SAN DIEGO -- When controversy erupted around hormone replacement therapy, women started turning to soy supplements to cool the uncomfortable symptoms of menopause.

Millions of women now swear by them, but are the supplements worth it?

Marilyn Noble said she wouldn't think of starting her day without a soy shake.

"I started drinking the shakes because of the hot flashes. For me, they've been a life saver," Noble said.

Noble chose soy supplements instead of hormone replacement therapy once menopause set in.

Same for Cathleen Partridge, who said she was desperate to stop the unbearable hot flashes.

"The soy completely relieves my symptoms," Partridge said.

Soy contains natural compounds called isoflavones, thought to have weak estrogen-like effects. Even though there's no conclusive evidence the supplements work to relieve menopause symptoms, devotees are dishing out tens of millions of dollars every year.

There are dozens of supplements to choose from, but experts say they're not all the same.

"It's a kind of a buyer beware situation," Tod Cooperman, with Consumer Lab, said.

Cooperman recently tested 33 leading brands to see if you get what you pay for.

"A few of the products on the market are bad in terms of their quality. We also found that some of the products labeled the ingredients differently," Cooperman said.

Cooperman said the biggest thing women need to know before they shop is how to read the labels. He said the amount of active ingredients can vary widely because isoflavones naturally have sugar attached.

"Some manufacturers can report the weight of the isoflavones including the sugar, which is actually not active, and others will report it not including the weight of the sugar," Cooperman said.

He stresses to look for isoflavone products that don't include the sugar in the weight.

"You can actually look on a label, and if you see the word aglycone isoflavones, that means without the sugar. You can (also) look at the actual type of isoflavones like genistein or daidzein," Cooperman said.

Sugar is not the only issue.

Three brands failed the Consumer Lab test -- two for having fewer isoflavones than advertised on the label, 10News reported.

Cooperman said the third wouldn't dissolve, meaning users couldn't absorb the ingredients.

"I hate to see people waste their money," Cooperman said.

Dr. Andrew Good is a menopause expert at the Mayo Clinic. He doesn't recommend isoflavones to his patients because the studies he's seen haven't shown real benefits.

"Women using isoflavones didn't have any increased help," Good said.

Good said while many women believe isoflavones are helping, it may just be a placebo effect.

"My caution would be that lots of women will spend a lot of money on something that really doesn't have any biologic effect," Good said.

But Noble and Partridge said no matter what the studies show, they have all the proof they need. They said the supplements have worked and have saved them from suffering during menopause.

Americans spent nearly $50 million on soy products for menopause relief in 2003, 10News reported.

If you're thinking about taking isoflavones, it's important to speak with your doctor first.