Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective
FOR IMMEDIATE RELEASE
The Soyfoods Association of
(202) 659-3520
Contact: Nancy Chapman, RD, MPH, Executive Director
Report of the World Cancer Research Fund International and The American Institute for Cancer Research
November 1-2, 2007
Overview
On October 31, 2007, the World Cancer Research Fund International and the American Institute for Cancer Research released a comprehensive report on cancer prevention and held a two-day workshop to explain the research and analysis covered in this report. The report recommendations are based on a review of 7,000 studies on all aspects of diet, physical activity, weight management and cancer that are predominantly case control and cohort population studies. Several speakers noted the limitations of drawing conclusions from epidemiological studies and called for funding human clinical trials to confirm the report’s recommendations. The human studies, as noted, are complicated by many factors, including genetic differences of subjects; confounding variables (i.e. the Aspirin effect on fiber, pesticide effect on hormones, and human adaptation to long term dietary intake and exposures); nutrient interactions; variations in food composition over years, climatic regions, soil differences, etc.; poor biomarkers; nutrient interactions; bioavailability of nutrients; and dose responses.
The authors of Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective, available through dietandcancerreport.org, find that events from early life influence a person’s risk of cancer long term. Introductory chapters in the report review the international trends in cancer, the potential causes of cancer and the lifecycle, and, most importantly, the pro-cancer effects and the anti-cancer effects of various factors. The factors were characterized in terms of effects on 18 different cancer sites, including stomach, pancreas, prostate, breast, and skin.
Recommendations for Cancer Prevention
The report describes the strength of evidence for suggesting relationships between numerous factors, (such as vitamin C, foods with fiber, processed meat, pulses (legumes such as soybeans), phytochemicals, and physical activity), that enhance or reduce cancer risk. The basis for the following recommendations is the panel of experts’ judgments of ‘convincing’ and ‘probable’ causal relationships between a factor and a specific cancer that are presented in an extensive matrix of the relationships. The most controversial findings have been met by opposition and efforts to undermine the integrity of this comprehensive five-year review by nine teams of international cancer experts that did not receive any funding from industry.
1. Be as lean as possible without becoming underweight.
2. Be physically active for at least 30 minutes every day.
4. Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans.
5. Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.
6. If consumed at all, limit alcoholic drinks to 2 for men and 1 for women a day.
7. Limit consumption of salty foods and foods processed with salt (sodium).
8. Don’t use supplements to protect against cancer.
Special Population Recommendations
10. After treatment, cancer survivors should follow the recommendations for cancer prevention.
Specific Findings Relevant to Soy
Eat mostly foods of plant origin.
Dr. John Milner of the National Cancer Institute and Dr. David Klurfield of the USDA, Agriculture Research Service’s Nutrition Program reviewed the role of fruits, vegetables, pulses (legumes), nuts, seeds, herbs, spices, and the nutrients and substances, such as vitamins A, vitamin E, cartenoids, folate, lycopene, and fiber, contained in these plants on cancer. In general, evidence of protection from consumption of plant foods is not convincing, but some probable evidence exists for mixture of components in plant foods. Folate probably protects against pancreatic cancer. Garlic was singled out as having a probable role in decreasing stomach and colorectal cancer risk; whereas no significant effect was found to be associated with any fruit, vegetable, or component of fruit, vegetables or legumes. The effect of fiber may be related to the folate fortification, an interrelationship that illustrates the complexities in identifying a single component versus a food that lowers cancer risk. The speakers also reviewed the extensive lists of potential mechanisms of action that phytochemicals or bioactive components have on the cancer process.
In the discussion of studies on pulses for the chapter on plant foods, the authors conceded that it is difficult to “detect an association between pulses, particularly soya intake, and cancer risk because consumption tends to be low.” The report notes that the evidence from the case-control studies is inconsistent, but presents two conclusions about soy and soy products that are important:
-
There is limited evidence suggesting that pulses (legumes), including soya and soya products, protect against stomach cancer.
-
There is limited evidence suggesting that pulses (legumes, including soya and soya products, protect against prostate cancer.
The report reviewed the studies providing probable and limited suggestive evidence that foods containing dietary fiber decreased the risk of colorectal and esophageal cancers. This section of the report identifies legumes and minimally processed cereals as particularly concentrated sources of fiber, and suggests fruits and vegetables as additional sources. The only concern regarding a increased risk associated with intake of plant foods pointed to convincing evidence that foods contaminated with aflatoxins are a cause of liver cancer.
Limit intake of red meat and avoid processed meat
Implementation of this recommendation of limiting red meat consumption to less than 500 gram (18 ounces) cooked weight per week, per individual and very little processed meat will require significant changes in the current American dietary pattern. The evidence reviewed in this section was convincing and associated red meat and processed meat with an increase risk of colorectal cancer and may be related to other cancers of the digestive track, but the data are limited. The Cantonese-style salted fish is a probable cause of nasopharyngeal cancer. The report recognizes that many foods of animal origin are nourishing and healthy if consumed in modest amounts; and the limitations on meat do not include poultry, eggs, and wild game. The mechanism of action may be the nitrosamine compounds and the heme-iron content. Cooking red meats appears to enhance the heterocyclic amines and the polycyclic aromatic hydrocarbons that are carcinogenic.
The expert panel determined that there is probable evidence that milk and calcium lower the risk of colorectal cancer and limited evidence that milk protects against bladder cancer. Unfortunately, diets high in calcium are a probable cause of prostate cancer and limited evidence that milk increases prostate cancer risk and cheese increases colorectal cancer risk. Legumes are identified as sources of calcium, but the high intakes were considered a marker for dairy intake.
The term ‘processed’ refers to “meat preserved by smoking, curing, and salting or by the addition of preservatives, such as nitrites”. As for an association between fish and foods containing vitamin D protecting against colorectal cancer, the evidence is limited, thus not appropriate for a recommendation.
Weight Control and Leanness
This recommendation for a healthy weight will require eating foods with high amounts of nutrients per calorie, limiting the energy dense foods to 125 kcal per 100 grams for the total diet, and increasing physical activity to at least 30 minutes per day to stay lean as possible. Sugary drinks and ‘fast foods’ become the target of this recommendation. Substituting soyfoods for other higher fat, saturated fat, and energy-dense foods tracks this recommendation to “limit consumption of energy-dense foods.
Food production, preservation, processing and preparation
This chapter did not discuss the processing of soybeans into any protein components, as one rumored. The only concerns related to processing are covered under the salting, smoking, and adding nitrites to meats and fish and the avoidance of aflatoxin-contaminated cereals and pulses. Caution is also given to reduce eating burned or charred foods frequently or in large amounts. A public health recommendation is to limit consumption of salt from all sources to less than 5 grams (2 grams sodium) a day which will certainly require less use of salt in food processing.
The report concludes that “changes made to processed foods and drinks within well regulated, modern food systems are of themselves unlikely to modify the risk of cancer significantly.” Here are some of the findings in this section:
- There was no epidemiological evidence that current exposures to pesticides cause cancers in humans.
- Any effect of modern methods of genetic modification of foods on the risk of cancer is unknown. The panel made no judgment on a relationship.
- There is too little evidence to draw any conclusion about the association between risks of cancer and any method of preservation, including fermentation, drying, canning, pasteurization, irradiation, and preservatives.
Organic foods: There was a statement in the report that noted “claims that foods produced by organic methods are biologically or nutritionally superior to food produced by intensive methods are not supported by clinical or epidemiological evidence, but some food compositional data indicates higher concentrations of some constituents like vitamin C and dietary fiber. There is evidence that organic products contain fewer residues from chemicals employed in conventional agriculture.”
Aim to meet nutritional needs through diet alone
The only convincing or probable evidence related to cancer risk and dietary supplements at certain doses is related to high-dose of beta-carotene supplements and lung cancer; calcium protects against colorectal cancer and selenium probably protects against prostate cancer.
In this section, there is a review of the macronutrients and under this protein section, “soya protein is the only plant food to contain all the essential amino acids in the proportions needed by humans, as is the case with eggs, milk, and meat. The panel found no evidence suggested that proteins specifically modified the risk of cancers of any sites. There is also a discussion of phytochemicals that have been shown to have anti-oxidant, anti-carcinogenic, anti-inflammatory, immunomodulatory, and antimicrobial effects in animals’ but no clear evidence exits for humans. Legumes are identified as a good source of phytochemicals.
In discussions of what dietary patterns are preferred the panel could make no judgment regarding possible relationships between patterns and cancer risks, independently of the various dietary components identified above. There is a statement that “dietary patterns of most of the world’s population – perhaps around 4 billion people – are plant-based. Often, other cultural habits such as smoking restrictions and high physical activity are related to certain dietary patterns, such as vegetarian diets.
« PREVIOUS: Real Men Eat Soy: The Truth about Soy and Sperm Count
