Ask the Nutritionist: Limiting red meat reduces risk of some cancers, other health problems

Q. Why do nutrition recommendations talk about limiting red meat? Can't I keep my saturated fat low by simply choosing lean cuts?

A. When eating red meat (beef, pork or lamb), choosing lean cuts is important in order to limit saturated fat and avoid excess calories. But eating too much of any red meat - more than 18 ounces cooked, weekly - increases risk for colorectal cancer. Red meats that are processed - such as bacon, hot dogs and sausage - are also available in leaner forms, yet even small amounts of these meats, eaten regularly, lead to higher risk for colorectal cancer. Processed meats are also consistently linked to increased risk of heart disease and Type 2 diabetes.

There are several potential theories as to why red meat may link to increased risk of these chronic diseases. Red meat (especially beef and lamb) is high in a form of iron called heme iron. Heme iron is also found in smaller amounts in chicken and fish. Higher heme iron content may partly explain links between excess red meat and risk of colon cancer, since it seems to promote formation of compounds that can damage intestinal cells. Some large population studies link higher consumption of heme iron and heme iron from red meat with increased risk of heart disease and Type 2 diabetes, respectively.

Emerging research also suggests that bacteria in the gut may play a role. It may convert compounds in red meat to substances that promote atherosclerosis ("hardening of the arteries") and/or cause less healthful types of bacteria in the intestinal tract to flourish.

Since unprocessed red meat in excess amounts is linked to colon cancer and may pose other health risks, choose lean cuts of fresh meat and also limit amounts to no more than 18 ounces per week. And be sure to save processed meats for special occasions.

Q. I'm trying to lose weight, but each afternoon around four o'clock my energy slumps and I end up eating junk food. How can I stop this habit?

A. It sounds like you're running out of fuel. Perhaps your lunch is too small to keep you satisfied through the afternoon. If you prefer to eat a lighter lunch, get pro-active and plan a small but nutrient-rich snack for a half-hour or so before your slump usually comes. Take this snack with you so you don't have only the junk food available. Keep the snack to 100 or 200 calories of foods that slowly release energy such as foods with protein, fat or fiber. For example, pair some fruit with yogurt, nuts or whole grains. Make sure you're drinking enough water, since if you get dehydrated that can also leave you feeling zapped.

The types of foods you choose for lunch may also affect your energy. If your lunch is nothing but refined carbohydrates, such as sweets or a low-fiber grain like a large bagel, or even plain vegetables or salad with no protein, your blood sugar may go up and down again within a few hours, leaving you feeling pretty rundown. To avoid that slump, focus your lunch around modest portions of whole grains plus vegetables and/or fruit, and make sure to include some healthy protein (poultry, seafood or lean meat, low-fat dairy, or a full serving of beans or nuts).

If you're simply skipping lunch or thinking you shouldn't eat more at lunch, you may not be getting enough energy to get you through the afternoon. Try doing what many people find works well: aim to get about a quarter to a third of your total daily calorie needs at lunch. People vary in what calorie level is right for them, but as an example, someone keeping calories to 1600 a day for weight loss might aim for 400 to 500 calories at lunch (depending on how much snacking they prefer to do and how they spread out meal times). That's why a small frozen entree, plain cup of soup, or energy bar usually won't suffice.

If these strategies don't work perhaps the slump you feel is not about hunger. You may need to get re-energized by getting up and moving around, switching tasks, or taking a few minutes for deep breathing breaks.

• Provided by the American Institute for Cancer Research.