Summary

A prestigious review of over 7,000 research studies has resulted in 8 recommendations for lifestyle changes as being the most important steps to take in avoiding cancer. Obesity is the major target for these changes.

Introduction

When is a meta-analysis a mega-analysis? Maybe when it includes 7,000 research studies reviewed by a 21-member board. Such a board was assembled by the American Institute for Cancer Research and the World Cancer Research Fund. It's the second report from these bodies; the first was issued in 1997, and since then much progress has been made in assessing the relationships between risk factors and the occurrence of 17 different cancers.

Only a small number of cancers are inherited; the rest are related to environmental factors, alterations of which can affect their frequency. These factors include smoking, infections, radiation, chemicals, pollution, medications, nutrition, physical activity, and body weight.

The board also looked at other aspects - birth weight, child-bearing, breast-feeding, and adult height. However, the most important risk factors were considered to be: food, nutrition, physical activity, and body composition. (Smoking was not mentioned in this list, but obviously should be included.) The recommendations, which are based on the strength of evidence established, are for people, as communities, families, and individuals.

What was found

The principal finding of the review was that obesity is likely to overtake smoking as the chief risk factor for cancer in the USA; it's now in second position, just behind tobacco. Excess weight and obesity can increase the risk for 6 cancers: colon, kidney, pancreas, esophagus, uterus, and breast (postmenopausal).

Excess alcohol consumption is also linked to 6 cancers: colon, breast, esophagus, mouth, larynx, and pharynx.

Red meat intake (beef, pork, and lamb) is associated with colorectal cancer. And processed meats (bacon, ham, sausage, and luncheon meat) are especially risky for this lower bowel type of cancer.

Some degree of protection can be demonstrated for diets that chiefly contain foods of plant origin (vegetables and fruits), and for increased physical activity.

The report's recommendations

These are the eight recommendations, as expressed in the report:

• 1. Be as lean as possible within the normal range of body weight
• 2. Be physically active as part of everyday life
• 3. Limit consumption of "energy-dense foods," foods that are high in calories, fat and sugar. Avoid sugary drinks.
• 4. Eat mostly foods of plant origin, including fruits, vegetables, whole grains and beans.
• 5. Limit intake of red meat and avoid processed meat
• 6. Limit alcoholic drinks to one per day for women, two per day for men.
• 7. Limit consumption of salt. Avoid moldy grains or legumes.
• 8. Aim to meet nutritional needs through diet alone, without dietary supplement.

More specifically, some of the personal recommendations are:

• Make sure your body weight is within the normal range from age 21 onwards, and avoid increases in your waist circumference.
• Aim for at least 30 minutes of exercise equivalent to brisk walking everyday. Plan to increase it to 60 minutes a day, or increase the energy expended in the activity. Limit sedentary habits (e.g. TV).
• Eat fast foods sparingly, if at all.
• Eat at least 5 portions or servings of a variety of non-starchy vegetables and fruits, daily. Choose unprocessed cereals (grains) and/or legumes (peas, beans) with every meal. Limit refined starchy foods (e.g. white bread).
• Limit red meat to less than 500 gram (18 oz) weekly; very little, if any, processed meats.
• Limit fat intake to 15% to 30% of your diet
• Alcohol - no more than two drinks for men, one drink for women, daily.
• Avoid salt-preserved, salted, or salty foods. Don't eat mold cereals or legumes (risk of aflatoxins causing liver cancer.

All of these are easier said than done. However, if you've stopped smoking (that was a "given" among the recommendations) you've done the hardest thing to prevent cancer, so the next steps - above - should be relatively easy.

A word of caution about the report. It has been posted on the Internet, and will be published, eventually. But it hasn't been peer-reviewed, yet. However, it's most unlikely that there are errors in a report from such a stellar board of reviewers.