What do we eat? ‘Diseases enter via the mouth,’ this generally refers to infectious diseases, but can it also be applied to cancers? These days a common topic of conversation around eating is healthy food and the relationship between food and cancer. People often enjoy eating meat and preserved foods all whilst worrying whether the food they eat may cause cancer. The people who have meals with me always eat what I eat. In fact, I am also vexed about what to eat, after all enjoying delicious food is one of the greatest pleasures of life.
Adequate nutrition can fight against various diseases of modern life. I have read books extensively in different countries about cancer and nutrition, all with varying opinions. But it is necessary for cancer patients at the rehabilitation stage to pay attention to the following points:
Eat less red meat: Excessive intake of red meat increases the incidence of colon, lung, breast, oesophagus, larynx, stomach, kidney, uterus, ovary and prostate cancer. According to a study in 1998, the recurrence rate of breast cancer patients who eat red meat, liver and bacon once a day increased by one time, while the recurrence rate increased by four times for those breast cancer patients who eat red meat, liver and bacon twice a day. The reasons of increased cancer recurrence include: (1) a high iron content in red meat, high iron contents cause the body to produce massive free radicals (highly reactive molecules), thereby causing DNA damage and mutations that promote cancer cell growth; (2) red meat and poultry meat contain arachidonic acid that is able to convert into prostaglandins, providing a good environment for cancer cell growth and metastasis; (3) Red meat contains cholesterol. There is evidence that patients with high serum cholesterol are prone to have cancer metastasis. Cancer cells that have absorbed cholesterol have a decreased sensitivity to chemotherapeutic drugs; (4) Red meat contains estradiol which can stimulate tumor growth, especially breast, ovarian, uterine and cervical cancer.
Different circumstances should be considered. For example, during chemotherapy, the body needs a lot of energy, if there is not enough adequate protein supply, then this is not conducive to repairing damaged normal cells and tissues. Many foreign experts recommend eating more steak during this period, which seems to be justified.
A balanced intake of meat and vegetables predominantly a plant-based diet is healthiest. The Oxford study of 11,000 volunteers shows that during fifteen years of follow-up, the probability of dying from heart disease for meat eaters is twice as high as for vegetarians, and the probability of dying from cancer for predators is 60% higher than vegetarians. There is research of 50,000 people in the US that also shows that the incidence of cancer is significantly lower in vegetarians than those Americans who like to eat meat. An American expert named Rollo Russell said in his ‘Notes on the Causation of Cancer’ that nineteen out of twenty-five countries where meat is consumed as the main food have a higher incidence of cancer. On the contrary, countries with plant-based diets have a lower incidence of cancer.
A vegetarian diet mainly refers to vegetables (including legumes) and fruits. Vegetables and fruits contain many potentially beneficial vitamins, minerals, fibre, carotene and other bioactive substances such as flavonoids, terpenes, sterols, indole and phenolic substances (see below). Different coloured fruits and vegetables contain different amounts of these substances. Existing data indicates that these substances can reduce the risk of lung cancer, oesophageal cancer, stomach cancer, colorectal cancer and other cancers.
However a completely vegetarian diet is not advocated. 1.5-2.0 g / kg of protein should be consumed per person each day. If a person’s weight is 60 kg, around 90-120 grams of protein are needed every day. Daily consumption of food for cancer patients is higher than ordinary people, so cancer patients need more protein, a vegetarian diet alone cannot supply enough protein. Eggs, fish and white meat rich in high-quality protein are essential. Furthermore, plant foods especially fungi are also necessary, which include mushroom, black mushroom, oyster mushroom, hericium erinaceus, tremella, black fungus and phoenix mushroom are all rich in protein.
Moderate consumption of milk and dairy products: There are differing opinions on whether cancer patients should consume dairy products. Dairy products are rich in protein, which can maintain a patient’s physical body and promote normal cell repair (chemotherapy and radiotherapy can destroy normal cells). But some people think that drinking milk can promote cancer recurrence, which is due to (1) Dairy products contain high calcium, which can combine with calcium stored in the body, causing free calcium decrease. The data shows that the survival time of patients who were diagnosed with breast cancer and lung cancer in winter is shorter than those patients who were diagnosed in summer in high-latitude areas. This is possibly because sunshine duration in winter is short and with less Vitamin D absorption the generation of calcium is reduced;
(2) Milk, especially full-fat dairy products contain large amounts of saturated fatty acids, which cause elevated cholesterol levels that promote cancer metastasis. Saturated fatty acids can also promote coagulation disorders, increasing complications of treatments; (3) Milk contains lactose and other sugars, causing blood sugar to increase thereby increasing insulin secretion. Insulin is a factor that promotes cancer growth. Many chemotherapeutic drugs can cause temporary intolerance to lactose. Drinking milk can cause abdominal pain and digestive disorders, which can reduce the quality of life for patients; (4) 80% of lactoprotein is casein, experimental studies have shown that casein will accelerate tumor growth and metastasis; (5) Natural milk contains a number of substances that can increase the level of growth-stimulating factors including oestrogen, insulin, insulin-like growth factor-1 and polyamines. These substances not only stimulate normal cell growth, but also promote the proliferation of malignant cells, particularly promoting a number of hormone-sensitive cancers (such as prostate and breast cancer) recurrence and metastasis. It has been proved that the survival period of upper gastrointestinal cancer, prostate cancer and laryngeal cancer patients who drink plenty of milk is shorter.
Less consumption of refined carbohydrates: Compared with normal cells, cancer cells consume five to fifteen times more sugar than normal cells. The faster a tumor grows, the more sugar it will consume. Researched experiments on animals with cancer have shown that the lifetime span of animals with normal or low levels of blood glucose is longer than those animals with higher levels. Glucose can promote cancer cells to grow uncontrollably. For patients with type 2
diabetes, high-sugar foods cause blood glucose and insulin levels to elevate and insulin may promote cancer cells to absorb sugar. Insulin itself can also promote cancer cell growth, especially colon cancer and breast cancer. In 2002, a research report published in the American Journal of Clinical Oncology showed that the chance of cancer metastasis of breast cancer patients after surgery with high insulin levels is three times higher than those breast cancer patients with lower blood sugar levels. Therefore, cancer patients should eat less refined foods with high sugar content but choose fibre rich complex carbohydrates such as brown rice, buckwheat and wheat pasta. Cellulose contained in these foods can dilute, combine, inactivate and eliminate carcinogens, cholesterol, bile acids and a variety of toxic substances, reducing overall glucose and insulin levels. This is the reason the survival period of breast cancer patients who eat more whole grains is longer than those who eat refined grains and low- fibre foods.
Less fat consumption: An intake of high-fat foods can cause DNA damage, leading to cell mutation, and influence the effect of radiotherapy and chemotherapy, thereby contributing to cancer progression. High-fat foods can also weaken the body’s immune function, promoting inflammation and angiogenesis which increase levels of in vivo tumour growth promoting factors. This is why it’s understandable why the opportunity of cancer is higher amongst Americans whom consume a high fat diet compared to the traditional higher vegetable content Japanese or Mediterranean diet which is lower in fat.
Suitable fat consumption: Hydrogenated oil is processed in a factory. Partial hydrogenated oil can promote the development of colon cancer. Data shows that the chance of the tumor suppressor gene (p53) mutation in colon cancer patients who eat high-hydrogenated-fat food increases by double. Many fast foods are often made with hydrogenated oil, so we should avoid eating these foods.
Although saturated fat is natural, it is not a suitable raw material for food. Saturated fat extracted from meat and milk can inhibit the immune function, reduce the body's ability to detoxify and increase oxidation levels promoting free radical generation. In 1991, it was reported that the mortality rate was higher if patients with breast cancer, prostate cancer, colorectal cancer or lung cancer consumed large amounts of butter and lard oil both rich in saturated fat. It was also reported that the mortality rate of prostate cancer patients whom consumed saturated fat is three times as high as those prostate patients whom consumed low saturated fat. According to the report in the International Journal of Cancer in 2008, there was a 50% reduction recurrence rate of prostate cancer patients who had less consumption of saturated fat. With breast cancer patients, those who consumed calories from saturated fat for each additional 5% (equivalent to an increase of two pieces of bacon, two spoons of butter and one ounce of cheese from food per day), the risk of dying from breast cancer can increase by 50%. Some experts believe that for any patients with progressive cancers, dietary calories ratio from saturated fat should not exceed 5%
to10%. If your daily calorie intake is 2,000 calories, of which five percent is from saturated fat that is 100 grams, which is equivalent to 4 spoons of butterfat or two pints of tallow.
Unsaturated fat: Unsaturated fat is beneficial to health, from which Omega 3 and Omega 9 aliphatic acid are the most beneficial while omega 6s aliphatic acid has minimal effect. It is known that omega 3s aliphatic acids can reverse cancer metastasis, reducing the resistance of cancer cells to chemotherapy and radiotherapy, increasing the efficacy of certain chemotherapeutic drugs and reducing its side effects. Omega 9 aliphatic acid has significant anticancer effects, which can inhibit the breast cancer gene HER2/neu and increase the efficacy of the targeted drug Herceptin.
For cancer patients, the ratio of omega 3 aliphatic acid and omega 6 aliphatic acid should be 1:1 to 1:2. Fish can provide not only protein, but also rich omega 3s aliphatic acid. Other foods rich in omega 3s aliphatic acid include vegetable oil, walnuts, flaxseed, various nuts, sesame seeds, leafy green plants, algae and marine plants. Eggs can provide omega 3 aliphatic acid, but the eggs you eat should be from chickens fed with omega 3 aliphatic acids. Omega 9 aliphatic acids are mainly contained in olive oil, vegetable oil and almonds, while omega 6 aliphatic acids are contained in grain oils and animal fats.
Choose foods with anti-inflammatory effects: The inflammation level in the body can be detected, including Creactive protein, fibrinogen, prostaglandin E2 and erythrocyte sedimentation rate. If the inflammation level increases, which indicates there is chronic inflammation in vivo, you can choose the following foods: 1) Foods rich in salicylic acid: natural antiinflammatory ingredients can be found in many plants, such as wintergreens, turmeric and tomatoes. Organic foods without pesticides are also rich in salicylic acid; 2) Vegetables and fruits rich in flavonoids, flavonoids are not only powerful antioxidants, but also cytokines that play a key role in inhibiting COX2 molecules and anti-inflammation. There are many colorized plants that contain flavonoids such as cherries containing abundant flavonoids, fresh blueberries and blackberries and so on. Quercetin in onions and apples has proven its ability to reduce inflammatory TNF- and interleukin- 8 level.
Some people have advocated that at least two to four kinds of vegetables rich in anti-inflammatory ingredients should be taken everyday: artichokes, broccoli, cucumber, onion, celery, spinach, yam, tomatoes and pumpkin.
Three to four kinds of fruits should be taken everyday including apple, apricot, blackberry, blueberry, cantaloupe, cherry, cranberry, prune, raspberry, red grapes, sour cherries and so on.
There still are many plants rich in anti-inflammatory factors, many of which are applied as traditional Chinese medicine including bay leaves, chilli, ginger root, turmeric curry, mustard, nutmeg, oregano, rosemary and so on.
Choose foods with antioxidant effects: To detect oxidation levels in vivo, if the total antioxidant capacity decreases, lipid peroxidation levels increase and vitamin C and E levels in serum, carotene, lycopene and flavin levels decrease, which indicate oxidation levels in vivo are high and antioxidant capacity is low. Such patients should choose foods rich in antioxidants (table 3). Many foods that include antiinflammatory effects also have antioxidant capacity, such as the antioxidant capacity of oregano is forty times more than apple’s, ten times as much as orange’s and four times as much as blueberry’s. Cumin, fresh garlic, ginger, rosemary, clove and chilli are also rich in anti-oxidants; more organic food and grains with antioxidant effects such as barley, millet and oats. Protein with antioxidant capacity: salmon contains the carotenoid antioxidant -astaxanthin; bean products such as tofu, soy-milk, as well as other plants including pinto beans, black beans, broad beans, kidney beans and small red beans that are all rich in antioxidants should be consumed everyday or every other day.
Proper food processing: Avoid prolonged and hightemperature cooking. Deep-fried or grilled carbohydrates and proteins produce glycotoxin, which is a highly proinflammatory substance. Therefore relatively low-temperature cooking methods are recommended.
Studies have shown that many ingredients in food have a preventive effect on cancer recurrence, these ingredients include glucosinolates, flavonoids, vitamin A / D / E, selenium, curcumin, carotenoids, etc. (Table 4). Each ingredient has anticancer effects to one or several types of cancers. These ingredients are contained in a variety of vegetables and the fish (Table 5).
Among the anticancer ingredients in various foods, plant pigments have special effects. The most notable plant pigment is lycopene, which can be found in tomatoes and many red vegetables such as watermelon, grapes and shaddocks (Figure 35). It is one kind of antioxidant, carotenoid that can inhibit prostate cancer. A randomized controlled study in 2002 of prostate cancer patients who were ready for surgery orally consumed 30 mg of lycopene everyday(11/3 cups of tomato juice) for several weeks. The result was smaller tumors and lower PSA levels were found during the operation than for those patients with similar cases without oral ingestion of lycopene. For newly diagnosed prostate cancer patients, if they take the measure of wait and observe, a diet rich in lycopene and soya milk can prolong a stable condition.
Among vegetables containing anti-cancer ingredients, cruciferous vegetables have the strongest anti-cancer effects. Broccoli, kale, cabbage and other cruciferous plants have a rich amount of sulforaphane (1-isothiocyanate-4-methanesulfonyl butane) that have strong antioxidant effects on pancreatic cancer, colon cancer, breast cancer, lung cancer and prostate cancer (Figure 36). An experiment was conducted on nude mice where cancer cells were injected into an experimental group to induce tumorigenesis and fed 15 nmol of sulforaphane everyday. The other controlled group of mice was not fed sulforaphane. After thirteen days, the tumor weight of the experimental group was 60% less than that of the controlled group. One American research report of 2010 also found that sulforaphane can inhibit stem cells of breast cancer, and cancer stem cells are the source of cancer recurrence. This type of substance can promote the excretion of the toxic products of drugs and reduce the side effects of chemotherapeutic drugs. In Baltimore, Dr. Paul Talalay cultivated one kind of broccoli. Its sprout extracts are rich in sulforaphane which could convert bad cells back into good cells. In New York, a research team found that after patients who suffered from laryngeal papillomas drank concentrated cabbage juice, there was no need for them to have surgery. Now sulforaphane is found to be the bioactive substance with the best anti-cancer effects amongst vegetables.
Cruciferous vegetables also contain indole-3-methanol that can prevent cancer metastasis and change oestrogen metabolism to reduce its role in promoting cancer. Cruciferous vegetables also contain 2-phenylethyl isothiocyanate which can cause cancer cells to commit suicide.
The purple pigments in strawberries called anthocyanin have antioxidant effects similar to lycopene. Anthocyanin in elderberry can be absorbed by vascular endothelial cells to prevent free radicals from functioning in these cells, resulting in cell mutation. Raspberry contains ellagic acids that can inhibit breast and cervical cancer cell growth in vitro experiments. Strawberry also contains a chemical substance that can inhibit the activity of vascular endothelial growth factor (VEGF), causing both ischemia and hypoxia in cancer cells. Quercetin is found in brightly colored vegetables and fruits such as apple, kale and red onion, which can restore the sensitivity of breast cancer cells that are resistant to chemotherapeutic drugs.
Tea can enhance the body’s constitution. It contains polyphenols which have antioxidants, anti-virals, antiinflammatory activities that can regulate detoxifying enzymes, boost immune function and reduce platelet aggregation. Among polyphenols, epigallocatechin gallate (EGCG) has the most promoting effects to health, with reference to EGCG contents, green tea is better than black tea. It has been proven that green tea can prevent cancer, induce tumor suppressor genes, inhibit gene expression resulting in DNA damage and inhibit tumourigenesis and cancer metastasis. An article published in Japan in 2012, showed that those women who drink ten cups of green tea a day can delay cancer development for seven years and people who drink ten cups of green tea a day have a 50% reduced risk of colorectal cancer. Further studies showed that green tea has certain preventive effects on non-small cell lung cancer and ovarian cancer.
Coffee has preventive effects on colon cancer. The American Institute for Cancer Research had conducted a survey on the living habits of 489, 706 men and women for up to ten and a half years. During that period, there were 2863 cases of proximal colon cancer, 1993 cases of distal colon cancer and 1874 cases of rectal cancer. 16% of these people drink four cups of coffee or more every day. Compared to those people who do not drink coffee, the people who drink coffee have a significantly reduced risk of colon cancer, particularly proximal colon cancer. People who drink six or more cups of coffee everyday have the lowest risk of colon cancer. Harvard University had a survey on 5,272 cases of breast cancer patients and found that menopausal women who have drunk containing caffeine have a reduced risk of breast cancer. Another group of scholars at Harvard University investigated the relationship of skin cancer and coffee and found that people who drink more than three cups of coffee a day have significantly lower risk of basal cell carcinoma than those people who drink less than a cup of coffee every day.