I attended a lecture today by Dr. Barry Boyd, an oncologist affiliated with Yale and Greenwich Hospital. Discussion focused on how cancers happen in the first place, and the effect of long-term diet and lifestyle on cancer risk, progression and recurrence. Cancers develop over many years, while they are acquiring added mutations, before they are diagnosed or detected. Most cancers in adults develop as random/chance spontaneous mutations in stem cells. Interestingly, tall people have a higher cancer risk simply because they have more stem cells! So I am glad I am petite! Some cancers are environmental in that they are promoted by carcinogens that damage and mutate DNA (uv light, smoking, radiation, pesticides like ddt, etc) or by acquired chronic viral-related process/inflammation ( chronic infections hepatitis B and C, HPV, fat infiltration). A small percentage of cancers are inherited ( loss of tumor suppressor genes, as seen in pediatric cancers such as medullary thyroid cancer MEN 2a), or loss of DNA repair genes as in breast cancer with BRCA 1 and 2 or in Lynch (multiple cancer) Syndromes).
Life style, activity and diet clearly affect the incidence of cancers, or frequency of spontaneous mutations. People who consume vegetarian/vegan diets do develop cancer, but at a much lower incidence compared to people who ingest the Western American diet. People with obesity, diabetes, metabolic syndrome, high fat high sugar diets, and inactivity have increase cancer risk because they have high insulin and insulin is growth factor for cancer – making cancers cells grow and replicate faster. Estrogen and progesterone are also well known growth promoters for breast and uterine cancer. Too much of anything such as selenium, iron, alcohol, shifts the cancer risk to a higher level. Vitamin B1 or thiamine and beta carotene are inducers of cancer proliferation so people with cancer or high lung cancer risk! should avoid B complex which has high thiamine content. A prospective study suggested that Thyroid cancer risk is increased by high intake of canned tuna and poultry, baked sweet diet, and goitrogens, like broccoli (goitrogens = foods that promote goiter and increase TSH, by interfering with iodine absorption and/or synthesis of thyroid hormone). Sadly, once cancer is present eating more vegetable and fruits does not decrease cancer recurrence risk and supplements, as noted above, may actually make things worst.
What helps decrease cancer risk? Plant based diets, calorie restriction (be hungry more and eat less!), staying active, keeping normal weight, drinking coffee and green tea. Once cancer has occurred the task is to starve the tumor by keeping sugar/fat intake low and lowering insulin because this does affect cancer recurrence. This is achieved by avoiding high fat / high sugar /processed food diets, loosing weight, daily exercise (30 min daily walking counts), intermittent fasting 2-3/7 days per week, or using the insulin lowering agent metformin. Drink coffee and or green tea. Some data suggest that low carbohydrate (ketogenic) diets which lower insulin also help.
In terminal cancer people should eat whatever they feel like, when they feel like, and as much as possible to maintain weight!
1) Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science. 2015 Jan 2;347(6217):78-81. doi: 10.1126/science.1260825. Authors: Tomaselli & Volgerstein.
2) Adolescent and mid-life diet and subsequent risk of thyroid cancer in the NIH-AARP diet and health study. Int J Cancer. 2015 Nov 15;137(10):2413-23. doi: 10.1002/ijc.29600. Epub 2015 Jun.