File under "whaaa...?": Metformin and cancer risk

Metformin and reduced incidence of some cancers?

Metformin is an interesting drug, which was rolled out in the early 20th century. Its mechanism of action is described as “complex” with multiple different biochemical effects. Its discovery was based upon refinement of a substance found in the French Lilac, which has apparently been in use as a herbal medicine for 3000 years (I am still searching for the citation on this).

But is metformin that most rare of drugs, one that can prevent cancer? This question has generated much optimistic study over the decades, and a devastatingly negative 2012 debunking also.

What’s fun about this subject is that it introduces the concept of metabolism - overall body chemistry/nutrition - to the subject of cancer. The long-known but little-discussed connection between cancer and metabolism was rejuvenated recently in a book called The Cancer Code (2020) by Toronto nephrologist and diabetologist Dr Jason Fung. An interview regarding this book which summarizes its contents can be found here. The one-sentence gist is that elevated levels of blood sugar are associated with cancer.

Dr Fung goes into some detail regarding the reason why cancer cells and elevated blood sugar appear to go together, in particular the observation that diabetics are more prone than non-diabetics to certain forms of cancer. The implication is that diabetics may be able to lower their risk of getting cancer by reducing their blood sugar, whether by drugs, nutrition, exercise, or other means.

One fascinating tidbit (for me, at any rate) is that cancer cells can use substances other than carbohydrates in order to create sugar for their own use - a process called gluconeogenesis. Here is a rather dense account of this process. One of metformin’s mechanisms of action is inhibition of gluconeogenesis (new sugar creation) by the liver, using either fats or proteins as a starting point. At this point in metabolics, I begin to lose the thread, where the precise enzymes and pathways involved in the creation of glucose in cancer cells is outlined. The clinician in me yearns for a simple yes/no: metformin in cancer patients?

I will leave the answer hanging for now…