June 16, 2005

“Diet, Lifestyle and Cancer Prevention: Getting the Message Across” is the theme of the World Cancer Research Fund (WCRF) Health Professional being held in Hong Kong on June 18th.  

It can seem that every month there is new research revealing the latest dietary innovation or wonder food that can radically change health and survival. Some of these reports of scientific advances offer promising benefits, but some of the research announcements are misunderstood or misinterpreted, and the latest news on food and health sweeping over the continent may be downright misleading or generate yet more confusion in the minds of consumers.

Getting the central messages, based on substantive established scientific evidence, about what each and everyone of us can choose to modify in our daily diet and lifestyle for cancer prevention is becoming an ever-more urgent priority for public health specialists whose goal is to reduce the incidence of cancer.

But with such a wide variety of dietary regimes to choose from, how are you to decide what’s best for you?

Your mother was right - Greens are good for you!

Health experts agree that 400 grams of fruit and vegetables per day per person and a high fibre diet (approximately 25-30 grams per day) are fundamental priority health targets.

According to the 1997 World Cancer Research Fund (WCRF) expert report, evidence of dietary protection against cancer is strongest and most consistent for diets high in vegetables and fruits. The WCRF panel of experts concluded that the consumption of 400 grams/day or more of a variety of vegetables and fruits - could, irrespective of other diet and lifestyle patterns, decrease overall cancer incidence by at least 20%. There is convincing evidence that diets high in vegetables and fruits protect against cancers of the mouth and pharynx, oesophagus, lung, stomach, colon and rectum, larynx, pancreas, breast and bladder.

Although there are other aspects of diet that could possibly modify the risk of cancers, there is essentially no evidence that dietary factors may decrease the risk of some cancers while increasing the risk of others. In other words, the risk of developing cancer will not be shifted around your body.

High dietary fibre is also associated with lower risk of some cancers, especially bowel cancer. The recommended daily intake of dietary fibre is 25-30g per day for a healthy adult. This can be only be achieved by incorporating high fibre foods such as whole grains, vegetables, fruit, nuts and seeds into eating patterns every day and/or using a bran supplement.. 

5-a-day

Adequate fruit and vegetable intake has a protective effect, helping ward off chronic diseases while helping to elevate resistance to infectious disease and reduce nutritional deficiencies. Fruit and vegetables actively promote health by providing our bodies with essential vitamins, nutrients, fibre and a myriad of phytochemicals which acts as antioxidants in the body. Antioxidants neutralize the free radicals that accelerate the process of cell decay and increase the chances of cells becoming cancerous.

400g of fruits and vegetables per person per day (excluding potatoes and other starchy tubers) for the prevention of chronic diseases translates to approximately “5-a-day”, that is, eating five or more servings of fruit and vegetables every day.

One serving is roughly the amount that fits into the palm of a cupped hand. Obviously, those of smaller body size will need to consume less than 400g/day, so the 5-a-day cupped handful works as a guideline for children, young people and their parents, as well as smaller adults.

For those who prefer more specific guidance, a portion of fruit or vegetables for an adult, is approximately equal to:

• 1 cup of raw salad greens

• 1 medium sized piece of fruit

• Small tumbler (150 mls) of 100% fruit or vegetable juice

• ½ cup of cooked veggies

• ½ cup of cut-up fruit and veggies

• ½ cup of cooked beans/peas

• ¼ cup of dried fruit

The general recommendation is to aim for three vegetable serves and two fruit serves. Also worth remembering that dried, canned and especially frozen foods can also count towards the 5-a-day target.

Are you a statistic?

The World Health Organization (WHO) reported that inadequate fruit and vegetable intake is among the top ten risk factors for global mortality. Insufficient consumption of fruit and vegetables is estimated to account for up to 2.7 million deaths globally every year. In fact, cancer rates for those consuming less than the recommended amount of fruits and vegetables are double that of those consuming healthy 400 g or more of fruit and vegetables on a daily basis.

Pesticide use in Asia

Consumers worry about what’s in their food. Fruits and vegetables treated with pesticides can be seen as undesirable, and this belief along with affordability, and time pressures all play a role in limiting fruit and vegetable consumption of many consumers in Asia.

Agricultural chemicals including pesticides have made significant contributions to the efficiency and productivity of Asian agriculture, making sure that the rise in Asia's food production has kept well ahead of its growing population. With responsible pesticide use, important benefits to agriculture and in turn society have been demonstrated, such as year round availability of agricultural produce; improved quality and variety; reduced production costs which in turn results in lower prices for consumers.

Crop protection chemicals, if used improperly or too frequently however, can pose potential dangers to both farmers and consumers, and bad practices by the few have contributed greatly to public anxiety, and left many wondering if they should or should not eat some produce because of concerns about pesticide residues.

It’s worth noting that whilst there are clearly improvements to be made in the use of agricultural chemicals, the majority of farmers use crop protection chemicals sparingly and in accordance with the rules of use. Published data from spot checks by public health officials in the Asian continent, find zero or very low residue levels on the bulk of samples tested. Encouragingly,  more of Asia’s farmers are turning to a modern breed of chemicals designed to act quickly and break down soon after application. Also, newer cultivation techniques such as Integrated Pest Management which eliminates the routine use of chemicals, and instead provides guidelines for more efficient, targeted applications, mean that chemical residues on horticultural produce are likely to fall to even lower levels in the future.

Pesticide Limits and Regulation

The Codex Alimentarius Commission is an international body which sets international guidelines on many elements of food safety, including pesticides residues on food. These guidelines are not mandatory, but many countries in Asia do use these guidelines, along with the scientific data determined by the national regulatory agencies to establish limits on use and also acceptable residue levels at point of sale.

Approval for use of any pesticide in a country is subject to its safety evaluation. Safety levels for any pesticide are calculated over a number of formal assessments. One of the most important is the calculation of what is an Acceptable Daily Intake (ADI). The ADI for any given pesticide is a measure of the quantity of a particular chemical in food that can be ingested daily over a lifetime without any observable risk to health. The ADI is based on assessment of typical consumption patterns of the national population, taking into account, not only the majority, but also those who may eat unusually large amounts of particular foods for example vegetarians, or who may be more susceptible to the effects of pesticides residues, such as children.

Maximum reside levels (MRLs), which are the maximum permissible quantity of pesticide that may still be present on the crop at point of sale, are based on the ADI figures, with additional safety margins built in to ensure that any individual’s total consumption of a given pesticide falls well within the confirmed established safe range.

Unbalanced Diet or Pesticides? The Real Causes of Cancer and other Chronic Diseases in Modern Society .

Cancer is principally caused by environmental factors, of which the most important are tobacco; diet and factors related to diet, including body mass and physical activity; and exposures to cancer-causing agents and the genes inherited from parents.

Studies conducted by the International Agency for Research on Cancer advise that of all dietary factors in cancer prevention, the most convincing and abundant evidence is for the protective effect of fruit and vegetable consumption. Multiple research projects find a strong association between cancer with unbalanced diets, high in fat, low in plant foods and dietary fibre, but to date all studies which have examined possible link between pesticide residues and cancer have been unable to establish a definitive, positive link..

Thus, getting the public health message across that the scientifically proven  health benefits that come with eating the recommended servings of fruit and vegetables, by far outweigh any theoretical risk  from residue levels present in the food consumed would seem to be a valuable goal in cancer prevention.

For those consumers who wish to take additional measures to reduce any possible pesticide residues on their foods, and wish to avoid the price premium associated with so-called ‘organic’ non-pesticide treated produce, here are some tips from the Asian Food Information Centre -

• All raw foods should be washed thoroughly before cooking and/or consumption. Washing in dilute vinegar solution, or solution of sodium bicarbonate, then rinsing with clean water will help to remove any chemical residues and also any soil or other foreign matter on the produce.

• Many chemicals applied to crops to protect from insects and disease are sprayed onto external surfaces, so peeling outer layer or skin when preparing fresh fruit and vegetables will remove any surface residues.

• Look out for the many of the quality assurance schemes, which guarantee chemical treatment of produce has strictly followed manufacturers recommendations and residues levels at point of harvest  are either zero or well below maximum permissible (and therefore safe) limits.