Epidemiological studies indicate that those on vegetarian diets, in particular vegan diets, tend to live longer than meat-eaters. A study of Seventh Day Adventists found that there was a 12% reduction in risk of death from all causes in vegetarians compared with non-vegetarians [194]. An earlier study in 34,192 Seventh Day Adventists found that cancers of the colon and prostate were significantly more likely in non-vegetarians (increased risk of 88% and 54% respectively). Also, those who ate meat frequently had a higher risk of bladder cancer [102]. In addition, the intake of legumes was negatively associated with risk of colon cancer (in meat-eaters) and risk of pancreatic cancer, and higher consumption of all fruit or dried fruit was associated with decreased risks of lung, prostate, and pancreatic cancers [102]. However, what also needs to be considered here is the social/family therapy provided within close-knit communities, as this might be just as important as the foods eaten.

The Mediterranean Diet is also known to be associated with better health outcomes including reduced total mortality and cardiovascular disease risk [26]. A review of observational studies indicated that it is probably protective against cancer also [263]. The diet is characterised by a high intake of olive oil and low intake of saturated fats, high consumption of fruit, vegetables, nuts, cereals and legumes (that in the past were largely unrefined), moderate consumption of ethanol (mostly as red wine at meals), moderately high consumption of fish (depending on proximity to the sea), low consumption of meat and meat products, and low-moderate intake of milk and dairy products (and then mostly in the form of cheese and yoghurt) [253].

The European Prospective Investigation into Cancer and Nutrition (EPIC) study investigated the dietary, lifestyle and other characteristics of more than half a million people in Europe before a diagnosis of cancer or another chronic disease. The study of 25,623 Greek men and women found that not only were there benefits of adopting the diet in terms of a significantly reduced incidence of cancer, but even adopting some aspects of the diet was sufficient to lower the incidence of cancer. The closer the adherence to the diet, the lower the incidence and risk of cancer. What was very interesting was that although the Mediterranean Diet was strongly and inversely associated with cancer risk, when they examined the association between the individual components of the diet, they did not find any significant associations between these and cancer risk. This could suggest that there are synergisms between the components of the diet that are important (though other explanations relate to how data is combined in research) [26]. Other studies have also found that a high degree of adherence to this diet is associated with significantly lower mortality from cancer as well as coronary heart disease [253].

A startling difference was found between rural China and the typical western diet in the U.S. The rural Chinese diet had less fat (14.5% of calories in rural China vs. 34–38% in the US), more dietary fibre, more iron, and less total protein. In rural China, 9–10% of total calories were consumed as proteins, with only 10% from animal-based foods (the majority coming from plant sources of protein). In contrast 15–17% of total calories of the American diet were from protein, and more than 80% of it was from animal sources. What was extremely interesting was that the rural Chinese diet, high in plants and low in animal protein, was higher in total calories than the U.S. diet, yet they were slimmer—average body mass index in rural Chinese was less than in the U.S. and this wasn’t explained by differences in physical activity [42].

What is missing from studies on diets such as the Mediterranean Diet is consideration of the context for eating. The Mediterranean Diet is not perfect—it contains preserved meats, recently pronounced as carcinogenic, and there are cakes and ice creams in the mix of what is eaten too (the latter are not listed as features of the diet however). What is likely to also be protective is the family structure that provides the context for eating in these cultures and regions of the world. Perhaps it is the social support that eating within a family environment that is more important? The social context of eating may be healing and protective in itself. It may even compensate for some of the poorer food choices. We won’t know for sure until we have a ‘university study’, but we can hypothesise.

Happiness is contagious and can positively impact on others. The Framingham Heart Study found that a friend who becomes happy and who lives within about 1.6 km (one mile) of another person increases the chance that the other person is happy by 25%; the effect is even greater (42%) when the friend lives within half a mile (0.8 km). Similar effects were found in relation to siblings who live within a mile (14% increase) and next door neighbours (34%) [103]. The positive changes that can occur within the immune system of people in the company of others, and other factors including Vitamin D levels, physical activity level and other behavioural factors are rarely considered in research designs, yet arguably they need to be. Research designs do need to consider foods and nutrition within a broader behavioural and social context. Food for thought (pardon the pun).

Overweight and obesity are risk factors for cancer, diabetes and Metabolic Syndrome (which are themselves risk factors for cancer), development of insulin resistance (visceral adiposity), as well as hypertension, stroke and coronary heart disease [27, 115, 178, 184]. Many cancer patients are overweight and therefore may have co-morbidities. Addressing weight, through healthy food choices, is likely to have many health benefits and this will be discussed later in the chapter.

As mentioned previously it has been estimated that up to 30–35% of cancers are linked to diet [7]. This is worth remembering, as it means quite a lot of cancer can be prevented through healthy food choices.

Dr. T. Colin Campbell and his colleagues originally conducted studies in rats to investigate the impact of animal-based foods including dietary protein on the initiation and promotion of cancer. These and other animal studies indicate some very important findings in relation to diet and cancer pathogenesis including the following:

Whilst these studies are in animals, nonetheless they are helpful in understanding how diet can impact the development of cancer which might be applicable to humans. See the book The China Study [42] for some very interesting reading.

Before we turn to how to incorporate dietary advice into an integrative consultation, it’s worthwhile noting what is considered the dominant theory of carcinogenesis, and describing (very briefly) another theory that has been forming for many decades that challenges it, for it does have some implications for diet. The Somatic Mutation Theory of Cancer which has dominated the last one hundred years of scientific research into cancer posits that cancer is primarily due to genetic mutations. The ‘Metabolic Theory of Cancer’, originating with Warburg and later developed further by others including Pederson and more recently Seyfried [233], posits that cancer is a metabolic disease first and foremost, rather than a genetic disease. According to this theory, the mitochondria have become damaged, leading to defective respiration. Genetic mutations occur downstream from this event, not prior to it. Seyfried sets out convincing scientific evidence that in cancer cells, the mitochondria have become damaged and fewer in number, and instead of using the oxidative phosphorylation pathway, utilise the less efficient glucose fermentation pathway [55, 232, 233]. This theory fundamentally challenges the direction of oncology research which has primarily focused on trying to understand and characterise genetic mutations. It also has profound implications for metabolic therapies that could be developed.

The ‘Ketogenic Diet’ was developed on the basis of this theory. The diet is characterised by caloric restriction, low in carbohydrates and protein, and the rest of the diet consisting of fats. The justification for this is that cancer cells have a high need for glucose, and when glucose is restricted, the cancer cells are forced to compete with healthy cells for available glucose. Healthy cells are able to switch to burning ketone bodies, but cancer cells are unable to, which creates metabolic and oxidative pressure [55]. Pre-clinically and in case studies, there is evidence that the diet can slow tumor growth [55].

For more information readers are referred to two excellent books, Tripping Over the Truth: the Return of the Metabolic Theory of Cancer Illuminates a New and Hopeful Path to Cure (Travis Chistofferson), an easy read, and for the serious science, Cancer as a Metabolic Disease (Thomas Seyfried) (see Reading Recommendations at the end of the book).

There are, of course, many other diets that have been devised for cancer sufferers. Readers are referred to other sources for information on these. We will now examine what kinds of information may be included in discussions with cancer patients in relation to eating and foods.

There are a few simple goals in the Ultimate Consultation when it comes to nutrition:

It is suggested that you put any dietary advice in writing (e.g. as part of a Wellness Plan) and review within 3 months. Generally, people forget most of what they have been told within 3 months [212]. Professor Sali gives his patients printed notes to take home with them, summarising key information and giving them sample breakfast, lunch and dinner ideas. In addition, it’s wise to remember that dietary changes should be doable: if changes are too difficult to make due to unaffordability or lack of access to particular foods, or if diet recommendations are too rigid, this can add stress to the patient. This is not desirable. The changes should be able to be sustained—rigid diets can simply make people miserable and be counterproductive. Finally, in the end the patient has to be responsible for making changes.

The first part of this chapter set out evidence in relation to how diet might impact both positively and negatively in relation to cancer. Some of these general facts and figures could be shared with the patient, emphasising what positive changes can be made going forward that will assist the patient in achieving better health overall. Here are some general topics that you could start with, before getting into discussions about specific foods:

In the consultation, it will be important to understand a patient’s food habits which can be done simply by asking the patient what they usually eat, as a rule, for breakfast, lunch and dinner. Also, you can ask them whether they skip meals, what they snack on, what beverages they have daily and how many cups approximately (which will give you an idea of liquid intake). For more details, you can ask the patient to complete a 5-day diet diary in which they record everything they eat and drink for 5 days, including at least one day on a weekend (since diets can change on weekends). Frequency of consumption of foods that are unhealthy, including fast foods is important: eating an occasional fast-food meal is unlikely to be problematic; however, eating them frequently and in large quantities will most certainly be and will most likely lead to weight gain plus changes within the body that can contribute to cancer (and other disease) pathogenesis.

Completing a diet diary is, in and of itself, educational for patients and that itself may encourage learning and change. What we eat is largely habitual, usually forged over a lifetime and often following family patterns of eating. Changing diet means changing habits and practising a new habit, one that is healthier. The key is to empower the patient with information and the knowledge that they can change.

In beginning a conversation about what foods can be added to diet and which ones to avoid the clinician can begin with talking about some overarching dietary recommendations. Key recommendations from the World Cancer Research Fund and American Institute for Cancer Research Second Expert Report [276] include the following:

Then one can move on to talking about 14 Key Dietary Principles, set out in Table 3.3, working through each of these systematically. Professor Sali has printed patient notes that summarise most of these principles that he gives to the patient to take home with them. He uses these as a framework to work through information about diet.

The remainder of this chapter will focus on each of these 14 Dietary Principles.

When a person has cancer, it is prudent to remember, particularly when there is cachexia or when they are undergoing treatment such as chemotherapy that appetite is disrupted and nausea may be prevalent. It is important that eating is perceived as enjoyable, as much as is possible under the circumstances. Adhering to strict diets, however, nutritionally justifiable (and many are not) may simply be counterproductive if the poor person is miserable. Sometimes too much emphasis can be placed on diet to the point that the person and their loved ones living with them are stressed out about food. We think that this is counterproductive.

As much as possible, meals should be regular and eating should be done in an atmosphere that is not rushed, and allows for plenty of time to chew (an important and often neglected part of the digestive process), bringing people together in a positive atmosphere (social therapy). The coming together over a meal is an opportunity to relax, enjoy company and unload stresses and the positive benefits of this should not be underestimated. A study found that when people were paired up and fed various foods, when they ate the same foods, rapport was better [274].

For those with poor appetite and/or nausea (which can be the experience of those having chemotherapy), including ginger in the meal or having a cup of ginger tea 30–60 min prior to meals can help improve appetite.

Where possible, organic foods are vastly superior to non-organic foods for a few reasons. First, there is evidence that they contain higher amounts of nutrients. Second, organic foods don’t contain the added pesticides and other contaminants that most commercially grown fruit and vegetables have which can add a toxic load to the body [21].

A recent review of nearly three decades of epidemiologic research (44 papers) on the relationship between Non-Hodgkin Lymphoma (NHL) and occupational exposure to agricultural pesticides found that several herbicides and insecticides were positively associated with NHL and two herbicides were associated with a subtype, B Cell Lymphoma [227]. Whilst occupational exposure in the agriculture industry is arguably different to the kind of exposure through eating foods that have been sprayed with pesticides, this nonetheless should sound a cautionary bell.

Eating a healthy diet with a variety of different colored vegetables and fruits helps ensure that the right balance of nutrients, including vitamins and minerals, is consumed. Vegetables, fruits, legumes, nuts and seeds provide a variety of micronutrients and other bioactive compounds, and many have anti-cancer properties. The health benefits of fruits and vegetables are also understood to be partly due to the presence of phytochemicals including carotenoids, sulphoraphanes, flavonoids, salicylates, phytosterols, saponins, glucosinolates, polyphenols, phytoestrogens, lectins and others. Several of these phytochemicals act as antioxidants, preventing damage to cells, protein and DNA [276].

There is convincing evidence that red meat should have a very limited place within diet and that consumption increases the risk of some cancers. Processed meat should be eliminated from diet as it is carcinogenic. There is no clear data on whether meat from grass-fed animals is better than non-grass-fed animals.

Approximately 64% of the total calories from whole cow’s milk are from fat [42]. Thus, diets high in dairy foods may contribute substantially to the overall amount of fats in the diet. This may be relevant if a person is overweight or obese. In relation to whether dairy foods might be associated with cancer, the evidence is mixed.

This section will discuss overall fat intake in diet, whilst the section following this will hone in on different kinds of fats and oils.

Fats and oils are the most energy-dense components of diets. Dietary fats sources include animal products, including meat, milk and other dairy foods, as well as plants, including nuts and seeds. Meat, milk and dairy are the major sources of fat in most high-income countries [276]. A number of oils and fats are beneficial for the body, whilst some have been linked with disease. High levels of trans-fatty acids have also been associated with coronary heart disease [276] and raised levels of CRP [167], a marker of inflammation, and because of this should definitely be avoided.

Dietary fat is mostly made up of triglycerides, three fatty acid molecules attached to a glycerol backbone. These fatty acids are either ‘saturated’ or ‘unsaturated’. Unsaturated fats are typically divided into monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). For further information see Table 3.6.

In this section, we will look at some popular beverages, including coffee, green and black tea, water, soy and alcohol. But first, a quick note about the temperature of drinks and what the current evidence indicates.