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Ask the cancer expert

We answer your questions on diet, lifestyle, weight management and cancer prevention.

Q1. I’ve read a few stories in the news about vegetables and fruits and cancer risk. What are the facts?

Q2. After years of having a family to look after, I find it hard to motivate myself to cook for one. Is it okay to cook in bulk and reheat food?

Q3. What is processed meat and why does it increase bowel cancer risk?

Q4. I have heard a lot about dairy products and breast cancer. Should I cut dairy products from my diet to prevent breast cancer?

Q5. Although I eat healthily I find it difficult to reach the recommended 5 A DAY. Often portions seem too large to fit in my average meal. Could you give a precise measure of what constitutes a "portion" of various vegetables?

Q1. I’ve read a few stories in the news about vegetables and fruits and cancer risk. What are the facts?

An independent expert panel of scientists looked at vegetables and fruits in relation to cancer prevention as part of our Expert Report.

They concluded that the evidence linking vegetables and fruits to a reduced risk of cancer was strong enough to recommend that people eat more of these, as part of a healthy diet, based on plant foods.

Current research shows vegetables and fruits probably protect against a range of cancers, including cancers of the mouth, pharynx, larynx, oesophagus, stomach and lung.

What’s more, one big study suggested that if all of us ate an extra two portions a day, around 2.5 per cent of cancers could be prevented.

In the UK, this equates to around 7,000 cases a year.

There is also evidence that people who eat plenty of vegetables and fruits are less likely to be overweight.

Scientists now say that, after not smoking, maintaining a healthy weight is the most important thing you can do for cancer prevention.

This is because there is strong evidence that being overweight is a cause of cancers of the:

  • oesophagus
  • pancreas
  • womb (endometrium)
  • kidney
  • breast (post-menopausal)
  • bowel
  • ovary
  • gallbladder

For these reasons, WCRF UK recommends that we should eat more of a variety of vegetables, fruits, wholegrains and pulses such as beans to lower our cancer risk.

For ideas on how you can include more vegetables and fruits in your diet, check out our healthy recipes.

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Q2. After years of having a family to look after, I find it hard to motivate myself to cook for one. Is it okay to cook in bulk and reheat food?

Cooking in bulk is a great idea if you want to eat well and save time and effort, particularly if you are cooking for one.

Simply allow your food to cool, divide into batches, label and freeze.

Just make sure you reheat food until it is piping hot when you are ready to eat it, otherwise bacteria can grow in the food and make you ill.

Contrary to popular belief, freezing food doesn’t affect its nutritional value. In fact, freezing food can stop it deteriorating and keep it at its best. For example, frozen vegetables and fruits such as peas and berries can contain more nutrients than fresh.

Some foods like lasagna, fish or cottage pie, casseroles, soups and stews lend themselves well to cooking in bulk. Including vegetables in these dishes is also an easy way to achieve one or more of your 5 A DAY.

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Q3. What is processed meat and why does it increase bowel cancer risk?

Research has shown that only about 40 per cent of Britons are aware that eating processed meat increases cancer risk. And many people are still unclear about what exactly we mean by processed meat.

What is processed meat?

The processed meat that has been linked to bowel cancer is usually red meat like pork or beef, which has been treated by various processing methods, including curing (adding salt and other additives), drying and smoking to add flavour to the meat and to help preserve it.

There are many different types of processed meat products on the market. Processed meat includes bacon, ham (raw, smoked or cooked), some sausages like hot-dogs or salami, black pudding, meat pâtés and some canned meats.

Minced meat and hamburgers are usually not classified as processed meat unless they contain meat that has been treated by one of these processes.

Processing methods

Among the various methods used to process meat, curing and smoking are especially common.

  • Curing is the addition of salt, sugar and substances known as nitrate and/or nitrite. Salt adds flavour to meat and preserves it by stopping the growth of bacteria. Nitrates and nitrites are naturally occurring compounds, which are added to meat to extend shelf life, to give processed meat its desirable dark red colour and help kill bacteria. Examples of cured meat include ham, bacon, salami and hot dogs.
  • Dry curing is the traditional way of preserving meat, especially used for ham. Traditionally only salt was used but the method required a lot of time. Nowadays most ‘traditional’ hams also contain nitrites and other preservatives.
  • Smoking has been used since ancient times to preserve meat as the smoke has an antibacterial effect. Nowadays this method is mainly used to add a particular 'smoked' flavour to meat. Pastrami is an example of smoked processed meat.

WCRF UK Recommendations

As part of the Expert Report, scientists worldwide reviewed the available evidence on food, nutrition, physical activity and cancer risk. The Report revealed that habitually consuming 50 grams of processed meat (the equivalent of approximately two rashers of bacon) every day, increased the chance of getting bowel cancer by around 20 per cent.

To help put this in context, more than 70 per cent of the UK population eats bacon and ham on a regular basis and bowel cancer is a common cancer in the UK.

The scientific review also showed that the more processed meat consumed, the greater the bowel cancer risk. The evidence is that it's best not to eat any processed meat, as there is no nutritional need for processed meat that cannot be easily met by other foods. That is why WCRF UK recommends people avoid processed meat to reduce their bowel cancer risk.

Why does processed meat increase bowel cancer risk?

There are many possible explanations for why processed meat increases the risk of bowel cancer. Here we look at the main ones:

  • Nitrates and nitrites. Nitrates are naturally occurring substances often found in vegetables and drinking water, and often used as meat preservatives. Although they are relatively harmless, when we swallow them, a small percentage is converted into another substance known as nitrites. Nitrites are also commonly added to meat as a preservative. Research has shown that nitrites can react with protein-rich foods (such as meat) to produce N-nitroso compounds (NOCs). Some types of NOCs are known to cause cancer. NOCs can be formed either when meat is cured or in the body when we have eaten meat.
  • Haem in red meat. Haem is an iron-containing molecule found in animal blood and meat, especially red meat. Haem is also linked to the production of NOCs in the body.
  • High-temperature cooking. There is some evidence to show that cooking meat at high temperature, especially frying and grilling, can produce cancer-causing compounds.

Make informed choices

Overall, there is strong evidence of a link between processed meat and bowel cancer. Being aware of the risk means that you can make an informed choice to avoid, or cut down on, processed meat as you wish.

Download our Red and Processed Meat: Finding the Balance for Cancer Prevention leaflet for ideas on alternatives to processed meat for packed lunches and traditional dishes.

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Q4. I have heard a lot about dairy products and breast cancer. Should I cut dairy products from my diet to prevent breast cancer?

We often hear news stories in the media about what can cause or prevent cancer. Some of the advice in websites, magazines and even books is not always objective or based on hard science. That is why in 2007, WCRF UK undertook the most comprehensive review of all the scientific evidence available on diet, lifestyle and cancer prevention, and published the Expert Report.

According to the Report there is no strong evidence to suggest that dairy products are a cause of breast cancer. Being overweight (only for postmenopausal women), drinking alcohol and not breastfeeding are the only lifestyle factors that convincingly increase breast cancer risk.

Diet is a very difficult aspect to study in people because of the variety of foods and complexity of dishes we eat. Due to the conflicting evidence WCRF UK does not make any recommendation with respect to cancer prevention for dairy foods. More studies are underway and so it is possible that in the future WCRF UK will be able to give advice about dairy foods.

In the meantime, it is important not to cut complete food groups from your diet unless your doctor or dietitian advises you otherwise. Dairy products are an important source of protein, calcium, vitamin B12 and riboflavin. However, some dairy products are high in fat, which can contribute to weight gain. Try to choose mainly low-fat varieties, like semi-skimmed or skimmed milk and low-fat yoghurt, which still contain all the nutrients but very little animal fat.

WCRF UK recommends eating a varied, mainly plant-based diet. So, limiting animal fat is a good step towards a healthier diet.

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Q5. Although I eat healthily I find it difficult to reach the recommended 5 A DAY. Often portions seem too large to fit in my average meal. Could you give a precise measure of what constitutes a "portion" of various vegetables?

If you find it difficult to fit 5 A DAY into your diet, it might help to look at reshaping your plate rather than feeling you have to add vegetables and fruits to what you’re already eating.

A good rule of thumb is to fill two thirds (or more) of your plate with vegetables, fruits, wholegrains and beans, and one third (or less) with animal foods like poultry, fish and meat.

Almost all vegetables and fruits count, apart from starchy tubers and roots like potatoes, yam, sweet potatoes and cassava. Pulses, such as beans and lentils, count as one of your portions too. You can use frozen, dried and canned vegetables and fruits. Try to sneak vegetables into your dishes, for example by adding tomato sauce and onions to your casserole, or frozen peas and spinach to your scrambled eggs.

One portion of your 5 A DAY is 80g of vegetables and fruits (so 5 A DAY is about 400g of vegetables and fruits in total).

If you find it difficult to measure exact portions, the following is a rough guide to help you visualise what an 80g portion is:

  • Three heaped tablespoons of cooked vegetables like broccoli or carrots
  • Three or four heaped tablespoons of pulses like beans, chickpeas and lentils – but these only count as one portion a day, no matter how much you eat
  • Small cereal bowl of salad vegetables like lettuce or spinach
  • Medium-sized piece of fruit like an apple or a banana
  • Slice of large fruit like melon
  • Handful of smaller fruit like grapes
  • One heaped tablespoon of dried fruit like raisins
  • Two small fruits like satsumas, plums or kiwi fruits
  • A small glass (150ml) of pure fruit juice – but fruit juice only counts as one portion a day, no matter how much you drink

Finally, try to include a variety of different coloured vegetables and fruits to get the most out of your 5 A DAY and avoid getting bored.

Here is an example of how you can fit in 5 A DAY

  1. Banana or strawberries (with porridge) for breakfast, or a glass of fruit juice
  2. Apple for mid-morning snack
  3. Baked beans (on jacket potato) for lunch
  4. (and 5.) Frozen peas and side salad (with grilled fish and new potatoes) for dinner

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Vegetables

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Page last reviewed: March 2014
Page next due for review: February 2015
The information on this page is based on the findings of our Expert Report and is covered by the Information Standard.

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