By Karen Collins, MS, RD, CDNAmerican Institute for Cancer Research

Q: Does low-carb ice cream help people lose weight?

A: Keep in mind that there is no legal definition of low-carb. Ice cream labeled “for use with low carb diets” uses sugar substitutes for sweetness and gums and cellulose gel for thickness. The brand most widely available right now produces an ice cream containing 130 to 140 calories in a half-cup serving, which is the same as regular ice cream. The total and saturated fat content of the products is about equal, too. Since the bottom line for weight control is how many calories you eat compared to how many you burn up, low-carb versions of ice cream offer no advantage. You should certainly avoid thinking that this “diet” ice cream allows you to eat larger portions. If you want to lose weight and still include ice cream in your diet, “light” ice cream is a better choice. This ice cream cuts the fat (and cholesterol-raising saturated fat) in half and reduces calories by 10 to 20 percent. Another option, “no sugar added light” ice cream, cuts fat about in half and uses sugar substitutes, so calories are reduced 30 percent below regular ice cream. Ice cream that is 98 percent fat-free lowers calories even further, but even this fat reduction only saves 50 calories in a half-cup serving. You’re almost sure to cut more calories than that by simply eating only half of your usual portion. Or instead of a nightly necessity make it a weekly treat.

Q: Are egg white omelets healthier than regular omelets?

A: If an omelet made from four to six egg whites was prepared in the same way as one made with two to three whole eggs, the egg white omelet would contain 80 to 120 fewer calories. An egg white omelet is also significantly lower in fat and cholesterol than one made with whole eggs. But be aware that some so-called “egg white omelets” are actually made with a mixture of whole eggs and egg whites. Furthermore, although whole eggs are commonly considered bad for your health, the cholesterol-raising saturated fat content of whole eggs is not particularly high. Egg yolks are high in cholesterol, but studies show that saturated fat is a much greater risk for many people than cholesterol in food. A whole egg omelet does provide more iron than an egg white one. Whichever form of omelet you choose, for a healthful version, limit any added cheese or use a reduced-fat kind. The total number of calories in any omelet depends on how much oil is added to the pan and whether cheese is added. By including plenty of vegetables, like onions, mushrooms, peppers, and spinach, you’ll have the best nutritional balance.

Q: Are brown eggs more nutritious than white eggs?

A: The breed of hen determines the color of the eggshell. White hens lay white eggs and dark hens lay brown eggs. Shell color has nothing to do with egg quality, flavor, nutritional value, or cooking characteristics.

Q: What are prebiotics?

A: Prebiotics are carbohydrates that pass through the upper part of your digestive system without breaking down, unlike most carbohydrates. There are two major types of prebiotics. Fructooligosaccharides are found in whole grains (like barley and oatmeal), dried beans, flaxseeds, and several vegetables and fruits (especially onions, spinach, kale, berries, and bananas). The other type of prebiotics, inulin, is found naturally in many fruits and vegetables. It is also sometimes added to yogurt, milk, and nondairy frozen desserts as a fat substitute. After arriving in the large intestine intact, these two kinds of carbohydrates are fermented by bacteria. This fermentation produces short-chain fatty acids that seem to protect against colon cancer. In addition to this possible benefit, these carbohydrates provide nutrients for healthy bacteria to grow. That’s why they’re called prebiotics. Although some people are concerned about the intestinal gas that accompanies their fermentation — and excessive amounts of prebiotics can have a laxative effect — these are often natural consequences of a healthy diet.

Q: Do the special products for washing vegetables and fruits make them safer?

A: Most food safety experts say that these special products are unnecessary. Especially for unwaxed produce, like broccoli, greens, or berries, running water is highly effective at removing dirt and germs. A scrub brush can help with some produce. Although these washing products are often advertised for their ability to reduce pesticide levels, the government does not require any tests to prove their cleaning effectiveness. In one study with unwaxed fruits, produce wash didn’t reduce pesticide levels any more than plain water did. Furthermore, although some ads and media reports make produce appear loaded with pesticides, the most recent scientific studies show pesticide residues to be quite minimal. If you feel more comfortable using a produce wash, you can, but be sure to follow the label’s directions. In any case, there’s no need to worry about the wax, which is often applied to apples, peppers, cucumbers, tomatoes, and some other produce after they are cleaned. This wax seals in moisture and protects the produce from contamination. These plant-based waxes are also used in candies. They pass through the digestive tract undigested.

Q: I hear that exercise helps fight breast cancer. Does that mean it helps prevent the disease or treat it?A: Exercise probably plays a role in both prevention and treatment. Studies have established that regular exercise lowers the risk of a woman first developing breast cancer. Researchers think breast cancer risk drops because exercise acts directly on physical factors, like hormones, and helps maintain a healthy weight. The benefits of exercise for women who have or had breast cancer are less clearly established. Regular exercise plays a large role in preventing weight gain, which is common among breast cancer patients and a link to poorer survival rates. Exercise also helps breast cancer patients and survivors return to a better quality of life by reducing stress and rebuilding stamina that early stages of treatment often diminish. Some researchers believe that modest exercise may directly improve breast cancer patients’ chances of survival, but more research is needed to support that point.