The Role of Diet in Cancer Prevention
Although we cannot deny that our genetics can play a role in the development of some cancers, most cancers are not clearly linked to the genes we inherit from our parents. In other words, we know that all cancers are triggered by altered genes (random mutations) over the course of a person’s life, but only about 10% of cancer cases are actually inherited – or genetic. That means the person was born with a factor that makes them more likely to get cancer.
What are the main risk factors for cancer and to what extent we can control them?
According to the research published in the journal Nature, a vast majority of cancer cases (70–90%) are not down to “bad luck” but have their roots in the environment and lifestyle, such as smoking, poor diet, obesity, alcohol, sun exposure, environmental pollutants, infections, stress, and physical inactivity.
While nothing we do can guarantee that we will never get cancer, there are steps we can take to help lower the risk of developing the disease over the course of our lifetime. Some of these things include using sunscreen, quitting smoking, exercising, and getting vaccinations.
While smoking is still by far the biggest cause of cancer and cancer deaths, obesity, poor diet and high alcohol misuse remain major controllable and preventable risk factors for cancer.
Can a healthy diet prevent cancer?
No single food or ”super food” (no matter how healthy it is) can protect us against cancer, but research shows that our overall diet (what we eat most of the time) plays a big role in cancer prevention. According to the American Cancer Society, having excess weight or obesity is one of the biggest risks for many cancers. Having a healthy diet helps us keep a healthy weight, or lose weight, which can reduce the risk of cancer.
This prevention strategy may raise a lot of questions as what a healthy diet is and whether there are specific foods to eat and avoid.
1. Mediterranean diet
A healthy balanced diet such as the Mediterranean diet is low in red meat, saturated fats and added sugar, and is build around a variety of anti-inflammatory, high–fibre, antioxidant–rich plant–based foods, such as fruit/berries and vegetables, beans, legumes, whole grains, healthier fats, such as extra virgin olive oil, avocado, nuts and seeds, lean protein (fish and seafood). The Mediterranean diet has been linked to cancer prevention (especially colon cancer) and other positive impacts on long–term health.
2. Enjoy Cruciferous Vegetables
Cruciferous vegetables such as broccoli, cauliflower, kale, cabbage, and Brussels sprouts are rich in phytonutrients that may help to lower inflammation and block cancer–causing chemicals.
3. Eat the rainbow
While eating more fruit and vegetables is essential for overall health, brightly–coloured plants are linked to higher levels of specific cancer–fighting antioxidants (phytochemical) and each pigment (red, green, orange and yellow, blue and purple, white and brown) provides various health–benefits, which is why a balance of all colours is important. Red fruits and vegetables are rich in carotenoid lycopene that is responsible for the red to pink colours seen in tomatoes, watermelon, red onion and other foods. Unlike many other bioactive compounds, lycopene is stable to processing and heat. Current research suggests that foods high in lycopene may prevent or slow down the progression of some types of cancer. Blue and purple fruits and vegetables contain anthocyanins and resveratrol and have been studied extensively for their anti–cancer and anti–ageing properties. Try to avoid peeling foods whenever possible (apples, courgettes, aubergines, nectarines) as skin is the richest source of fibre, antioxidants, vitamins and minerals.
Tip: How to eat the rainbow. Try to eat at least 2–3 colours at each meal and snack. Try new fruit or vegetable every week. Try different cuisines while travelling or exploring markets and restaurants (South American, Indian, Mexican, Greek and Cypriot, Lebanese, Korean).
an omelette or scrambled eggs with red cherry tomatoes, orange peppers, green olives, purple kale, white onions
a Greek yoghurt with granola, blueberries, raspberries, blackberries and kiwi
a bowl of porridge topped with banana and pear
mixed berry pancakes with coconut yoghurt
Lunch and Dinner:
chicken with roasted parsnips, sweet potato, broccoli and garlic
a mixed salad with leafy greens, cherry tomatoes, orange and yellow peppers, purple cabbage paired with a protein source (fish, roasted turkey, or chickpeas and beans)
vegetable soup with lentil, black beans, cauliflower and onion, garnish with fresh coriander or parsley
a goat cheese salad with pickled beetroot, rocket, spinach, nuts and seeds
seafood pasta with aubergine, courgette, mushrooms and tomato sauce
veggie sticks (carrots, celery, cucumber, bell peppers) with hummus
apple with peanut or cashew butter
wholegrain toast with avocado, cherry tomatoes and seeds
grapes and cheese
4. Limit processed foods and sugar – sweetened drinks
Fast foods and sugar – sweetened drinks are causes of weight gain, overweight, and obesity, which are a risk factor for many cancers. The standard Western diet tends to be nutrient –poor (low in fibre, vitamins and important nutrients) and energy–rich (high in calories, added sugar, sodium and fat) that appeal to the human palate and are often consumed in large portions. The concept of energy density can really help with weight control without calorie counting.
5. Limit red and processed meat
Red meat is a good source of protein, iron, zinc and vitamin B12 and can form part of a healthy diet. But eating a lot of red and processed meat increases your risk of bowel cancer.
Over 800 studies have shown that eating processed meat can cause bowel cancer and eating lots of red meat can increase the risk of bowel cancer.
This does not mean you have to cut out all red and processed meats from your diet. Research suggests avoiding processed meat and eating red meat occasionally (think of red meat as you do lobsters, something you would usually eat only for a special occasion). So, if you are eating processed and red meat at every meal most days, it’s a good idea to cut down to 70g or less per day, which is the equivalent of roughly: 3 slices of ham or two medium–sized sausages, one lamb chop or a small piece of steak (about the size of a deck of cards). A traditional “full English” breakfast with two sausages and two rashes of bacon is equivalent to 130g.
What’s the difference between processed and red meat?
Processed meat is any meat that has been preserved or altered by smoking, curing, salting, canning or other processes to enhance flavour. Processed meat includes bacon, salami, ham, hot dog, pepperoni, chorizo and sausages. But this does not include mince or fresh burgers.
Red meat includes all fresh, minced, and frozen pork, beef, veal, lamb, mutton, horse and goat meats.
How does red and processed meat cause cancer ?
The exact mechanism why processed and red meats can cause cancer is not fully understood yet. However, there are several possible reasons:
Red and processed meat contain haem iron, which makes meat red in colour. When haem is broken down in the gut it forms N–nitroso compounds. These can damage the DNA of the cells that line the digestive system, which can lead to cancer.
The preservatives (nitrates and nitrites) used in processed meat to keep it fresher for longer are more strongly linked to bowel cancer than fresh red meat.
Cancer causing chemicals (heterocyclic amines and polycyclic amines) develop when meat is cooked at high temperatures (grilling and barbequing). They can also damage cells in the bowel.
Tip: One of the steps to take in reducing your processed and red meat intake but still enjoy it in moderation is to make small changes that last.
If you eat red meat at every meal – try cutting down your intake to once a day and swap out red meat for other healthier alternatives (fish, poultry, tofu, legumes, nuts).
Try Meatless Monday. Replace meat with plant–based alternatives such as lentils, beans, or tofu on Mondays.
Substitute some meat (half of your regular portion) for lentils, chickpeas or red kidney beans in beef bolognese, meatballs, curry and casseroles.
Reduce your portions – try having one sausage instead of two, or replace some of your meat with mushrooms and tofu.
Try refried beans – a good substitute for meat in tacos and burritos.
Add additional vegetables, mushrooms, and zucchini to your favourite homemade pizza.
Our team of experts at PAAR are here to help you with any dietary concerns and nutrition–related questions. Book a session with one of our nutritionists to learn more.