Roughly one in six Americans can’t digest lactose (milk sugar). One out of every 130 can’t eat gluten products, and one in 100 is allergic to either peanuts or treegrown nuts.

Due to a combination of diagnostic testing, greater awareness and an apparent increase in prevalence, more Americans than ever are changing their dietary habits because of food allergy or intolerance.

Skeptics’ doubts aside, most people who claim food sensitivities are not hypochondriacs, and their dietary needs should be respected by anyone who’s cooking for them. Following is a simple guide on how to do that.

Gluten intolerance. When people with this condition eat gluten (protein found in wheat, barley, rye and oats), their autoimmune system sees it as a threat and responds in a way that can damage the small intestine. Even small amounts can trigger a response, so don’t use any products containing gluten when preparing meals for anyone with this condition.

Some are no-brainers: pastas, cereals, breads, cakes, pizza and pie crusts, cookies, crackers, granolas and energy bars containing grains. However, grain glutens also can be found in some pretty surprising places: malted milk and cocoa mixes, nondairy creamers, canned soups, lunch meats, egg substitutes, processed cheeses, licorice, most soy sauces, ketchup, horseradish and mustard -- just to name a few.

Many online sources provide tips on gluten-free cooking, and one’s doctor can advise on avoiding other sources of gluten such as certain medicines, vitamins and dietary supplements.

Peanut and tree nut allergies. About 3 million Americans are allergic to either peanuts or tree nuts such as cashews, pistachios, pecans and almonds. Their symptoms range from mild (skin irritation, swollen lips and upset stomach) to anaphylaxis, which can include tracheal constriction, lowered blood pressure and cardiovascular shock. Each year, 15 to 20 Americans die from allergic reactions to nuts.

Nut allergies can be triggered by very small quantities of whole nuts or even fumes of nut oil or roasted or boiled peanuts. Because some nut allergies go undetected in early childhood, it’s best not to serve nuts or foods containing nut products to children 3 years old or younger.

Lactose intolerance. Lactose intolerance is inability or difficulty in digesting lactose, the main sugar found in dairy products. An estimated 50 million Americans have the condition. The most common symptoms include bloating, gas, cramps, nausea and diarrhea.

It’s generally easier to cook for people with lactose intolerance than those with nut or gluten sensitivity. Some with the condition are able to have dairy products in small quantities -- for example, a small glass of milk or a dab of whipped cream on a dessert. Just be sure to ask your dinner guests in advance if they’re lactose intolerant, and, if so, what their limits are.

Most foods and beverages containing dairy products are clearly labeled, but many processed foods, breakfast cereals, breads and other baked goods have a fair amount of lactose.

Although margarine is vegetable based, it does contain lactose. So do many salad dressings, processed lunch meats, instant potatoes, instant soup mixes and breakfast drinks.

Some proven cooks’ strategies include using special low-lactose milks, substituting soy milk when feasible, and using dairy products with minimal amounts of lactose, such as cottage and Swiss cheese.

Many lactose-intolerant people also are able to eat yogurt (regular, not frozen) that has live probiotic bacterial cultures.

Information sheets on gluten and lactose intolerance can be downloaded from the Texas Department of State Health Services Web site at www.dshs.state.tx.us. Type in the search phrase “WIC Interactive Distance Learning.” The top result is a page with a “Nutrition” link to a WIC Training Section. Fact sheets can be found on module 3.