Q&A: Is There A ‘Safe Level’ for Peanut in Foods?
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ST: Zero isn’t feasible. Logically, you can never attain zero. Unless you’re willing to live in a plastic bubble, you cannot completely avoid the allergenic food. It will be on the floor, in the air, in other foods – to some very low degree that doesn’t cause a reaction in you. In toxicology, every chemical has safe doses. Allergen residues are noteworthy because of the safe level is very, very low.
From a practical perspective, the consumers have been given absolutely the right advice, and that is to avoid as completely as possible the allergen to which they are reactive. When we say that safe doses of allergenic foods exist for everyone, we have to be very sure that people understand what that means; that we’re not telling them they can chuck their avoidance diets. They can’t.
GS: But how do we wrap our heads around the concept of a safe level – or “threshold dose” in food science terminology – when many of us are avoiding even the slightest peanut residue?
ST: [He says we need more context.] In the clinical diagnostic studies, especially the ones done a few years back, they used to do food challenges of allergic individuals and they started those challenges at doses of 100 milligrams up to 500 milligrams. That’s well above zero. And those doses did not provoke reactions in every case. In many cases, they had to escalate the doses beyond that in order to document that the person was allergic to the food. But some people did react to the very first dose, and some of them had fairly significant reactions. But I point out that was hundreds of milligrams, which is well above zero.
We now know that for peanut that in very low dose challenge studies that have been done on hundreds of individuals now, that the most sensitive ones react to less than a milligram of peanut, down to a half a milligram of peanut.
GS: This leads to the question, though, if you do see such a range in allergic response in peanut allergy, how do you come up with a safe level? How do you make one size fit all?
ST: When you look at threshold doses [the level at which an individual reacts] over a large population – as we have for peanut – you find that some people react as levels as low as one-half a milligram. But, other people do not begin to react until eight or 10 grams of peanut, and that’s equivalent to a handful of peanuts.
They [the latter group] have a pretty easy time with their avoidance diet, they’d have to make a pretty king-sized mistake in order to have an allergic reaction. But the people at the lower end of that curve are exquisitely sensitive and probably are at risk of experiencing reactions even with their best attempts to avoid. We have to be very cautious about those most highly sensitive individuals.
[Dr. Baumert mentions that FARRP has now established the peanut threshold levels of 750 individuals through oral challenges in clinical settings. Dr. Taylor notes that if you plot those findings on a curve, you can predict what levels will be safe for 90 or 95 or even 99.9 percent of the population. But statistically, you could never get to 100 percent.]
ST: What we would like to do is to have enough data that we know it protects 99 percent of the peanut-allergic population. [For the remaining 1 per cent], we think reactions will be mild. But we can’t promise that no one will have a reaction.
Next page: The One-Shot Experiment