Can supplements save your sex life?

They'll tempt you with their marketing promises, but beware the dangers hidden within.

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It's February — time to think about roses, chocolates, sweethearts, and romance. And if those sentiments bring you to a certain drugstore aisle stocked with pills and potions promising to boost your sex life, you may want to think twice before buying any. "Most are a phenomenal waste of money, in my opinion," says Dr. Michael O'Leary, a urologist at Harvard-affiliated Brigham and Women's Hospital.

Unicorn juice?

With a few exceptions, most supplements for sexual function haven't been studied scientifically. At best, says Dr. O'Leary, they have a placebo effect (a beneficial result from an inactive treatment).

"That's not trivial in itself," he notes. "For example, when researchers did clinical trials for the prescription medication sildenafil [Viagra], the placebo response was about 30%. Which tells you that the most important sex organ you have is your brain. In men, the brain controls the stimulus to get blood flow to the penis, and furthermore, it controls orgasm and ejaculation. That's why a lot of people with normal vascular function still have sexual dysfunction."

But what about the claims that over-the-counter supplements can increase your libido or sexual endurance? They are simply marketing promises designed to sell you a bottle of pills, and nobody's checking in advance to make sure they're accurate. For example, a 2015 review of top-selling supplements for men's sexual health, published in The Journal of Sexual Medicine, found little or no evidence to support claims they could improve aspects of sexual performance.

Risky business

While the FDA has the responsibility to approve the use of any conventional pharmaceutical and to monitor how it is manufactured, the FDA has no such responsibility with regard to supplements. That means unscrupulous companies can sell any products they like, and the supplements won't be pulled from the shelves until and unless the FDA proves they're unsafe. So when it comes to supplements, buyer beware!

Some sexual function supplements may contain potentially dangerous impurities or small amounts of hidden pharmaceutical drugs — like traces of PDE5 inhibitors, medications in the same class that includes prescription erectile dysfunction drugs like Viagra. This can produce dangerous, even life-threatening, reactions.

A few exceptions

Popular sexual performance supplements often contain a blend of ingredients (sometimes dozens of them). Some of the best-selling include DHEA (short for dehydroepiandrosterone, an adrenal hormone), ginkgo biloba, fenugreek, ginseng, horny goat weed, L-arginine, maca, tribulus, yohimbine, and zinc.

Dr. O'Leary says most of those won't help your love life. But there may be a few exceptions.

L-arginine. This amino acid provides the raw material from which the body makes nitric oxide, a molecule that helps relax and open blood vessels, a necessary step to achieve an erection of the penis. "But putting that into a pill isn't proven to produce an erection," Dr. O'Leary says. Moreover, people with heart disease should avoid it. A study of L-arginine's effect on heart attack survivors had to be stopped early after six people taking the supplement died.

Yohimbine. This comes from bark of a tree native to Africa. "It does promote penile blood flow, but you have no idea whether the supplement you're taking has too much or too little," warns Dr. O'Leary. Another warning: yohimbine may damage heart function and may cause high blood pressure (hypertension), headaches, agitation, insomnia, and sweating.

Natural performance boosters

Lifestyle changes can help boost sexual activity without medication. "Very good data have shown that in men, weight loss alone improves sexual function. It's probably because fat makes estrogen, which fights testosterone needed for sexual function," Dr. O'Leary says.

Other things that can help for both sexes: exercising and smoking cessation, which improve blood flow to the sexual organs; limiting alcohol intake, since large amounts can dampen sexual reflexes and the ability of men to maintain an erection; and eating a healthy diet, which helps maintain a healthy weight.

If these approaches aren't helping, your doctor may be able to find a solution — that could involve treating an underlying condition or prescribing medication (for men) or lubricants and low-dose vaginal estrogen products for vaginal dryness and painful sex in women.