A new review summarizes what we know about the Mediterranean, keto, and plant-based diets and their effects on cancer risk and progression [1].
Diet matters
Since the War on Cancer began in the early 1970s, science has made giant strides in understanding and treating cancer. However, the war is far from over. Cancer remains a deadly age-related disease, its advanced stages are still mostly untreatable, the response to therapies is not nearly universal, and those therapies themselves can be harmful and accelerate aging.
The upshot is clear: it’s better not to get cancer at all. In recent decades, studies have shown that a variety of lifestyle factors affect your chances of getting cancer and sometimes its progression. Smoking is the most obvious case, but other behaviors, such as diet, can also affect your fate. Processed meat is recognized by the World Health Organization as carcinogenic and red meat as probably carcinogenic. Bad dietary choices can lead to numerous problems associated with cancer, such as type 2 diabetes, which has been shown to substantially increase the risk of getting some cancers [2].
This new review summarizes the research into the relationships of three popular diets with cancer. The authors scrutinized literature on the Mediterranean diet (MD), ketogenic diets, and plant-based diets. Of the 23 papers included in the review, 15 were related to MD, the best-studied diet of the three, four to keto diets, and four to plant-based diets.
Breast cancer
One study followed 114 women with breast cancer. Higher adherence to MD was linked to smaller tumor size, absence of nodular metastases, and recurrence-free survival [3]. Here and elsewhere, this review does not report how the original study treated possible confounding variables.
Another study followed a cohort of about 10,000 women and found that the occurrence of breast cancer was significantly lower in those with high adherence to MD versus those who followed a Western diet (defined as higher in whole-fat dairy, processed meals, fast foods, and red meat while being lower in fruits, vegetables, whole grains, and fish) [4].
Yet another breast cancer study, which followed 1,017 patients versus a control cohort, found that participants who followed MD for five years prior to the diagnosis were less prone to getting breast cancer and had smaller tumor size on average. The researchers concluded that shifting to MD could be protective against the development and the progression of breast cancer [5].
The authors mention two connected keto diet studies by the same team in which keto diets were initiated in breast cancer patients. The treatment led to a significant decrease in tumor size and in overall survival rates compared to a control group. It also improved markers of inflammation [6].
Two studies evaluated the impact of plant-based diets on breast cancer. One study that was run in 412 patients and 456 controls found that adherence to a healthy plant-based diet dependently and highly significantly decreased the risk of developing the disease [7]. Another study in an even larger cohort reached similar conclusions. However, unhealthy plant-based diets were associated with a considerably higher risk.
Gastric and colorectal cancer
Overall, MD was associated with significantly lower risk of gastric and colorectal cancer. One study found a 68% reduction in chances of developing gastric cancer for people who adhered to a well-balanced and strict MD [8].
One study concluded that keto had no effect on gastric cancer risk [9]. However, according to another, interventional, study, keto diets as a treatment (in addition to chemotherapy) resulted in longer survival periods, although not in higher overall survival rates [10].
Conversely, a large study of 1,404 survivors of colorectal cancer showed that plant-based diets caused a significant reduction in mortality rate seven years into remission. As with some other studies, the quality of the plant-based diet was important, although this particular finding did not quite reach statistical significance [11].
Other cancers
The review only mentions other cancers in relation to MD, with the exception of a single study of plant-based diet in hepatocellular carcinoma patients. This large longitudinal study of 89,000 women and 48,000 men with 32 years of follow-up showed reduced risk for those who adhered to a plant-based diet. Substituting carbohydrates and refined grains for plant fats reduced the risk even more [12].
One study of 4000+ current or recent smokers, of whom 178 developed lung cancer, found that high consumption of vegetables, fruits, olive oil, and fish was associated with a significantly lower risk of getting the disease, while red meat consumption was associated with an even more substantial increase [13].
In a study that recruited a treatment group of 690 people and a control group of 665, high adherence to MD reduced the risk of bladder cancer development by 35% compared to the low-adherence group [14]. Finally, in a study of thyroid cancer patients, low adherence to MD was associated with more thyroid nodules and higher malignancy [15].
Literature
[1] Nagy, S., Petrosky, S. N., Beckler, M. D., & Kesselman, M. M. (2023). The Impact of Modern Dietary Practices on Cancer Risk and Progression: A Systematic Review. Cureus, 15(10).
[2] Shahid, R. K., Ahmed, S., Le, D., & Yadav, S. (2021). Diabetes and cancer: risk, challenges, management and outcomes. Cancers, 13(22), 5735.
[3] Mantzorou, M., Tolia, M., Poultsidi, A., Vasios, G. K., Papandreou, D., Theocharis, S., … & Giaginis, C. (2022). Adherence to Mediterranean Diet and Nutritional Status in Women with Breast Cancer: What Is Their Impact on Disease Progression and Recurrence-Free Patients’ Survival?. Current Oncology, 29(10), 7482-7497.
[4] Gardeazabal, I., Romanos-Nanclares, A., Martínez-González, M. Á., Castello, A., Sánchez-Bayona, R., Perez-Gomez, B., … & Toledo, E. (2020). Mediterranean dietary pattern is associated with lower incidence of premenopausal breast cancer in the Seguimiento Universidad de Navarra (SUN) Project. Public health nutrition, 23(17), 3148-3159.
[5] Castelló, A., Pollán, M., Buijsse, B., Ruiz, A., Casas, A. M., Baena-Cañada, J. M., … & Martín, M. (2014). Spanish Mediterranean diet and other dietary patterns and breast cancer risk: case–control EpiGEICAM study. British journal of cancer, 111(7), 1454-1462.
[6] Khodabakhshi, A., Akbari, M. E., Mirzaei, H. R., Seyfried, T. N., Kalamian, M., & Davoodi, S. H. (2021). Effects of Ketogenic metabolic therapy on patients with breast cancer: A randomized controlled clinical trial. Clinical Nutrition, 40(3), 751-758.
[7] Sasanfar, B., Toorang, F., Booyani, Z., Vassalami, F., Mohebbi, E., Azadbakht, L., & Zendehdel, K. (2021). Adherence to plant-based dietary pattern and risk of breast cancer among Iranian women. European Journal of Clinical Nutrition, 75(11), 1578-1587.
[8] Álvarez-Álvarez, L., Vitelli-Storelli, F., Rubín-García, M., Aragonés, N., Ardanaz, E., Castaño-Vinyals, G., … & Martín, V. (2021). Relationship between the Risk of Gastric Cancer and Adherence to the Mediterranean Diet According to Different Estimators. MCC—Spain Study. Cancers, 13(21), 5281.
[9] Toorang, F., Zendehdel, K., Sasanfar, B., Hadji, M., & Esmaillzade, A. (2021). Adherence to low-carbohydrate diet in relation to gastric cancer: findings from a case-control study in Iran. European Journal of Cancer Prevention, 30(4), 297-303.
[10] Furukawa, K., Shigematsu, K., Katsuragawa, H., Tezuka, T., & Hataji, K. (2019). Investigating the effect of chemotherapy combined with ketogenic diet on stage IV colon cancer.
[11] Ratjen, I., Enderle, J., Burmeister, G., Koch, M., Nöthlings, U., Hampe, J., & Lieb, W. (2021). Post-diagnostic reliance on plant-compared with animal-based foods and all-cause mortality in omnivorous long-term colorectal cancer survivors. The American Journal of Clinical Nutrition, 114(2), 441-449.
[12] Liu, Y., Yang, W., VoPham, T., Ma, Y., Simon, T. G., Gao, X., … & Zhang, X. (2021). Plant-Based and Animal-Based Low-Carbohydrate Diets and Risk of Hepatocellular Carcinoma Among US Men and Women. Hepatology, 73(1), 175-185.
[13] Gnagnarella, P., Maisonneuve, P., Bellomi, M., Rampinelli, C., Bertolotti, R., Spaggiari, L., … & Veronesi, G. (2013). Red meat, Mediterranean diet and lung cancer risk among heavy smokers in the COSMOS screening study. Annals of oncology, 24(10), 2606-2611.
[14] Bravi, F., Spei, M. E., Polesel, J., Di Maso, M., Montella, M., Ferraroni, M., … & Turati, F. (2018). Mediterranean diet and bladder cancer risk in Italy. Nutrients, 10(8), 1061.
[15] Barrea, L., Muscogiuri, G., Alteriis, G. D., Porcelli, T., Vetrani, C., Verde, L., … & Savastano, S. (2022). Adherence to the Mediterranean diet as a modifiable risk factor for thyroid nodular disease and thyroid cancer: Results from a pilot study. Frontiers in Nutrition, 9, 944200.
