Meatless diet no guarantee against cancer

Q. If plant-based diets are recommended for lower cancer risk, does that mean that a vegetarian diet is best?

A. Not necessarily.

Two recent studies, one in Britain and one in China, repeat previous findings showing that simply being a vegetarian does not necessarily mean lower cancer risk or better health.

Diets heavy on red meat and sweets -- sometimes referred to as Western diets -- have been linked with greater cancer risk. Note that poultry and seafood consumption show no link to increased cancer risk. Some research even suggests high-omega-3 fish may offer some protection.

Although a few studies have shown a somewhat lower cancer risk among vegetarians, much of that may be due to the overall healthier lifestyles of many vegetarians (for example, higher activity levels and tobacco avoidance).

In considering the health impact of a vegetarian diet, it's important to look not only at what is not eaten, but also at what is eaten, namely vegetables, fruits, whole grains and beans. Simply omitting animal foods while loading up on sweets, chips, French fries and refined grains is not likely to produce the same protection as a diet rich in plant-based foods.

In addition, now that maintaining a healthy weight is clearly identified as an important part of reducing cancer risk, choosing a diet that supports this goal is equally important.

Q. Exactly which foods are included in the "processed meat" category that we are now advised to avoid? Are any processed meats safe to eat?

A. Processed meats include bacon, sausage, ham, hot dogs and lunchmeats such as bologna and salami. Frequent consumption of these meats is linked to greater risk of colorectal cancer (and perhaps other cancers as well). In fact, a recently released international report on diet and cancer risk cites convincing evidence supporting this link; the report points to an estimated 12 percent increase in colorectal cancer risk for every ounce of processed meat eaten each day (roughly equivalent to one slice of lunchmeat).

Although occasionally enjoying a serving or two is not taboo, for those who have been eating these meats regularly, it's worth rethinking old habits.

Research is ongoing to determine which mechanisms are most strongly implicated in cancer development, but scientists point to three primary agents. Risk may be related to the nitrites that are often added to maintain color and prevent bacterial contamination. Once eaten, these nitrites can be converted within our bodies to nitrosamines, compounds found to cause cancer.

Furthermore, processed meats frequently contain high levels of salt and many are smoked as well; both of these processes may increase cancer risk. Finally, products made from pork and beef (red meats) may pose a risk due to their heme iron content.

In the U.S., reduced-fat processed meats made with chicken and turkey and, more recently, nitrate-free processed meats are becoming more common. However, until we know more conclusively where the risks from processed meats arise, you are best advised to avoid frequent use of these products as well.

Q. I'm confused: is a high-energy food one that gives me more energy or one that's high in calories and therefore fattening?

A. Technically, a high-energy food (not to be confused with an energy-dense food) is one that is high in calories. Just as we use inches to measure size or miles to gauge distance, calories are simply the unit with which we measure energy.

When people talk about high-energy foods, what they often mean is foods that give you longer-lasting energy. Some foods -- candy, for example -- can provide a lot of calories, but these are not considered high-energy foods.

Because your body processes the calories in these foods so quickly (producing a rapid rise and subsequent drop in blood sugar), you are left feeling anything but energetic just a short time later. True high-energy foods, like whole grains, may not be particularly high in calories, but are metabolized more slowly, leading to a longer-lasting supply of energy.

Secondly, classifying a food as "fattening" in itself is a misnomer. Weight gain depends on the overall calorie load of your diet, not on the calorie content of one food. If your total energy intake is greater than the amount of energy you burn, weight gain is inevitable.

The more high-calorie foods you eat, the more quickly those calories add up. In the end, it's the total calories you eat over a few days or a week that really matters.