The prevalence of food allergies is on the rise. You may have personal experience with food allergies amongst your friends, family, or even your own kids. I decided to ask my friend David Jeong, M.D. to offer some insight on the topic of food allergies. Dr. Jeong grew up in Iowa, attended Northwestern University for his undergraduate work, the University of Iowa for medical school, the University of Michigan for his residency in Pediatrics, and the University of Washington for his fellowship training in Allergy/Immunology. Here is his response to my questions: Thank you Dr. Jeong!
What are some of the common ways food allergies present?
What are some of the more widely accepted theories amongst allergists as to why there has been a dramatic rise in food allergies in recent years? a) Hygiene hypothesis: lack of early childhood exposure to (allergens)...leads to an imbalanced immune system, skewing its development more toward allergy.
b) Food preparation: roasting vs boiling peanuts, for example. Western countries roast more than boil, which leads to higher cooking temps (180C) and leads to increased stability of heat stable proteins in peanut...leading to greater allergenicity.
c) The Dual Exposure Hypothesis. This has to do with what happens to the immune system when a person is exposed to a food by skin contact vs oral ingestion. Incidental skin contact on household surfaces can be (allergy) promoting, and...food exposure via oral ingestion can promote immune tolerance. Up until 2008, in countries like the US, pediatric and allergy guidelines advised avoidance of high risk foods until between one and three years of life, which left the only likely mode of exposure during those years of life through incidental skin contact. Without the oral exposure to...promote immune tolerance, the incidence of allergies began to rise. As of 2008, both the American Academy of Pediatrics and the American Academy of Allergy Asthma & Immunology revised their guidelines to suggest that delayed introduction of milk, eggs, nuts, and seafood may not be the right thing to do. There has been plenty of literature to support this over the last 5-10 years. What are the most common food allergies? Is there a mechanism behind why certain foods are more allergenic than others?
Milk, egg, wheat, soy, nuts, and seafood account for more than 90% of all food allergies in western countries. All of these foods are "allergenic" to equal degrees, particularly early in life. What is different is the natural history of certain foods compared to others. Nuts and seafood allergies persist into adulthood to a greater degree (> or = 80% as opposed to less than 20% with the other foods listed), likely because of the very heat stable proteins within these foods, leading to a persistent immune response with repeated exposures.
Why are some food allergies diminished by cooking (i.e. cooked fruits?)
It has to do with the protein structures within the foods. The classic example is oral allergy syndrome, aka pollen food cross-reactivity syndrome. There are proteins in certain fruits, vegetables, and nuts that share a high degree of cross reactivity to pollens from birch tree or timothy grass, to name a few. When a person is allergic to these pollens and then eats a fresh fruit (ie apple), that person could develop a sensation of itching, tingling and a lump in the throat. When that same person eats an apple pie, no reaction! The baking process essentially denatures or destroys the protein, rendering them unrecognizable to the allergic person.
What is the role of blood tests in identifying food allergy? We have to distinguish whether a person is "positive" without ever having eaten that food versus being "positive" but eats the food regularly without any symptoms. If the former and the test is done by blood testing...then it is strongly recommended that the patient consult with an allergist. (Allergists use) certain predictive value cut offs based on the medical literature, and these cut offs show that even if a person has a "positive" result it may not be necessary to avoid that food. If the latter, keep eating the food!! The test is not perfect, and...antibodies can be picked up by testing that have nothing to do with true clinical reaction.
If there is a strong family history of allergy, what can parents do to prevent food allergies from developing in their children?
Remember, blind avoidance is not necessarily required. In this case, innocent until proven guilty. If a mother is pregnant, it is not recommended that she blindly avoid nuts, seafood, or any other food with the thought that it will prevent her soon to be born child from developing food allergies. The current evidence (suggests that) exposure to a food early and often seems to be more allergy preventive than delayed and infrequent exposure early in life. (i.e. consider introducing peanut containing foods at age one rather than age three). The only action that has been shown to provide any benefit is if the mother can breastfeed for at least the first four months of life. This could lessen the chance that this child develops allergies down the road.
Fresh food just tastes better. Therefore, if you want to get your kids to embrace vegetables, serve them fresh vegetables that are in season. You can check out the application at the bottom of my blog to see what foods are in season in your area. Unfortunately, if you live in an area like mine that actually has four seasons, nothing is in season right now. Wintertime is an ideal time to eat frozen vegetables. Frozen vegetables are picked at peak season, then flash frozen to preserve their freshness. By cooking frozen vegetables, your kids can continue to enjoy the taste and benefits of vegetables anytime and anywhere. One of the key historical figures we can thank for high quality frozen vegetables is Clarence Birdseye of the Birds Eye Frozen Food Company. In his biography, Birdseye: The Adventures of a Curious Man, Mark Kurlansky shows that Birdseye was much more than just a man with a clever name. He was a brilliant inventor, hunter, entrepreneur, and teacher. He is also considered to be the founder of the modern frozen food industry. While ice fishing with the Intuit, Birdseye discovered that the fish he caught froze instantly and tasted fresh when thawed. He later discovered that the key to fresh tasting frozen food was how rapidly the food was frozen. Food that is frozen slowly develops large ice crystals while food that is frozen quickly develops smaller ice crystals. Larger ice crystals are more damaging to the cellular structure of food. Additionally, when slowly frozen foods thaw, cellular fluids leak from the ice crystal-damaged tissue, resulting in a mushy and unappetizing consistency to the food. Birdseye developed new technology to quickly freeze food, preserve their architecture, and enhance their taste. After running countless experiments, he found that certain types of food such as fish fillets, spinach, and peas are particularly amenable to freezing. In the following movie trailer, I introduce Dr. Freeze, an infamous character with the power to freeze food. Happy Holidays!
Developing healthy eating habits is only partially about distinguishing healthy from unhealthy foods. It is also about developing a healthy psychology about food choices. In my previous post, Dr. Stewart Zelman discussed how children use food to express choice. In this post, Dr. Zelman discusses the importance of modelling healthy eating behaviors for children. Chris : What tips do you have to help kids develop positive eating habits? Dr. Zelman : Be a positive role model for your children. When you model positive eating habits, they will follow suit. Children are open to the messages they receive from their environment and are easily influenced. It is imperative that as a parent, you set a good example for them so that they can carry these positive habits into adulthood. Drinking water daily, choosing healthy snacks, and moderating portions are all important habits to develop at a young age. Try to pack your child's lunch as often as you can to continue the positive eating habits you set at home. Stick to a structured eating schedule with children. Set aside specified mealtimes and snack times. Do not force children to eat if they aren't hungry. Also, do not allow children to replace a skipped meal with an unhealthy snack. Instead, offer them a healthy snack option and then allow them to eat a full meal at the next mealtime. Chris : What do studies show regarding how early eating habits develop in kids and how that affects eating behavior over the long run? Dr. Zelman : Studies show that kids develop early eating habits from what they observe in their surroundings. Parents should ensure that they are setting a good example by monitoring their own eating habits, attitudes, and choices. Children pick up cues very quickly and begin to mimic their parents' behaviors. Positive eating habits can lead to a child developing positive habits in other domains as well. Chris : What tips do you have for picky toddlers? Dr. Zelman : Toddlers are going to be picky about what they eat and this is a normal part of their development. Parents should try not to become anxious or overwhelmed by this fact. You just have to get a little creative. Also, parents should try to make mealtime as relaxing and anxiety-free for their child as possible. Eat together as a family. Children are more likely to feel comfortable with eating particular foods if everyone else is eating the same food at the same time. They need reassurance that the food is good and safe. Give small portions to toddlers so that they can taste the food and do not feel too pressured by a large amount of a food. Also, get your toddler involved not only in meal preparation but in shopping for ingredients as well. If they are able to see the entire process that goes into preparing the foods they are served, they are less likely to refuse to eat them.
Being a positive role model for you kids is easier than you might think. I show you just how easy, in the following clip:
Dr. Stewart Zelman, Ph.D. is a psychologist and founder of the Centers for Motivation. During his thirty years of professional practice, he has developed a deep understanding of human potential and motivation. He is the author of Think: Mindful and Mindless Tools For Weight Management, and an expert on cognitive behavioral management of food. He has also contributed his time and expertise to the treatment of physically and emotionally challenged youth. I attribute and thank Dr. Stewart Zelman and the Centers for Motivation for their contribution to this post. References C. Vereecken et al. Associations of parenting styles, parental feeding practices and child characteristics with young children's fruit and vegetable consumption. Appetitie 2010 55(3):589-596. Bao Y. et al. Association of nut consumption with total and cause-specific mortality. NEJM 2013 369;21:2001-11.
Who is in control in your household? There is a clear hierarchy in my house. Colin and Cailya are at the top, Cassie is a strong second, and if you squint hard enough, you can see me way down at the bottom. A perfect example of this hierarchy is watching the dynamic at our kitchen table. Although we serve our meals on our kitchen table, sometimes it feels more like a poker table. Perhaps you have had your fair share of table-side negotiations, bluffs, and power struggles with your own children. Introduction of new foods, designated mealtimes, and eating out are all opportunities for kids to exercise control. Rather than approach these impasses in a confrontational way, you can take the opportunity to teach your kids important life skills like decision making, compromise, and independence. To gain more insight into the psychology of kids, I interviewed the brilliant cognitive behavioral psychologist, Dr. Stewart Zelman (biography below). Here is what he had to say: Chris : What should I do when my kid refuses to try something new? Dr. Zelman : New foods can be an opportunity for a child to exert power and control in their lives. Children who are managed by teachers and parents, or older siblings, find that this is one of their few opportunities to be in charge. Look at the bigger picture and see if your child has the chance to take charge of his or her life in other areas. Then a request that they try one bite of the new food will not be so much of a struggle. Also, it is helpful to create a culture that the whole family tries a new food once a week. Implement the new food you want your child to try during mealtime and let them be a part of the meal preparation. They will want to eat what they helped to create.
Chris : What should parents do when kids no longer want to eat their favorite foods? Dr. Zelman : Perhaps your child has grown tired of eating that food. This is a good opportunity to introduce new foods to your kids. Parents can try to remove some of their favorite foods for a while and then try to reintroduce the favorite foods at a later point. We can all grow tired of eating the same foods regularly. Toddlers are still developing and may be developing new food interests as well. Allow them to explore their eating options and never forget to make mealtime fun and interesting.
Chris : What suggestions do you have for parents trying to "reason" with their kids? Dr. Zelman: Explain to children that it is their choice whether or not they would like to eat. However, there are certain foods that they should eat and certain other foods that are not good for them. Give children some choices and some control over what they can eat, so that they are equipped to make good decisions in the future about their eating habits. For example, if they do not want to eat their dinner that night, explain that if they are not hungry, they do not have to eat but that they cannot have any snacks or dessert in place of dinner. If they are truly hungry, they will eat dinner. Also, explaining to a child that you would like them to eat what has been prepared so that they can be healthy and grow strong can be helpful. Chris : What tips do you have for taking kids out to eat? Dr. Zelman : Make sure that you are taking your child to a family restaurant that is kid-friendly. Never bring a tired child out to eat because this will increase the likelihood that they will be fussy and picky. Be sure that the establishment has a kids menu or that you can order a smaller portion size. Some menus are over-spiced or too salty for a child's taste. Review the menu before your child does, and pick out the ones you find to be most healthy or appropriate. Give your child an option out of the ones you think will be best for them. This way, they will be eating healthy and they will also be a part of the decision-making. In the following video, I play food poker with Colin. See who wins:
Dr. Stewart Zelman, Ph.D. is a psychologist, trainer and founder of the Centers for Motivation. During his thirty years of professional practice, he has developed a deep understanding of human potential and motivation. He is the author of Think: Mindful and Mindless Tools For Weight Management, and an expert on cognitive behavioral management of food. He has also contributed his time and expertise to the treatment of physically and emotionally challenged youth. I attribute and thank Dr. Stewart Zelman and the Centers for Motivation for their contribution to this post.
