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“Barebones” FDA Review of Impossible Burger’s Soy Leghemoglobin Inadequate, Says CSPI

Statement of CSPI Senior Scientist Lisa Y. Lefferts

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CSPI welcomes products that can have a reduced impact on the environment. However, ensuring the safety of their ingredients is essential, and critical to consumer acceptance of such products.

The Food and Drug Administration should have done a more thorough job in assessing the safety of soy leghemoglobin (SL), a key ingredient in the Impossible Burger, before reaching its decision to approve it as a color additive for beef analogue products that will likely be consumed by millions of people.

In its decision, FDA made no mention of its guidance on recommended toxicity testing for additives used in food, nor why it chose to ignore that guidance in approving SL as a color additive. FDA’s guidance recommends long-term safety testing for additives like soy leghemoglobin, which fall in the agency’s highest “concern level” category due to the extent of exposure. Instead, FDA relied heavily on a short-term (28-day) study, which provides no evidence of long-term safety.

Soy leghemoglobin is a protein that contains heme, a compound also found in red meat (specifically, in the myoglobin in red meat) and blood (in hemoglobin). According to the International Agency for Research on Cancer (IARC), an agency of the World Health Organization, there is “strong evidence” that heme contributes to the carcinogenic mechanisms associated with red and processed meats. Impossible Food told FDA: “Once cooked and digested, both soy leghemoglobin and animal-based myoglobin release identical heme B molecules into the digestive system.”

FDA should have considered this issue and required testing to determine whether the heme in soy leghemoglobin could contribute to an increase in cancer risk. At a minimum, it should have determined whether SL is associated with excretion of N-nitroso compounds, which is increased by heme and thought to play a role in meat-associated cancers.

The relevant safety question for additives—in contrast to naturally occurring substances—is whether they meet the applicable safety standard. Color additives, under U.S. law, must satisfy a more stringent “convincing evidence” standard for safety than other food additives.

FDA’s barebones review of the safety of heme excluded key endpoints well known to be associated with cancer risk and thus was inadequate under the law. We call on the company to conduct such tests given its responsibility to consumers and to other regulators around the globe.

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The Center for Science in the Public Interest is America's food and health watchdog.

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Jeff Cronin (jcronin[at]cspinet.org) or Richard Adcock, (radcock[at]cspinet.org).