If I have food allergies, does that mean my immune system is out of whack?
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If I have food allergies, does that mean my immune system is out of whack?

Food allergies are indeed related to your immune system-and, while it's not exactly out of whack, it might be doing its job a little too zealously. Due to a genetic quirk, your immune system may recognize an otherwise harmless substance (such as milk) as a foreign invader and attack it, causing an allergic reaction.

In a true food allergy, your immune system mistakenly identifies a specific food or a component of food as a harmful substance and triggers certain cells to produce immunoglobulin E (IgE) antibodies to fight the allergen. The next time you eat even the smallest amount of that food, the IgE antibodies sense it and signal your immune system to release histamine and other chemicals into your bloodstream, which causes a range of allergic signs and symptoms, including dripping nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, labored breathing and even anaphylactic shock. The majority of food allergies are triggered by certain proteins in eggs, peanuts, fish, shellfish (such as shrimp, lobster and crab), nuts (such as walnuts and pecans).

Other reactions to food don't involve your immune system or the release of histamine. These reactions aren't true food allergies but rather a food intolerance. The symptoms-nausea, vomiting, cramping and diarrhea-are often the same, although you may be able to eat small amounts of problem foods without a reaction.

See a doctor or allergist if you experience food allergy symptoms shortly after eating. Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as constriction of airways that makes it difficult to breathe, rapid pulse, dizziness or lightheadedness. The only way to avoid an allergic reaction is to avoid the foods that cause signs and symptoms.

Do food allergies make you fat?

There is no evidence at all to suggest that food allergies contribute to weight gain or weight retention, says Brian Smart, M.D., an allergist with DuPage Medical Group in Glen Ellyn, Illinois. "Food allergy is related to IgE antibodies and these have no influence at all on hormones that affect weight, such as thyroid hormone, growth hormone or insulin, or on any other regulatory process that can affect overall metabolism."

I've heard that mushrooms contain carcinogens. Is that true?

Some researchers have suggested that enzymes in the digestive system can convert agaritine, a natural substance found in several mushrooms of the Agaricus species (which includes the common "button" mushroom) into carcinogenic by-products or free radicals. However, there is no conclusive evidence showing a link. In fact, the reverse may be possible since mushrooms contain selenium, beta-glucans and other substances that may have anticarcinogenic properties. So dig in and enjoy, from portobellos to porcinis! Search for healthy mushroom recipes.

I've heard that flaxseed oil reduces inflammation from arthritis. Is that true?

We know that the omega-3 fatty acids found in flaxseed oil and fish oils "have an anti-inflammatory property that is beneficial to the heart," says Suzanne R. Steinbaum, D.O., director of the Women and Heart Disease program at Lenox Hill Hospital in New York. "Part of the risk of heart disease is correlated with inflammation, which can be reduced with flaxseed oil. This anti-inflammatory property is systemic, and therefore can most likely be beneficial for inflammation throughout the body." For heart disease prevention, a typical daily dose for flaxseed is 1,000 mg, which can be taken up to three times a day, says Steinbaum. Fish oil doses can range from 850 mg up to 4 grams. "The benefits can start at that lower dose, and higher doses have an effect on triglyceride levels."

Can getting enough vitamin D help my immune system?

Evidence is growing that the "sunshine vitamin" is very important to the proper functioning of the immune system. One clue to the importance of vitamin D is that cells throughout the body have receptors for the vitamin that, when activated, are important to the regulation of cell growth and division. Vitamin D is one of the most actively studied nutrients and researchers around the globe are learning that the role of this vitamin goes far beyond regulating bone health and development.

Exciting new research suggests that vitamin D may offer protection against some types of cancer, including breast and prostate cancers and, in particular, colorectal cancer. How vitamin D fights cancer isn't known for sure, but it "helps reduce cell proliferation and differentiation, and it may reduce inflammation," says Edward Giovannucci, M.D., professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.

Research is also revealing vitamin D's promise in autoimmune disease. For example, a sufficient level of vitamin D may confer some protection against developing multiple sclerosis (MS). Vitamin D may also play a protective role in diabetes, which is also considered an autoimmune disease since it involves immune-cell attack on the insulin-secreting cells of the pancreas. Experts are not sure about how vitamin D protects against autoimmune diseases, but believe that it may serve as a brake on the overactive immune cells.

Other, preliminary research hints at a connection between inadequate prenatal vitamin D and asthma in young children. Recent data even suggest that low vitamin D may be linked with epidemic influenza (which tends to strike, after all, during sun-deprived winter months).
Currently, the Dietary Reference Intakes (DRI) for vitamin D range from 200 to 600 international units (IU) per day, but many researchers believe 1,000 IU daily of vitamin D is optimal for most people, and that the upper limit (the amount not to exceed to avoid risk of toxicity), which is currently set at 2,000 IU per day, can safely be raised to as high as 10,000 IU per day. But vitamin D isn't widely available in the food supply (best sources include fatty fish and vitamin-D-fortified milk, orange juice and cereals), so to achieve those levels, you'll likely need to take a supplement.