It Drops Your Testosterone Level — Even Messes Up Your Lab Tests

This century’s version of “real men don’t eat quiche” might turn out to be “real men don’t eat sugar”… based on a recent study in which testosterone levels were found to plunge after men consumed sugar.

Researchers at the Harvard Reproductive Endocrine Sciences Center and Massachusetts General Hospital in Boston gave a glucose tolerance test to 74 men, average age 51. This is a standard test in which subjects drink a 50-gram, 75-gram or 100-gram dose of pure glucose (in this case, 75 grams), after which their blood levels of sugar and insulin are measured at 30, 60, 90 and 120 minutes. Researchers also measured testosterone levels and found that for 73 of the 74 subjects, testosterone was significantly reduced after drinking the glucose.

Aside from the fact that few men feel comfortable messing with their testosterone levels, another reason this is important is that it demonstrates how eating sugar could have a profound effect on the results of medical tests for hormones. Where men had previously been told that they didn’t need to fast prior to having blood drawn for such a test, it appears that the results are skewed by blood sugar levels — so fasting may be necessary.

Testosterone, the major male sex hormone, affects energy, well-being and libido and helps maintain bone density, muscle mass and even red blood cell production. Testosterone production peaks in adolescence for males, and though there are considerable individual variations, it generally begins to wane around age 40 as men experience andropause. So it is no wonder that testosterone replacement therapy has become big business and is frequently prescribed by doctors who advertise themselves as specialists in “antiaging medicine.”

When I asked our medical editor, Andrew L. Rubman, ND, about these findings, he said they make perfect sense. “Men are becoming aware of the fact that stressful lives, poor diet and poor lifestyle can depress testosterone levels,” he said, “so it’s wise to now look at yet another factor — sugar — that influences this important hormone.” He notes that not only is this a significant finding that will likely impact how testing is done going forward, it also raises questions about how reliable results are for men whose testosterone levels were checked with a nonfasting test. “It may be that not only do they not need it, but men may be doing themselves harm by taking testosterone that they don’t need or by taking the wrong dosage.”

Interestingly, the men who were the most “normal” in their response to the glucose test had the greatest drop in their testosterone levels, though Dr. Rubman said this isn’t as surprising as it might seem. He pointed out that people who focus on eating pure and organic foods and who don’t take many medications often can feel the effect of a single aspirin, whereas a drug abuser could take several codeine tablets and hardly notice. The effect with sugar is similar — a little bit has a greater impact in people who don’t eat much of it.

His advice is to consider sugar a “recreational substance, to be enjoyed as a condiment and in close proximity to meals.” He suggests that men taking testosterone replacement ask their doctor for a retest of their levels after three days of simple sugar avoidance with a 24-hour urine catch and an overnight fast. (Your last meal before fasting should be light protein, such as chicken or fish, and a salad.) “The results will be much more clinically significant and will help keep your doctor from giving you an unintentional overdose of testosterone,” said Dr. Rubman, adding that “sugar is like cheap wine — the pleasurable effect is short-lived and the payback may not be worth it.”