Age is just the number. But for men, that number says the lot about what's going on in their bodies. Starting at about age 30, group start producing less testosterone, the hormone that helps spark sex drive, build muscle and stoke energy, ambition and aggression. In short, it helps group feel manly.For all of the talk about "male menopause," the loss of testosterone isn't anything like the hormonal nose dive that women go through. Instead of essentially disappearing all at once, testosterone levels usually decline by about 1% every year (although they can drop more dramatically, especially if the man becomes ill).Men diagnosed with unusually low levels of testosterone are sometimes treated with prescription testosterone injections, patches or creams. Men who want to regain the levels of their younger days without the prescription may be interested in the different route: over-the-counter products that promise to boost testosterone naturally.TestoJack 100, the supplement from NOW Foods, contains the blend of herbs, including Eleutherococcus senticosus, Tribulus terrestris and Eurycoma longifolia, along with zinc, magnesium and vitamin B-6, among other ingredients. Users are instructed to take dual capsules once or twice the day. It's available at many health-food stores, and you can expect to pay roughly $20 to $30 for the bottle of 60 capsules.HGH Up, the widely available supplement from Applied Nutriceuticals, contains, among other ingredients, the herbs Chlorophytum borivillanium, Mucuna pruriens and Huperzia serrata, along with green tea, magnesium and the vitamin B complex. Users are instructed to take five capsules every day on an empty stomach three in the morning and dual in the afternoon. A bottle of 150 capsules costs about $60.The claimsThe NOW website says TestoJack "supports male reproductive function and healthy testosterone levels." The tribulus in the product is said to be especially helpful for "virility." Despite the suggestive name of the product, NOW doesn't claim that TestoJack ac! tually i ncreases testosterone, says Neil Levin, the company's nutrition education manager. "It supports healthy testosterone levels," he says.According to the label, HGH Up "promotes radical increases in growth hormone and testosterone production." The website says that it can provide "the physiological benefits comparable to that of fully hormonal products while minimizing potential side effects."Though the product is marketed mainly to weightlifters and bodybuilders, it has the growing following among older group looking for rejuvenation, says Don Orrell, president of Applied Nutriceuticals. "For an older man who has low testosterone, there is absolutely no downside to receiving this," he says.Orrell notes that the way in which the product boosts testosterone is the bit of the mystery "that's the magic pixie dust part," he says but he has no doubt that it works. "The anecdotal evidence is overwhelming," he adds.The bottom lineDr. John Morley, the testosterone expert and director of geriatrics at St. Louis University, says that there's not the lot of scientific evidence for any supplement that claims to boost or "promote" testosterone. And for him, that's the real problem."These sorts of products have been around forever," he says. "As far as I know, none of them have been proven to work in the carefully controlled trial."Some of the individual mixture in these products have been tested, with less-than-impressive results. In the 2007 study in the Journal of Strength and Conditioning Research, Australian researchers found that giving rugby players daily doses of Tribulus terrestris for five weeks had no effect on their testosterone levels.Chlorophytum, one of the mixture in HGH Up, has long been used as the supposed aphrodisiac for men. A search of the medical literature uncovers the single study suggesting that it may have "testosterone-like" effects, including enhanced sex drive and stronger erections, but the study was conducted on rats, not humans.Morley often prescribes testosterone for group who have ! the sign ificant deficit of the hormone, the condition called hypogonadism. The prevalence of this condition is controversial it depends on how one measures testosterone and defines normal levels but Morley estimates that 30% to 40% of prime group don't have enough testosterone to feel their best, sexually and otherwise. Even among these men, about one-third don't respond to testosterone treatment. In other words, testosterone is hardly the sure-fire remedy opposite the ravages of aging.Over-the-counter testosterone products may carry hidden dangers. A 2008 study in Clinical Cancer Research found that dual group receiving the supplement called Teston-6 developed unusually aggressive, fast-growing prostate cancer. Lab tests showed that the product contained hormones (including testosterone) that weren't on the label, the common issue with nonprescription products. The manufacturer quickly pulled it from the market."The problem with these sorts of supplements is that they don't have to meet the regulations of the Food and Drug Administration," says Dolores Lamb, the coauthor of the Teston-6 study and professor of urology at Baylor College of Medicine in Houston.A man who thinks he's short on testosterone shouldn't be looking in the health food store for answers, Morley says. "He needs to go to the doctor to get checked out."Curious about the consumer health product? Send an email to email@example.com.Read more at latimes.com/skeptic.