As Tom Harkin, the long-serving Democratic senator for Iowa and a national hero for liberals, has embarked on something like a retirement tour as of late (with Harkin stepping down after 30 years in the Senate next January), national Democratic figures, including many Democratic presidential hopefuls have taken the opportunity to heap praise upon the beloved native son of Cumming, Iowa.

Maryland Gov. Martin O’Malley, a probable 2016 contender, speaking at Harkin’s induction into the Iowa Democratic Hall of Fame, opined, “[E]ven more important than his length of service, I believe, is his strength of service. A strength that has always flowed from his belief in the dignity of every individual and his belief in our own responsibility to advance the common good.”

Vice President Joe Biden, an old friend of Harkin and fellow long-serving senatorial figure, also paid tribute to Harkin, saying, “As long as I’ve known you, from the time you first came to the House to your Senate days, you’ve been the conscience of the Democratic caucus.”

Most of this fawning praise is much deserved, with Harkin being one of the best friends the left has ever had in the Senate. Harkin introduced and was one of the key figures behind the passage of the Americans with Disabilities Act, the most prominent civil-rights legislation passed since the 1960s, which prohibited discrimination based on disability. Harkin has always been a strong supporter of labor unions, universal health care, reproductive rights for women, Social Security, a high minimum wage, and other causes near and dear to the hearts of many American lefties (me included).

However, this recent Harkin exaltation session has obfuscated one of the darkest parts of the senator’s prolific legacy, his unwavering support for one of the most corrupt and shameful American industries: dietary supplements.

In 1994, Harkin, along with Sen. Orrin Hatch, R-Utah, cosponsored the Dietary Supplement Health and Education Act. On Harkin’s website, the law is described as part of an effort by the two to “improve Americans’ access to safe products that help improve their health.”

It seems, however, that Harkin’s press team is playing very loosely with the term “safe.” Dietary supplements such as ephedra and methylhexanamine (OxyElite) have ravaged consumers, plaguing thousands with liver damage, heart problems, hemorrhaging, and, in some cases, death. The two dietary supplements, unlike hundreds of other less than scrupulous products, were taken off the market only after years of FDA handwringing.

And one of the reasons the FDA can only, in many cases, wring its hands over dangerous dietary supplements is because Harkin has led the successful effort to atrophy the FDA’s power in the matter. The 1994 law mandated that the dietary supplement providers did not have to provide the FDA with evidence showcasing the safety of their products, because the FDA does not have the authority to test products before they are marketed, providers can make claims about their products effectiveness without any FDA-approved evidence, and companies do not have to set limits on the amount of nutrients in one serving of supplement.

It’s abundantly clear that dietary supplements are grossly under-regulated and are acutely harmful to American consumers, both in the money they extract for at best ineffective and at worst destructive products (it is estimated that the industry collects $32 billion in profits every year) and the suffering they’ve heaped on hundreds of thousands of Americans. But why has a liberal lion such as Harkin attached himself to such a grotesque industry? Perhaps the answer can be found in Harkin’s campaign contributions; the dietary-supplements industry has always been one of Harkin’s largest donors (he is the second largest beneficiary of industry funds after, shockingly, Hatch.

Harkin is a hero to the millions of Americans whose lives he’s touched through good, moral, progressive legislation, and that should not be forgotten. However, when it came to a dangerous industry promising a treasure trove of campaign cash, “the conscience of the Democratic caucus” was anything but.