Can cancer be prevented? "Yes", in some cases, is the answer. It is estimated that two in five cancers are preventable if we make healthy lifestyle changes.
Research reveals that one in two people living in Ireland will have a cancer diagnosis in their lifetime. This equates to 24,000 invasive cancers and sadly, 9,ooo cancer deaths in this country every year.
There are more than 200 different types of cancer. Prostate, breast, colorectal, lung, and melanoma skin cancer are the most common ones diagnosed in Ireland.
There are many ways that food, nutrition, and lifestyle can influence your risk of getting cancer, according to Dr Erin Stella Sullivan, a dietician and lecturer in nutritional sciences at King's College in London. She was speaking at a recent talk organised by the Health Service Executive.
Watching your weight, eating well, being physically active, drinking less alcohol, and giving up smoking are all ways of cutting your cancer risk, she said.
In 2016, the National Cancer Registry of Ireland estimated the percentage of invasive cancers which were caused by the following factors:
• Eating processed meat (such as sausages, ham, bacon, salami, pate, and canned meat such as corned beef ) caused less than one per cent of cancer cases
• Drinking alcohol caused 2.4 per cent of cancers
• Having a high body weight resulted in five per cent of cases
• Smoking caused 13 per cent of cancers
Good evidence
Making multiple positive changes with small effects can add up and help reduce your overall risk significantly, she said. "The World Cancer Research Fund's [a cancer prevention charity in the UK] recommendations are simple and explain how we can alter our diet and lifestyle to reduce our risk of cancer overall. We have really good evidence that if you follow these guidelines, you will have a lower risk of cancer, and, even if you get cancer, it will reduce the risk of it coming back again. "
Alcohol is one of the risk factors for the condition. It increases your chance of getting at least seven types of cancer, including mouth, throat, larynx, oesophagus, breast, stomach, and bowel. When alcohol is broken down in your body, it can damage its cells which can raise your cancer risk. Experts say if you choose to drink alcohol, limit the amount you take. The less you drink, the lower your risk.
Dr Sullivan said it is worth noting that alcohol contains calories, for example, a standard drink (also known as a unit ) has 10g of alcohol which provides 70 calories. Beer, wines, etc, also contain carbohydrates which have additional calories. This can impact on weight management.
Smoking increases your risk of getting at least 15 types of cancer, according to the HSE. If you smoke, get help to give up the habit. Quitting cigarettes will reduce your risk of cancer, even if you smoked for a long time. It can be hard to make a change like this, but, it is possible, and there are a lot of free supports available.
When giving up cigarettes, people often worry about whether they will gain weight, said Dr Sullivan. The risk of cancer from smoking is much higher than that associated with weight. Quitting smoking is always worth it. "You can speak to your GP to get a referral to a registered dietician to support you with healthy eating and weight management when quitting smoking."
Being physically fit is an important factor in managing your weight. The recommended guidelines for adults are 150 minutes of aerobic activity, such as brisk walking, swimming, running, or cycling or 75 minutes intense aerobic activity on at least two days a week. She said it is not necessary to go to the gym, any activity that engages your muscles is beneficial.
Reducing your sugar intake helps you avoid becoming overweight, which is another risk factor for cancer. The dietician and lecturer said people should avoid sugar sweetened drinks such as soft drinks (excluding diet/zero-free versions ), sports and energy drinks or electrolyte replacement drinks, flavoured juice drinks, sweetened tea and coffee, and flavoured milks.
Free sugar
"We recommend mostly drinking water and unsweetened drinks like milk - low-fat milk for most people in the population. While smoothies and juices can be a source of fruit and vegetables, they only count for one of your five to seven a day [a well-balanced diet should include this number of portions of fruit and vegetables] because they contain a lot of free sugar.
"Foods high in salt, fat, starches (including fast foods and confectionery ) should be avoided, too. There is media attention around ultra processed foods now, but for cancer prevention, the concern is not the additives, preservatives, or processing methods (except for processed meats ). Instead, we are concerned that they contain a lot of energy and this can cause weight gain. Foods high in both energy and sugar promote weight gain around our abdominal organs which is the most harmful location to gain fat. These foods can be very tasty and not very filling which promotes over eating. We also recommend avoiding processed meat and limiting red meat."
She said a cancer prevention diet need not be meat-free. Red meat is a good source of protein, iron, zinc, and vitamin B12. She recommended limiting red meat, for example, beef, pork, and lamb to three servings per week (about 350 to 500g cooked weight ) and minimising or totally avoiding processed meat such as ham, sausages, rashers, pudding and charcuterie.
"To get the benefit of fibre, which is lower in energy and healthy phytochemicals, we recommend eating more plants and lots of colours. This includes wholegrains, vegetables, salad, fruit, and legumes (peas, beans, lentils ). Fill up half your plate with plant foods and each day, aim for five to seven servings of vegetables, salad, and fruit and three to five servings of wholegrains."
Can we reduce our cancer risk by taking supplements? "No," said Dr Sullivan. She warned that taking high doses of some supplements can, in fact, be harmful. "However, there are supplements we recommend for other reasons," she said. "These include folic acid - anyone who could become pregnant should take 400 micrograms a day to prevent neural tube defects. Vitamin D3 is also recommended for some people. Take 15 micrograms/600 IU per day from Hallowe'en to St Patrick's Day all year if you are over 65 or have darker skin (which makes it harder to make Vitamin D ) or are pregnant."
Breastfeeding also reduces your risk of getting cancer. It helps babies' immune systems and reduces their risk of getting many diseases throughout their lives. It is recommended exclusively for six months and as a complementary food for up to two years. Breastfeeding, even for a short period, is beneficial, she said.
Maintaining a healthy body weight can reduce your chance of getting several types of cancer. "A higher body weight (especially fat ) is associated with an increased risk of many cancers. High amounts of visceral fat (the fat around your abdominal organs ) is most harmful. To reduce your cancer risk, you should aim to have a body mass index (BMI ) [a measurement of your body fat based on your height and weight] close to the lower end of the healthy range (20 to 25 ), and closer to 20 than 25. Avoid weight gain (increasing your BMI or waist circumference ) during adulthood."
Weight gain
She stated that people often struggle to lose weight and maintain weight loss over time. Rapid weight loss achieved using restrictive diets is commonly followed by weight gain (often more than was lost ), she said.
"By following the healthy eating, alcohol, and physical activity guidelines, you are best placed to lose weight in a healthy manner and even without weight loss, these changes will improve your cancer risk status. Another way of thinking about that is as a seesaw, balancing your risks.
"If you do all of those good things, increasing plant foods, decreasing processed food intake, and reducing drinking alcohol, even if your weight is not in the healthy range, all the good things you are doing outweigh the other risks. The take home message is: weight is one risk factor. Don't focus on weight loss alone at the expenses of other recommendations."
If you've had a cancer diagnosis, what represents healthy eating for you will depend on your situation, according to Dr Sullivan. "For many cancers, the first sign is weight loss. Even if you have previously been told to lose weight, any sudden, unexplained weight loss should be addressed by your GP. For people with cancer, we usually discourage weight loss during active treatment as protecting muscle is the most important nutritional goal."
How can you prevent a cancer recurrence ? "If you have finished treatment and have no long-term nutritional issues as a result of your cancer or treatment, we recommend following the prevention guidelines [outlined earlier] to reduce a recurrence risk. We have really good evidence that people who follow the guidance after cancer have lower rates of cancer coming back.
"Books such as "The truth behind food and cancer", "The anti-cancer cookbook", and "Healthy eating for cancer survivors" are available from www.breakthroughcancerresearch.ie These books answer a lot of questions about areas where people aren't sure what to believe and about myths around food and cancer. There are lots of recipes available, too, that are based around these guidelines."
