The group explained in a statement that this step was necessary in order to "reduce confusion and improve the efficiency of industry's implementation of new labeling requirements".
The requirements for both rules are supposed to become effective on 1 January 2006. However, many in the food industry believe there is a problem of clarity, that the trans fat rule requires compliance by the "date of initial introduction into interstate commerce" while the food allergen legislation requires "date of production".
These differences, think the signatures of the letter, will introduce significant confusion into the process of food labeling and distribution as most food companies will have to comply with both sets of requirements.
"To remedy this problem, we request that the FDA harmonize these requirements so that all labels need to meet the same effective date, triggered in the same way," said the letter.
As the food allergen labeling requirements are statutory and therefore not subject to change by the agency, the letter recommended that the FDA harmonize the two sets of rules to be in line with this legislation.
"This would mean the trans fat rule would likewise be enforced in such a way that food products with a 'date of labeling' on or after 1 January 2006 would be subject to the new rule," concluded the letter.
Organizations that were signatures of the letter included the American Bakers Association, the American Frozen Food Institute, the International Food Additives Council and the Grocery Manufacturers of America (GMA).
In December rejected the Center for Science in the Public Interest's campaign to free America of trans fats, saying that the CSPI had "oversimplified" the issue.
The CSPI began officially petitioning the FDA earlier this year to remove trans fats from the US food chain, stating that: "Partially hydrogenated vegetable oils […] cause thousands of heart-attack deaths each year" and that "safer alternatives are widely available".
However, Alison Kretser, director of scientific and nutrition policy, for the GMA, said last month that the CSPI has oversimplified the trans fat issue. She noted that one of the main challenges faced by food companies is finding alternative oils that can give products the taste, texture and shelf life that consumers have come to expect.
And added, that once a substitute oil is located, food companies need to know they can secure enough of it to satisfy demand.
Perhaps more worryingly for the health lobby is that Kretser thinks an effort to force companies to use alternatives to PHOs before substitute oils are available "would have the unintended consequence of increasing saturated fat consumption".
GMA thinks instead that realistic goals and an achievable time frame should be put in place.
Michael Jacobson, the executive director of CSPI, assured FoodNavigatorUSA.com at the time that his organization was not asking for an immediate ban on trans fats, but was simply getting the ball rolling because it was aware of the slow pace at which the FDA works and agreed with then GMA's worries over supply.
"Many food companies, especially the bigger ones, such as Kraft and Campbell's are hard at work to come up with alternatives," Jacobson said, adding that he believes that in five years time trans fats will be virtually gone from the prepared food supply, though he is more skeptical about the restaurant business where labeling will not be required.
Trans fatty acids (TFAs) are formed when liquid vegetable oils go through a chemical process called hydrogenation. Common in a range of food products - biscuits, chips, doughnuts, crackers - the hydrogenated vegetable fat is used by food processors because it is solid at room temperature and has a longer shelf life.
But research suggests that trans fats raise LDL (bad) cholesterol levels, causing the arteries to become more rigid and clogged. An increase in LDL cholesterol levels can lead to heart disease.