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The Immune System, Part One: Diet and Allergies

Based on the posting "The Immune System: Part I" by Christine Cox, at

Edited Article and Commentary by Dr. Don Rose, Writer, Life Alert


Even the healthiest of senior citizens can sometimes find themselves with compromised immune systems, for various environmental or psychological reasons (allergens, poor diet or sleep patterns, stress, etc.). The older we get, the more effort it can take to keep our immune systems functioning optimally. Luckily, getting older usually means getting wiser as well, and there is more health information available today (via the internet and other easily-accessible sources) than ever before in history. This article is one example, in which dietary as well as allergy related issues are discussed that can influence the body's personal defense system. -Dr. Don Rose



Your immune system is your personal defense system against attack of all kinds from viruses, bacteria, toxins and other enemies. Like all armed forces, the immune system is complex, with an array of weaponry at its disposal. It includes the lymph system (thymus, spleen, tonsils and lymph nodes), and specialized white blood cells called T-cells which, in addition to many other activities, produce interferon -- a substance particularly helpful in fighting viruses. Other white blood cells, B-cells, produce antibodies in response to invading bacteria, fungi and parasites. If any of these invaders begin a new assault, the antibodies "recognize" them before they have time to spread. Quickly attaching themselves to the invader, they thus "tag" the enemy for attack by phagocytes, another type of white blood cell. Other members of the white blood cell battalion are natural killer cells (known as NK), which destroy cancer cells, virus-infected cells, free radicals and other harmful substances. In addition, the immune system arsenal contains many other specialized cells and operations.

The immune system is very sensitive to subtle changes in the balance of nutrients in the body. Deficiencies of nutrients are reflected quickly as a weakening of our immune defenses. Although we rarely see severe malnutrition in the West, with its resulting poor immune systems, we nonetheless know that a large number of people are not consuming the right kinds and amounts of nutrients. The result is less than optimal immunity.


There are times, such as when battling a sore throat or other infection, when our immune systems can use an extra boost. In this section, we present some ways to accomplish this via our diet. But first, we list some ways in which our dietary choices can result in the opposite effect.
Foods that lower immunity
  • Fats - particularly polyunsaturated oils such as corn and safflower oils - weaken our immune system in many ways. Diets high in any kind of fat are associated with a reduction in immune functioning. One study conducted at the University of Massachusetts showed that reducing fat from 32 to 23% of the diet boosted natural killer cell activity by 48%!
  • Alcohol ingestion has been shown to severely depress neutrophils, cells that "eat" and destroy bacteria and tumor cells.
  • Sugar and other sweets have been shown to reduce the ability of certain white blood cells to destroy bacteria. When 100 grams are eaten (Americans typically consume more than 150 grams a day), neutrophil activity can be reduced by 50%. In one experiment, this effect lasted as long as five hours after the sweets were consumed. Fruit sugar and honey, unfortunately, had just as negative effects as white sugar, while starchy foods had no effect at all.
Foods that boost immunity
  • Vegetarian diet. A German study, reported in Nutrition and Cancer, found that the white blood cells of vegetarians were twice as effective against tumor cells as those of meat eaters. The precise reason is unknown, but may have something to do with higher levels of phytochemical-rich vegetables and fruits as well as lower levels of fats in the diet.
  • “Vitamin C rich” foods. While this vitamin's reputation as an immune-enhancer has fluctuated over time, we do know that vitamin C boosts antibodies as well as white blood cell activity. Stress of any kind, psychological or physical, increases our need for this vitamin. When you think vitamin C, think more than orange juice. You may be surprised to learn that broccoli contains three times as much vitamin C as citrus. Even potatoes are packed with this helpful nutrient.
  • Chinese mushrooms. Shiitake mushrooms appear to be powerful immune stimulants. They contain an antiviral substance that boosts T-cells and macrophages, large cells that engulf and destroy foreign particles. This beefy mushroom is becoming more readily available in many supermarkets as demand for it increases.
More immune-boosting dietary items
  • Garlic. Several studies indicate that the "fragrant bulb" does as much for our immune systems as it does for our taste buds. It appears to increase not only the numbers of natural killer cells but also their potency. T-cells, as well, are stimulated by garlic intake.
  • Zinc. This mineral positively affects many immune mechanisms, from the thymus to antibodies to T-cells. An Italian study found that small amounts of zinc quickly raised blood levels of T-cells in elderly people to those usually seen in much younger people. Since borderline zinc deficiencies are quite common, it's important to eat plenty of legumes such as black-eyed peas and pinto beans, and adequate amounts of whole grain breads; the yeast helps make the zinc available. Pumpkin and squash seeds are particularly rich in zinc, and make a delicious snack.
  • Carotenoids. Although beta carotene is best known in the huge carotenoid family, there is evidence that many members of this antioxidant group are helpful to our immune systems. Studies indicate that a high intake of carotenoid-rich foods (orange-colored vegetables and fruits, in particular) increase T-cells, natural killer cells, and antibody response. Pumpkins and winter squashes, as well as carrots, peaches, and cantaloupe, are especially good sources, though many green vegetables are also rich in carotenoids.
Herbs and immunity
Several herbs have extensive folk histories that indicate they can help us fight a variety of diseases. And, in the last few decades, laboratory studies have shown that indeed many of these herbs contain substances that work specifically to boost the immune system in various ways.

  • Echinacea (purple coneflower) is perhaps the best known of the Western immune-stimulating herbs. This attractive perennial grows in many cultivated gardens, but was originally a wildflower commonly found in the Midwest. Native Americans used echinacea for anything from blood purification to snake bite. Laboratory studies show echinacea to enhance the immune system through several mechanisms, most notably through activating T-cells and increasing virus-fighting interferon. It's particularly helpful with yeast and ear infections, and the common cold.
  • Ginger. This pungent root stimulates the production of interferon, besides aiding with nausea and being just plain delicious. Grate some into vegetables, or treat yourself to small pieces of the candied root.
  • Licorice has been used for thousands of years, in Eastern as well as Western cultures, by people wishing to benefit from its medicinal properties. It's particularly helpful in fighting viruses such as influenza and herpes. If you like your licorice sweet, read labels when buying licorice candy. Many of those tasty black twists are flavored with anise rather than the real thing. And a word of warning: take licorice in moderation; too much can cause the body to retain sodium, causing bloating.


Approximately 50 million people in the U.S. alone sneeze in the fall, itch when they eat peanuts, wheeze when they pet cats or exhibit one of the many other symptoms of allergy. Some people are even at risk of dying from severe allergic reactions to various substances that are benign or only slightly irritating to most people. Even when allergy symptoms like hives, sneezing and migraine are not life-threatening (and thankfully, they usually are not), they can certainly affect our ability to enjoy life. Of the 15% of North Americans that suffer from sneezing and itchy eyes, nearly one half claim they would rather have heartburn, while almost one third would prefer the flu to their allergies!
What is an allergy?
Health professionals often disagree about the precise definition of what constitutes an allergy. Some call any sensitivity reaction an allergy, while others claim that only reactions involving a specific antibody called IgE are true allergies. And there are many opinions in between these definitions.

In general, it is agreed that an allergic reaction is one that involves the immune system in varying ways. The immune system is designed to attack threats to the body such as bacteria and viruses. In the case of allergy, the immune system reacts to a harmless substance as though it were a threat. It mobilizes antibodies which attach themselves to the allergen as well as to basophils and mast cells -- defensive cells packed with histamine. The combination is explosive: the cells break open, spewing histamine into the tissues where it attracts scavenger cells that cause swelling, itching and other familiar symptoms of allergy. Symptoms can appear virtually anywhere in the body; a skin rash may be the result of poison ivy or something you ate.
Common allergy symptoms
  • Sneezing, and itchy eyes.
  • Hives.
  • Eczema and other rashes.
  • Asthma.
  • Bloating, diarrhea, headaches, usually from food sensitivities.
  • Anaphylactic shock, a rare but severe allergic reaction that can lead to death. The most common triggers are peanuts, shellfish, bee stings, and penicillin.
Avoiding allergies
The tendency to have allergies is probably genetically determined. If both parents suffer from allergies, a person has a greater than 65% chance of also developing allergic symptoms. If only one parent has allergies, then the risk drops to around 30%. Whether or not the genetic tendency lives itself out or not is dependent on many factors that are little understood at this time.

But even if we are allergy-prone, there are things we can do to help lessen the symptoms:

  • To help reduce the sneezes and itchy eyes of hay fever at night, keep bedroom windows closed if possible. Units that filter the air are readily available; look for one containing a HEPA filter, excellent for removing allergens of all types from the air.
  • Quercetin, a natural phytochemical in many foods, appears to dampen allergic responses by inhibiting the release of histamine. Red grapes, yellow squash, shallots and broccoli are good sources.
  • Onions contain diphenyl-thiosulfinate, a natural chemical that has a very high anti-inflammatory activity. And onions also contain large amounts of quercetin. One study reduced asthma attacks by 50% in subjects who drank onion juice before inhaling a known asthma-inducing chemical. While we're unlikely to want to drink onion juice, a few raw slices of pungent onion on our salads may be a good idea.
  • Vitamin C also works to tamp down inflammatory responses in the body. The American Journal of Epidemiology reports that adults eating the most vitamin C-rich foods had far fewer asthmatic attacks than those eating little of these foods. Drink a glass of orange juice for breakfast, and eat several slices of red peppers with your lunch and a cup of broccoli with dinner to provide a vitamin C boost to your body.
  • A new British study found that children eating an all-Asian diet had far fewer allergic symptoms than their schoolmates eating a typical Western diet.
Food allergies
Many people suffer from food allergies or sensitivities, commonly to milk, wheat, peanuts and soy, although almost any food can trigger symptoms in certain people.

Food allergies (like all allergies) involve an over-reactivity of the immune system. Antibodies that are designed to protect us from disease for various reasons can react against proteins in foods, causing injury to our tissues and symptoms of food allergy such as bloating, headaches, hives and diarrhea.

Of course, unlike inhaled allergens such as ragweed or tree pollen, food allergens enter the body through the intestinal tract. The gut is ordinarily lined with an antibody called IgA, which helps attack food allergens that inappropriately "leak" across the mucosal surfaces of the intestine and cause trouble. Trans-fatty acids, found in all hydrogenated oils, appear to encourage this destructive permeability of the intestine.

People with food sensitivities have unusually low levels of IgA in their blood. And stress, besides its many effects on the immune system, can decrease the amount of IgA. This may help explain why allergies are often worse during high-stress periods.

There are many other immune system reactions involving the four other major types of antibodies as well as T-cells that can come into play in food allergies of various types.

In addition, there are food "sensitivities" that, although they are not technically allergies, cause similar symptoms. Some foods contain substances such as histamine or other amino acids that can cause reactions in the blood vessels, leading to allergy-like symptoms.
Foods that commonly cause allergy-like symptoms
  • Casein-rich foods: milk, cheese, ice cream, other dairy
  • Histamine-rich foods: sauerkraut, wine, tomato, spinach
  • Tyramine-rich foods: cabbage, cheese, citrus, potato, seafood, dates, figs
  • Phenylethylamine-rich foods: chocolate
  • Serotonin-rich foods: banana
Rotation Diet
Whether our unpleasant symptoms are caused by a true food allergy or by food sensitivities of various kinds, a dietary scheme known as the "rotation diet" can be helpful. This diet does not prescribe or forbid any particular food; rather, it suggests that we avoid eating the same foods or food groups every day. The idea behind this is that the body can become over-sensitized to certain food components if it has to deal with them constantly, whereas if it has to metabolize them only infrequently (not more often than every four days) it is less likely to develop a sensitivity or allergy to them. Theoretically, the body completely clears any food substance within 3 days.

The main rule of thumb with the rotation diet is to try to vary your foods from day to day, particularly foods that are common allergens: soy, wheat, citrus, potatoes. For example, if you tend to have food allergies, it's probably wise to rotate your morning orange juice with apple and other juices and fruits. Also, try substituting corn bread or rice crackers for wheat toast.

The diet is certainly helpful in avoiding the development of new food sensitivities. With already existing sensitivities, if they are not severe, you could try eating a small portion of the offending food not more frequently than every four or five days. Some people can avoid triggering reactions this way, while others will have to completely remove allergy-provoking foods from their diets. Experiment cautiously!

Botanically speaking, foods belong to families. If you are sensitive to one member of a family, it is best to avoid other members as well during the 4-day break from your allergen. For example, people sensitive to potatoes should avoid too frequent consumption of eggplant, tomatoes and peppers -- all members of the same family. And if cashews cause symptoms, be careful with their botanical cousins, mango and pistachio. Lists of plant families are available in many nutrition books.

This article is based on an excerpt from a posting entitled “The Immune System, Part I” by Christine Cox, on the website. The information provided is, to the best of our knowledge, reliable and accurate. However, while Life Alert always strives to provide true, precise and consistent information, we cannot guarantee 100 percent accuracy. Readers are encouraged to review the original article, and use any resource links provided to gather more information before drawing conclusions and making decisions.

The article on this Life Alert website and the content it is based on are covered by a Creative Commons License. You are free to copy, distribute, display, and perform the work; to make derivative works; to make commercial use of the work -- under the following conditions: Attribution -- You must attribute the work in the manner specified by the author or licensor. For any reuse or distribution, you must make clear to others the license terms of this work. Please go to the Creative Commons License site for more information on the CC license that applies to this work.

Don Rose writes books, papers and articles on computers, the Internet, AI, science and technology, and issues related to seniors.

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