Tide of seaweed promises can ebb and flow

Seaweed can shrink your waistline. Grow your hair. Bring down your blood pressure along with your blood sugar. Build up the strength of your bones and your brain. Make your joints stop aching and your bowels get moving. Give cancer short shrift, and give cellulite and wrinkles the old heave-ho.

That is, if you believe the hype — only some of which is backed up by reliable evidence.

The data are strongest that seaweed can reduce inflammation, premenstrual syndrome symptoms and even the growth of tumors (in animals), says Dr. Mary Hardy, a nutrition and food supplement expert at UCLA.

Dr. Karthik Krishnamurthy, a dermatologist at Montefiore Medical Center in the Bronx, also cites the widespread use of alginate, a component of seaweed, in wound dressings that yield excellent healing results.

But overall, they and many other doctors, including those at the National Institutes of Health, are reserving judgment. “Seaweed is really big right now,” Krishnamurthy says. “Still, a lot of claims about it are unfounded at this time. I hope something comes of it, but we’re not there yet.”

Others, though, are already convinced of at least some of the powers of seaweed. Lydia Sarfati, in fact, was convinced more than 30 years ago, and she founded the skin care company Repechage, which offers 167 products, all seaweed-based.

Known to many as “the queen of seaweed,” Sarfati says, “I know what I’ve done for thousands of women, women in their 60s who still look beautiful, without surgery.”

So what to do? Hold your sea horses until more is known? Or jump on the seaweed bandwagon — along with Katherine Heigl, Ashley Olsen and Madonna, just for examples. Heigl is a fan of Repechage’s Triple Firming Cream, and Olsen has visited the company’s New York City spa for seaweed-based skin and body treatments.

From the experts, here are some pros and cons to keep in mind.

As a food

The upside: Seaweed is loaded with all sorts of substances that make it good-for-you eating: vitamins, minerals, fiber, high-quality protein, and omega 3 and omega 6 fatty acids. (Seaweed can have up to 10 times as much calcium as milk.)

Seaweed is available reasonably readily — in Asian restaurants (in soup or salad or wrapped around your sushi) and in Asian and other specialty markets (fresh or dried or in snack foods).

The downside: “It’s an acquired taste,” says Miriam Pappo, director of clinical nutrition at Montefiore Medical Center. And if perchance you have a hard time acquiring the taste, you’re also likely to have a hard time eating enough to actually affect your health.

As a supplement

The upside: This is an easy way to get a lot of seaweed.

The downside: There are thousands of species of seaweed, ranging from edible to poisonous, Krishnamurthy warns, and since supplements don’t require FDA approval, you can’t always be sure what you’re buying. “Anyone can go get seaweed, mix it up, grind it up and sell it,” he says.

Even supplements made from the safest of seaweeds can present dangers by possibly giving you too much of a good thing. For instance, the iodine in seaweed is considered a big plus -- up to a point. After all, getting too little iodine can cause thyroid problems (and can be especially serious for pregnant women and their fetuses). Unfortunately, getting too much iodine, a possibility with a seaweed supplement, is another way to throw your thyroid out of whack.

Besides these specific concerns, Pappo has a broader one: “The longer I work, the more I believe in the benefits of eating food and the less I believe in taking supplements.”

In skin care products

The upside: Evidence is pretty reliable that seaweed’s anti-inflammatory properties can be helpful with acne and rosacea, Krishnamurthy says.

Others believe that seaweed is also a potent weapon in the war on wrinkles. Seaweed is a pure concentration of sea water, Sarfati says, and like sea water it’s similar in composition to human plasma. So the skin can be rehydrated by this “sister substance,” making it “plump, smooth, without wrinkles.”

The downside: Like supplements, seaweed-based skin care products are not regulated by the FDA, so you can’t always be sure what you’re getting. There’s a risk of severe allergic reactions associated with some kinds of seaweed, Krishnamurthy says, “And there you are rubbing it all over your face.”

The verdict

Many are true believers in the wonders of seaweed. Sarfati’s faith was born during a visit to Israel 33 years ago when she marveled at how fresh the food tasted and how beautiful it looked. Told that this amazing produce was grown with seaweed fertilizer, she had an idea: Perhaps seaweed could have the same enhancing effect on people’s skin. And, she now says, she was absolutely right.

Others remain seaweed agnostics. “The only broad statement I can make,” Krishnamurthy says, “is that I can’t make any broad statement.”