Getting a diagnosis of prostate cancer can be a big challenge for many families. In Australia, it is the second most common cancer diagnosed in men. While there are many different treatment options available, some men are choosing to combat the disease with diet in conjunction with their treatment. There is growing evidence that a plant-based low carbohydrate ketogenic diet can improve prognosis and slow tumour growth. In this blog post, we will take a closer look at prostate cancer and how this targeted diet can help.
Prostate cancer is caused by the abnormal growth of cells in the prostate gland, which is a small, walnut-sized gland located just below the bladder and in front of the rectum. Prostate cancer is often without symptoms in its early stages. However, as the tumour grows, it may cause urinary problems, such as difficulty urinating or a decreased flow of urine.
What are some of the risk factors?
There are many different risk factors for prostate cancer, including age, family history, and ethnicity, with European men having a significantly higher chance of developing prostate cancer than Asian men.
A man’s risk of developing prostate cancer is also linked to metabolic syndrome, insulin resistance and being overweight. Metabolic syndrome is associated with worse outcomes for aggressive tumours and being overweight is linked with the progression and aggressiveness of prostate cancer.[1] For men over 65, the recurrence of prostate cancer is associated with insulin resistance, which is where cells in muscles, fat, and liver don't respond well to the hormone insulin in taking up glucose from the blood.[2]
You may be wondering whether diet really can make a difference?
Research certainly suggests that it can influence outcomes. Dietary choices that cause higher than normal levels of insulin in the blood worsen outcomes. Benjamin Fu and his team from Harvard University reviewed data from over 41 000 men to determine which dietary choices were associated with the incidence and mortality of prostate cancer. Their study showed that a diet that causes high level of insulin in the blood is associated with a greater risk of developing aggressive prostate cancer. They found that a proinflammatory diet (a diet that is high in refined carbohydrates, high in animal protein, and high in processed foods) is associated with earlier-onset of lethal prostate cancer in men under the age of 65.[3] Unfortunately, these types of diets, which are very common in our society, are not going to be helpful if you want to avoid getting prostate cancer.
Does a ketogenic diet help?
A Ketogenic diet is a low carbohydrate, high fat diet that shifts the body’s metabolism from burning glucose to burning fats for energy. This causes elevated levels of ketones in the blood.
An interesting study conducted by Jen-Tsan Chi and colleagues from Duke University compared men with prostate cancer eating a low carbohydrate diet (20 grams of carbs per day) for 6 months, with patients given usual care. Although it was not planned, some patients entered ketosis even though they were not specifically eating a ketogenic diet. The results showed that higher ketones in the blood correlated with longer PSA doubling times, demonstrating that there is an association between ketogenesis and slower prostate cancer growth.[4]
A low carbohydrate or ketogenic diet will have other benefits as well. Eating less carbs will lead to lower levels of insulin in the blood stream.
Is there anything else that could help?
Many ketogenic diets involve eating significant amounts of animal proteins, and yet there is evidence that eating less animal-based fat and more plant-based fat may be more beneficial. Erin Richman and colleagues found that among men with non-metastatic prostate cancer, replacing carbohydrate and animal fat with vegetable fat was associated with a lower risk of lethal prostate cancer and death from all causes.[9]
Dean Ornish, a leader in the field of lifestyle medicine, found that men with early-stage prostate cancer may be able to avoid or delay conventional treatment for at least 2 years by making changes in their diet and lifestyle. In 2005 he published the result of a clinical trial he and his colleagues conducted with 93 men with early prostate cancer looking at the effects of comprehensive changes in diet and lifestyle. One group of patients were encouraged to adopt a plant-based, low-fat diet, to exercise and practice stress management, and to attend group support sessions. The comparison group received usual care. The results showed that patients in the first group had a reduction in prostate-specific antigen (PSA) levels.[7] This was followed up with a study published in 2008 in the same group of men, which reported that 27% of the control patients and only 5% of the experimental patients had undergone conventional prostate cancer treatment (radical prostatectomy, radiotherapy, or androgen deprivation). [8]
Early studies suggested that eating animal protein from fish or chicken as opposed to red meat and dairy may have benefits. However, a recent meta-analysis of studies of the vegan diet which contains no animal protein at all, consistently showed favourable outcomes for prostate cancer. [5]
This is also seen in work done by Stacy Loeb (Department of Urology and Population Health, New York University) and her associates, who examined the relation between eating a plant-based diet and prostate cancer in more than 6 600 men. The research team found that consuming healthful plant-based foods is associated with a lower risk of aggressive forms of prostate cancer, with stronger benefit among men younger than 65. Greater consumption of a plant-based diet is associated with a significantly lower risk of fatal prostate cancer.[6]
Further insights into the benefits of particular plant nutrients and prostate cancer has found that plant-based proteins from soy, vegetable, seeds and nuts, may reduce the risk of getting prostate cancer.[10] Cruciferous vegetables such as broccoli and cauliflower, and Allium vegetables such as garlic, leeks, chives, and shallots, decreased the risk of prostate cancer and increase PSA doubling times.[11][12] Dietary intake of tomatoes containing lycopene, a red-pigmented carotenoid, has also been associated with lower incidence and aggressiveness of prostate cancer. [13][14]
So what does this mean for someone with prostate cancer?
Firstly, following a diet that will lower insulin levels, increase metabolic flexibility and be anti-inflammatory in nature may be of great benefit.
Given the role of insulin resistance and excess weight on prostate cancer, dietary strategies such as ketogenic or low carbohydrate diets which target metabolic syndrome, diabetes, and obesity may be worthwhile considering.
Ketogenic diets can be beneficial because of their favourable influence on weight loss and metabolic parameters (blood sugar, triglycerides, high-density lipoprotein (HDL) cholesterol, blood pressure, and waist circumference).
In addition to this, increasing plant foods containing important phytonutrients such as broccoli and cauliflower, tomatoes, soy, garlic, cabbage, berries, turmeric and other spices, as well as eating less red meat and dairy, could help slow prostate tumour progression and improve outcomes.
Prostate cancer is a serious disease, but there are things you can do to lower your risk, or if you already have a diagnosis, help to improve outcomes. A healthy diet that is low in carbohydrates and high in plant nutrients, such as the one in Nutritious, can be one of the best defences against prostate cancer.
References
[1] Kaiser A, Haskins C, Siddiqui MM, Hussain A, D'Adamo C. The evolving role of diet in prostate cancer risk and progression. Curr Opin Oncol. 2019 May;31(3):222-229. doi: 10.1097/CCO.0000000000000519. PMID: 30893147; PMCID: PMC7379157.
[2] Saboori S, Rad EY, Birjandi M, Mohiti S, Falahi E. Serum insulin level, HOMA-IR and prostate cancer risk: A systematic review and meta-analysis. Diabetes Metab Syndr. 2019;13(1):110-115. doi:10.1016/j.dsx.2018.08.031
[3] Fu, B. C., Tabung, F. K., Pernar, C. H., Wang, W., Gonzalez-Feliciano, A. G., Chowdhury-Paulino, I. M., Clinton, S. K., Folefac, E., Song, M., Kibel, A. S., Giovannucci, E. L., & Mucci, L. A. (2021). Insulinemic and Inflammatory Dietary Patterns and Risk of Prostate Cancer. European urology, 79(3), 405–412. https://doi.org/10.1016/j.eururo.2020.12.030
[4] Chi, J. T., Lin, P. H., Tolstikov, V., Howard, L., Chen, E. Y., Bussberg, V., Greenwood, B., Narain, N. R., Kiebish, M. A., & Freedland, S. J. (2022). Serum metabolomic analysis of men on a low-carbohydrate diet for biochemically recurrent prostate cancer reveals the potential role of ketogenesis to slow tumor growth: a secondary analysis of the CAPS2 diet trial. Prostate cancer and prostatic diseases, 10.1038/s41391-022-00525-6. Advance online publication. https://doi.org/10.1038/s41391-022-00525-6
[5] Gupta N, Patel HD, Taylor J, et al. Systematic review of the impact of a plant-based diet on prostate cancer incidence and outcomes. Prostate Cancer Prostatic Dis. 2022;25(3):444-452. doi:10.1038/s41391-022-00553-2
[6] Loeb S, Fu BC, Bauer SR, et al. Association of plant-based diet index with prostate cancer risk. Am J Clin Nutr. 2022;115(3):662-670. doi:10.1093/ajcn/nqab365
[7] Ornish D, Weidner G, Fair WR, et al. Intensive lifestyle changes may affect the progression of prostate cancer. J Urol. 2005;174(3):1065-1070. doi:10.1097/01.ju.0000169487.49018.73
[8] Frattaroli J, Weidner G, Dnistrian AM, et al. Clinical events in prostate cancer lifestyle trial: results from two years of follow-up. Urology. 2008;72(6):1319-1323. doi:10.1016/j.urology.2008.04.050
[9] Richman EL, Kenfield SA, Chavarro JE, Stampfer MJ, Giovannucci EL, Willett WC, Chan JM. Fat intake after diagnosis and risk of lethal prostate cancer and all-cause mortality. JAMA Intern Med. 2013 Jul 22;173(14):1318-26. doi: 10.1001/jamainternmed.2013.6536. PMID: 23752662; PMCID: PMC3935610.
[10] Applegate CC, Rowles JL, Ranard KM, Jeon S, Erdman JW. Soy Consumption and the Risk of Prostate Cancer: An Updated Systematic Review and Meta-Analysis. Nutrients. 2018 Jan 4;10(1):40. doi: 10.3390/nu10010040. PMID: 29300347; PMCID: PMC5793268.
[11] Liu, B., Mao, Q., Cao, M., & Xie, L. (2012). Cruciferous vegetables intake and risk of prostate cancer: a meta-analysis. International journal of urology : official journal of the Japanese Urological Association, 19(2), 134–141. https://doi.org/10.1111/j.1442-2042.2011.02906.x
[12] Hsing, A. W., Chokkalingam, A. P., Gao, Y. T., Madigan, M. P., Deng, J., Gridley, G., & Fraumeni, J. F., Jr (2002). Allium vegetables and risk of prostate cancer: a population-based study. Journal of the National Cancer Institute, 94(21), 1648–1651. https://doi.org/10.1093/jnci/94.21.1648
[13] Rowles, J. L., 3rd, Ranard, K. M., Applegate, C. C., Jeon, S., An, R., & Erdman, J. W., Jr (2018). Processed and raw tomato consumption and risk of prostate cancer: a systematic review and dose-response meta-analysis. Prostate cancer and prostatic diseases, 21(3), 319–336. https://doi.org/10.1038/s41391-017-0005-x
[14] Rowles, J. L., 3rd, Ranard, K. M., Smith, J. W., An, R., & Erdman, J. W., Jr (2017). Increased dietary and circulating lycopene are associated with reduced prostate cancer risk: a systematic review and meta-analysis. Prostate cancer and prostatic diseases, 20(4), 361–377. https://doi.org/10.1038/pcan.2017.25