Francis Pottenger (1901-1967) studied the effects of diet on cat health over the course of several generations. He found that feeding an nutritionally inappropriate diet to cats caused extensive changes, including deformities, social and psychological disorders, allergies, and reproductive difficulties. Continuing to feed the same diet to subsequent generations of cats exacerbated these changes, leading ultimately to a complete inability to produce live offspring. Cats did not experience normal health until several further generations were permitted to eat an appropriate diet.
In our times, Pottenger’s field of study is known as epigenetics, “the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself” (Wikipedia). That is, his cat experiment showed that diet can affect how the genes work even when the genes themselves remain unchanged. The DNA of the cats did not change at all: a genetic test would show no substantial genetic difference between the first generation of cats who suffered mild problems, and the third generation who were in extremely poor health and could not reproduce.
Our culture makes much of genetic testing to determine our risk for diseases such as cancer, Alzheimer’s, and heart disease. However, an understanding of epigenetics shows that the presence or absence of an inherited tendency does not determine our health future. For good or ill, our genes are not our destiny. More important is how genes are expressed: even with a strong family history of heart disease (showing a likely genetic component), not every single family member will actually develop heart disease. For some, that gene is never ‘turned on’, while in others it is.
Pottenger found, and scientists continue to find today, that diet (among other factors) can affect the expression of our genes. Eating an appropriate diet can help ensure that health-promoting genes are ‘turned on’, and can prevent disease-promoting genes from being ‘turned on’. Furthermore, our decision to follow an appropriate diet (or not) may have effects on our children and grandchildren which may persist regardless of their own dietary choices.
Understanding what an appropriate human diet is, and making eating choices that reflect that appropriate diet, is therefore urgently important. We can ‘turn on’ or ‘turn off’ genes that promote health or disease by our choices because our genes are not our destiny. But also, our poor choices can lead to an increased likelihood that our children, and grandchildren, will be permanently burdened with worse health than us, even if they choose to eat a diet entirely centered on appropriate foods.