These are some of the most frequently asked questions when it comes to food and cancer risk. I am not an expert and my answers are certainly not definitive, but they are my best interpretation of the evidence available at the time of writing (November 2012). The advice and instructions of your doctor and treatment team should take precedence over my answers.
Should I be eating organically?
If you are hoping that organic foods will be a great deal more nutritious, the answer is probably ‘no’, but if you are doing so to avoid pesticides, and the nitrates in fertiliser, that’ll be ‘yes’.
There is conflicting evidence as to whether organic plant foods are nutritionally superior to conventionally grown produce. A recent Food Standards Agency study of the current data (to 2008) concluded that there is little difference nutritionally between organic and non-organic produce. An even more recent study – the Stanford meta-analysis study (2012) – similarly concluded. Other studies are more positive about the nutrients in organic food (eg studies published by the Quality Low Input Food organisation, a Europe-wide group based at Newcastle University).
The FSA and Stanford studies have been criticised for only looking at nutrient values rather than including the impact of pesticides on health. Most people who buy organic are doing so not just because of what they contain (nutrients, perceived superior flavour, better for planet) but also what they don’t (synthetic fertilisers, pesticides, hormones, unnecessary antibiotics). Not enough is known about the so-called ‘cocktail effect’ of pesticide use on foods we – and livestock – eat, but so far there is no evidence that the amounts found on our food is harmful to us. Contaminant samplings of common foods are taken at very regular intervals in most Western countries. Even so, we should thoroughly wash all of our fresh produce – organic or not as all produce will have microbes that need removing. Organic crops are fertilised with natural nutrients from animal manure, fish emulsion and composted plants – washing reduces these residues and minimizes possible traces of bacteria such as salmonella and E Coli.
Nutrient values in plants are affected by growing conditions, the plant variety, nutrients in the soil (which can be affected over time by bad farming practices), and storage. Regardless of whether a food is organic or not it is important that it is fresh and of good quality. It’s no use buying organic produce if it is limp and damaged. Buying seasonally and locally tends to deliver more of a nutrient benefit, organic or not, since it tends to be fresher.
As for organic meat and poultry, there is more consensus that it may be a better buy for your health - fewer overall hormones and antibiotics, and more healthy Omega-3 fats if it is free range and grass-fed (pastured). The same is true for milk and dairy products. When it comes to cancer, it is more important to have a varied and high quality diet than to eat exclusively organic, as the latter can be much more restrictive due to availability.
See my page on Pesticides In Food – a Quick Guide to Cleaner Eating for a list of the most commonly and least commonly sprayed foods in the US, as well as links and advice on eating in the UK.
Does sugar ‘feed’ cancer?
By promoting obesity and raising insulin levels, high sugar intake may indirectly increase cancer-risk generally. Refined and simple carbohydrates from added sugar (and also white grains and grain products) trigger insulin release more often, and in greater amounts, than complex carbohydrates found in unprocessed plant foods. Over time, in susceptible people, this greater insulin output can lead cells to not respond to insulin as selectively and sensitively as they should. This is known as ‘insulin resistance’, a condition that is on the increase in the UK as we become more overweight and obese. With this condition insulin is ‘free’ in the body and acts as a growth promoter and, in combination with sex hormones, encourages more rapid cell division, leading in some instances to the hormone-related cancers: breast, prostate, endometrial (womb) and ovarian (Kazer, RR, international Journal of Cancer 1995; 62). Independent of interaction with sex hormones, high levels of insulin are associated with cancers of the bowel, pancreas, kidney and endometrium. The good news about all of this is that there appears to be no clinical evidence that modest levels of sugar in the diet is harmful: the occasional cake, biscuit and white baguette can be enjoyed as part of a balanced and healthful diet.
Added sugar provides ‘empty’ calories: increasing calorie intake without providing any nutrients. All sugar is the same to your body, whether it is white (refined), brown (unrefined), honey or agave. Limiting foods such as cakes, sweets, biscuits, sweetened cereals, and sweetened drinks (including alcohol and fruit juice) can help reduce sugar intake. Although fruit contains sugars, the nutrients and fibre they provide are important to our health and should be eaten freely in the context of a balanced diet.
Should I give up dairy?
This is a question that those with hormone-related cancers (eg breast, prostate, endometrial and ovarian) sometimes ask themselves. Evidence so far is inconclusive: some studies show risk, others don’t. It is known that high amounts of dairy (as it contributes to saturated fat) are a risk factor for heart disease. With this in mind it makes sense to choose naturally lower-fat dairy products (cottage cheese, yogurt, Quark) or smaller amounts of higher fat cheeses. These include hard cheeses such as Cheddar and Parmesan -grate these to make them go further rather than eating slices.
You may also like to choose organic, too, as it has fewer naturally occurring hormones than milk from conventionally reared dairy cows. High amounts of calcium in the diet and through supplements is known to be risk factor for prostate cancer, but the amount in an average balanced diet is not thought to raise risk. Low-fat dairy is our best source of vital calcium, and cheese gives us a modest amount of difficult-to-get Vitamin D.
Can I still drink tea and coffee?
Luckily, earlier studies suggesting a link between bladder cancer and coffee have proved unfounded. In fact coffee drinkers seem to be at less risk of Alzheimer’s than non-coffee drinkers. Very hot drinks are to be avoided however, as they damage the lining of the esophagus and increase the risk of cancer in this area. In fact, green tea releases more of its active compounds when brewed warm rather than hot for 10 minutes. Both tea and coffee contain helpful polyphenol antioxidants, so although they aren’t nutritious as such they are good beverages to have in a balanced diet and count towards your fluid intake. Keep it under 5 cups as a day if your cuppa has caffeine – more than that can interfere with absorption of key minerals.
As for tea, black, green and oolong (a type of tea between green and black) are all good for us. Some people find that drinking green tea instead of their normal hot beverages helps with the side effects of chemotherapy. Green tea has more polyphenol activity than black and it also has an amazing compound called epigallocatechin-3-gallate, EGCG for short, that is effective at helping to destroy cancer cells without damaging healthy cells. It also helps protect healthy cells from damage. Although further research is ongoing, ECGC may potentially be used in treating some cancers of the brain, prostate, cervix and bladder. It isn’t advised to have large quantities of green tea (ie more than 3 cups a day) until much more is known about effectiveness and side effects.
It should be noted that there is strong evidence to suggest that those undergoing chemotherapy treatment for multiple myeloma or mantle cell lymphoma should not drink green tea as it interferes with treatment. Drugs treating lung cancer may also be less effective. Ask your doctor for advice if this is an issue for you.
What about alcohol?
Although moderate amounts of alcohol can be heart protective it is unfortunately a risk for at least seven cancers: mouth, upper throat, esophageal, laryngeal, breast, bowel and liver. Although the risk is stronger for the other listed cancers, breast cancer risk starts at a lower level of alcohol intake. Smoking and drinking together substantially increases risk for all digestive tract cancers. To reduce your risk of these cancers it is recommended that you keep to 2 units a day for men and one a day for women. A small (125 ml) glass of 12% alcohol by volume wine is 1.5 units. Try and have several alcohol-free days a week and avoid binge drinking as there is more harm associated with this style of drinking. For information about calculating units visit the alcohol tracker page of nhs.uk, or go to drinkaware.co.uk . The Centers for Disease Control and Prevention also have an interesting FAQ page for those of you in the US. Incidentally, eating peanuts, grapes and blueberries (and drinking cranberry juice), as well as exercising, will give you all of the heart healthy benefits of red wine without the cancer risk.
What are ‘super-foods’ and should I be eating them?
There is a great deal of fuss made about so-called super-foods. These are fruits, vegetables, juices and grains believed to give us an extra nutritional boost superior to anything else we might pick up in the produce section. Eat a super-food often enough and you will supercharge your immune system, fend off illness and disease, live longer – so the newspapers and so-called experts would have you believe. But no food is ‘super’ if is not part of a balanced, healthy and varied diet. Research has shown that there is no specific food, or foods, that can improve memory, boost energy levels, or indeed, destroy tumours. In fact, eating too much of a particular food or nutrient isn’t actually helpful: some excess nutrients are easily excreted but some are not and can potentially be toxic. Going for variety and balance avoids this risk – and tastes better too. It is also worth noting that normal, inexpensive, easily available foods such as kale, onions, oats and apples have many of the same nutrients as boosted in ‘superfoods’. If they’re fresh, they’re good.
I have always eaten healthily, how come I got cancer?
Unfortunately eating well, exercising and not smoking are no guarantee of protection against cancer. Many forms of cancer are what are known as multifactorial, meaning that they will have a number of causes and risk factors – known and unknown, controllable and uncontrollable. Eating a healthy, balanced and varied diet is one way for you to help your body to fend off and cope with disease. Eating well can help in various ways once you have been diagnosed and in your life beyond cancer.
Will taking supplements help me?
The short answer is ‘no’, but there will be situations where it is necessary. Some treatments cause deficiencies in some key nutrients. You will be monitored and advised if you need to take any supplements. Additionally, the side effects of treatment can make it difficult to eat a varied diet, or enough food, to get adequate nutrition. Depending on your personal situation, you may be told to drink prescribed supplement drinks or start a course of multivitamins.
Taking individual supplements - whether as vitamins and minerals, or as herbal preparations – without medical advice is not recommended. Certain supplements and herbal preparations – especially those that are taken to help immune function – may interfere with the effectiveness of treatment. If you wish to take supplements discuss this with your doctor or hospital pharmacist. If you haven’t been able to eat well during treatment you may want to take a good all-round multivitamin/multi-mineral supplement to ‘restock’ after treatment ends. Again, ask your doctor or pharmacist for advice on when it is safe to supplement and what may be best to take.
I have breast cancer: should I be including soy, or avoiding it?
Whether or not to include soy in the diet to prevent cancer, prevent recurrence, and slow down tumour growth is very controversial. Some studies show that it slows tumour growth, others have shown that it can stimulate growth, and still others don’t show an effect either way. Studies vary in their applicability to humans. There is much still to learn about how the phyto-estrogenic components of soy behave in the human body. It is likely that individual genetics and nutrient metabolism will play some part, at least.
It seems probable from the evidence so far that soy products eaten in a broad, mixed diet are safe. In fact the latest evidence points to little or no risk when soy, in the form of tofu, tempeh, natto and miso, is eaten as a part of a varied diet of mixed proteins. Women with estrogen sensitive cancers may however be advised to reduce or limit soy, or limit direct consumption of soy foods to no more than a few servings a week as it may interfere with the effectiveness of the medication. It’s worth noting that many commercial breads and packaged goods use soy flours and soy components to extend the shelf life and improve texture. This briefing paper from the American Institute of Cancer Research summarises the most up to date reporting on this rather confusing subject.
Ask your doctor for advice if this is a concern for you. The view on supplemental phytoestrogen is somewhat clearer: most health professionals currently agree that herbal phytoestrogen supplements should not be used by those with a history of breast cancer.
Besides diet, what are other things I can do to help myself?
First and foremost – don’t smoke, and avoid second hand smoke. In addition to an estimated 90 % of all lung cancers being caused by smoking, it also contributes to bladder, pancreatic, esophageal, cervical, throat and stomach cancers.
Enjoy the sunshine but use sunscreen after 10-20 minutes of exposure (according to skin type). Most of our Vitamin D comes from sun exposure so do try and get some sun on your bare arms, legs and face before putting on sunscreen.
Make being physically active part of your daily life.
Make steps to cope positively with stress. Maggie’s Centres offer free stress management courses that can teach you useful techniques for managing stress.