The marketing for Bayer’s One A Day brand of multivitamins makes some very specific claims about what these products can do to improve a user’s health. But a new lawsuit brought against the over-the-counter drug giant argues that Bayer’s statements aren’t always backed up by the science necessary to make those claims.

The proposed class-action suit [PDF], filed in a federal court in California by the Center for Science in the Public Interest, contends that Germany-based Bayer AG and its U.S. subsidiaries Bayer Corporation and Bayer HealthCare, of false advertising, unjust enrichment and violation of California consumer protection laws.

The plaintiffs seek an injunction preventing Bayer from making what they allege are misleading statements in One-A-Day ads and on the product packaging, along with refunds for consumers who purchased these products based on the at-issue statements.

“Bayer commands a premium price for its One A Day multivitamins by distinguishing them from regular multivitamins with targeted multivitamins aimed at various segments of the population based on age, gender, and even health concerns,” reads the complaint, which cites phrases like “heart health,” “immunity,” and “physical energy” that Bayer uses to market various One A Day products.

The complaint alleges that Bayer “deceives consumers about One A Day Multivitamins” by “bombarding” them with “messages of purported health benefits, and even using scare tactics to convince consumers that they need Bayer’s multivitamins.”

According to the plaintiffs, Bayer is allegedly trying to hide the fact from consumers there is “very little difference” between the numerous One A Day varieties.

The One A Day website currently breaks down the products into four categories — “Products Specially For Women,” “Products Specially For Men,” “Products For Healthy Lifestyles,” and “VitaCraves Gummy Multivitamins.”

Then each of these has multiple varieties. For example, the page for female-targeted vitamins lists 10 different One A Day products that specifically target everyone from teens, to prenatal women, to the over-50 crowd, to “petite” women to menopausal women, to females with “active metabolism.”

Males have fewer options, with only five varieties listed.

Bayer’s “heart health” claims are based on the use of vitamins B6, B12, C, E, and folic acid in their products.This recent ad features regular guy talking about taking care of his “engine” with “One A Day Men’s, a complete multivitamin with nutrients to help support heart health.”

But the plaintiffs argue that scientific investigation, including research from the National Institutes of Health and the American Heart Association, has shown that supplementing your diet with these vitamins is not proven to prevent or reduce the risk of heart disease.

Thus, CSPI alleges that Bayer is illegally making a false claim of disease prevention.

The complaint also cites NIH and AHA research in attempting to debunk Bayer’s “support physical energy” claims based on the presence of many of the same vitamins in One A Day products.

Another example of supposedly questionable marketing cited by the complaint involves claims that various One A Day products “support immunity,” based on the presence of vitamins A, C, E, selenium, iron, beta-carotene, and zinc.

Again, CSPI points to what it believes is a lack of scientific evidence to back up this claim. In fact, the complaint contends that randomized clinical trials demonstrate that multivitamins do not affect the number, severity, or length of any illnesses.

“A multivitamin can be beneficial to those who are vitamin deficient, which few Americans are,” said CSPI litigation director Steve Gardner in a statement. “None of Bayer’s multivitamins can unclog arteries, prevent heart attacks, or otherwise ameliorate heart disease. And to the extent these claims prompt people to take vitamin pills instead of doctor-prescribed heart medicines, Bayer may be harming people’s health as well as their wallets.”

Bayer has been down this road before, having previously settled in 2010 with multiple states’ attorneys general over claims that the use of selenium in One A Day products might protect against prostate cancer.

The company also paid millions in 2007 to close a federal investigation into bogus weight-loss claims about One A Day products.

That 7-year-old settlement came back to bite Bayer on the derriere in September, when the Justice Department asked that the company be held in contempt for violating that consent order because it was allegedly making unsubstantiated claims about Phillips’ Colon Health pills.

We’ve reached out to Bayer for comment, but have not yet heard back from anyone.

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