By Julie Redfern, R.D., L.D.N.
We've been told that nuts are a "super food" of the decade. These little nuggets are rich in protein, fiber, folic acid and vitamin E. However, for some people they bring disaster. In the United States, 1.5 million people are severely allergic to peanuts alone. Half the people allergic to peanuts are also allergic to tree nuts. The number of children with peanut allergies has increased dramatically over the past couple decades. It may be hard to explain why, but this increase does parallel an increase in allergic diseases of childhood.
Food allergies are immune system reactions to foods. Reactions can be mild to severe, in some cases causing life-threatening anaphylactic shock. These reactions are referred to as an "allergic cascade." First the allergic food, such as peanuts, enters the body by ingestion, inhalation or skin contact. The body senses the protein in peanuts as a foreign invader. In response to the threat, IgE antibodies are released into the bloodstream. The IgE triggers cells to release substances called histamines that cause allergy symptoms.
Multiple body systems can be involved in the allergic response. A typical reaction starts with hives — raised spots on the skin that turn red and itch. This may be followed by swelling in various parts of the body, including the breathing passages.
More severe reactions might cause difficulty in breathing, nausea, vomiting and abdominal pain. The most severe reaction, anaphylaxis, results in very low blood pressure (shock) that requires emergency treatment. Severely allergic individuals need to carry self-injectable adrenaline (an epinephrine shot such as the EpiPen) to slow down the cascade of symptoms.
Clinicians use four methods to help diagnose food allergies:
Consult your physician if you think you may have a food allergy.
While several theories abound, there is no conclusive explanation. Possible explanations include:
Exposure to peanuts very early in life appears to increase the risk of developing allergy to peanuts. The Avon Longitudinal Study, a British study of 13,971 preschool children, was designed to collect information from early pregnancy throughout childhood regarding the incidence of peanut allergies. Results did not show any definitive evidence that peanuts in a pregnant woman's diet cause an increased sensitivity to peanuts for the fetus. Further tests showed no peanut-specific IgE detected in cord blood.
Instead, other explanations for peanut allergy have been proposed, including family history of peanut allergy, skin exposure to preparations containing peanut oil (especially if skin rashes or breaks in the skin are present), and early exposure to soy protein.
Women who are breastfeeding may want to avoid eating peanuts. Some studies have shown that peanut protein is secreted into breast milk, which may sensitize at-risk infants.
Obviously, managing nut allergies will depend on how mild or severe the allergies are. Mild reactions that cause hives, sneezing, runny nose or gastrointestinal upset may improve with antihistamines. Bronchodilators may help relieve shortness of breath and wheezing. Epinephrine, a synthetic form of adrenaline, is a powerful bronchodilator, reserved for severe anaphylactic shock.
Peanuts are legumes, as are peas, beans and lentils. Tree nuts are large, edible seeds of trees, some of which include cashews, almonds, pecans, walnuts, beechnuts and pistachios. The most successful method of managing peanut or tree nut allergies is to avoid them, including hidden sources. Besides the obvious sources of peanuts, peanut protein can be found in hydrolyzed plant or vegetable protein; cereals; ice cream and other desserts; Chinese, Indonesian or Thai foods; salad dressings; curry and satay sauces, as well as topical creams and shampoos. This is not an all-inclusive list.
Always read packaging labels carefully for information on the ingredients. If you are unsure about the ingredients, the best bet is to contact the manufacturer. Highly allergic people need to avoid anything or anyone who comes in contact with peanuts.
When a peanut or nut allergy occurs in a child, it impacts the entire family and the extended community. Because severe reactions can be life-threatening, children with peanut allergies are faced with challenging food and social restrictions. Children who are highly allergic must avoid contact with or inhalation of any peanut products.
When peanuts cannot be a part of your diet, the foods below will help you get the nutritional benefits they provide:
For more information on food allergies, see the Food Allergy and Anaphylaxis Network (FAAN) website, www.foodallergy.org.
Julie Redfern, R.D., L.D.N., is a registered dietitian in the Nutrition Consultation Service at Brigham and Women's Hospital. She specializes in nutrition counseling for the Obstetrics and Gynecology Department. She is a graduate of the University of Vermont and completed her dietetic internship at the University of Cincinnati Medical Center.