Exercise Performance - Another Reason to Go (Wal-)Nuts? Study Demonstrates Ergogenic Effects of the Literal Handful of Walnuts ☆ Heart, Brain, Prostate & Breast Benefit, Too!

The ergogenic effects are just the latest addition to the list of proven benefits of regular walnut consumption.
I don't have to tell you that I am real "nut nut". Despite the fact that I had to realize years ago that almonds, aren't, but strawberries are nuts and irrespective of the constant turmoil about their high energy content, nuts have and probably will always be on my meal plan (on a daily basis, by the way).

It goes without saying that the publication of Dae-Ik Kim's and Kil-Soo Kim' recent paper in the Journal of Laboratory Animal Research won't change this. Who would after all complain about the following possible side effects of regular walnut consumption?

Increased endurance & glutamine, glycogen, decreased lactate & ammonia levels

No one, would complain about theses - correct! What I do yet expect is that you will complain about this being a rodent study.... but honestly, we have hashed and rehashed time and again, so let's just content ourselves with what we have: A 4 week study in the course of which twenty-eight male ICR mice were randomly divided into four groups, a
  • Walnut extract preparation - 1kg Walnuts were soaked in 10L of 70% ethanol for 24h, filtered, lyophilized and powdered. The results were 56 g of walnut extract - "the dosage (600 mg/kg/day) was based on the daily recommended intake as raw walnut (adult standard: 42 g/day)" (Kim. 2013)
    vehicle (control)
  • walnut extract (WE300) at 300mg/kg per day
  • walnut extract (WE600) at 600mg/kg per day
  • walnut extract (WE900) at 900mg/kg per day
The extract (preparation see box) was administered to the mice once a day for 4 weeks. As the scientists point out, the mice were thus consuming the human equivalent of the recommended intake in raw walnuts, of which at least Kim et al. believe that it was 42g/day.

Forced swimming = endurance performance + stress test

Over the whole four week study period the mice were subjected to a weekly forced swimming test. Basically, that's like dropping you in a water tank where you can't stand or hold onto something and waiting. Needless to say that this is both, an endurance, as well as a stress test with which therodents "on" walnuts coped much better, than their peers in the vehicle control group.
Figure 1: Changes in in Lactate, Glucose, Glutamine, Ammonia and Triglyceride as well as the corresponding increases in time to exhaustion during forced swim test (Kim. 2013)
As Table 1 of Kim & Kim's paper tells us (not shown here), the changes in Lactate, Glucose, Glutamine, Ammonia and Triglyceride as well as the corresponding rapid (effects were visible after only 1 week) performance increases (see Figure 1) occurred in the absence of any differences in food or water intake. Moreover, "walnut intake did not cause weight gain, despite an increased energy intake".

I am honestly not sure about the energy content of the walnut extract, but in view of the fact that the mice consumed ~140g/kg of their chow (remember mice weigh only ~46g, so this leaves them at a total food intake of ~6.5g/day), it does not seem reasonable to assume that the walnut extract (~5.85mg at the highest dosage) would influence their body weight.

Apropos body weight

The questionable supposition that the mice in the walnut extract group should weigh significantly more than their peers because of a laughable 5.85mg of walnut extract in their diets, segues nicely into the promised brief review of the walnut studies that were published in 2013 - studies with pretty outstanding results:
  • Improved lipid profiles, even in healthy individuals (Wu. 2013) -- Significant reductions in non-HDL cholesterol and Apo-B (reduction in heart disease risk, Alzheimer's etc.) levels of 40 subjects (mean ± SEM: age 60 ± 1 years, BMI 24.9 ± 0.6 kg/m2; 30 females) after consumption of 43g of walnuts per day for 8 weeks (Figure 2, left)
    Figure 2: Changes in serum lipids (left) and serum fatty acid composition (right) in Wu (2013)
    The improvements occurred despite / because higher total fat, polyunsaturated fat, omega-6 and omega-3 content, and lower protein, carbohydrate and saturated fat content of the diet and were accompanied by signifcant changes in the serum fatty acid compositoin (Figure 2, top) of the subjects.
  • Acute beneficial effect on endothelial health and cholesterol efflux (Berryman.2013) -- Both changes, the walnut oil (51g) induced improvements in endothelial function and the increase in cholesterol efflux in response to the ingestion of 85g of walnuts contribute to increases in heart health. Interesting side note, separated nut skins (5.6 g), and de-fatted nutmeat (34 g) did not work the same magic.
  • Impressive figures: According to Lloyd-Williams et al. (2009) replacing the "average snack" with walnuts (or other healthy snacks) could result in approximately 2400 fewer CHD deaths and 425 fewer stroke deaths per year.
    Reduced prostate cancer risk (Reiter. 2013) -- It's only a rodent study, but it confirms epidemiological evidence from human studies (Spaccarotella. 2008, Carvalho. 2010) and the effect size of -25% is quite impressive.
  • Improved flow-mediated dilatation + improved systolic BP (Katz. 2013) -- Despite the additional 56g of walnuts in their diet the forty-six overweight adults (average age, 57.4 years; 28 women, 18 men) experienced no weight gain. What they did experience, though was a significant increase in FMD (1.4% ± 2.4% versus 0.3% ± 1.5%; p = 0.019) and beneficial effects on systolic blood pressure.
  • Healthy brain aging and improved cognitive performance (Willis. 2009; Pribis. 2011) -- Willis et al. observed a significant and dose-dependent improvement in cognitive abilities in old rats on diets with 2%+ walnuts. Pribis et al. found that the inferential verbal reasoning of their young subjects increased significantly (11.2 %); and that inspite of the fact that the subjects ingested only minimal amounts of walnuts in banabreads.
I guess I could extend this list with at least 10 additional studies. What I could not find, by the way, was more than one study reporting weight gain in response to the addition of 35g walnuts to the diet (the researchers expected a weight gain of 5.3 kg, de facto the participants gained 0.4kg and saw improvements in body composition, see Figure 3) and the overall effect was an improvement in body composition (see Figure 3). Studies such as the one by Bes-Rastrollo et al. (2012), which showed that a frequent nut consumption is associated with a reduced risk of weight gain (5 kg or more) in 8865 adult men and women who participated in te Seguimiento Universidad de Navarra project. A brief look at Joan Sabaté's 2003 review of the literature confirms that this is not just an outlier, but in line with previous research on the effects of walnuts on body weight:
"In well-controlled nut-feeding trials, no changes in body weight were observed. Some studies on free-living subjects in which no constraints on body weight are imposed show a nonsignificant tendency to lower weight while subjects are on the nut diets. In another line of evidence, preliminary data indicate that subjects on nut-rich diets excrete more fat in stools. Further research is needed to study the effects of nut consumption on energy balance and body weight. In the meantime, the available cumulative data do not indicate that free-living people on self-selected diets including nuts frequently have a higher body mass index or a tendency to gain weight." (my emphases in Sabaté. 2003) 
For someone as active as yourself (*lol*) even the extra 277kcal from a the suggested 43g of walnuts shouldn't be a problem. If you look back at the Kim study, it would furthermore appear that significant ergogenic effects can be achieved with half of that, as well.
Figure 3: Changes in body comp. during 6 months of consuming addi- tional 35g (~12 % energy intake) of walnuts (Sabate. 2005)
Bottom line: Walnuts are more than ergogenics, but in view of the fact that people are still afraid they may make them fat (often people who add an extra spoon of virgin olive or coconut oil to their protein shakes *rofl*), the ergogenic effects Kim & Kim observed in the study at hand could actually be the incentive they needed to eventually go nuts. And you know what? Their hearts (reduced CVD risk; Banel. 2009; Li. 2009), their prostate / breasts (reduced cancer risk; cf. Hardman. 2008; Carvalho. 2010; Reiter. 2013) and even their brains (Willis. 2009; Pribis. 2011) will thank them. If that's not convincing enough, just take another look at the improvements in body composition in the Sabaté study from 20035 (Figure 3).
  • Berryman, Claire E., et al. "Acute Consumption of Walnuts and Walnut Components Differentially Affect Postprandial Lipemia, Endothelial Function, Oxidative Stress, and Cholesterol Efflux in Humans with Mild Hypercholesterolemia." The Journal of nutrition 143.6 (2013): 788-794.
  • Carvalho, Márcia, et al. "Human cancer cell antiproliferative and antioxidant activities of Juglans regia L." Food and Chemical Toxicology 48.1 (2010): 441-447.
  • Katz, David L., et al. "Effects of Walnuts on Endothelial Function in Overweight Adults with Visceral Obesity: A Randomized, Controlled, Crossover Trial." Journal of the American College of Nutrition 31.6 (2012): 415-423.
  • Kim, Dae-Ik, and Kil-Soo Kim. "Walnut extract exhibits anti-fatigue action via improvement of exercise tolerance in mice." Laboratory Animal Research 29.4 (2013): 190-195.
  • Li, Tricia Y., et al. "Regular consumption of nuts is associated with a lower risk of cardiovascular disease in women with type 2 diabetes." The Journal of nutrition 139.7 (2009): 1333-1338.
  • Pribis, Peter, et al. "Effects of walnut consumption on cognitive performance in young adults." Br J Nutr 107 (2011): 1393-1401.
  • Reiter, Russel J., et al. "A Walnut-Enriched Diet Reduces the Growth of LNCaP Human Prostate Cancer Xenografts in Nude Mice." Cancer investigation (2013).
  • Sabaté, J. (2003). Nut consumption and body weight. The American journal of clinical nutrition, 78(3), 647S-650S.
  • Sabaté, J., Cordero-MacIntyre, Z., Siapco, G., Torabian, S., & Haddad, E. (2005). Does regular walnut consumption lead to weight gain?. British Journal of Nutrition, 94(5), 859-864.
  • Willis, Lauren M., et al. "Dose-dependent effects of walnuts on motor and cognitive function in aged rats." British journal of nutrition 101.08 (2009): 1140-1144.
  • Wu, Liya, et al. "Walnut-enriched diet reduces fasting non-HDL-cholesterol and apolipoprotein B in healthy Caucasian subjects: a randomized controlled cross-over clinical trial." Metabolism (2013).
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