will be reduced because estrogen is a testosterone lowerer.
If you think about it, alcohol fights your testosterone in almost every negative way possible: its breakdown products directly lowers Leydig cell production and it increases cortisol and estrogen, both of which are known testosterone blockers! And, as I have covered in another link on the Pros and Cons of Alcohol, drinking raises the risk for all GI cancers as well.
Many guys drink for social reasons and the heart benefits, but I just cannot see the advantage considering the fact that it can affect testosterone, estrogen and cortisol levels in such a negative way. This is especially important for use middle aged and beyond guys who are already struggling with these three hormones just from the aging process! If you are exercising with a Low Fat Diet, for example, your heart will be strongly protected anyway. In other words, you don't need alcohol.
And that's my summary really: you don't really need alcohol, so why bother? An occasional social drink is no big deal, but otherwise I'd stick to good, clean livin' and optimizing your testosterone. You need every last drop you can get!
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2) Alcoholism, Clinical and Experimental Res, 1997, 21(1):128-133, "Testicular function in asymptomatic chronic alcoholics : Relation to ethanol intake"
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4) Oxford Journals Medicine Alcohol and Alcoholism, 1987, 22:17-22, "ETHANOL-INDUCED INHIBITION OF TESTOSTERONE BIOSYNTHESIS IN VITRO: LACK OF ACETALDEHYDE EFFECT"
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6) Endocrinology Vol, 1979, 105(4):888-895, "Alcohol-Induced Testicular Atrophy in the Adult Male Rat"
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10) Mary Ann Emanuele, M.D., and Nicholas Emanuele, M.D., "Alcohol and the Male Reproductive System", http://pubs.niaaa.nih.gov/publications/arh25-4/282-287.htm