CANSA's 5-a-day campaign refers to five servings of fruit and vegetables a day for better health. Dietdoc tells us about the role of nutrition in the fight against cancer.
We are what we eat
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The food we consume determines our physical and often also our psychological health.
Eating a balanced diet rich in protective nutrients can determine what kinds of diseases we either avoid or succumb to, the quality of life we enjoy, and also our longevity.
Research indicates that these facts are particularly relevant to the prevention of cancer.
It has been estimated that dietary factors play a role in up to 35% of all human cancers.
This means that if we eat a balanced diet rich in protective nutrients, we humans could prevent nearly 40% of the different types of cancer that we suffer from.
A balanced diet consists of:
A variety of foods
Plenty of fresh fruits and vegetables
Plenty of minimally processed grains
Plenty of legumes and some nuts
Low-fat or skim milk and dairy products, plus moderate amounts of lean meat, fish, and eggs
Moderate amounts of mono- or poly-unsaturated fats and oils
Plenty of clean water
Moderate quantities of sugar and sweetened foods and drinks
Very small quantities of salt and alcohol
Combined with: regular physical exercise.
What do our Modern, Western Diets consist of?
Too much fat
Too much salt
Too much alcohol
Too much processed starch and sugary foods and drinks
Too little dietary fibre
Too few protective nutrients
Fruit and vegetables
My personal favourite food category is the Fruit and Vegetable one, which is why I am so delighted that CANSA has launched this ‘5-A-DAY’ Campaign
Exciting research
Exciting research evidence is accumulating which shows that by increasing our intake of fruit and vegetables we can prevent cancer:
A meta-analysis of 46 well designed studies (case control and cohort studies) showed that increased consumption of vegetables and fruit conferred the strongest protection of all foods against the non-hormone-dependent cancers, i.e. cancer of the oral cavity, stomach, pancreas and lung.
In another even bigger review of 206 human epidemiological studies and 22 animal studies consistent evidence was found that greater fruit and vegetable consumption protects against cancers, particularly stomach, oesophagus and lung cancer.
Protective nutrients
Scientists have identified 20 nutrients in fruits and vegetables that may be protective against cancer, e.g. dithiolthiones, isothiocyanates, allium compounds, isoflavones, flavonoids, protease inhibitors, saponins, phytosterols, inositol hexaphosphate, dietary fibre, vitamins C and E, folic acid, beta-carotene, lutein, lycopene, selenium, D-limonene, coumarins, and indol-3-carbinol.
What anticarcinogenic effects do these nutrients have?
Act as antioxidants
Protect cells against abnormal cell changes
Increase the activity of enzymes that detoxify carcinogens
Alter oestrogen metabolism
Bind and dilute carcinogens in the GI tract
Change the colonic environment by increasing the ‘good’ bacteria, changing the bile acid composition, the pH, the transit time and faecal bulk
Preserve intercellular matrix structures
Promote normal DNA methylation
Support normal DNA repair
Promote apoptosis of cancer cells
Decrease cell proliferation
Why do we require five or more servings of vegetables and fruit a day?
There is a theory that the human body adapted to high intakes of plant foods over millennia and that cancer may be a disease that results from maladaptation to the reduced intake of most people living in western societies. This theory is borne out by the finding that populations with the lowest intake of fruit and vegetables have the highest incidence and mortality of cancers of the oesophagus (Iran and China), stomach (Poland and Hungary) and intestine (Britain and North America).
How many servings do we actually eat?
Research studies have shown that:
Black rural populations eat green leafy vegetables, wild spinach, pumpkin about twice a day - fruit is only eaten if seasonally available and then mainly by women and children
Black urban populations eat about one small portion twice a day, and women consume significantly more than men
In the Cape (which is ironically one of our main fruit producing areas in South Africa), some studies found that black urban dwellers eat hardly any fruit and vegetables at all
Indian and white populations eat vegetables in small amounts at both main meals
The majority of South Africans therefore do not meet the international/global recommendations of five portions of fruit and vegetables a day.
We are not unique in this aspect. In the USA a national survey showed that the average intake of fruits and vegetables is about three to four servings a day and only 23-32% of Americans eat five or more servings a day.
Why 5-a-day?
According to many international and national health promotions organisations, five portions/servings (400g) of fruit and vegetables a day, is the most manageable, minimum recommendation.
Previous success stories
The 5-A-Day For Better Health was successful in the USA, and the “2 Fruits ‘n 5 Vegs Every Day” campaign gave good results in Victoria, Australia. These campaigns promoting the increased use of fruit and vegetables in other parts of the world proved successful to increase public awareness of the health benefits of eating more fruit and vegetables.
The 5-A-Day Campaign launched by CANSA deserves the full support of all South Africans, but particularly of the press and organisations and professions linked to health and the prevention of cancer.
Members of the public should put this good advice into practice and start eating at least five portions of fruit and vegetables a day to improve their health. – (Dr I V van Heerden, registered dietician)
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