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Food Allergy for Beginners: Sugars

What is a Sugar?

Sugar is one those loaded words that can have a variety of  meanings.  For example sugar can mean sucrose, the white granules you put in your coffee, or it can refer to the level of glucose in your blood, as in: “I need to up my insulin because my blood sugar is sky high after putting all that sugar in my coffee”.

Sugar can also refer to carbohydrates (“carbs”), one of the three categories of chemicals, along with fats and proteins, which make up the food we eat.

Carbohydrates can be single molecules or joined together to form large chains.  Single molecules are called monosaccarides and include glucose, galactose and fructose. Any two of these simple sugars combined are called disaccharides. For example, sucrose (table sugar) is a disaccharide combing the two simple sugars glucose and fructose. Lactose is a disaccharide containing glucose and galactose. Polysaccharides are long chains of monosaccharide joined together and are used in plants and animals for structure and storage. Sugar is stored as starch in plants and as glycogen in animals.

Monosaccaride - glucose

Monosaccharide – glucose

Disaccharide Sucrose

Disaccharide Sucrose

Polysaccharide

Polysaccharide Starch

Sugars can combine with proteins to form glycoproteins and with fats to form glycolipids.

It’s All About Glucose

Glucose is our body’s primary source of energy and also the primary product of photosynthesis, the process in plants that turns sunlight into food.  Most of the carbohydrates that we eat are converted to glucose during digestion. We crave sweet things because they usually contain lots of simple sugars that require very little or no work to convert to glucose. Most of the cells in our body can run on either glucose, fats, or proteins but the brain needs glucose to work.Glucose metabolism

Can You Be Allergic to Sugar?

The short answer is no. Simple sugars and disaccharides such as sucrose and lactose are not allergens and cannot cause true allergic reactions.

However, people have become allergic to glycoproteins, sugars combined with proteins. An example of this is allergy to galactose-alpha-1,3-galactose, also know as alpha-gal.   Alpha-gal is a common glycoprotein found on all animal cells except humans and primates and those sensitized can have allergic reactions to a variety of meats including beef, pork, and lamb.   Interestingly, a large number of alpha-gal allergic patients developed symptoms after being bitten by a tick, particularly the lone star tick found in the Southern and Eastern United States. Skin testing to meat and a blood test for allergic antibodies to alpha-gal can make the diagnosis.

Lactose Intolerance

Although sugars rarely cause true allergic reactions, they are a common cause of food intolerance. Because the cells in our body can only use glucose for fuel, all complex sugars (disaccharides and polysaccharides) have to be chopped-up or digested to make the glucose available. To do this, we produce enzymes that make the process of digesting the complex sugars possible.   Many of these enzymes are specific for a particular type of sugar. For example lactase is the enzyme that facilitates the break down of cows milk sugar (lactose) to yield glucose and galactose that is then easily absorbed into circulation to be used as fuel.

Without lactase the milk sugar passes intact into the colon where it provides nutrition for colonies of fermenting bacteria. These bacteria feed on the sugar and as a by-product, produce a large amount of methane gas and fluid retention causing intestinal bloating, cramping, and gas.   Treatment is avoidance of all mammalian milk and/or taking supplemental lactase (Lactaid) whenever milk products are consumed.

In summary, true allergic reactions to carbohydrates are rare while food intolerance, such as lactose intolerance, are more common.  Other problems associated with sugar (weight gain, diabetes, etc) is another topic for another day.

chick-fil-a peanut

Food Allergy for Beginners: Fats and Oils

As discussed in the previous article (Food Allergy for Beginners: Proteins), primarily it is protein in foods that causes the majority of allergic food reactions. Our diet also contains fat (oils) carbohydrates (sugars), and minerals but these rarely cause true allergic reactions.   This is an important point because many oils, such as peanut oil, are made from very allergenic nuts or seeds.

Is peanut oil safe to eat if you have a peanut allergy?

The answer to this question depends on the type of processing used to extract the oil.

Most vegetable oils used for cooking are produced using an extensive multistep mechanical and chemical process that begins by heating and crushing the seed or nut.   The oil is then extracted using the chemical hexane. Additional steps may include adding acids and steam distillation. The final product contains so little protein that the FDA does not require oils processed this way to be listed as a potential cause of allergic reactions.

Chick-fil-a, a fast food chicken chain, uses peanut oil and posts the following information about food allergies:

     “Chick-fil-A(r) cooks in 100% refined peanut oil. According to the FDA, highly refined oils such as highly refined soybean and peanut oil are not considered major food           allergens and therefore are not listed here”

Oils may also be extracted from nuts and seeds using only mechanical press without heat or chemicals.   This method produces much smaller amounts of oil but the oil produced retains more of the natural flavor and also may contain significant amounts of protein.  For this reason, contact with cold pressed oils can cause allergic reactions if you are allergic to the nut or seed used to produce the oil.Untitled design (42) (1)Untitled design (43) (1)

Storm Trooper Food Allergy

Food Allergy for Beginners: Proteins

A Few Introductory Facts

  • Living things, including you and the food you eat, are made up of proteins, fats, sugars (carbohydrates) and minerals.
  • For the most part proteins – not sugars, fats, or minerals- cause food allergies.
  • Proteins are like Lego creations. They are large, complex structures made up of a slew of small, simple units (amino acids) stuck together.
    Amino Acid

    Single Amino Acid

    Protein Structure

    Protein Structure containing hundreds of amino acids.

     

  • A Millennium Falcon made out of red, green, yellow, blue, and white Lego pieces put together in a particular way “looks” like a Millennium Falcon.

Mellinium falcon lego

 

  • A pile of colorful, unconnected Lego pieces does not.

 

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  • Our immune system “sees” protein like we see a Lego-block Millennium Falcon, It does not recognize unconnected amino acids.
  • To stay healthy your body needs amino acids from the food you eat. It does not need intact proteins.
  • If your immune system decides that proteins looking like the Millennium Falcon are a threat, it may launch an attack with sophisticated weapons that go off when in contact with any Millennium falcon-looking food taking you down the dark path to… Allergy!

 

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Oral Desensitization for Peanut Allergy

This week the Lancet reported results of an oral desensitization study in children with peanut allergy.   Peanut allergic children age 7-16 were gradually exposed to increasing oral doses of peanut over a six month period.  The goal of the study was to achieve a level of desensitization that would allow the children to safely ingest 1400 mg of peanut protein (about 10 peanuts) without symptoms.

At the end of the study period, 62% of the children had reached the target goal and were able to tolerate 1400 mg of peanut protein. 84% were able to tolerate 800 mg of peanut protein, the equivalent of about five peanuts.  In the untreated control group, none of the children were able to tolerate the full dose of peanut protein.  Side effects in the group receiving peanut including vomiting, itching of the mouth and wheezing.  One child had an allergic reaction to the peanut severe enough to require an injection of epinephrine.

This is another study showing that oral desensitization to peanut in peanut allergic children can be successful and relatively safe.  The process does require significant time and effort and is associated with some risk.  It is a procedure that cannot be undertaken at home and requires careful monitoring in an allergy specialist’s clinic or hospital setting.

Is it worth the effort?  Currently, oral desensitization may significantly reduce the risk of a life threatening allergic reaction occurring in a peanut allergic child who is exposed to peanut by mistake.   The procedure is not a cure and does not allow children to enjoy peanut butter or a granola bar without concern of a reaction.

Progress in the Treatment of Food Allergy

Immunotherapy is a form of treatment in which small amounts an allergen (pollen, mold, or animal dander) is given to an allergic patient in slowly increasing doses to induce long-lasting tolerance to that allergen.  Immunotherapy is very effective in reducing allergy symptoms and is the closest treatment that we have to a cure. The trick is to be able to safely deliver a substance that a patient is very allergic to (usually a protein) in a manner that allows the immune system time to develop a protective tolerance response without triggering an allergic reaction.  This is routinely accomplished with allergy shots for airborne allergens.  Unfortunately, efforts to treat life-threatening food allergy with immunotherapy without triggering a severe and possible fatal allergic reaction have had limited success.

One of the goals of research efforts in food allergy has been to develop a food look-alike protein – one that can stimulate an effective tolerance response to a food but without the ability to trigger an allergic reaction.   Somewhat like a novice sword fighter  using wooden swords to train until he is experienced enough to handle the real thing.

Recently researchers at The Centre for Plant Biotechnology and Genomics in Spain have developed three hypoallergenic variants of the protein most commonly responsible for allergic reactions to peach (Pru p 3).  Peach is the most common food allergy in Spain and Mediterranean region.   The hope is that these proteins can be used safely as a vaccine in specific immunotherapy to treat patients with allergy to peach for whom the only currently available treatment is life long avoidance.

When You Should Give In To Your Craving for a Snickers Bar

For the past decade, pediatricians have recommended avoiding peanuts and tree nuts during pregnancy because of the concern that exposure to an allergen at this time might increase the likelihood of the baby having a food allergy, particularly if there is a strong family history of nut allergy.  In spite of these recommendations, not only did the prevalence of allergies fail to decline, but significantly increased during this period, with reported cases of nut allergy tripling from 1997 to 2010   Noting this disturbing trend, in 2008 the American Academy of Pediatricians withdrew their recommendation to avoid any foods during pregnancy to prevent food allergy.

And now, a recent study from Boston Children’s Hospital suggests that eating nuts during pregnancy can actually decrease the risk of allergy in their children.  This study found that the children of moms who ate five or more servings of peanuts and tree nuts a week were less likely to develop allergies to these foods than kids whose mothers ate less than one serving a month.   Pregnant mothers who are allergic to nuts, of course, should continue to avoid these foods.

The results of this study highlights a principle that has become clearer over the past several years as more research is directed at the growing problem of food allergy: withholding exposure to an allergen, particularly in young  children may end up causing the problem that we are trying to prevent.

Alien Allergy Attack from the Planet Alpha-Gal

It sounds like science fiction.  A hideous blood-sucking alien creeps into the bedroom of an unsuspecting victim while they sleep.  With razor sharp fangs the monster begins to feed, injecting a cocktail of chemicals to keep the blood flowing. As the fiend’s venom works it’s way through the body, a frightening change takes hold.  Forever transformed, the victim is doomed to live in fear of pleasures he once enjoyed.

As bizarre as it sounds, this scary story (with a few embellishments) is not science fiction but true.  Here are the unsettling details.

The blood sucking alien is Amblyomma americanum – the lone star tick.  The tick is found primarily in the Southeastern part of the United States, although some believe that it’s territory may extend further west.  In some individuals, a bite from the tick triggers the immune system to produce antibodies to a sugar found in the saliva of the tick called galactose-α-1,3-galactose or alpha-gal.   This sugar is also found in meats such as beef, lamb, and pork and so once a victim becomes “immunized” by the tick bite, eating a steak, for example, can cause hives or even more severe allergic symptoms.

Unlike most allergic reactions to foods, the alpha-gal reaction can occur 4-6 hours after eating meat.  And although a blood test for the alpha-gal antibody is available, it may not be ordered if the connection between a patients severe allergic reaction and eating a hamburger six hours earlier is not made. To make matters worse, patients who have become sensitized to alpha-gal by a tick bite can also have severe allergic reactions to cetuximab, a new medication used to treat cancer.

So far, the only treatment for alpha-gal sensitivity and the resulting meat allergy is avoidance.

Food Allergy Boot Camp

In sports and other competitive pursuits the saying “whatever does not kill you makes you stronger” seems appropriate and possible even comforting.  To have this applied to the topic of food allergy, particularly in children, seems anything but comforting.   Recent research aimed at understanding the complex problem of food allergy suggests that this principle may not be too far from the truth and underlies a significant paradigm shift in how we approach food allergy prevention.  The result is creating a squeeze felt by families with food allergies as well as the physicians who care for them.

Until recently, the American Academy of Pediatrics recommended that infants who were considered at increased risk of developing food allergy because of their family history should avoid peanuts during the first three years of life,  milk for the first year, egg until age two, and tree nuts and fish until three years of age. Also,  it was suggested that mothers avoid peanuts and other allergenic foods during pregnancy and breast-feeding.

Recently, however, these recommendations were withdrawn by the American Academy of Pediatrics because of a lack of current evidence supporting the assumption that delaying introduction of allergenic food helps to reduce the occurrence of food allergy and other allergic disease.  Also noted was a lack of evidence supporting dietary restrictions during pregnancy and breast feeding.  Even the World Health Organization’s strategy to prevent allergy by recommending exclusive beast-feeding for the first six months of an infants life has come into question.  Although breast feeding until four months of age is still recommended, evidence seems to suggest that prolonging breast feeding beyond 4 months of age may acutely increase the likelihood that a child will develop allergies!

So what options are available to parents and physicians to determine if a child is at risk of a serious food allergy because of a family history or other concerns and how can we prevent or reduce the likelihood of a serious food allergy from developing?

The “dual-allergen exposure hypothesis” is a new theory that may shed light on these questions .  This theory suggests that infants come into contact with small amounts of food through the skin as they explore the environment and as a result of this cutaneous contact, become sensitized.  Sensitization is the process of developing allergic antibodies to something in the environment.  These allergy causing antibodies can be detected on an allergy skin test or blood test.

Sensitization does not always lead to clinical allergy.  Why not?  Because between sensitization and allergy symptoms is a third factor:  tolerance.  Tolerance is our bodies way of reining in the inappropriate allergic response, preventing inflammation that we experience as symptoms.  We want tolerance: it’s natural and very effective, and without it, we would be at risk of reacting to many of the foods that we require for adequate nutrition.

The second part of the dual-allergen exposure hypothesis states that, although sensitization may occur through the skin, tolerance occurs through oral exposure.  In other words, eating the food helps to prevent allergies from developing.  The timing and balance of cutaneous and oral exposure determines whether a child at risk will develop adequate tolerance or else develop harmful adverse reactions because of allergy.

The dual-allergen exposure hypothesis has important implications for the use of allergy blood tests in children.  The use of blood tests to diagnose food allergy in children may in fact be causing more severe allergy problems because parents are frequently told to restrict from the diet foods that show up on a blood test (indicting sensitization but not necessarily allergy) and in the process, push the child from sensitization to true food allergy.

There is always some risk when a child is exposed to a food for the first time (as there is with taking their first step or attending their first day of school), but in spite of the risk of a few bumps along the way, early oral exposure to a food may in the end make the child stronger and less vulnerable to more serious food allergies in the future.

Define Your Terms

“If you wish to converse with me,” said Voltaire, “define your terms”.

In my practice as an allergy specialist, I find the principle of first defining terms before beginning a discussion with a patient to be key.  Particularly the term “allergy”.   “Allergy” is a very common word, frequently used in general conversation, therefore its definition should be fairly clear.  But this may not always be the case, and subtleties of variance in how we define this term can lead to significant misunderstanding.

From an immunologist’s point of view, a scientific definition of allergy could go something like this:

“Allergy is a  hypersensitivity disorder of the immune system which occurs when a person’s immune system reacts to normally harmless substances in the environment. These reactions are acquired, predictable, and rapid. Allergy is one of four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity. Allergic reactions are distinctive because of excessive activation of certain white blood cells called mast cells and basophils by a type of antibody called Immunoglobulin E (IgE). This reaction results in an inflammatory response which an range from uncomfortable to dangerous”.

In this definition there are a few key points.  Allergy is reaction to specific substances involving a class of antibodies call IgE,resulting in symptoms.

A more conventional, laymen definition of allergy might look like this:  “An allergy is a reaction of the body to something that you eat, drink, breath or come into contact with that makes you itch, sneeze, wheeze, break out in a rash, get a stomach ache, or swell up”.

There are several medical problems that clearly meet this definition of allergy but in fact, are not allergy at all.  An example of this is lactose intolerance.   This is a problem with mammalian milk (cow, goat, even human) which is caused by the lack of an enzyme which is required to digest milk sugar.    Without this enzyme to turn the big lactose sugar molecule into its much smaller and absorbable bits, drinking milk will cause uncomfortable intestinal bloating, gas, and pain.  Although this a clear reaction to a food, no antibodies are involved,  so it is not an allergy.

Another example is Celiac disease.  In  this rare condition, patients become very ill with abdominal cramping, diarrhea, and even severe weight loss when exposed to even small amounts of gluten in their diet.  This difficult condition is definitely caused by an antibody reaction to a particular food, although the antibody is IgA, not IgE, and is therefore by definition, not an allergy.

Allergy has also been defined in terms of a result on a laboratory test  as well as in terms of symptoms.  For example, if a patient has a laboratory blood test that looks for IgE antibodies to food, any positive result might be viewed as proof of a food allergy.   However,  our definition of  allergy also  requires the presence of symptoms.     When a patient shows evidence of IgE antibodies to a food on an allergy test, we use the term “sensitization”.    A blood test for food allergy may show multiple sensitivities, but unless there is a history of adverse symptoms caused by a particular food, there is no allergy.    This means that you could be “sensitized” to something without being “allergic”, but you cannot be allergic if you are not sensitized.   Essential to the diagnosis of food allergy is the presence of symptoms caused by exposure to a food and laboratory evidence (skin test or blood test) of anti-food IgE antibodies.

Sensitivity, the antibody response on a laboratory test for allergy,  is an important definition to keep in mind when we discuss other tests for food allergy, such as the IgG test.  This test is commonly used in Naturopathic  Medicine, a form of alternative medicine, that places a strong emphasis on the role of diet  and food allergy in health and well being. IgG, like IgE, is a class of antibodies produced by our immune system.  Unlike IgE, IgG’s primary job is to defend against infections such as viruses and bacteria.  When you get a flu shot you are boosting the bodies production of anti-flu virus IgG antibodies.  When the real flu tries to invade and make you sick, the anti-flu IgG antibodies are ready to squash them.    Results of these IgG tests for food allergy frequently return a long list of positive reactions, and patients, upon seeing this list, frequently ask the question, “so what am I supposed to eat if I am allergic to all these foods”.

It does seem strange that our bodies would produce antibodies to a food if there is not a problem of some kind. Why would our immune system react to a food unless it had an issue with it, even if I am not aware of a problem or what that issue is?  Naturopaths use this line of reasoning to suggest that some foods cause “hidden allergy” and can be a source of inflammation.  This inflammation could lead to a variety of chronic conditions such as fatigue, headaches, weight gain, depression, mental fogginess, and many others.  However, this assumption is often a misunderstanding.  Some experts believe that the IgG antibody response occurs to the foods we eat the most and may play a role in the proper development of tolerance.  Tolerance is a good thing. Therefore the IgG food allergy test may simply reflect the foods that we eat most commonly, rather than being harmful.  For this reason, most experts agree that the IgG test for food  allergy is unhelpful and may in fact lead to excessive and dangerous food restriction diets.

When Healthy Foods and Allergies Collide

Although food and diet fads come and go, there is general agreement that we should eat more raw fruits and vegetables.  Uncooked fruits and vegetables are the richest source of vitamins, minerals and antioxidants- nutrients often lacking in our over-processed, carbohydrate and fat-loaded, American diets.

For many people with pollen allergy, however, eating fruits and uncooked vegetables is not an option.  When they do, the result is often intolerable itching and irritation of the mouth, palate, and throat, and If they eat too much or too fast, they can develop abdominal pain and symptoms of a full blown allergic reaction.

This condition is called the oral allergy syndrome or pollen-food allergy syndrome and occurs when the antibodies that cause seasonal allergy symptoms, usually directed at grass, tree, or weed pollen, react with similar proteins found in food.   For example, patients with ragweed allergy may have problems with bananas, cucumber, and melons because these contain proteins that are similar to proteins found in ragweed pollen. When these anti-ragweed antibodies in the mouth and throat come into contact with the food, a mild allergic reaction occurs with itching and mild swelling. So eating a banana or piece of cantaloupe ends up making you feel like you just ate a bowl of fresh ragweed leaves.

In the same way, if you are allergic to birch tree pollen you may have problems eating a variety of fruits, vegetables, and nuts including apple, peach, apricot, cherry, plum, pear, almond, hazelnut, carrot, celery, parsley, caraway, fennel, coriander, aniseed, soybean and peanut.  Birch trees are common throughout the northern United States and Europe but are rare in Arizona.  However, allergy to Arizona Sycamore, a tree common to mountain and transition zones of Arizona, has been associated with reactions to apple, hazelnut, lettuce, corn, kiwi, peach, and peanuts, and green beans.  Sensitivity to Mugwort, an allergenic weed also prevalent in the Northern United States and Northern Europe, can cause reactions to carrot, celery, parsley, caraway, fennel, coriander, aniseed, bell pepper, black pepper, garlic, and onion as well as mustard, cauliflower, cabbage, and broccoli.

More important to the Southwest is sagebrush sensitivity, which is associated with reactions to carrot and celery.

An important distinction between the oral allergy syndrome and other types of food allergy is the rare occurrence of more serious allergic symptoms.  This is because the proteins in the fruits and vegetables that cause the oral allergy syndrome are very fragile and easily destroyed by digestive enzymes in the mouth and stomach.   So by the time the food leaves the mouth or stomach, the body no longer recognizes it as an allergen.  Cooking also denatures or destroys the allergenic proteins so that foods that cannot be tolerated when raw can be eaten after cooking.  This works out for banana bread and apple pie but cooked watermelon is just not the same.