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Walnuts benefit your heart, brain, bones and more. Here's why you need to eat more of them
Researchers from the University of California Davis say the U.S. government is wrong when it comes to demonizing high fat foods. In fact, one study shows eating high fat whole walnuts or walnut oil can slow prostate cancer growth.
The researchers wanted to know what it is about walnuts that give them the prostate cancer powers observed in earlier studies.
In their study published online in the Journal of Medicinal Food, the researchers fed animals either whole walnuts, walnut oil, or an oil mixture with the same fatty acid content as walnut oil.[i]
After 18 weeks the walnuts and the walnut oil slowed prostate cancer growth. They also reduced cholesterol and increased insulin sensitivity. And they reduced levels of the hormone IGF-1 which has been linked to both breast and prostate cancer.
The walnut-like oil did not have the same benefits. In other words, it isn't the omega-3 fats in walnuts that have the anti-cancer effects. It's something else but the scientists couldn't pinpoint what it is. They ruled out fiber, zinc, magnesium, and selenium.
And they noted that as with many foods, the health benefits cannot be broken down to one compound. It's multiple components that nature combined into one natural food that produces health benefits. That's why whole foods are more than the sum of their parts.
Here are 12 more proven reasons to add a few walnuts to your daily routine:
1. Nuts Reduce Risk of Death
The PREDIMED human study, which assessed the Mediterranean diet, found that eating walnuts reduced cancer mortality. And a study of 118,000 people by the Harvard School of Public Health found people who ate a handful of nuts every day were 20% less likely to die from any cause over a 30-year period.
2. One Ounce of Walnuts Decreases Cardiovascular Risk
In a University of Wisconsin study 36 people ate 30 grams of English walnuts per day for 30 days. Their blood lipid profiles and endothelial function improved and they didn't gain weight.[ii] Black walnuts didn't have the same effect. To learn more about the difference between English and black walnuts watch this video.
Other studies show that adding walnuts can significantly decrease total and LDL cholesterol. In an Iranian study, 52 volunteers were divided into 2 groups. One group ate 20 grams of walnuts per day and the other group ate none. After eight weeks, the walnut group lowered their triglyceride levels by 17.1% and increased their HDL (good) cholesterol by 9%.[iii]
3. Walnuts Help Control Weight
In a Harvard Medical School study 20 men and women with metabolic syndrome participated in a randomized, double-blind, crossover study of walnut consumption. Everyone was fed a diet of the same number of calories. But for breakfast subjects consumed a shake containing either walnuts or a placebo. After just three days, those drinking the walnut shake reported feeling more satisfied and less hungry.
4. Walnuts Improve Endocrine Parameters in PCOS
In another study from UC Davis, 31 patients with polycystic ovary syndrome (PCOS) randomly received either walnuts or almonds containing 31 grams of total fat per day for 6 weeks. PCOS is commonly associated with insulin resistance, dyslipidemia and increased inflammation. The walnuts decreased LDL cholesterol by 6%.They also increased insulin response and sex hormone-binding globulin.[iv]
5. Walnuts Help Control Insulin in Diabetics
Australian researchers studied 50 overweight adult diabetics in a one year program where participants received low-fat dietary advice. But half the subjects also ate 30 grams of walnuts per day. In the first three months the walnut group significantly lowered their fasting insulin levels.[v]
6. Walnuts Increase Male Fertility
Researchers from UCLA studied 117 young men who ate a typical American diet.[vi] They gave 59 of the men 75 grams of walnuts per day while the others avoided tree nuts. After 12 weeks those who ate walnuts significantly improved sperm vitality, motility and quality.
7. Walnuts Improve Thinking Ability
In a crossover study researchers assigned 64 college students to eat walnuts or a placebo. After eight weeks they found that walnut eaters had increased their inferential verbal reasoning abilities by 11.2%.[vii] Other studies show that greater intake of high-antioxidant foods such as walnuts may increase "health span" and enhance cognitive and motor function in aging.[viii]
8. Walnuts Suppress Breast Cancer Tumors
Animal studies show consuming walnuts significantly reduced the number and size of breast cancer tumors. Researchers suggested that omega-3 fatty acids, antioxidants, and phytosterols in walnuts are responsible for the benefits.[ix]
9. Walnuts Inhibit Growth of Colorectal Cancer
Harvard Medical School researchers found that mice fed walnuts had a 27% slower tumor growth rate and 33% smaller tumors compared to mice fed corn oil. The walnuts worked by significantly decreasing angiogenesis.[x]
10. Walnuts Are Number One in Antioxidants
Walnuts have almost twice as many healthful antioxidants as any other nut. They also have the highest quality and most potent antioxidants. One study measured the antioxidants in walnuts as 2 to 15 times more potent than vitamin E.[xi]
11. Walnuts Help Build Bone
Greek researchers found that walnut extract has a remarkable bone-building activity at the cellular level. They credit ellagic acid, one of the major polyphenols in walnuts, for the bone benefits.[xii]
12. Walnuts Help Beat Stress
According to researchers at Penn State University, a diet rich in walnuts may prepare the body to deal better with stress. In a study of 22 healthy adults with elevated LDL cholesterol participants were subjected to stress either by giving a speech or immersing a foot in cold water. The results showed that when participants were following a diet that included walnuts and walnut oil, their blood pressure and stress responses were lower.
Unfortunately the standard American diet includes no nuts at all on a daily basis. But just a quarter cup of walnuts provides more than 100% of the daily recommended value of omega-3 fats, along with high amounts of copper, manganese, molybdenum, and biotin.
Look for walnuts that are marked organic and raw. Otherwise they may be irradiated and pasteurized.
The papery covering of a shelled walnut is very bitter and most people don't like it. But up to 90% of the walnut antioxidants are in that flaky cover so it's worth eating.
Once out of the shells, walnuts can become rancid. Store them in an airtight container in your refrigerator or freezer. And don't leave them there too long. Throw them on salads or in smoothies and yogurt. And of course bake them into brownies, cookies, cakes and breads.
For more information visit Green Med Info's page on walnut research.
[i] Kim Hyunsook, Yokoyama Wallace, and Davis Paul Andrew. Journal of Medicinal Food. October 29,2014 ahead of print. doi:10.1089/jmf.2014.0061.
[ii] Peter J Fitschen, Kristofer R Rolfhus, Michael R Winfrey, Brian K Allen, Michelle Manzy, Margaret A Maher. Cardiovascular effects of consumption of black versus English walnuts. J Med Food. 2011 Sep ;14(9):890-8. Epub 2011 Apr 13. PMID: 21488754
[iv] S Kalgaonkar, R U Almario, D Gurusinghe, E M Garamendi, W Buchan, K Kim, S E Karakas. Differential effects of walnuts vs almonds on improving metabolic and endocrine parameters in PCOS. Eur J Clin Nutr. 2011 Mar ;65(3):386-93. Epub 2010 Dec 15. PMID: 21157477
[v] L C Tapsell, M J Batterham, G Teuss, S-Y Tan, S Dalton, C J Quick, L J Gillen, K E Charlton. Long-term effects of increased dietary polyunsaturated fat from walnuts on metabolic parameters in type II diabetes. Eur J Clin Nutr. 2009 Aug ;63(8):1008-15. Epub 2009 Apr 8. PMID: 19352378
[vi] Robbins WA, Xun L, Fitzgerald LZ, Esguerra S, Henning SM, Carpenter CL. Walnuts Improve Semen Quality in Men Consuming a Western-Style Diet: Randomized Control Dietary Intervention Trial. Biol Reprod. 2012 Aug 15. [Epub ahead of print] PMID: 22895856
[vii] Peter Pribis, Rudolph N Bailey, Andrew A Russell, Marcia A Kilsby, Magaly Hernandez, Winston J Craig, Tevni Grajales, David J Shavlik, Joan Sabatè. Effects of walnut consumption on cognitive performance in young adults. Br J Nutr. 2011 Sep 19:1-9. Epub 2011 Sep 19. PMID: 21923981
[viii] James A Joseph, Barbara Shukitt-Hale, Lauren M Willis. Grape juice, berries, and walnuts affect brain aging and behavior. J Ethnopharmacol. 2008 Aug 13;118(3):396-404. Epub 2008 May 20. PMID: 19640963
[ix] W Elaine Hardman, Gabriela Ion, Juliana A Akinsete, Theodore R Witte. Dietary Walnut Suppressed Mammary Gland Tumorigenesis in the C(3)1 TAg Mouse. Nutr Cancer. 2011 Jul 20. Epub 2011 Jul 20. PMID: 21774594
[x] Jutta M Nagel, Mary Brinkoetter, Faidon Magkos, Xiaowen Liu, John P Chamberland, Sunali Shah, Jinrong Zhou, George Blackburn, Christos S Mantzoros. Dietary walnuts inhibit colorectal cancer growth in mice by suppressing angiogenesis. Nutrition. 2011 Jul 26. Epub 2011 Jul 26. PMID: 21795022
[xi] Joe A Vinson, Yuxing Cai. Nuts, especially walnuts, have both antioxidant quantity and efficacy and exhibit significant potential health benefits. Food Funct. 2012 Feb ;3(2):134-40. Epub 2011 Dec 21. PMID: 22187094
[xii] Z Papoutsi, E Kassi, I Chinou, M Halabalaki, L A Skaltsounis, P Moutsatsou. Walnut extract (Juglans regia L.) and its component ellagic acid exhibit anti-inflammatory activity in human aorta endothelial cells and osteoblastic activity in the cell line KS483. Br J Nutr. 2008 Apr;99(4):715-22. Epub 2007 Oct 5. PMID: 17916277