Diagnosis: Truth - MonaVie is light on health benefits, heavy on price

MonaVie claims to the company's own website. Far from shying away from the potential medicinal benefits, the company arranges them into easy-to-read bullet points.

Among other things, it asserts that MonaVie:

- Is "formulated to enhance your body's joint health by increasing mobility and flexibility."
- "Boasts healthy levels of plant sterols to protect your heart and cardiovascular system."
- "Delivers the antioxidant capacity of approximately 13 servings of common fruits and vegetables in just four ounces."

Let's unpack those statements.

The flexibility claim appears to be tied to the inclusion of glucosamine. A compound found in healthy cartilage, glucosamine has been shown to offer some benefit to people with mild to moderate osteoarthritis, particularly of the knee, according to the Mayo Clinic's website.

But an analysis by the Cochrane Review of 25 studies involving nearly 5,000 patients showed little difference in osteoarthritis-pain improvement between taking glucosamine and placebos. When older and lower-quality studies were considered, the scale tipped in favor of the real thing.

MonaVie contends that the type of glucosamine it uses, called glucosamine hydrochloride, is more concentrated than the other commonly available form, glucosamine sulfate. It's tough to say that's a big selling point because the concentration doesn't really matter when you get into larger doses (say, 500 milligrams or more).

On the plant sterol front, MonaVie rests its claims on a curious fruit called the acai (pronounced ah-SIGH-ee) berry, which is loaded with the stuff. Found in whole grains, unrefined vegetable oils and nuts, phytosterols help block the absorption of cholesterol in the body.

The evidence is strong enough that the FDA allows companies to claim that consuming 0.8 gram of plant sterols a day may reduce the risk of heart disease. And that happens to be the amount of plant sterols you get with the recommended daily intake of 4 ounces of MonaVie.

But some studies show that higher doses may limit cholesterol absorption further, and critics have noted there are cheaper ways to get the supplement into your diet. A tablespoon of Promise's Take Control spread, for example, contains twice as much plant sterol at a fraction of the price.

A common theme pops up for the antioxidants.

Pretty much everyone agrees that antioxidants are good for you, because they help protect against cell damage. A chemical analysis of so-called "superjuices" for Men's Journal in 2008 found that apple juice contained more of a key antioxidant than MonaVie. And MonaVie has five times less vitamin C, another antioxidant, than Welch's grape juice.

Overall diagnosis: Look elsewhere for a more nutritional bang for your buck.