Diet and Cancer: Choosing the Eating Plan (diet) that’s Best for You
Put ‘diet and cancer’ into your internet search engine and you will be overwhelmed by the number of results. He is some answers to common questions about diet and cancer.
To start with, there is no one size fits all answer to the question. A better way to think about diet and cancer is to frame the question around the person who has the cancer diagnosis and ask what is the best diet for them. Even then you will probably be overwhelmed by the number of results.
Information that can inform the choice of diet plan for people with cancer includes:
· The person themselves: age, gender, overall health, current diet, their medical history, even their ethnicity may have an influence
· The type of cancer the person has – what stage are they at? Has the cancer spread? What treatment are they having or have they had? How did they react to that treatment?
· Support network: who will support them in changing their diet, socio-economic factors (can they afford to change their diet)
· How willing are they to change – motivation to change can be the key.
It’s worth noting that often when a person changes from a less healthy diet to one which is more focussed on getting the right nutrition into the body there can be benefits. For example, body composition may change, blood glucose levels may stabilise, patients may have improved energy, blood lipid profiles may improve. These factors together may lead to an overall improvement in prognosis. These benefits may happen regardless which particular diet the person chooses to follow.
Cancer Diets and Research
Research into diets and cancer is limited. When choosing a diet for cancer take into account the research that has been done.
This is the diet I am asked the most about when it comes to cancer.
The theory behind a ketogenic diet is that the low carb nature of the diet will ‘starve’ cancer cells of the glucose they rely on to proliferate.
In the past 50+ years there has been a limited number of human studies into the benefits of a ketogenic diet in cancer. While encouraging, current research into ketogenic diets and cancer does not draw an overwhelming positive conclusion. While there may be clear benefits in some cancers, the same cannot be said for all cancers.
This doesn’t mean a ketogenic diet won’t be of benefit.
Changing to a ketogenic diet can be challenging. The change to complex carbohydrates, and vegetables that have a moderate or high amount of carbohydrate can feel limiting. Generally, carbohydrates in the diet are replaced with fats and protein. You can still eat vegetables like spinach, zucchini, kale, cabbage, cauliflower, eggplant, green beans, lettuce, cucumbers and avocado (for example). Foods like bread, pasta, crackers and biscuits, potatoes, carrots, beetroot, onions, and parsnips, and legumes are to be excluded.
It’s worth noting that once starved of sugar, cancer cells my start looking elsewhere for nutrients.
This diet is high in plant foods and low in animal foods. Food is fresh, seasonal, and diverse. There is very little refined foods. Eating a Mediterranean diet provides a balance of food factors that can influence (lower risk, and/or slow progress) the development, progression and invasion of tumours.
Research has indicated that the Mediterranean diet does reduce the risk of certain cancers: i.e gastric, colorectal, liver, and breast cancers. For other cancers there are mixed results.
Like the ketogenic diet, research into the Mediterranean diet and cancer is currently limited.
Changing to a Mediterranean diet is often seen as relatively easy. The emphasis on the wide variety of fresh vegetables and fruits, and legumes, is often easier to adjust to. The emphasis on vegetables and other plant foods can reduce the amount of carbohydrates in the diet.
Plant Based or Vegetarian Diet
Similar to the Mediterranean diet without the meat. High in plant fibre (good for the gut), antioxidants and anti-inflammatory foods.
Difficulty with this diet is getting adequate protein (plant-based protein foods need to be correctly combined to ensure people get a full range of essential amino acids).
Some nutritional deficiencies are more common with a plant-based diet. People would benefit from having their nutritional status assessed to ensure they are not deficient in key nutrients.
Low Fat Diet
A low fat diet may be combined with other diets, e.g low fat plant based diet.
While saturated fat in the diet is linked with increased risk of some cancers, a low fat diet is not necessarily beneficial to people with cancer. A better way to think about fat in the diet is to look at saturated versus unsaturated fat. People with cancer may benefit from limiting saturated fat in the diet. Saturated fat is commonly found in animal based foods, as well as some vegetable based foods like coconut.
No discussion on diet and cancer is complete without looking at fasting.
Fasting is defined as no food for periods of time lasting 12 to 72 hours.
Research on fasting and cancer is still in the early stages, However, early evidence indicates that positive changes in metabolism may be beneficial to cancer management.
Different types of fasting include:
· Time restricted eating where the person abstains from food for 12 to 16 hours. Another way to look at this is to only eat during an 8-10 hour window
· Whole day fasting is when a person doesn’t eat for 24 to 72 hours
· 5/2 diet is where the person eats a normal diet 5 days a week, then only eat 500-600 calories on the next 2 days.
Which type of fasting you choose is up to you. For many people time restricted eating the is easiest, while others prefer to fast for 1-3 days at a time. The key with fasting is to choose a regime that suits you. While fasting, it’s essential to follow a healthy diet in between. Fasting doesn’t mean a free for all when you do eat. Continue to eat a wide variety of plant based foods and animal protein (if you choose to eat meat), avoid saturated fats, processed foods, added sugar, and excessive carbohydrates.
There is some evidence that fasting around some chemotherapy treatments is beneficial to the efficacy of the treatment.
Fasting is not recommended for people who are losing weight or have suffered significant weight loss.
Seek Professional Advice
Before you start on a new eating plan or diet consult a qualified nutritionist – someone who has experience with people with cancer.
Be wary of anyone who offers a ‘miracle’ diet. If a diet looks too good to be true it probably is. While some people get excellent results following a particular diet, this does not mean you will as well.
Questions to ask if a clinician recommends a particular diet for you
What studies are they basing the recommendation on?
Are these studies in vitro, animal or human studies?
What clinical evidence do they have to support the diet they recommend?
Were the studies conducted in patients with the same or similar cancer to you?
The Cancer Council provides quite a bit of useful information on diet, exercise and cancer.