Last partial update: June 2019 - Please read disclaimer before proceeding

Introduction

Environmental factors, a large percentage of which are dietary related, account for about 50 to 80 per cent of all cancers. It is thus not surprising that dietary modifications can play an important part in cancer prevention. It is thought that a reduction in cancer deaths of 30 to 40 per cent can be achieved in Australia (about 30,000 people each year) by dietary change alone. Well over half of this benefit originates from the consumption of at least 400g per day of vegetables and fruit; the optimum mix being at least five servings of vegetables and two of fruit.)

Compounds in food can either increase or decrease the likelihood that a cancer will develop. A food compound may prevent cancer by protecting the cell from cancerous changes to genes, by inhibiting other chemicals that cause cancerous gene changes, or by helping the immune system to help fight early cancers that are already present; and visa versa. As well as influencing cancer initiation, food compounds may influence the rate of cancer growth.

As an example of the important role diet can play in cancer, African-Americans have a much higher rate of colon cancer than genetically similar populations living in Africa.

(Back to top)

Assessing the effect of nutrients in food on disease is difficult

Studying food in the diet is difficult for a number of reasons.

  1. It is difficult to estimate the intake of individual food groups and individual nutrients.
  2. It is difficult to separate out the individual effects of different food and nutrient groups in a normal mixed diet.
  3. The long time frame that is usually required when studying the influence on cancer of nutrients and other compounds in food makes food research expensive and difficult to control. (Influences may take tens of years to become apparent.)
  4. As foods etc can usually not be patented and the results of food research are often long in coming and ambiguous, food research is relatively poorly funded by the private sector.

For all these reasons, research into food and cancer often gives results that are far from certain and sometimes even contradictory. Thus, recommendations are rarely made with certainty and often are expressed in terms of whether an effect is fairly definite, probable or possible. It needs to be emphasized that the categories probable and possible in many cases indicate that there is just not enough evidence to be more definite. Thus it may still be quite reasonable to adopt these measures into a dietary plan.

My personal view is that where evidence is weak, the main priority should be to do no harm. Generally speaking, sensible alterations in diet to include more foods that are likely to reduce cancer (mainly fruit and vegetables) are unlikely to increase levels of nutrients to harmful levels. Also, the act of trying to improve one's health will have psychological benefits (even if there is no overall cancer benefit) and the positive effect of this on self-esteem should not be underestimated.

On the other hand, onsuming large quantities of many nutrient supplements can lead to excess intake and this can be hazardous. For example, excessive beta-carotene has been found to increase the incidence of lung cancer in smokers. There is no good evidence that dietary supplements are of any benefit in reducing any type of cancer.

(Back to top)

World Cancer Research Fund dietary recommendations to prevent cancer

In 2018 the World Cancer Research Fund published its third major review of scientific studies relating to diet and cancer prevention. This review assessed all the good evidence available on this subject; a mammoth task that involving assessing many tens of thousands of studies. It is undoubtedly the most comprehensive source of information about this important topic.

It is the report's opinion that about one third of all cancers can be prevented by appropriate food consumption combined with adequate physical activity and avoidance of obesity (and perhaps as many again would be prevented by stopping smoking).

Ten recommendations regarding diet and reducing cancer

The report's findings resulted in the following set of eight general and two special recommendations regarding diet and reducing cancer being made. (The actual recommendations appear in blue italic type. Additional information provided is either adapted from the report or from the author of this web site.)

1. Be a healthy weight

  • This includes children, adolescents and adults. It is important to avoid weight gain and increases in waist circumference in adult life.
  • An adult body mass index of 21 to 23 is ideal for adults

2. Be physically active as part of everyday life - Walk more, sit less

  • Aim for 60 minutes of moderate activity, such as brisk walking, every day or 30 minutes of more vigorous physical activity per day. (Adults presently doing little physical activity will need to increase activity levels gradually.) Sedentary activities such as watching television should be limited.

3. Eat a diet rich in wholegrains, vegetables, fruit and pulses (Iegumes; including beans and lentils) as a major part of your usual daily diet

  • Eat a diet that provides at least 30g of fibre per day from food soiurces
  • Include in most meals foods containing wholegrains,, non-starchy vegetables, fruit and pulses (legumes) such as beans and lentils
  • Eat at least five servings of a good variety of fruit and non-starchy vegetables per day. (Presently Australian authorities recommend five servings of vegetables and two servings of fruit.) Adult servings of vegetables weigh 60 to 90 g (equivalent to about half a cup) and an adult portion of fruit weighs about 150g (for example one apple or two apricots). Sizes for young children are in the section on Child Nutrition. Raw vegetables, salads, green vegetables, tomatoes, onion family, carrots and citrus fruits are especially good, but a good variety of all fruits and vegetables is vital. Fruit and vegetable juices are good options, as are dried fruits.
  • Limit starchy vegetables that are high in energy and are thus less beneficial. They include rice and roots and tubers such as potatoes, sweet potato, dalo and yams.
  • Eat relatively unprocessed cereals (grains) and/or pulses (legumes) with every meal.

4. Limit consumption of fast foods and other processed foods high in fat, starches and sugar. Avoid sugary drinks.

These foods promote weight gain. Energy dense foods are classified as those with more than 225 to 275kcal per 100g of food. Such foods include many foods in the following groups:

  • Drinks with added sugar (e.g. soft drinks). Large amounts of fruit juices (including those with no added sugar) can also provide excessive dietary energy.
  • Takeaway / 'fast' foods
  • Pre-prepared foods
  • Processed foods
  • Confectionery and bakery foods
  • Snack foods
  • 'Sweets' / treats type foods such as icecream, doughnuts, cakes / biscuits etc

5. Limit consumption of red meat and eat little if any processed meat

  • Limit red meat consumption to no more than 3 portions per weeek. This is about 350g to 500g of red meat per week (An appropriate serving size is about 80g, which is a piece of meat about the size of a pack of playing cards).
  • Alternatives to red meat include a variety of fish and poultry. All meats should be lean and have visible fat removed (or the skin removed in the case of poultry).
  • Processed meat includes meats that are smoked cured or salted. (Such meats can be eaten occasionally but ideally should not form a regular part of the diet.)

6. Limit consumption of sugar sweetened drink - Drink mostly water

  • Do not consume sugart sweetened drinks

7. Limit alcoholic consumption - For cancer prevention, it's best not to drink alcohol at all

  • There is no safe level of alcohol consumption with regard to preventing cancer
  • If alcohol is consumed, intake should be limited to no more than 20g (2 standard drinks) per day for men and 10g (one standard drink) for women. (To avoid the likelihood of addiction, all people should have two 'alcohol free' days per week.)
  • Children under 18 years of age and pregnant women should consume no alcohol.

8. Do not use supplements for cancer preventionim - Aim to meet nutritional needs through diet alone

  • Dietary supplements are not recommended for cancer protection. It is important to remember that most of the evidence relating the benefit of foods in preventing cancer was gained by looking at taking foods, not dietary supplements. The fact that a particular food helps reduce cancer does not imply that a supplement containing one or two of the food's constituent compounds will provide the same benefit.
  • High dose supplements should be avoided

9. For mothers: breastfeed your baby if you can - Breastfeeding is good for both mother and baby

  • Aim to breastfeed infants exclusively up to six months and continue with complementary feeds thereafter.

10. All cancer survivors to receive nutritional care from an appropriately trained professional.

  • If able to do so, and unless otherwise advised, cancer survivors should aim to follow the recommendations for diet, healthy weight, and physical activity.

As well as the above overall recommendations, this review outlined many more specific findings regarding the effect of food, food constituents, body attributes and physical activity on cancer and these are listed in the table below. (This the table only mentions associations where the available evidence was judged to either be convincing or probable with regarding to the causal relationship of the factor involved. There were numerous less certain associations mentioned in the report but these were not included as the associations are probably not reliable enough to make them worthy of consideration when making health recommendations. These less certain associations can be viewed on the report's web site: www.dietandcancerreport.org

(It is worth noting that few of the more specific findingsmentioned in the table below were considered worthy of inclusion in the fundamental advice stated in the ten recommendations outlined above. As stated previously, studying food / nutrition and cancer is extremely difficult and this is one reason why this may have been the case.)

 

World Cancer Research Fund 2018: Judgements regarding the strength of evidence relating food, nutrition and physical activity as causes of various types of cancer.

Type of cancer

Increases risk

Decreases risk

Convincing evidence for increased risk

Probable evidence for increased risk

Convincing evidence for decreased risk

Probable evidence for decreased risk

Lung

High dose beta-carotene supplements

Arsenic in drinking water

 

 

 

Breast

(pre-

menopausal)

Height

Alcohol

High birth weight

Physical activity

Body fatness (obesity)

Breast feeding

 

Breast

(post-

menopausal)

Alcohol

Body fatness (obesity) in adult life

Height

 

 

 

Physical activity

Breast feeding

Body fatness in young adult life

Colorectal

Processed meat

Alcohol (men)

Body fatness (obesity)

Height

Red meat

Physical activity

 

Wholegrains

Dietary fibre

Dairy products

Calcium supplements

Prostate

 

Body fatness (obesity),

Height

 

 

Kidney

Body fatness (obesity)

Height

 

 Alcohol (recommended intake only)

Stomach

 

Foods preserved by salting

Alcohol

Body fatness (obesity)

 

 

Oesophageal

Body fatness (obesity)

Alcohol

  Mate

 

 

Mouth, pharynx, larynx

Alcohol

  Body fatness (obesity)

 

 

Nasopharynx

 

Cantonese-style salted fish

 

 

Pancreas

Body fatness (obesity)

Height

 

 

Ovary

Height

Body fatness (obesity)

 

 

Urterus (endometrial)

Body fatness (obesity)

Height,

High glycaemic load in diet

 

Physical activity,   Coffee

Liver

Alcohol

Aflatoxins

Body fatness (obesity)

Alcohol

 

Coffee

Gall bladder

 

Body fatness (obesity)

 

 

Skin

Arsenic in drinking water

 Height (in melanoma only)

 

 

Nutrients mentioned in table
Carotenoids: A ‘family’ of orange-coloured plant pigments, 50 members of which can be converted to vitamin A in the body. The most widespread is beta-caroteine

 

The table above was adapted from information contained in:
World Cancer Research Fund / American Institute for Cancer Research
Food, Nutrition, Physical Activity, and Cancer: a Global Perspective. Washington, DC: A Summary of the Third Report: AICR, 2018

https://www.wcrf.org/sites/default/files/Summary-of-Third-Expert-Report-2018.pdf

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Back to top)

Obesity and cancer

Obesity causes about 7.5 per cent of all illness in Australia and increases the risk of developing a variety of cancers. (Obesity is thought to be directly responsible for about three per cent of cancer deaths in Australia.) About 14 per cent of the disease burden caused by obesity is due an increased incidence of cancer. (It mainly causes illness through increasing cardiovascular disease, diabetes and osteoarthritis.)

In obese women, the extra fat tissue present causes increased production of the hormone oestrogen and this extra oestrogen increases the risk of developing postmenopausal breast cancers and endometrial cancer (cancer of the uterus or womb). They occur to a greater extent in women who have abdominal rather than ‘hip’ obesity. Other cancers linked to obesity in both men and women include colon, kidney, gall bladder, and digestive tract cancers and, to a lesser extent, cancers of the liver, pancreas and (in women) ovaries.

Cancer attributable to obesity

Type of cancer

Proportion of cancer incidence attributable to obesity

Colon

11%

Breast cancer (post menopausal only)

9%

Uterine (endometrial)

39%

Renal (kidney)

25%

Oesophageal (adenocarcinoma)

37%

Gall bladder

24%

 

 

 

 

 

 

 

 

 

(Back to top)

Fruit and vegetables and cancer reduction

Inadequate fruit and vegetable consumption is thought to cause about 11 per cent of illness due to cancer in Australia and 2.5 per cent to 3.0 per cent of the total burden of disease in Australia, with about 75 per cent of this disease burden being due to an increase in cancer incidence. Most of this illness occurs relatively early in life, in the 55 to 74 year age group (and to a lesser extent in the 45 to 55 year age group).

In Australia, the intake of vegetables is low in both adults and children and this intake has actually decreased in the past 20 years. A survey conducted in 1999 found that, on the day of the survey, 10 per cent of adults and 20 per cent of children ate no vegetables and 40 per cent of both adults and children ate no fruit!! Most people need to at least double their intake of fruit and vegetables.

Serving sizes of fruit and vegetables

Type of food

Adult portion size in one serving*

Whole fresh fruit

150g

one apple or two apricots

one cup of chopped fresh fruit (fruit salad)

Whole vegetable*

75g

(half a cup cooked vegetables)

(one cup of salad vegetables)

(one medium potato)

Fruit and vegetable juices (100% pure)

125mL of pure juice

Dried fruits

one and a half tablespoons 

Canned fruit

one cup

For Preschoolers: Serving sizes for preschool children need to be reduced.  As a guide, the size of a serving of vegetables should be third age in tablespoons. (i.e. The serving size for a two year old would be two tablespoons. The size of the palm of their hand is a good guide to the size of a serving of meat in younger children.

 

 

 

 

 

 

 

 

 

 

 

 

 

Daily recommended number of servings of fruit and vegetables

Age

(years)

Number of servings of vegetables

Number of servings of fruit

4 to 7

2

1

8 to 11

3

1

12 to 18

4

3

19 and older

5

2

 

 

 

 

 

 

The World Health Organisation advice regarding vegetables and cancer in 2003 stated that it was probable that an adequate intake will reduce the incidence of cancer of the oral cavity (mouth and pharynx), oesophagus, stomach and colorectum (large bowel). (The level of evidence is highest for the upper gastrointestinal cancers.) Inadequate intake of vegetables has been implicated in causing numerous other types of cancer, such as prostate, breast and lung cancers but evidence is less strong for these associations.

The study of many individual vitamins and phytochemicals (compounds from plants) in vegetables (and fruit) thought likely to be protectiveagainst cancer , including  salicylates, tannins, phytoestrogens, isoflavones, flavenoids, polyphenols and  isothiocyanates, has produced no conclusive evidence that any one compound has anti-cancer properties on its own and it is very likely that people need the full range of compounds available from a wide variety of vegetables (and fruit) to receive a beneficial effect.

It is also likely that taking supplements of vitamins, antioxidants etc is not beneficial in reducing cancer and one of the recommendations of the recent World Cancer Research Fund report on nutrition and cancer (mentioned above) is to 'Aim to meet nutritional needs through diet alone'.  This is because it is not yet know which nutrients/chemicals are beneficial, let alone in what quantity, and because supplements do not provide the diversity of nutrients/chemicals required. Also, more is not necessarily better when consuming natural compounds, and in some cases, taking quantities significantly in excess of that provided by a healthy diet can increase the risk of disease, including cancers. For this reason, the Cancer Council of Australia advises against the use of supplements for cancer prevention except in certain people likely to suffer from nutrient deficiencies. (See section 'Vitamin supplements') A much wiser investment would be weekly visits to the green grocer.

For some tips on ways of getting five servings of vegetables and two servings of fruit each day go to: www.gofor2and5.com.au People who have a garden should consider growing some herbs, vegetables and fruit trees.

(Back to top)

Hints for preserving nutrients in vegetables and fruit

Start with fresh vegetables and herbs whenever possible and try not to not store fresh foods for long periods (a week at most).

Fresh fruit and vegetables are still alive when bought and continue to respire; breathe in oxygen and breathe out carbon dioxide and water vapour. This process is necessary for the food to stay healthy and requires oxygen. Thus, don't seal them in an airtight container. A cold environment (putting them in the fridge) slows this process down. Whether you want to slow this process down or not depends on the type of fruit / vegetable.

Storing food in the fridge

  • Foods that should be stored in the fridge include leafy salad vegetables, asparagus, broccoli, capsicums, cucumbers, beans, mushrooms, carrots and fruit that is already sweet and won't get sweeter with ageing, such as berries and citrus fruit.
  • Put them in the fridge as soon as you get home and don't leave them in the car in the heat for long periods on the way home.
  • Fruit and vegetables stay crisper in a humid environment, as provided in your fridge crisper, and this is improved by keeping them in a plastic bag (but not an airtight one). (An exception is cuccumbers which last longer if the are tightly wrapped in plastic. Some can be bought like this.)
  • Too much moisture is also harmful as as the extra moisture encourages the growth of micro-organisms and thus causes food to rot quicker. It is therefore best to avoid washing fruit and vegetables until they are about to be eaten. (If you use lettuce spinners make sure most of the water is removed. Lots of spinning.) Also, remember that fruit and vegetables produce moisture as they age and this can add to the problem if there is inadequate ventilation.
  • Special plactic containers that have vents and a raised shelf on the bottom are ideal as they keep food moist, avoid the problem of sitting in a puddle of water on the bottom and allow oxygen entry.
  • Beans and cuccumbers like warmer parts of the fridge and tend to go off more quickly. They should be eaten soon after purchase.
  • Carrots tend to lose water quickly and should be kept in a container in the fridge.
  • Mushrooms are praticularly susceptible to rot from exposure to excess water. Storing them in a paper bag prevents rot occurring and putting that paper bag in an open plastic bag prevents the mushrooms drying out.

Foods that should not be stored in the fridge

  • Some foods need to soften and go sweet (ripen) before eating and the cool fridge slows this process. Thus, these foods should be kept in a bowl and in a cool shaded place. They include tropical fruits, stone fruit, pears, apples, kiwifruit, tomatoes and avocadoes. These fruits also emit a gas (ethylene) that can cause a bitter taste in carrots and increase the ripening of foods in the fridge; something you are trying to slow down. (If you do want to speed up the ripenning of avocadoes and tomatoes, put them in a fruit bowl with 'ethylene emitting' ripening bananas.)
  • Tropical fruits such as mangoes, banans and pineapples are sensitive to chill injury and are best kept in a bowl.
  • Potatoes,, onions and garlic should be kept out of the fridge as the humidity will make them sprout. They should not be kept in a plastic bag. Potatoes need to be kept in a dark place as light exposure makes the go toxic. A potato that is green is likely to be toxic and should not be eaten. (This process does not occur in sweet potatoes.)

Cooking food

  • Keep pieces as large as possible when chopping/slicing.
  • Water soluble vitamins are the ones that are destroyed by cooking / lost by dissolving into cooking water. Maximum losses during cooking vary from 10 per cent for vitamin B12 to 100 per cent for more unstable vitamins, such as folate and vitamin C. Fat soluble vitamins are more hardy and don’t dissolve in cooking water.
  • When cooking vegetables, minimise both cooking time and cooking water to reduce vitamin losses. Vitamin losses with cooking vary from about 10% with steaming or micro-waving to about 50% with boiling. Most of the vitamins lost are the water soluble ones. The preferred cooking method for reducing vitamin loss is micro-waving (with little water), followed by steaming, stir-frying and lastly, boiling. If boiling, add food only when the water is boiling and boil in the smallest amount of water possible. Do not soak vegetables before cooking.
  • Do not use copper pots or utensils as they can increase losses of some vitamins, particularly vitamin C.
  • Use cooking water and liquid from canned foods in sauces, gravies etc.
  • Do not use baking powder to preserve vegetable colour during cooking as it increases vitamin losses.
  • Heating is not always bad. While heating tomatoes decreases its vitamin C content, it increases the availability of antioxidants including lycopene.

Finally, fruit and vegetables are one of the largest causes of food waste, with the average household throws away about $2,000 worth of fruit and vegetables each year. Doing the above will save you money.

 

(Back to top)

Other dietary influences on cancer (alcohol, fibre, red meat, charred foods)

Alcohol and cancer

There is convincing evidence that alcohol increases the risk of developing numerous cancers, including those of the liver, breast, mouth, pharynx, larynx, oesophagus and colon, and there is a possible association with lung cancer. Alcohol is not associated with cancers of the pancreas, bladder and prostate.

Cancer and a high fibre diet

It is likely that any effect of dietary fibre on bowel cancer would take many years to occur and unfortunately the good studies on this topic were not done over a sufficiently long period to show any effect. Thus, it is difficult to interpret evidence on this topic. However, it is generally felt that a high fibre diet, particularly one with a high content of insoluble fibre, will probably cause a reduction in the risk of developing colorectal cancer. (This was the judgement of the World Cancer Research Fund's report.)

Meat consumption and cancer

Red meat, particularly processed meats such as salami, has been implicated in causing cancer, particularly colon cancers. However, red meat is an important source of nutrients (especially iron) and thus the advice regarding its consumption is to eat it in moderation. The World Cancer Research Fund's report recommends limiting consumption to no more than 500g per week. With regard to cancer prevention, it is advised that processed meats should not be a routine part of the diet, with the World Cancer Research Fund recommending they be avoided. They are, however, part of the food culture of many people and as with most things in life, compromise is at times needed. In any case, it is reasonable to assume that occasional 'treat' consumption is unlikely to do significant harm.

Smoked/salt-cured foods

Smoked/salt-cured foods contain nitrites and nitrates which can form nitrosamides in the stomach. These compounds may increase the incidence of stomach cancer. Such foods include smoked fish, hot dogs, corned beef, bacon and ham.

Charred foods and cancer

Charred food, including meat, toast and vegetables, can create chemicals that increase the risk of cancer, particularly bowel cancer. These chemicals include polynuclear aromatic hydrocarbons and heterocyclic amines. Polynuclear aromatic hydrocarbons are absorbed by foods when they are smoked (especially fatty meats) or are produced by charring foods. High temperature cooking (frying, grilling and barbequing) of meats and fish turns some protein compounds into heterocyclic hydrocarbons, which are weakly carcinogenic.

Once again the evidence that these chemicals cause cancer is inconclusive and there is no specific recommendation in the World Cancer Research Fund's recent report regarding this type of food preparation. For those who wish, the intake of charred foods can be reduced by cooking using low heat methods such as steaming, micro-waving or stewing and cooking over the hot-plate rather than over coals when barbequing. Also, micro-waving the meat briefly first reduces the creatine content that gives rise to heterocyclic amines. Try using marinades to add extra flavour rather than charring food. (Avoid too much soy sauce as it has a very high salt content, even in the low-salt variety.)

Dietary fat and cancer

The World Cancer Research Fund in 1997 indicated a possible link between high dietary fat intake and several cancers. Subsequent research has changed this view and it is now felt that there is insufficient evidence to make such associations and it is not mentioned in the World Cancer Research Fund's more recent report. However, a high fat intake is likely to increase obesity and, as mentined above, obesity is linked to several cancers, including breast and bowel cancer.

Specific foods and specific cancers

The role of diet is reducing specific cancers is mentioned in the above discussion of the findings in the World Cancer Research Fund's report. They are also discussed in the sections on each particular cancer. (The cancers thus covered include colorectal cancer, prostate cancer and breast cancer.) Below are some comments about specific foods that are commonly viewed to have cancer prevention attributes by the general community. Those with probable benefit are mentioned before those considered to have only a possible benefit.

Foods with a probable benefit

Beans (or legumes) - Probable benefit in preventing colorectal cancer: The active ingredients in beans that scientists believe may play a role in cancer prevention include saponins, protease inhibitors and phytic acid. These compounds, called phytochemicals, are found naturally in plants and appear to protect our cells from damage that can lead to cancer. Beans are also rich in fibre which probably helps reduce colorectal cancer.

Cruciferous vegetables - Probable benefit in preventing gastrointestinal cancers: The cruciferous vegetables include broccoli, cauliflower, cabbage, brussels sprouts, bok choy and kale. Research on cruciferous vegetables highlights several components that have been linked to lower cancer risk, including glucosinolates, crambene, indole-3-carbinol and, especially, isothiocyanates (which are derived from glucosinolates). Research has shown that these vegetables probably protect against some types of cancers, with the strongest protective effect occuring in cancers of the mouth, pharynx, larynx, esophagus, and stomach.

Dark leafy-green vegertables - Probable benefit in preventing colorectal cancer: Spinach, kale, romaine lettuce, leaf lettuce, mustard greens, collard greens, chicory and Swiss chard are excellent sources of fiber, folate and a wide range of carotenoids such as lutein and zeaxanthin, along with saponins and flavonoids. Researchers believe that carotenoids seem to prevent cancer by acting as antioxidants – that is, scouring potentially dangerous “free radicals” from the body before they can do harm. Also, foods containing folate decrease risk of pancreatic cancer and that foods containing dietary fibre probably reduce one’s chances of developing colorectal cancer.

Tomatoes - Probable benefit in preventing prostate cancer: The tomato’s red hue comes chiefly from a phytochemical called lycopene. Lycopene, a powerful antioxidant, together with a group of related compounds collectively called the “red family,” has displayed anti-cancer potential in a variety of laboratory studies. Tomatoes have attracted particular attention from prostate cancer researchers because lycopene and its related compounds tend to concentrate in tissues of the prostate. There is substantial and convincing evidence that foods containing lycopene probably protect against prostate cancer.

Whole grains - Probable benefit in preventing colorectal cancer: The term “whole grain” means that all three parts of the grain kernel (germ, bran and endosperm) are included. Refined grains usually have the bran and germ removed, leaving only the starchy endosperm. Brown rice is a whole grain, white rice is not. Other whole-grain foods include wheat breads, rolls, pasta and cereals; whole grain oat cereals such as oatmeal, popcorn, wild rice, tortilla and tortilla chips, corn, kasha (roasted buckwheat) and tabouleh (bulghur wheat). Whole grains are rich in fiber, vitamins, minerals and hundreds of natural plant compounds, called phytochemicals, which protect cells from the types of damage that may lead to cancer. In addition research points to specific substances in whole grains that have been linked to lower cancer risk, including antioxidants, phenols, lignans (which is a kind of phytoestrogen) and saponins. There is probable evidence that whole grains reduce the risk of developing colorectal cancer.

Garlic - Probable benefit in preventing gastrointestinal cancers, particularly colorectal cancer: Garlic belongs to the family of vegetables called Allium, which also includes onions, scallions, leeks and chives. These allium vegetables contain many substances now being studied for their anti-cancer effects, such as quercetin, allixin and a large group of organosulfur compounds that includes allicin, alliin and allyl sulfides. Foods belonging to the allium family of vegetables probably protect against stomach cancer and garlic also has been found to probably decrease the risk of developing colorectal cancer.

Foods with a possible benefit.

Soy products - Only possible benefit in breast cancer prevention - Soy beans are a type of lugume or bean. Foods made from them include tofu, soymilk, soynuts, miso (soy paste), tempeh, and soynut butter. Scientists believe that several active ingredients in soy may have anti-cancer effects, including isoflavones (which have been studied most), saponins, phenolic acids, phytic acid, phytosterols, and protein kinase inhibitors. Soy appears to contain some components that resemble very weak forms of the body’s natural hormones. As a result, soy foods can mimic the actions of hormones under certain conditions and counteract these hormonal actions at other times. Because of such complexities, most of the studies that have investigated soy’s role in cancer development have dealt with hormone-related cancers such as those of the breast and prostate.

The consumption of soy products has for some time been considered beneficial by many in the community with regard to preventing breast cancer. To date there has only been limited evidence to suport this view and thus the benefits should only be regarded as possible. Current research shows that it is safe to eat moderate amounts of soy foods, up to two to three servings per day.

Berries - Possible benefit in cancer prevention: Berries are good sources of vitamin C and fibre. Foods high in vitamin C probably protect against cancer of the esophagus, while foods containing dietary fiber probably decrease colorectal cancer risk. All berries, but particularly strawberries and raspberries, are rich in ellagic acid. In laboratory studies, this phytochemical has shown the ability to prevent cancers of the skin, bladder, lung, esophagus and breast. Strawberries also contain a wide range of other phytochemicals, called flavonoids, each of which seems to employ a similar array of anti-cancer strategies.

Green tea - Possible benefit in cancer prevention: Both black and green teas contain numerous active ingredients, including polyphenols and flavonoids, which are potent antioxidants. One class of flavonoids called catechins has recently become the focus of widespread study for their anti-cancer potential. Tea is the best source of catechins in the human diet, and green tea contains about three times the quantity of catechins found in black tea. Unfortunately the limited amount of evidence available in regard to the potential benefit of tea in reducing cancer means that it is not possible to make a recommendation regarding any potential beneficial relationship.

Grapes and grape juice - Possible benefit in cancer prevention: Both grapes and grape juice are rich sources of resveratrol, a type of natural phytochemical that belongs to a much larger group of phytochemicals called polyphenols.
The skin of the grape contains the most resveratrol, and red and purple grapes contain significantly more resveratrol than green grapes. Grape jam and raisins contain much smaller amounts of this phytochemical. Red wine also contains resveratrol but any potential cancer benefit from resveratol in wine is definitely outweighed by the increased risk of cancer caused by the alcohol content. (See above.) Studies suggest that polyphenols in general and resveratrol, in particular, possess potent antioxidant and anti-inflammatory properties and reseach has demonstrated resveratrol’s ability to slow the growth of cancer cells and inhibit the formation of tumors in lymph, liver, stomach and breast cells. Resveratrol has also triggered the death of leukemic and colon cancer tumors.

 

(Back to top)

Further information

World Cancer Research Fund / American Institute for Cancer Research
Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. Washington, DC: AICR, 2007
www.dietandcancerreport.org

Nutrition Australia   
www.nutritionaustralia.org
A non-government, non-profit, community-based organisation that has offices in all states and territories. It aims to promote the health and well-being of all Australians.

Food Standards Australian & New Zealand (FSANZ)
www.foodstandards.gov.au  
Provide current recommendations regarding food standards in Australia. Lots of good information.)  Ph 02 - 6271 2222

OzFoodnet  
http://www.ozfoodnet.gov.au
A health network designed to enhance the surveillance of food-borne diseases in Australia.

  

(Back to top)