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Walnuts and Prostate Cancer

January 27, 2012 Written by JP       [Font too small?]

The good news about life expectancy is that both men and women are living longer than ever before. The bad news about longevity is that it is often accompanied by certain diseases. When it comes to older men, prostate cancer tops the list. Fortunately, there is a growing body of evidence that certain dietary and lifestyle choices can minimize the risk of prostatic malignancies.

A new study published in the British Journal of Nutrition informs that a diet rich in walnuts may slow prostate cancer (PC) growth in an animal model of the disease. Groups of PC prone mice were fed either a soybean oil or walnut-enriched diet over a 24 week period. A human equivalent of approximately 2.4 ounces was given to the mice in the walnut group. At the conclusion of the trial, the researchers determined that the mice fed walnuts developed tumors about half the size of the soybean oil fed mice. Further analysis noted a 28% reduced rate of tumor growth in the group receiving the walnut chow.

Upon reading the encouraging news about walnuts and prostate cancer in mice, I set out to find supportive evidence. The first item I discovered was a publication in the May 2008 issue of the Nutrition Journal. In it, a small group of men at risk for PC were asked to eat 75 grams/day (~ 3 oz) of walnuts for 8 weeks. Before and after blood tests confirmed several significant changes in biomarkers related to prostate cancer. Specifically, an increase in plasma levels of gamma tocopherol, a form of Vitamin E that may confer a chemoprotective affect, and the ratio of free PSA (prostate specific antigen) to total PSA was documented. A decline in estradiol, a variety of estrogen that tends to rise in older men, was also noted. All three of these changes indicate a positive shift in physiology that is conducive to prostate health.

Exactly how walnuts influence the progression of PC is currently a matter of debate and speculation. A few emerging theories postulate that antioxidants (polyphenols) found in a variety of beverages and foods such as green tea and walnuts may reduce certain growth factors that spur malignant growth. Another possibility is that walnuts increase a specific protein (apolipoprotein A or ApoA) that is normally associated with a healthy cardiovascular system. Preliminary research indicates that low concentrations of ApoA may increase prostate cancer risk. This latter finding offers the tantalizing potential that eating walnuts daily may be an excellent tonic for the hearts and prostates of older men.

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

To learn more about the studies referenced in today’s column, please click on the following links:

Study 1 – A High-Fat Diet Containing Whole Walnuts (Juglans Regia) Reduces (link)

Study 2 - The Effect of Walnut Intake on Factors Related to Prostate and Vascular (link)

Study 3 - Cancer-Preventive Activities of Tocopherols and Tocotrienols(link)

Study 4 - Nuts, Especially Walnuts, Have Both Antioxidant Quantity and (link)

Study 5 - Chemoprevention of Prostate Cancer with Nutrients and Supplements (link)

Study 6 - Short-Term Walnut Consumption Increases Circulating Total (link)

Study 7 - Low Levels of Apolipoprotein A-I and HDL are Associated with Risk (link)

Walnuts Possess a High “Antioxidant Efficacy” Value

Source: Food Funct. 2012 (link)

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14 Comments & Updates to “Walnuts and Prostate Cancer”

  1. healthy living Says:

    Thank you yet again for a great post, and with studies to help me with my research! I love walnuts but have to take their skins off, as they irritate my throat. We really love walnut oil as well, especially on a salad of romaine.

  2. JP Says:

    I’m glad it was of value, HL!

    Be well!

    JP

  3. healthy living Says:

    I just added your blog actually to my favorite health sites. Thank you for doing what you do! I would love to interview you as part of my wellness coach/holistic nutrition series, if you have time one of these days!!
    Blessings,
    Billy

  4. JP Says:

    Thank you, Billy. I’ll be in touch.

    Be well!

    JP

  5. liverock Says:

    Interesting that according to the graph of antioxidant levels roasting walnuts increases antioxidant levels by 400% over raw walnuts. Normally heating most foods lowers antioxidant levels.

  6. JP Says:

    Hi Liverock,

    Yes, I found that interesting as well. It’s also fascinating to see that not all nuts (and legumes) are affected by thermal processing in the same manner. Also, in the case of some foods, roasting lowers the levels of some antioxidants while creating other free radical fighters. A case in point, coffee:

    http://www.beveragedaily.com/Formulation/Antioxidants-in-coffee-traced-to-roasting-process-study

    Be well!

    JP

  7. JP Says:

    Update: Coffee may reduce prostate cancer risk in a dose dependent manner …

    http://www.tandfonline.com/doi/full/10.1080/01635581.2015.1004727#abstract

    Nutr Cancer. 2015 Feb 23:1-9.

    Coffee Consumption and Prostate Cancer Risk: A Meta-Analysis of Cohort Studies.

    This meta-analysis was conducted to assess the association between coffee consumption and prostate cancer risk. Thirteen cohort studies with 34,105 cases and 539,577 participants were included in the meta-analysis. The summary relative risks (RRs) with 95% confidence intervals (CIs) for different coffee intake levels were calculated. Dose-response relationship was assessed using generalized least square trend estimation. The pooled RR for the highest vs. lowest coffee intake was 0.90 (95% CI: 0.85-0.95), with no significant heterogeneity across studies (P = 0.267; I2= 17.5%). The dose-response analysis showed a lower cancer risk decreased by 2.5% (RR = 0.975; 95% CI: 0.957-0.995) for every 2 cups/day increment in coffee consumption. Stratifying by geographic region, there was a statistically significant protective influence of coffee on prostate cancer risk among European populations. In subgroup analysis of prostate cancer grade, the summary RRs were 0.89 (95% CI: 0.83-0.96) for nonadvanced, 0.82 (95% CI: 0.61-1.10) for advanced and 0.76 (95% CI: 0.55-1.06) for fatal diseases. Our findings suggest that coffee consumption may be associated with a reduced risk of prostate cancer and it also has an inverse association with nonadvanced prostate cancer. Because of the limited number of studies, more prospective studies with large sample size are needed to confirm this association.

    Be well!

    JP

  8. JP Says:

    Update 05/18/15:

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4259176/

    J Med Food. 2014 Dec;17(12):1281-6.

    TRAMP prostate tumor growth is slowed by walnut diets through altered IGF-1 levels, energy pathways, and cholesterol metabolism.

    Dietary changes could potentially reduce prostate cancer morbidity and mortality. Transgenic adenocarcinoma of the mouse prostate (TRAMP) prostate tumor responses to a 100 g of fat/kg diet (whole walnuts, walnut oil, and other oils; balanced for macronutrients, tocopherols [α-and γ]) for 18 weeks ad libitum were assessed. TRAMP mice (n=17 per group) were fed diets with 100 g fat from either whole walnuts (diet group WW), walnut-like fat (diet group WLF, oils blended to match walnut’s fatty acid profile), or as walnut oil (diet group WO, pressed from the same walnuts as WW). Fasted plasma glucose was from tail vein blood, blood was obtained by cardiac puncture, and plasma stored frozen until analysis. Prostate (genitourinary intact [GUI]) was weighed and stored frozen at -80°C. Plasma triglyceride, lipoprotein cholesterol, plasma multianalyte levels (Myriad RBM Rat Metabolic MAP), prostate (GUI), tissue metabolites (Metabolon, Inc., Durham, NC, USA), and mRNA (by Illumina NGS) were determined. The prostate tumor size, plasma insulin-like growth factor-1 (IGF-1), high density lipoprotein, and total cholesterol all decreased significantly (P<.05) in both WW and WO compared to WLF. Both WW and WO versus WLF showed increased insulin sensitivity (Homeostasis Model Assessment [HOMA]), and tissue metabolomics found reduced glucose-6-phosphate, succinylcarnitine, and 4-hydroxybutyrate in these groups suggesting effects on cellular energy status. Tissue mRNA levels also showed changes suggestive of altered glucose metabolism with WW and WO diet groups having increased PCK1 and CIDEC mRNA expression, known for their roles in gluconeogenesis and increased insulin sensitivity, respectively. WW and WO group tissues also had increased MSMB mRNa a tumor suppressor and decreased COX-2 mRNA, both reported to inhibit prostate tumor growth. Walnuts reduced prostate tumor growth by affecting energy metabolism along with decreased plasma IGF-1 and cholesterol. These effects are not due to the walnut’s N-3 fatty acids, but due to component(s) found in the walnut’s fat component.

    Be well!

    JP

  9. JP Says:

    Update 05/31/15:

    http://jn.nutrition.org/content/144/4/555S.long

    J Nutr. 2014 Apr;144(4 Suppl):555S-560S.

    Walnuts have potential for cancer prevention and treatment in mice.

    Cancer may not be completely the result of novel or inherited genetic mutations but may in fact be a largely preventable disease. Researchers have identified biochemicals, including n-3 (ω-3) fatty acids, tocopherols, β-sitosterol, and pedunculagin, that are found in walnuts and that have cancer-prevention properties. Mouse studies in which walnuts were added to the diet have shown the following compared with the control diet: (1) the walnut-containing diet inhibited the growth rate of human breast cancers implanted in nude mice by ∼80%; (2) the walnut-containing diet reduced the number of mammary gland tumors by ∼60% in a transgenic mouse model; (3) the reduction in mammary gland tumors was greater with whole walnuts than with a diet containing the same amount of n-3 fatty acids, supporting the idea that multiple components in walnuts additively or synergistically contribute to cancer suppression; and (4) walnuts slowed the growth of prostate, colon, and renal cancers by antiproliferative and antiangiogenic mechanisms. Cell studies have aided in the identification of the active components in walnuts and of their mechanisms of action. This review summarizes these studies and presents the notion that walnuts may be included as a cancer-preventive choice in a healthy diet.

    Be well!

    JP

  10. JP Says:

    Update 05/31/15:

    http://pubs.rsc.org/en/Content/ArticleLanding/2014/FO/C4FO00542B#!divAbstract

    Food Funct. 2014 Nov;5(11):2922-30.

    Walnut polyphenol metabolites, urolithins A and B, inhibit the expression of the prostate-specific antigen and the androgen receptor in prostate cancer cells.

    Walnuts have been gathering attention for their health-promoting properties. They are rich in polyphenols, mainly ellagitannins (ETs) that after consumption are hydrolyzed to release ellagic acid (EA). EA is further metabolized by microbiota to form urolithins, such as A and B, which are absorbed. ETs, EA and urolithins have shown to slow the proliferation and growth of different types of cancer cells but the mechanisms remain unclear. We investigate the role of urolithins in the regulatory mechanisms in prostate cancer, specifically those related to the androgen receptor (AR), which have been linked to the development of this type of cancer. In our study, urolithins down-regulated the mRNA and protein levels of both prostate specific antigen (PSA) and AR in LNCaP cells. The luciferase assay performed with a construct containing three androgen response elements (AREs) showed that urolithins inhibit AR-mediated PSA expression at the transcriptional level. Electrophoretic mobility shift assays revealed that urolithins decreased AR binding to its consensus response element. Additionally, urolithins induced apoptosis in LNCaP cells, and this effect correlated with a decrease in Bcl-2 protein levels. In summary, urolithins attenuate the function of the AR by repressing its expression, causing a down-regulation of PSA levels and inducing apoptosis. Our results suggest that a diet rich in ET-containing foods, such as walnuts, could contribute to the prevention of prostate cancer.

    Be well!

    JP

  11. JP Says:

    Update 06/06/15:

    http://onlinelibrary.wiley.com/doi/10.1002/cncr.29421/abstract

    Cancer. 2015 May 18.

    A phase I trial of mushroom powder in patients with biochemically recurrent prostate cancer: Roles of cytokines and myeloid-derived suppressor cells for Agaricus bisporus-induced prostate-specific antigen responses.

    BACKGROUND: Each year in the United States, nearly 50,000 prostate cancer patients exhibit a rise in prostate-specific antigen (PSA) levels, which can indicate disease recurrence. For patients with biochemically recurrent prostate cancer, we evaluated the effects of white button mushroom (WBM) powder on serum PSA levels and determined the tolerability and biological activity of WBM.

    METHODS: Patients with continuously rising PSA levels were enrolled in the study. Dose escalation was conducted in cohorts of 6; this ensured that no more than 1 patient per cohort experienced dose-limiting toxicity (DLT). The primary objective was to evaluate treatment feasibility and associated toxicity. The secondary objectives were to determine WBM’s effect on serum PSA/androgen levels; myeloid-derived suppressor cells (MDSCs); and cytokine levels.

    RESULTS: Thirty-six patients were treated; no DLTs were encountered. The overall PSA response rate was 11%. Two patients receiving 8 and 14 g/d demonstrated complete response (CR): their PSA declined to undetectable levels that continued for 49 and 30 months. Two patients who received 8 and 12 g/d experienced partial response (PR). After 3 months of therapy, 13 (36%) patients experienced some PSA decrease below baseline. Patients with CR and PR demonstrated higher levels of baseline interleukin-15 than nonresponders; for this group, we observed therapy-associated declines in MDSCs.

    CONCLUSIONS: Therapy with WBM appears to both impact PSA levels and modulate the biology of biochemically recurrent prostate cancer by decreasing immunosuppressive factors.

    Be well!

    JP

  12. JP Says:

    Updated 1/4/16:

    Walnuts contain fewer metabolizable calories than once thought: http://jn.nutrition.org/content/146/1/9.full

    Be well!

    JP

  13. JP Says:

    Updated 03/05/16:

    http://jaha.ahajournals.org/content/5/1/e002771.full

    J Am Heart Assoc. 2016 Jan 25;5(1).

    Effects of Diet Composition and Insulin Resistance Status on Plasma Lipid Levels in a Weight Loss Intervention in Women.

    BACKGROUND: Optimal macronutrient distribution of weight loss diets has not been established. The distribution of energy from carbohydrate and fat has been observed to promote differential plasma lipid responses in previous weight loss studies, and insulin resistance status may interact with diet composition and affect weight loss and lipid responses.

    METHODS AND RESULTS: Overweight and obese women (n=245) were enrolled in a 1-year behavioral weight loss intervention and randomly assigned to 1 of 3 study groups: a lower fat (20% energy), higher carbohydrate (65% energy) diet; a lower carbohydrate (45% energy), higher fat (35% energy) diet; or a walnut-rich, higher fat (35% energy), lower carbohydrate (45% energy) diet. Blood samples and data available from 213 women at baseline and at 6 months were the focus of this analysis. Triglycerides, total cholesterol, and high- and low-density lipoprotein cholesterol were quantified and compared between and within groups. Triglycerides decreased in all study arms at 6 months (P<0.05). The walnut-rich diet increased high-density lipoprotein cholesterol more than either the lower fat or lower carbohydrate diet (P<0.05). The walnut-rich diet also reduced low-density lipoprotein cholesterol in insulin-sensitive women, whereas the lower fat diet reduced both total cholesterol and high-density lipoprotein cholesterol in insulin-sensitive women (P<0.05). Insulin sensitivity and C-reactive protein levels also improved.

    CONCLUSIONS: Weight loss was similar across the diet groups, although insulin-sensitive women lost more weight with a lower fat, higher carbohydrate diet versus a higher fat, lower carbohydrate diet. The walnut-rich, higher fat diet resulted in the most favorable changes in lipid levels.

    Be well!

    JP

  14. JP Says:

    http://www.nature.com/bjc/journal/vaop/ncurrent/full/bjc2016181a.html

    Br J Cancer. 2016 Jun 9.

    Nut consumption and prostate cancer risk and mortality.

    BACKGROUND: Little is known of the association between nut consumption, and prostate cancer (PCa) incidence and survivorship.

    METHODS: We conducted an incidence analysis and a case-only survival analysis in the Health Professionals Follow-up Study on the associations of nut consumption (updated every 4 years) with PCa diagnosis, and PCa-specific and overall mortality.

    RESULTS: In 26 years, 6810 incident PCa cases were identified from 47 299 men. There was no association between nut consumption and being diagnosed with PCa or PCa-specific mortality. However, patients who consumed nuts five or more times per week after diagnosis had a significant 34% lower rate of overall mortality than those who consumed nuts less than once per month (HR=0.66, 95% CI: 0.52-0.83, P-trend=0.0005).

    CONCLUSIONS: There were no statistically significant associations between nut consumption, and PCa incidence or PCa-specific mortality. Frequent nut consumption after diagnosis was associated with significantly reduced overall mortality.

    Be well!

    JP

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