Q: I know we need protein in our diets and that beans are a good source. But I've read that meat is a great source of protein and iron. Which is a better choice?
A: Meat is an excellent source of protein and iron, but unfortunately, red meat is also full of saturated fat -- one of the "bad" fats.
Leaner cuts contain less saturated fat, but eating lean red meat still causes you to consume lots of saturated fat. The saturated fat is not always visible. In addition to the layer of fat that may cover a cut of red meat, and any visible fat "marbled" inside the meat, there is plenty of invisible saturated fat.
Just because you can't see it doesn't mean it's not there. That's why I generally avoid red meats more than once a week.
In contrast, I have a salad sprinkled with beans nearly every day. Over the years, many good studies have linked high-meat diets to heart disease and certain types of cancer.
Particularly bad for us are processed meats that use red meat as a source, such as salami.
Beans (particularly legumes such as lentils, chickpeas and soybeans, and dry beans and peas such as black, lima, fava, pinto, kidney and navy) also contain many important nutrients. (On my website, AskDoctorK.com, I've put a table listing nutrients found in a variety of beans.)
People who regularly eat beans generally have lower body weight, waist circumference and blood pressure. Beans are also high in fiber, which helps prevent diabetes and improve cholesterol levels.
You may worry about bloating and gas. To minimize the problem, introduce legumes into your diet slowly. Or try an over-the-counter enzyme such as Beano to help metabolize the difficult-to-digest complex carbohydrates found in beans.
As for red meat, I'm not saying you should never eat it. I enjoy a good steak now and then (though I strip off the visible fat). But I used to eat red meat five or six times a week, and I've long since stopped that. I pretty much always avoid processed meats.
• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com.