While it is true that genes play a role in disease, they are not the primary cause. We see this most clearly in numerous examples of people moving from one area of the world, where they consume a largely whole food plant-based diet, to a developed country like America where they (and especially their children and grandchildren) consume more Western foods. With the change of diet comes a dramatic increase in the incidence of chronic illness. Their genes did not change; their diet did.

Reference: "The China Study" book page 191, by Campbell and Campbell.

One of the most notable diet-based mutations is the human ability to digest milk. All human babies can digest the lactose in milk, but for most people, this ability fades after childhood. Europeans evolved the ability to digest dairy for their entire life.

The extra calories from dairy had an evolutionary advantage. However, surviving beyond the age of 40 had little evolutionary advantage.

Pizza and cheese are the biggest food sources of saturated fat in the U.S. diet. Dietary saturated fat contributes to heart disease, diabetes, and some cancers.

Cancer begins with a mutation. Tumor growth is influenced by the environment. Diet appears to have the greatest influence.

https://nutritionfacts.org/video/never-too-late-to-start-eating-healthier/
1:13 If you look at countries that switched from eating traditional, more plant-based diets to more Westernized diets, it may take 20 years for cancer rates to shoot up. It takes decades for most tumors to grow. For example, if you look in Asia, their dietary shift was accompanied by a remarkable increase in mortality rates of breast, colon, and prostate cancers… Same thing shown with migration studies. Men moving from rural China to the U.S. experience a dramatic increase in cancer risk.

https://nutritionfacts.org/video/plants-with-aspirin-aspirations/
0:25 Animal products made up only about 5% or less of the Japanese diets, until Japanese people began to Westernize their diets. Note that age-adjusted death rates from cancers of the colon, prostate, breast, and ovary were on the order of 5-10 [times] lower in Japan than in the US: [with] mortality from pancreatic cancer, leukemias, and lymphomas…3-4 fold lower. But, this phenomenon was by no means isolated to Japan; Western cancers were likewise comparatively rare in other…societies [where]…people ate plant-based diets.”

Cancer Prevention and Treatment by Wholistic Nutrition 2017 by Campbell
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5646698/

• When people transition from diets of rural cultures (low in fat and [animal] protein), to diets to diets of urban cultures (high in fat and [animal] protein), rates of heart disease, diabetes and cancer, as a group, generally increase.
• Cancer begins with a mutation and there is convincing evidence that mutations accumulate as cancer advances toward metastasis. But this does not mean that cancer is primarily caused by a series of subsequent mutations. Experimental animal evidence shows that cancer development can be reversed by nutritional means.
• Cancer growth in laboratory animals initiated by a powerful mutagen/carcinogen can be repetitively turned on and off by non-mutagenic mechanisms, even completely, by modifying the levels of protein intake. The nutrient-based effects were not attributed to mutations because increased activities were readily reversible.
• Consider, for example, the highly variable cancer rates for different countries as a function of diet and other lifestyle practices. If we assume that the lowest observable cancer rate is that which is theoretically achievable and if we were to know the factors causing the higher rates, then all rates above the lowest rate are avoidable. A survey of total cancer rates for 65 counties in China showed that 88.5% of male cancers and 80.3% of female cancers are avoidable. These estimates of avoidable cancers may be even greater because countries/counties with the lowest rates are likely experiencing the same causal factors observed in the high rate region but at much lower levels of exposure.
• Many epidemiological studies of the past 40–50 years have shown impressive associations of various cancers with diet and nutrition practices.
• These experts said 70–90% of human cancer is caused by environmental factors:
  • The UN Agency for Research on Cancer stated, about four decades ago, that 80–90% of total cancer was caused by dietary and environmental factors.
  • Wu et al concluded that 70–90% of human cancer is derived from extrinsic (environmental) factors.
  • The director of the International Agency for Research on Cancer of the director of the International Agency for Research on estimated that approximately 90% of all human tumors are influenced by exogenous factors, thus are “theoretically preventable”.

A WFPB diet reversed prostate cancer.

https://nutritionfacts.org/video/cancer-reversal-through-diet/

• 1:20 PSA levels are typically what’s used to follow the progression of prostate cancer. In the [Ornish study] standard diet group, they got worse; in the vegan diet group, they got better.
• 3:15 Ornish’s two-year follow-up was just published last year. A significant number of the standard diet group were forced to go into surgery for what’s called a radical prostatectomy, which often leads to urinary incontinence and impotence in 60% of men coming out of surgery. But not a single one of the men on the plant-based diet had to go to surgery.

https://nutritionfacts.org/video/treating-advanced-prostate-cancer-with-diet-part-1/

• 1:06 - 2005 Ornish et al. enrolled 93 men in a 12-month diet intervention on early low-grade cancer.
• 1:13 - 2001 Saxe et al. enrolled 10 men in a 4-month diet intervention on advanced cancer.

https://nutritionfacts.org/video/treating-advanced-prostate-cancer-with-diet-part-2/

• 1:42 There are huge differences in prostate cancer rates, USA rates are up to a hundred times higher than some places in Asia.
• 1:58 And, it’s not just genetic; within one generation of coming to the U.S., cancer rates shoot up, and the grandkids end up with the same top-of-the-pile rates … diet appears to have the greatest influence.

A WFPB diet prevents breast cancer.

https://nutritionfacts.org/video/brca-breast-cancer-genes-and-soy/

• 1:17 Soy food intake is associated with longer survival and lower recurrence among breast cancer patients.
• 2:56 Only about 5% of breast cancers run in families.

https://nutritionfacts.org/video/which-seaweed-is-most-protective-against-breast-cancer/
As the traditional diets of East Asia Westernize, their breast cancer rates have risen, which some have linked to a quadrupling of animal product consumption. This is the breast cancer rate of Japanese women living in Japan. If they emigrate to the United States, within ten years, they’re up to here [much higher on graph].

https://nutritionfacts.org/video/is-soy-healthy-for-breast-cancer-survivors/
Breast cancer rates are so much higher here than in Asia—yet, when Asians come over to the U.S. to start eating and living like Americans, their risk shoots right up. But, it’s not just genetic, since when they move here, their breast cancer rates go up generation after generation, as they assimilate into our culture.

A WFPB diet prevents colon cancer.

https://nutritionfacts.org/video/the-best-diet-for-colon-cancer-prevention/
Colon cancer is our second leading cancer killer, but some places, like rural Africa, have more than 10 times lower rates than we do. The reason we know it’s not genetic is that migrant studies have demonstrated that it only takes one generation for the immigrant population to assume the colon cancer incidence of the host Western population. The change in diet is most probably responsible for this.

A WFPB diet prevents Alzheimer’s.

https://nutritionfacts.org/video/alzheimers-disease-grain-brain-or-meathead/
The rates of dementia differ greatly around the world.

https://nutritionfacts.org/video/the-alzheimers-gene-controlling-apoe/
The risk for Alzheimer’s disease from treatable factors — elevated cholesterol and blood pressure — appears to be greater than that from the dreaded Alzheimer’s susceptibility gene.