|The ergogenic effects are just the latest addition to the list of proven benefits of regular walnut consumption.|
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
- 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
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)|
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)
- 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.
- 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.
"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.
- 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).