23/09/2014 13:14 BST | Updated 23/11/2014 05:59 GMT

Lemonade and Sweet and Sour Sauce, the Relationship Between Cancer and Food

When was the last time you thought about food?

Last night? This morning? Just now?

For sure, it's a topic close to all our hearts; a basic human requirement and, for many of us, a source of great comfort and enjoyment.

But for people living with and beyond cancer, their relationship with food can be somewhat different - and frustratingly complex.

Even before treatment starts, patients are about the benefits of a balanced diet and how following one will make them cope better with treatment. Yet shockingly up to 20% of cancer deaths are caused by a form of malnutrition.

For many the enjoyment they used to get out of food disappears.

For some it's as a direct result of their cancer. For example, someone with an oesophageal tumour may need to avoid solid foods because chewing and swallowing is uncomfortable, so meals become supplemented with protein and vitamin shakes.

Others say that being told about the critical need to manage their diet for their overall wellbeing, means that food is no longer a pleasure but becomes purely a necessity.

And some patients tell me that the foods they once loved no longer taste the same. The pleasure of sitting down with a few biscuits and some tea no longer exists.

Cancer itself can affect the way things taste - some tumours can secrete substances which means foods don't have the same flavour. Treatments can also affect it. Chemotherapy is designed to destroy rapidly-dividing cancer cells, but it can also damage normal cells which divide rapidly - such as those in your mouth. The spread of chemotherapy drugs can damage taste receptors and cause taste changes. The association of chemotherapy with feeling nauseous and vomiting can also lead to a loss of taste. Some patients find that radiation therapy can also affect tissues in the head and neck - including taste buds and salivary glands - often leading to a dry mouth.

I often hear that patients find lots of foods have a metal aftertaste - that usually comes as a result of chemotherapy. I suggest that they ditch their usual knife and fork for a bit and try using plastic ones - it's not refined, but it can help. Often people find that red meats are prone to tasting metallic, so you can always replace them with things like chicken or eggs. I recommend experimenting with what patients cook meat in too. Trying sweeter-tasting foods can also work - things like sweet and sour sauce, citrus fruit juice or even vinegar can help.

Tart foods like oranges or grapefruit can also help to get rid of the metallic taste, as can lemonade - though this should be avoided if you have mouth sores.

Some patients complain that foods can taste too strong. If that is the case, I would say that there are ways to try and 'tone down' tastes. Patients can supplement foods with the likes of plain crackers, or toast. Mashed potato is also quite a good addition, as are plain noodles. For those who can face sweeter things, I would suggest custard and plain yoghurt.

I agree that it can be tough for patients to 'normalise' their diet - by that I mean getting back to eating as they did before diagnosis. Being told by your consultant that you need to eat fresh foods, or those low in saturated fats and high in other 'good' fats is all well and good, but some simply can't face it. Which is fine. It is totally normal to not fancy eating certain foods at first. In fact, it's also totally normal to stop liking the foods you once loved. I tell people to take advantage of this and try something new. Never liked artichokes or olives? Give them a try now. Don't ruin your enjoyment of foods you loved. I also suggest people try to eat nutrient-dense foods, so if they are put off by a plate full of food, have half an avocado and some seeds or nuts instead. They are rich in monounsaturated fats and can contain a high content of Omega-3 fatty acids. I regularly hear from patients who tell me that before treatment they had three square meals a day, but now can't manage that. This isn't unusual. If three meals aren't working, I suggest having a number of regular snacks instead. It's about finding what works for you.

If a patient has always eaten a very healthy, low fat diet, sometimes they want to avoid foods that they believe will make them gain weight - this can be a tough one. I usually encourage people to think about their quality of life and not avoid having foods which are high in fat if they fancy them. I also talk to people about the range of healthier options available to try and make sure they're getting the calorie and fat intake they need to help them cope with chemo which can be incredibly draining.

Patients can also find that cold or chilled foods may taste better than foods which are warm or hot, so I'd recommend trying that. Also, food served cold or at room temperature usually have a less strong smell which some people struggle to stomach. For those patients who do want to eat hot foods, I'd suggest making sure you use your extractor fan because that can help eliminate any feelings of nausea as a result of cooking smells.

As I say, food can be complex issue: one of life's great pleasures for the majority but a source of frustration, change and disappointment for those living with and beyond cancer. There is a reason health professionals recommend a healthy, balanced diet for cancer patients. It can help reduce the risk of becoming unwell again and it also helps retain fitness for treatment. But we are also realistic and know that maintaining the right diet is not always easy.

On days when it is too hard, my advice would be to put food to the back of your mind and look for enjoyment elsewhere. Watch your favourite film, get out in the garden or spend some time with friends and family... After all, tomorrow things might be different.