Mediterranean, keto, and plant-based diets vs. Cancer

New review summarizes what we know about Mediterranean, keto and plant-based diets and their effects on cancer risk and progression [1].

Diet is important

Since the War on Cancer began in the early 1970s, science has made tremendous strides in understanding and treating cancer. However, the war is far from over. Cancer remains a deadly disease associated with aging, its advanced stages are still largely untreated, the response to therapies is far from universal, and the therapies themselves can be harmful and accelerate aging.

The result is clear: it is better not to get cancer at all. In recent decades, studies have shown that various 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 possibly carcinogenic. Poor dietary choices can lead to a number of cancer-related problems, such as type 2 diabetes, which has been shown to significantly increase the risk of some types of cancer [2].

This new review summarizes research on the relationship of three popular diets to cancer. The authors carefully studied the literature on the Mediterranean diet (MD), the ketogenic diet, and the plant-based diet. Of the 23 papers included in the review, 15 were on MD, the best-studied diet of the three, four on the keto diet and four on plant-based diets.

Breast cancer

One study followed 114 women with breast cancer. Greater adherence to MD was associated with smaller tumor size, absence of nodular metastases, and recurrence-free survival [3]. Here and elsewhere, this review does not report how the original study handled potential confounding variables.

Another study followed a cohort of about 10,000 women and found that the incidence of breast cancer was significantly lower in those with high MD adherence compared to those who followed a Western diet (defined as higher in whole-fat dairy products, processed meals, fast food, and red meat, and there is less fruit, vegetables, whole grains and fish) [4].

Another study on breast cancer, which followed 1,017 patients against a control cohort, found that participants who followed MD for five years before diagnosis were less likely to develop breast cancer and had smaller tumor sizes on average. The researchers concluded that switching to MD could protect against the development and progression of breast cancer [5].

The authors mention two related keto diet studies by the same team in which keto diets were initiated in breast cancer patients. The treatment resulted in a significant reduction in tumor size and overall survival compared to the control group. It also improved markers of inflammation [6].

Two studies evaluated the effect of a plant-based diet on breast cancer. One study of 412 patients and 456 controls found that following a healthy plant-based diet significantly and significantly reduced the risk of developing the disease. [7]. Another study in an even larger cohort reached similar conclusions. However, an unhealthy plant-based diet was associated with a significantly higher risk.

Stomach and colon cancer

Overall, MD was associated with a significantly lower risk of gastric and colorectal cancer. One study found a 68% reduction in the chance of developing stomach cancer in people who followed a well-balanced and strict MD [8].

One study concluded that keto has no effect on the risk of stomach cancer [9]. However, according to another, interventional, study, the keto diet as a treatment (in addition to chemotherapy) resulted in longer survival periods, but not higher overall survival rates [10].

In contrast, a large study of 1,404 colon cancer survivors found that a plant-based diet caused a significant reduction in mortality rates seven years after remission. As with some other studies, the quality of the plant-based diet was important, although this particular finding did not reach statistical significance [11].

Other cancers

The review only mentions other cancers in association with MD, with the exception of one study of a plant-based diet in patients with hepatocellular carcinoma. This large longitudinal study of 89,000 women and 48,000 men with 32 years of follow-up showed a reduced risk for those who followed a plant-based diet. Replacing vegetable fats with carbohydrates and refined grains reduced the risk even more [12].

One study of more than 4,000 current or recent smokers, of whom 178 developed lung cancer, found that high consumption of vegetables, fruit, olive oil and fish was associated with a significantly lower risk of developing the disease, while consumption of red meat was associated with more significant increase [13].

In a study that recruited a treatment group of 690 people and a control group of 665, high MD adherence reduced the risk of developing bladder cancer by 35% compared with a low adherence group. [14]. Finally, in a study of thyroid cancer patients, low MD adherence was associated with more thyroid nodules and higher malignancy [15].

Literature

[1] Nagy, S., Petroski, SN, Beckler, MD, & Kesselman, MM (2023). Impact of modern dietary practices on cancer risk and progression: a systematic review. Cureus, 15(10).

[2] Shahid, RK, 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, GK, Papandreou, D., Theocharis, S., … & Giaginis, C. (2022). Adherence to the Mediterranean diet and nutritional status in women with breast cancer: what is their influence on disease progression and survival of patients without recurrence?. Current Oncology, 29(10), 7482-7497.

[4] Gardeazabal, I., Romanos-Nanclares, A., Martnez-Gonzlez, M., Castello, A., Snchez-Baiona, R., Perez-Gomez, B., … & Toledo, E. (2020). A Mediterranean diet is associated with a lower incidence of premenopausal breast cancer in the Seguimiento Universidad de Navarra (SUN) project. Public Health Nutrition, 23(17), 3148-3159.

[5] Castell, A., Polln, M., Buijsse, B., Ruiz, A., Casas, AM, Baena-Caada, JM, … & Martn, M. (2014). Spanish Mediterranean diet and other dietary patterns and risk of breast cancer: the EpiGEICAM case-control study. British Journal of Cancer, 111(7), 1454-1462.

[6] Khodabakhshi, A., Akbari, ME, Mirzaei, HR, Seifried, TN, Kalamian, M., & Davoodi, SH (2021). Effects of ketogenic metabolic therapy on breast cancer patients: a randomized controlled clinical trial. Clinical Nutrition, 40(3), 751-758.

[7] Sasanfar, B., Toorang, F., Booiani, Z., Vassalami, F., Mohebbi, E., Azadbakht, L., & Zendehdel, K. (2021). Adherence to a plant-based dietary pattern and risk of breast cancer in Iranian women. European Journal of Clinical Nutrition, 75(11), 1578-1587.

[8] Álvarez-Álvarez, L., Vitelli-Storelli, F., Rubn-Garca, M., Aragons, N., Ardanaz, E., Castao-Vinials, G., … & Martin, V. (2021). Relationship between gastric cancer risk and adherence to the Mediterranean diet according to different evaluators. MCCSpain Studies. Cancers, 13(21), 5281.

[9] Toorang, F., Zendehdel, K., Sasanfar, B., Hadji, M., & Esmaillzade, A. (2021). Adherence to a 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). Examining the effect of chemotherapy combined with a ketogenic diet on stage IV colon cancer.

[11] Ratjen, I., Enderle, J., Burmeister, G., Koch, M., Nthlings, U., Hampe, J., & Lieb, V. (2021). Postdiagnostic reliance on plant-based versus animal-based foods and all-cause mortality in omnivorous long-term survivors of colorectal cancer. The American Journal of Clinical Nutrition, 114(2), 441-449.

[12] Liu, I., Yang, W., VoPham, T., Ma, I., Simon, TG, Gao, X., … and Zhang, X. (2021). Plant- 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, ME, Polesel, J., Di Maso, M., Montella, M., Ferraroni, M., … and Turati, F. (2018). Mediterranean diet and bladder cancer risk in Italy. Nutrients, 10(8), 1061.

[15] Barrea, L., Muscogiuri, G., Alteriis, GD, Porcelli, T., Vetrani, C., Verde, L., … and Savastano, S. (2022). Adherence to the Mediterranean diet as a modifiable risk factor for nodular thyroid disease and thyroid cancer: Results of a pilot study. Frontiers in nutrition, 9, 944200.