This section is for people who limit the types of foods that they eat. This could be because of a medical condition, such as food allergy or lactose intolerance. Or it could be because of a desire to follow a vegetarian eating plan.
About one in four people think that they are allergic to certain foods. In fact, only about 4 percent of persons age 5 and older actually have a food allergy.
In a true food allergy, your body's defense system, called the immune system, reacts to a certain food or food component as if it were a harmful substance. Symptoms of an allergic reaction to a food usually develop within a few minutes to an hour after eating the food.
If you are allergic to a particular food, you may first feel itching in your mouth as you start to eat the food.
Your nose could become stuffy or itchy.
You might start sneezing.
Your eyes could itch and develop tears.
You may get swelling of the lips, face, tongue, throat, or other parts of your body.
After the food reaches your stomach, you may have symptoms such as vomiting, diarrhea, or stomach cramps.
Your skin could become red, itchy, or develop a rash.
For some people, an allergic reaction to a food is uncomfortable but not serious. For others, an allergic food reaction can lead to death. A life-threatening reaction caused by allergy is called anaphylaxis (an-uh-fuh-LAK-suhss). Symptoms of anaphylaxis include:
Hoarseness, throat tightness, or a lump in your throat
Wheezing, chest tightness, or having a hard time breathing
Rapid heart rate
Dizziness, lightheadedness, or fainting
Tingling in the hands, feet, lips, or scalp
Cold, clammy grayish or bluish skin
If you or someone you know is having these symptoms after eating something, call 911 right away. Anaphylaxis needs emergency treatment with a medicine called epinephrine (ep-uh-NEF-rin).
Problem foods for people with allergies
In adults, the foods that most often cause allergic reactions include:
Shellfish, such as scallops, oysters, shrimp, crayfish, lobster, and crab
Tree nuts, such as walnuts, cashews, and pecans
Medical problems similar to food allergy
Other medical problems can have some of the same symptoms as a food allergy, such as:
Food poisoning from contaminated food or foods containing poisons, such as certain mushrooms
Reactions to large amounts of some food additives, such as MSG (a flavor enhancer)
Diagnosis and treatment of food allergy
If you have food allergy symptoms shortly after eating, see a doctor or allergist. If possible, see your doctor when the allergic reaction is occurring. This will help your doctor diagnose your problem.
The best treatment for a food allergy is to avoid eating the foods that cause your symptoms. This may require reading the ingredients on food labels to make sure that the foods don't contain anything that might cause you to have symptoms.
If you have anaphylactic reactions to certain foods, your doctor may give you a prescription for injectable epinephrine. You need to carry this medicine with you at all times so that you or someone you're with can give you an emergency injection if needed.
Does your stomach churn after you drink milk? Do you have diarrhea soon afterward? If so, you may be lactose intolerant.
Lactose intolerance means that you cannot digest foods with lactose in them. Lactose is the sugar found in milk and foods made with milk. You cannot digest lactose because your small intestine does not have enough of an enzyme called lactase.
Symptoms of lactose intolerance usually begin within a half hour to two hours after eating or drinking foods that contain lactose. Symptoms include:
Lactose intolerance is not the same as milk allergy. Milk allergy is due to a problem with your body's defense system, called the immune system. In contrast, lactose intolerance is caused by not having enough lactase. Symptoms of milk allergy start right after drinking milk. But symptoms of lactose intolerance take longer to develop.
Lactose intolerance is more common in some ethnic groups — in particular, Asians, blacks, Hispanics, and Native Americans. The condition is also more common in older people, since our bodies produce fewer lactase enzymes as we age.
Dealing with lactose intolerance
Although it is uncomfortable, the condition is not serious. One way to avoid symptoms is to eat less food with lactose. Besides milk, lactose is also in:
Some cheeses (including cottage cheese)
Lactose is also added to some prepared foods, such as:
Breads and other baked goods
Mixes for cakes, cookies, pancakes, and biscuits
Instant potatoes, soups, and breakfast drinks
If you plan to eat foods with lactose, you can try taking a lactase tablet just before eating. The tablet supplies your body with the lactase that it's missing. Another option is to drink lactose-reduced milk. It contains the same nutrients as milk, including calcium and vitamin D, but less lactose.
Some people with lactose intolerance find that they can eat a small amount of some foods with lactose. For instance, they may be able to eat yogurt or aged cheeses, like cheddar or Swiss. Others find that they can tolerate milk if they drink it in small amounts or drink it at meals.
If you cannot tolerate any amount of milk or milk products, you should find other ways to get enough calcium. Calcium is needed for healthy bones and teeth. See our list of foods rich in calcium. Also, ask your doctor if you should take a calcium supplement every day.
You can get all the nutrients you need from a vegetarian eating plan by eating a variety of foods. But you may need to take extra steps to make sure that you are getting enough protein, iron, calcium, zinc, and vitamin B12.
What extra steps you need to take depends on what type of vegetarian you are. Vegetarians fall into three groups:
Vegans eat only plant-based foods. They do not eat any meat or animal products, including milk and eggs.
Lacto-vegetarians consume milk and milk products along with plant-based foods. They do not eat eggs.
Lacto-ovo vegetarians eat eggs and milk and milk products, in addition to plant-based foods.
Keep in mind that plants provide incomplete protein. In order to get all the amino acids your body needs, you have to eat a variety of plant foods. So, for instance, eating brown rice with beans will give you complete protein because each food contains the amino acids that the other food lacks.
With careful planning, vegetarian eating plans can be quite healthy. Because you are primarily eating foods from nonmeat sources, you tend to get less fat and cholesterol and more fiber than from meat-based eating plans.
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