Food sensitivities - the umbrella term for both food allergies and intolerances - can affect anyone. Food-sensitive vegans, however, may face even more difficult challenges than omnivores because common vegan allergens, such as nuts, seeds, soy and wheat, contribute important nutrients to the vegan diet. For this reason, when building a healthful vegan diet, it is important to first accurately identify true food sensitivities (see Vegetarian Voice Volume 29, No. 1) so as to prevent needless elimination of healthful foods. Then, once trigger foods are identified and removed, the main goals are to design a health-supporting diet and to manage (and perhaps even overcome) the food sensitivities.
The gut is the main interface between "us" and the outside world. The intestinal lining (or gut wall) is a semi-permeable membrane, like a sieve, that allows small molecules (the products of digestion) to pass through, and blocks the larger molecules. These larger molecules then travel through our intestine and are eliminated. When functioning as intended, the gut wall prevents these molecules from stimulating food sensitivity reactions. Unfortunately, certain factors in our lifestyles can create and sustain unwanted holes in this barrier. Maintaining the health of the gut wall may play a role in minimizing food sensitivities and preventing the development of further reactions to foods.
A healthy and unbroken gut wall is essential to our well-being; it affords protection against numerous diseases and food sensitivities. The state of health of the gut wall is variable; it can be healthy most of the time but suffer during illness, for example. It is clear that many of the lifestyle choices we make can have an impact on this membrane and the many microorganisms that dwell there.
The complex assortment of immune system cells interspersed along the gut wall provides a slew of surveillance and protection activities, monitoring every molecule that encounters it. A major role of these cells is distinguishing between friend and foe; they can either welcome a food particle or organism (bacteria) with open arms, or initiate an immune system (allergic) response to it. Our ability to keep out unwanted bacteria, destroy any that might get through the intestinal barrier, and decide which substances (such as food proteins) to tolerate depends upon the intestine's state of health.
The gut is home to more than 400 species of one-celled organisms. Some of these are "friendly" types of bacteria, whereas others have the capacity to produce toxic substances, invade the intestinal wall, encourage allergic responses or promote disease. Our relationship with the friendly bacteria is one of symbiosis, or mutual benefit. The bacteria benefit because they have access to food and water that pass down the intestine. We benefit because these bacteria perform a myriad of functions for us: they destroy toxic substances, aid us in digestion, produce certain vitamins and help protect us from unfriendly organisms.
Normally, the amount of "unfriendly" organisms are kept in check by the "friendly" bacteria. However, if anything decreases the friendly flora, a higher percentage of unfriendly organisms - such as clostridium, hafnia, citrobacter and candida - seize the opportunity, move into the area that was vacated and multiply. The result is an abnormal overgrowth of harmful bacteria. As these aggressive organisms take over, they produce damaging substances that set off a chronic, low-grade, inflammatory reaction, injure the intestinal membrane and make it more permeable or "leaky."
A healthy gut wall is an effective barrier against unwanted substances. When the wall is compromised, it starts to allow these substances to "leak" into the body. "Leaky gut" syndrome applies to an intestinal wall with increased permeability, allowing some harmful contents (that would normally be excluded) to pass through. Naturally, this can place a greater burden on our body's detoxification and immune systems.
Certain conditions and substances can injure the intestinal wall or change its environment in a way that allows large molecules to leak through, possibly leading to food sensitivities. These include:
Antibiotics deserve a special mention in regard to leaky gut. While antibiotics kill off the bacteria causing the infection, they also destroy the beneficial bacteria, setting off a chain reaction that permits more harmful bacteria to enter the gut lining and allow foreign proteins to leak into the bloodstream. Adverse reactions may ensue, such as allergic reactions in the skin. Of course, there are occasions where it may be absolutely necessary to take antibiotics. If you have to take them, take as directed, and take good care of yourself through proper diet and supplements.
Here is the good news: our intestinal membrane has an immense capacity to regenerate and heal itself. If we wish to restore a "leaky gut" to health, it makes sense to avoid the substances that may destroy beneficial bacteria (listed above), to provide a nutritious diet and to take supplements that promote a healthy balance of bacteria.
Complex carbohydrates, minerals, vitamins, protein, essential fats and phytochemicals are needed to build, maintain and repair the many cells that line our intestinal wall. A balanced diet of whole plant foods will provide the many nutrients that we require. Of course, when food sensitivities arise, this may seem like an immense challenge because some of the foods that have been part of our diet are now prohibited. However, the range of foods available to us is massive. Additionally, a multivitamin-mineral supplement can help to "top up" your nutrient intake; this can be particularly important when your system has been depleted. As always, vegans need to find a reliable source of vitamin B12.
As a vegan, you already know that nutrient-dense whole foods (vegetables, fruits, whole grains and legumes) support health and reduce disease risk. As a person with food sensitivities, you may feel at a loss as to how to compensate for foods you need to eliminate. Read on for some tips to help you.
Vegetables: Fortunately, most vegetables are low on the food sensitivity scale. The most common type of vegetable-related food sensitivity - oral allergy syndrome - occurs most often in people allergic to pollen. If you have a reaction to a vegetable, avoid it, or eat it only in its cooked form, if tolerated. Since there are hundreds of vegetables available, eliminating one or several rarely poses a problem; simply keep up your variety by getting in several different types a day that you can tolerate. Be sure to eat plenty of leafy green vegetables.
Fruits: Like vegetables, raw fruits may cause oral allergy syndrome. If you suffer from this, avoid the offending fruits and focus on the bounty of fruits you can tolerate. Don't forget the more unusual types, and experiment with frozen (no sugar added) fruits if finding good fresh fruit is a problem. Some fruits, like strawberries and citrus fruits, are rather high on the food sensitivity scale. If you are allergic to a fruit, read labels carefully and be aware of possible cross-contamination at restaurants and markets.
Grains: By far the most common offending grain component is gluten, found in wheat, barley and a few other grains. About one person in every 133 is sensitive to gluten. A smaller percentage of people has a true wheat allergy (but can tolerate gluten found in other grains). Either way, the approach is similar: avoid the wheat or gluten and seek healthful, tasty grain substitutes. Fortunately, foods like bread, pasta and baked goods are now available wheat- and gluten-free, and many of them are vegan as well. Recipes for vegan, gluten-free baked goods can be found on the Web and in many books.
However, these specialty items should not comprise the bulk of your grain intake. Incorporating more intact whole grains, such as millet, amaranth, brown rice and quinoa, is important in any healthful vegan diet. These grains are unrefined and provide vitamins, trace minerals and phytonutrients that are often missing in flour-based pastas and baked goods. If you can't have wheat, try eating more of these intact grains and you may find that you don't even miss wheat bread and pasta. Intact grains are superb in pilafs (mix cooked grains with lentils or beans, diced sauteed vegetables, herbs and seeds); hot cereals (add nondairy milk, fresh and dried fruits and nuts); burgers (cook grains with extra water, add shredded vegetables and form into patties); and salads (toss with fresh greens and a zesty vinaigrette). Sprouting whole grains is yet another healthful way to enjoy them. If you are extremely sensitive to wheat or gluten, avoid bulk bins at the grocery store and order your grains from trusted companies that work to avoid cross-contamination.
Legumes: Legumes (nuts, seeds, beans, lentils, peas and soy products) are extremely health-supporting. Because the body reacts mainly to proteins in foods and legumes that are high in protein, it is the food group with the most associated food sensitivities. This is a shame because legumes are important in the vegan diet; they are a concentrated source of protein and fiber, and, depending on the type, many vitamins, minerals, antioxidants and essential fats.
The good news is that with a little creativity, those with a legume sensitivity can still enjoy foods in the legume family. If you are anaphylactic to one or more nuts, it makes sense to avoid all nuts unless you are absolutely certain that alternate nuts are safe and have not come into contact with other nuts. However, it is extremely rare to have allergies to all nuts, all seeds or all beans. Most people with nut allergies can still enjoy seeds, for example. Seeds provide similar nutrients and are excellent substitutes. It is best to consume a wide variety of seeds, including pumpkin, sunflower, flax, hemp and sesame (sesame is the most allergenic of the seeds). Seed butters are excellent nut butter substitutes and some are produced in allergen-free facilities (read labels).
Some allergists recommend the complete removal of all legumes from the diet, including beans, for those allergic to peanuts, for example. (Some maintain this recommendation even if it is known that beans and lentils have been tolerated well in the past.) Such advice can do more harm than good, because needlessly avoiding hundreds of healthful foods may compromise our health, making us even more prone to food sensitivities. If you have been told to avoid all legumes, find a health care provider who is understanding of your needs and will work with you to determine a nutritional plan that is the most beneficial to your health, while minimizing the risk of a reaction.
Soy sensitivity can be particularly challenging for vegans. It seems that just about every vegan specialty item is soy-based. Soy can also be hidden in food ingredients like gums and starches, thickeners and flavor enhancers, so those extremely sensitive have to be especially careful. Nutritionally speaking, there's nothing in soy that you can't get easily from other sources. A wide variety of tolerated beans, nuts, seeds and grains, as well as soy-free items like rice milk, almond milk (look for fortified types) are acceptable substitutes.
Glutamine has been promoted as a supplement to help build, maintain and transport substances across our intestinal wall. A typical dosage is 250 to 500 mg taken three times a day. Glutamine is the most abundant amino acid in the bloodstream; our bodies can manufacture it and it is present in plenty of plant foods. Eating a whole-foods vegan diet, you'll receive glutamine, plus plenty of other amino acids, minerals and vitamins, too. No conclusive studies have been done assessing the effectiveness of glutamine, but given the available anecdotal evidence and its relative safety, there may be some benefit in taking glutamine in its concentrated form.
The wisdom behind, "An apple a day keeps the doctor away" may be related to quercetin, a protective bioflavonoid that is present in the skin of apples. In theory, we may be able to make our gut less leaky and tighten up the tight junctions between cells by using 250 to 500 mg of quercetin two or three times per day. Formulations that contain mixed bioflavonoids including quercetin may be used as well. We also get quercetin from oranges, grapes, green beans and from other fruits and vegetables, but not as much as a concentrated supplement.
The mineral zinc is known to be important for the immune system to function effectively and to maintain the epithelium that lines the intestine. It makes sense to support our immune system by meeting recommended zinc intakes (the best vegan sources are beans, nuts, seeds and whole grains). Taking zinc supplements alone can throw off the balance of copper and other minerals, and excess zinc may even disturb immune system function. If you want to take zinc supplements, aim for one with about 15 mg of zinc, in a pill containing 1 to 2 mg copper as well. This can be part of a multivitamin-mineral supplement.
Omega-3 fatty acids reduce inflammation and may have direct influence on the gut wall. Get your omega-3s from flax seeds and oil, hemp seeds and oil, canola and soybean oils and walnuts. You can also take DHA supplements (several vegan varieties are available), 300 to 500 mg per day.
Probiotics are live microorganisms in cultured/fermented foods or supplements that promote good health by improving the balance of intestinal bacteria. Since the bacterial population in our gut can change depending on our food and lifestyle choices, we can help tip the balance in our favor by introducing "friendly" bacteria, or probiotics, via treated foods, pills, powders or liquids. Fermented and cultured foods have been used safely in human diets for many centuries and during the last decade, the health potential of probiotics has caught the attention of scientists worldwide.
Examples of foods that may be cultured or fermented include vegetables, grains, beans, fruits and tea. Cultured soy (soy yogurt) and miso are the most widely used among vegans in North America (unrefrigerated miso does not contain live bacteria). Companies are now formulating probiotic-containing foods, such as energy bars, cereals, juices and snacks. Currently there are no formal quality control measures for probiotics in foods, so it is important to buy from reputable manufacturers. (Note: People who are particularly sensitive to histamine and tyramine should avoid fermented and cultured foods that are high in these compounds, including cultured soy products and miso.)
The most frequently used bacteria in probiotics are those in the lactobacillus and bifidobacterium species (such as L. acidophilus, L. bulgaricus, L. casei, L. salivarius; and B. bifidum and B. lactis). Mixtures of these, in pill and powder form, are available at natural foods stores and at many pharmacies.
Though research is at an early stage, we are likely to see the development of standards for optimal doses and the content of live bacteria at the end of the shelf life of products. With the flurry of research on these topics, we are gaining more insight into specific actions of specific probiotics.
Prebiotics are food substances that pass undigested into the lower intestine and support our health by feeding and thereby encouraging a favorable balance of beneficial bacteria.
Think of prebiotics as food for probiotics. Prebiotics are specific types of soluble fiber and exist naturally in vegetables (asparagus, broccoli, garlic, Jerusalem artichokes, leeks, okra, onions, summer squash), fruits (bananas, apples, citrus fruits and many others), legumes (beans, peas, lentils), and grains (corn, barley, oats, wheat). Prebiotics can be purchased as supplements. The two most common types are fructooligosaccharides (FOS) and inulin. The recommended dose of prebiotic supplements is 5 grams per day.
Maybe. It depends upon the sensitivity, genetics and our health. If our intestinal membrane is in poor health, we may be able to nourish it back to health. With time, it may recover its ability to block the passage of proteins and other large molecules. A favorable balance of intestinal flora may be restored and our tendency to develop new food sensitivities may diminish.
A healthful vegan diet, providing all essential nutrients, will support the health of the gut (and the rest of the body). Furthermore, avoiding food and lifestyle components that compromise gut health (refined sugars, alcohol, stress, drugs, smoking) is important. Finally, supplements and other therapies show promise in gut healing. A main goal, of course, is to overcome your food sensitivities. But if you find that you are still responding to trigger foods, your efforts are not for naught! Keep focusing on good health, and over time, you might notice an enormous improvement.
How can you find out if you have a leaky gut and/or bacterial imbalance?
Several laboratories test for intestinal permeability and/or intestinal dysbiosis (imbalance). Contact Great Smokies Diagnostic Laboratory, 1-800-522-4762, www.gsdl.com, and Metametrix Clinical Laboratory, 800-221-4640, www.metametrix.com.
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