15 November 2002 16:30 EST

by Julie Clayton

The popular spice cinnamon contains cinnamaldehyde, a compound that may be toxic to human cells, says a leading pharmacologist. He is calling for a thorough risk assessment of the spice, particularly in view of its widespread use in both foods and cosmetics.

Without wishing to be alarmist, says Peter O'Brien, he has evidence that cinnamaldehyde blocks mitochondrial respiration and causes lysis of cultured liver cells. Building on others' results that cinnamaldehyde causes fetal abnormalities in rats, O'Brien is using the new data to "build a stronger case."

O'Brien, a researcher at the University of Toronto, is due to publish his results in the December issue of Chemico-Biological Interactions.

Before alarming the public, O'Brien says, researchers should first find out how much cinnamaldehyde people get in daily usage, and whether those amounts are likely to affect the developing fetus.

Manufacturers are now permitted to add pure cinnamaldehyde not only to food and drinks, but also to cosmetics for its aroma-enhancing property. But, O'Brien notes, they are not obliged to include it in the list of ingredients.

"It's found in so many products that it would take about 5 minutes to list them all," said O'Brien. Among the products: Bath oil, bath salts, lipsticks, soaps, toothpaste, mouthwash, hair cosmetics, candy, soft drinks and pastries.

In addition, cinnamaldehyde is used as a preservative for herbal remedies, and people of Middle Eastern origin use cinnamon sticks - whole pieces of bark from cinnamon trees in Sri Lanka - to flavor their tea.

In Canada, the "safe" daily intake for cinnamaldehyde is 1.25 milligrams per kilogram of body weight, O'Brien says. "At that concentration I wouldn't worry, but I think people are taking in more than that," he said.

In the UK, the safe dose is even lower - 0.7mg per kilogram - according to the UK Food Standards Agency. Cinnamaldehyde is now one of many flavoring agents under review by the European Union's Scientific Committee on Food, which is responsible for advising the new European Food Safety Authority.

Because the spice is widely used, finding out who is exceeding safe limits, and by how much, would not be easy, O'Brien says. To assess the risk posed by any particular dose would also require considerable testing, including animal studies, he adds.

In vitro studies, such as those O'Brien is due to report, are merely the starting point for risk assessment, says Andrew Smith, senior scientist at the Medical Research Council Toxicology Unit at Leicester University. Only animal data would enable extrapolation to humans, Smith says.

Epidemiological studies would be "the best work possible," but for most mutagens these are non-existent and "very difficult" to do, Smith added. "It's not like a drug where you've gone out and tested it on healthy people."

According to O'Brien, there are no human epidemiological data for cinnamaldehyde. It is well known, however, as an allergen and skin irritant in perfumes and hair cosmetics, and is now one a prime candidate for contact dermatitis.

O'Brien conducted the study on behalf of Health Canada, as part of a broader attempt to set new priorities for public health. He was originally called to investigate exposure to aldehyde compounds in general, following concerns about the inhalation of aldehydes derived from ethanol and methanol vapors at gas stations.

"I was a bit surprised to find some fairly toxic aldehydes in our diet," he said. "We had always assumed that they got metabolized rapidly but some of them inactivate the system that is trying to detoxify them."

Ironically, the toxic effects of cinnamaldehyde appear to be due to its ability to bind directly to aldehyde dehydrogenase, the enzyme needed for its destruction.

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See also:
Threshold of toxicological concern for chemical substances present in the diet ...
[Review]
R. Kroes, C. Galli, I. Munro, et al.
Food and Chemical Toxicology, 2000, 38:2-3:255-312

A procedure for the safety evaluation of flavouring substances
[Review Section]
I. C. Munro, E. Kennepohl, R. Kroes
Food and Chemical Toxicology, 1999, 37:2-3:207-232

The application of in vitro data in the derivation of the Acceptable Daily Intake ...
[Review]
K. Walton, R. Walker, J.J.M. van de Sandt, et al.
Food and Chemical Toxicology, 1999, 37:12:1175-1197
 

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