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There is Nothing Simple About Nuts:

Jacob Schor ND, FABNO

February 27, 2010

 

Life is rarely as simple as we are led to believe.  [or, as we would want to believe]  Just as soon as we think we’ve got things sorted out, along comes a new revelation that shakes up our view of the world.

 

I’m thinking about nuts as I write this.  A decade ago, we started telling patients to eat more nuts.  This trend was started by Wanda Morgan’s 2000 paper that reported eating a daily ½ cup serving of pecans improved cholesterol profiles.[1]  I had almost perfected my pecan pie recipe when Iwamoto’s study came out saying that walnuts were equally beneficial so I switched my experiments to walnut tortes.[2]

 

Over the last ten years similar studies have shown the cardiovascular benefit from pretty much every kind of nut you can shake a stick at.

Nuts contain omega-3 fats, the same kind of fat as found in cold water fish.  Eating fish or taking fish oil is good for your heart so the explanation for the beneficial effects of eating nuts has been simple, “Nuts contain omega-3 fats.”

 

A hint that this was an oversimplification showed up in Kris-Etherton’s September 2008 review of nuts and cardiovascular disease.  Pooling data from 4 large epidemiological studies showed that people who ate a lot of nuts reduced their risk of heart disease by more than a third.  Clinical studies that measured the effect of nuts on lipids, lipoproteins, and various heart disease risk factors, including oxidation, inflammation, and vascular reactivity showed a beneficial effect but the cholesterol-lowering response seen was, “… greater than expected on the basis of blood cholesterol-lowering equations that are derived from changes in the fatty acid profile of the diet.”  In other words, nuts do more good things than explained by simply being ‘good fats.’

 

The researchers came to what we find an unsurprising conclusion, “… nuts and peanuts contain other bioactive compounds that explain their multiple cardiovascular benefits. Other macronutrients include plant protein and fiber; micronutrients including potassium, calcium, magnesium, and tocopherols; and phytochemicals such as phytosterols, phenolic compounds, resveratrol, and arginine.”[3] 

 

In other simpler words, nuts contain lots of chemicals that are good for us.  Again, no surprise here.

 

The results of a study published in January 2010 did come as a surprise; they suggest nuts somehow trigger the repair of damaged DNA. Clinical Nutrition published a paper by López-Uriarte and colleagues from Spain titled, “Effect of nut consumption on oxidative stress and the endothelial function in metabolic syndrome.”[4]

 

Perhaps we should back up a moment and mention that nuts have a positive effect on diabetes.  A 2002 paper in the Journal of the American Medical Association written by Harvard researchers reported an inverse association between nut consumption and risk for type 2 diabetes.  That is, the more nuts people ate, the less likely they were to get diabetes.[5]  A more recent paper, published in 2009 reported that nuts reduced the risk of heart disease in women with type 2 diabetes.[6]   In fact, some of the same Spaniards behind this paper I’m so fascinated with, reported in a December 2009 paper, that eating nuts reduced insulin resistance.[7]  Thus this January’s study was really a continuation of earlier investigations on the effect of nuts on blood vessel function and risk of diabetes and heart disease.

 

In the 2010 paper, Lopez-Uriarte and colleagues measured a host of biochemical markers in fifty patients with metabolic syndrome before and after a three-month period of eating an ounce of nuts per day. No significant differences were seen as a result of eating the extra nuts in most of the chemical markers measured.  The only difference, and it was quite statistically significant, was a reduction in DNA damage in the nut-eating group compared to the control group.  The authors suggest, “The decrease in DNA damage observed in this study could contribute to explain the beneficial effects of regular nut consumption on … several chronic diseases.

 

This idea that nuts fix DNA is striking.  We don’t know of many other things that do this.  Let me confess, off the top of my head, I cannot name any other food known to repair DNA.  Foods come to mind that protect DNA.  The proanthocyanidins extracted from grape seeds are one example.[8,9] 

[Well, but who eats grape seeds?] The ellagic acid in raspberries and pomegranate is another example, but again, they protect DNA from damage and don’t repair it.[10]

 

The only example of ways to trigger DNA repair I can think of are not food.  The first is hormesis, the purported beneficial effect of low doses of poisons or low dose radiation exposure, neither of which we would encourage anyone to try at home. [11,12]  

There is evidence that exercise will trigger DNA repair through a mechanism similar to caloric restriction. [13]  Caloric restriction is a euphemism for staying hungry all the time. It’s well known that underfed animals will outlive their contented well fed counterparts. [14]  Obviously not eating doesn’t qualify for a list of foods that trigger DNA repair.

 

Which leaves nuts as the only food on I can list.  That was a hard thing to write as no doubt just as soon as I push send and this ends up in your mailbox, more examples will crop up.  [and, in truth, if you know of other examples, I’d like to hear them]

Whether I do find more examples or not, the striking thing for us to understand is that nuts have far more benefit than can be explained by the fats they contain.  The, ‘nuts are like fish oil’ explanation is now outdated, a drastic oversimplification.  As we see future studies about the protective effect nuts have against chronic disease, we should think of this DNA repair concept; something in nuts fixes things, not just repairs tissue, but actually fixes the DNA that serves as a blueprint to all cellular activities.

 

The biological world that we are part of is a complex place and it’s tempting to latch onto simple explanations, ‘sound-bites’ of a sort.  But sound-bites rarely do justice to the whole truth and it is time we learned this, even if we are just talking about nuts.

 

References:

1. Morgan WA, Clayshulte BJ. Pecans lower low-density lipoprotein cholesterol in people with normal lipid levels. J Am Diet Assoc. 2000 Mar;100(3):312-8.

2. Iwamoto M, Sato M, Kono M, Hirooka Y, Sakai K, Takeshita A, Imaizumi K.

Walnuts lower serum cholesterol in Japanese men and women. J Nutr. 2000 Sep;130(9):2407.

3. Kris-Etherton PM, Hu FB, Ros E, Sabaté J. The role of tree nuts and peanuts in the prevention of coronary heart disease: multiple potential mechanisms. J Nutr. 2008 Sep;138(9):1746S-1751S.

4. López-Uriarte P, Nogués R, Saez G, Bulló M, Romeu M, Masana L, Tormos C, Casas-Agustench P, Salas-Salvadó J. Effect of nut consumption on oxidative stress and the endothelial function in metabolic syndrome. Clin Nutr. 2010 Jan 9.

5. Jiang R, Manson JE, Stampfer MJ, Liu S, Willett WC, Hu FB. Nut and peanut butter consumption and risk of type 2 diabetes in women. JAMA. 2002 Nov 27;288(20):2554-60.

6. Li TY, Brennan AM, Wedick NM, Mantzoros C, Rifai N, Hu FB. Regular consumption of nuts is associated with a lower risk of cardiovascular disease in women with type 2 diabetes. J Nutr. 2009 Jul;139(7):1333-8.

7. Casas-Agustench P, López-Uriarte P, Bulló M, Ros E, Cabré-Vila JJ, Salas-Salvadó J. Effects of one serving of mixed nuts on serum lipids, insulin resistance and inflammatory markers in patients with the metabolic syndrome. Nutr Metab Cardiovasc Dis. 2009 Dec 21.

8. de Rezende AA, Graf U, Guterres Zda R, Kerr WE, Spanó MA. Protective effects of proanthocyanidins of grape (Vitis vinifera L.) seeds on DNA damage induced by Doxorubicin in somatic cells of Drosophila melanogaster. Food Chem Toxicol. 2009 Jul;47(7):1466-72.

9. Bagchi D, Sen CK, Ray SD, Das DK, Bagchi M, Preuss HG, Vinson JA. Molecular mechanisms of cardioprotection by a novel grape seed proanthocyanidin extract. Mutat Res. 2003 Feb-Mar;523-524:87-97.

10. Sudheer AR, Muthukumaran S, Devipriya N, Menon VP. Toxicology. Ellagic acid, a natural polyphenol protects rat peripheral blood lymphocytes against nicotine-induced cellular and DNA damage in vitro: with the comparison of N-acetylcysteine. 2007 Jan 25;230(1):11-21.

11. Schumacher B. Transcription-blocking DNA damage in aging: a mechanism for hormesis. Bioessays. 2009 Dec;31(12):1347-56.

12. Sakai K. [Biological responses to low dose radiation--hormesis and adaptive responses]

Yakugaku Zasshi. 2006 Oct;126(10):827-31.

13. Koltai E, Szabo Z, Atalay M, Boldogh I, Naito H, Goto S, Nyakas C, Radak Z. Exercise alters SIRT1, SIRT6, NAD and NAMPT levels in skeletal muscle of aged rats. Mech Ageing Dev. 2010 Jan;131(1):21-8.

14. Exp Gerontol. 2010 Mar;45(3):208-216. Epub 2009 Dec 11.

Effect of caloric restriction on base-excision repair (BER) in the aging rat brain.

15. Kisby GE, Kohama SG, Olivas A, Churchwell M, Doerge D, Spangler E, Cabo RD, Ingram DK, Imhof B, Bao G, Kow YW.