Both High-Protein and High-Fat Diets Promote Cancer Progression

In 2023, Nature published a study by Li Ming's team at Memorial Sloan Kettering Cancer Center showing that, under a normal diet, breast cancer cells overexpressing the oncogene MYC become the competitive winners: they outcompete MYC-low breast cancer cells, causing them to die, absorb the nutrients released by the dying cancer cells, and promote tumor growth.

But when the diet is switched to low protein, MYC-overexpressing cancer cells become the losers, and the competitive winners are TAMs (tumor-associated macrophages). Far from helping the tumor, TAMs directly phagocytose the cancer cells that undergo apoptosis from losing the competition, ultimately controlling tumor growth.

This study suggests that people who maintain a long-term low-protein diet are less likely to develop cancer, and that cancer patients who adhere to a low-protein diet will see a marked slowdown in cancer progression and longer survival.

In addition, in May 2024, the Proceedings of the US National Academy of Sciences (PNAS) published a study on how high-fat diets accelerate tumor growth. It showed that a high-fat diet increases the abundance of a certain gut bacterium in mice and suppresses their immune system, speeding up tumor growth.

It has long been recognized that obesity is a high-risk carcinogenic factor, second only to smoking among carcinogenic risks. The classic TCM text Huangdi Neijing (Yellow Emperor's Inner Canon) also states that "rich, greasy, heavy flavors breed large ulcers." Newer research shows further that not only obesity but also an unreasonable diet after cancer diagnosis — eating too much high-fat food — can accelerate tumor growth.

Here, "high-fat foods" includes not only animal-derived high-fat foods such as fatty meat, organ meats, and egg yolks, but also plant-derived high-fat foods such as walnuts, peanuts, sesame seeds, avocados, and durian, as well as deep-fried foods.

The researchers found that mice on a high-fat diet had higher blood levels of leucine and more myeloid-derived suppressor cells (MDSCs) than mice on a normal diet. When the researchers treated the mice with antibiotics that kill Desulfovibrio, MDSC and leucine levels returned to normal. MDSCs suppress immune-cell responses; when their levels are too high, tumor growth accelerates.

This study shows that tumor patients who maintain a low-fat diet can slow tumor progression and extend survival, providing scientific support for the earlier recommendation of the American cancer-prevention society that tumor patients eat more low-fat plant-derived foods.

We often hear of tumor patients who, by adjusting their diet, achieve good dietary-therapy outcomes; there is a scientific basis for why these patients recover better. Epidemiological big data also show that as humans consume more meat and other high-fat, high-protein foods, the incidence of tumors, cardiovascular and cerebrovascular diseases, and diabetes keeps climbing. The Food and Agriculture Organization has repeatedly urged humanity to reduce meat, egg, and fish consumption, which eases the burden on the planet and improves human health.

The harm of delicious high-fat, high-protein foods is no less than that of cigarettes; a light diet is better for the body. But few can give up the pleasure of delicious food, so fundamentally, disease is caused by human beings' own flaws.