Why Some Foods Are More Allergenic Than Others

An absolutely fascinating piece of research was just published in The Journal of Allergy and Clinical Immunology

(DOI: 10.1016/j.jaci.2007.08.019.) "Evolutionary distance from human homologues reflects allergenicity of animal food proteins," by John Jenkins, Heimo Breiteneder, and Clare Mills.

Articles explaining the research can be found in more - ScienceDaily.com - or less - FoodNavigator.com - straightforward English on those sites.

The investigating team compared several types of proteins across a wide variety of types of animals, from insects to mammals to humans. If the protein was at least 55% identical to the human protein, few if any allergic reactions were produced. But proteins less similar triggered the immune system of the human body in some people.

"This explains why people who are allergic to cow's milk can often tolerate mare's milk but not goat's milk", said Dr Clare Mills of the Institute of Food Research. "Proteins in horse milk are up to 66% identical to human milk proteins, while known allergens from cows and goats are all less than 53% identical to corresponding human proteins.

Overall, the researchers believe that the reason why just a few percent of humans have milk allergies is that the protein similarities are so close to the border of tolerance.

"Animal food proteins lie at the limits of the capability of the human immune system to discriminate between foreign and self proteins", said Mills.

The researchers looked at all the main types of proteins and made a major discovery.

For the first time the researchers found that the majority of animal food allergens could be classified into one of three protein families. Tropomyosins, proteins found in muscle tissue, are the most important family.

"Tropomyosins in mammals, fish and birds are at least 90% identical to at least one human tropomyosin and none have been reported to be allergenic. In contrast, the allergenic tropomyosins are all from invertebrates such as insects, crustaceans and nematodes and at most are only 55% identical to the closest human homologue", said Dr Heimo Breiteneder of the Medical University of Vienna.

EF-hand proteins form the second largest animal food allergen family. Those in birds and mammals are not allergenic, while those in frogs and fish can cause allergy. The third animal food allergen family, caseins, are all mammalian proteins from milk. The researchers analysed milk from rabbits, rats and camels as well as sheep, goats, cows and horses.

In previous analyses of plant food allergens published in 2005, the scientists found that most belong to a highly restricted number of protein superfamilies. The research will make it easier to identify new allergens and help explain how they trigger an immune response.

I reported a year ago that work was underway to develop a vaccine for allergies, but that 7 to 10 years was likely to be needed. See Cure for Allergies? Don't Hold Your Breath. I'm not sure if this work makes that wait any shorter. However, it's extremely promising research and a critical needed step.

More Uses for Whey and Lactose May Be Coming

Whey is a cheap by-product, effectively what the cheese industry used to throw away. Naturally, food scientists saw whey as an opportunity. Sure enough, whey started to be added to a million packaged food products.

Since lactose is most easily refined from whey, whey is the source of the lactose used in food products and also in medications.

Good for the food industry, bad for us.

Now the food scientists, who can't seem to let anything alone, are interested in finding a new use for whey and lactose. Microencapsulating aerogels.

Stephen Daniells pays that into English for us at FoodNavigator.com, discussing an article, "Use of whey proteins for encapsulation and controlled delivery applications," by S. Gunasekaran, S. Koa and L. Xiao in Journal of Food Engineering (Elsevier), Volume 83, Issue 1, Pages 31-40.

Whey proteins hydrogels - 3D networks with the ability retain water in its structure when dissolved - have the potential to encapsulate sensitive ingredients, suggests a new study.

"The advantages of using whey protein-based gels as potential devices for controlled release of bioactives is that they are entirely biodegradable and there is no need for any chemical cross-linking agents in their preparation," wrote the authors.

...

They also report that the swelling and release behaviour could be easily slowed by coating the gels with alginate, a result that could lead to targeted release of bioactives at specific points in the gastrointestinal tract.

So the idea is that a drug, a vitamin, a nutrient, or whatever is needed could be encapsulated like time-release capsules, only much, much smaller, and delivered to the exact point in the intestines where it is needed. Actually, that sounds pretty good. Much better than just swallowing a pill, hoping the medication survives the acid bath of the stomach, and assuming that the right dosage will be absorbed before the whole mess is pushed out of the system.

The question for us, as yet unanswered, is whether the whey protein - or possibly lactose - would create symptoms in those who are susceptible to the proteins or milk sugar.

Too soon to tell, I suppose. As Daniells wrote:

More research is needed to further explore the potential of whey protein hydrogels, and whether other bioactives, both lipid and water soluble, could be encapsulated in this way.