13 July 2013

Blueberries and endurance running

Less than 60 days left to Sunday September 8 and the start of Tor des Géants in Courmayeur. From having wished that the there would be more time until then, I am now wishing that time would pass more quickly. A very good sign that I am starting to get as prepared as I could be I guess. I am still in a period where I focus a lot on getting distance in my legs and I have started to feel very strong. The problems I have had with my Achilles tendons and my left ankle have all subsided despite my ramping up the weekly milage even further. It is soon time for a short vacation in Southern Italy and I will then start to focus on adding more quality to my training and starting to gain speed and further up/downhill running technique.

I am writing this on a flight on my way to Chicago – I think my seventh business trip overseas to the US during the past year. Back home in Sweden there has been a lovely July weatherwise and there is plenty of wild blueberries in the forests. Blueberries are and have since my childhood always been my favorite berries. I simply love blueberry pie, blueberry ice cream or just simply milk or yoghurt and blueberries. I therefore became doubly happy when stumbled across some studies showing that the blueberry fruit exhibit antioxidant and anti-inflammatory properties and can facilitate recovery from exercise-induced muscle damage (EIMD). Although blueberries are low in vitamin C and E they contain the broadest range of anthocyanin and polyphenolic antioxidant compounds among common berryfruits (Wu X et al. Lipophilic and hydrophilic antioxidant capacities of common foods in the United States. J Agri Food Chem 2004, 52: 4026).  


In a study from New Zeeland ten healthy females in underwent a randomized cross-over study where they consumed a blueberry smoothie or placebo of a similar antioxidant capacity 5 and 10 hours prior to and then immediately, 12 and 36 hours after EIMD induced by 300 strenuous eccentric contractions of the quadriceps (McLeay et al. Effect of New Zealand blueberry consumption on recovery from eccentric exercise-induced muscle damage. J Int Soc Sport Nutr 2012, 9: 19). A significant (p < 0.001) decrease in isometric, concentric and eccentric torque was observed 12 hours following exercise in both treatment groups. During the 60 hour recovery period, a significant (p = 0.047) interaction effect was seen for peak isometric tension suggesting a faster rate of recovery in the blueberry intervention group. There was a faster rate of decrease in oxidative stress observed in the blueberry group, however, it was not significant (p < 0.05) until 36 hours post-exercise and interestingly coincided with a gradual increase in plasma antioxidant capacity. The ingestion of the blueberry beverage had no effect on perceived muscle soreness or pain.

Another interesting study was performed in the US were twenty-five well-trained subjects were randomized into two groups receiving either 250 g of blueberries per day for 6 weeks and 375 g given 1 h prior to 2.5 h of running at 72% maximal oxygen consumption (n = 13) or receiving control (McAnulty LS et al. Effect of blueberry ingestion on natural killer cell counts, oxidative stress, and inflammation prior to and after 2.5 h of running- Appl Physiol Nutr Metab. 2011; 36: 976-84). Markers of oxidative stress (F2-isoprostanes) and nucleic acid oxidation (5-OHMU) were significantly less increased in the blueberry group and plasma IL-10 and NK cell counts were significantly greater in the blueberry group. Changes in all other studies markers did not differ. The authors claim that the study indicates that daily blueberry consumption for 6 weeks increases NK cell counts, and acute ingestion reduces oxidative stress and increases anti-inflammatory cytokines. It is as the study by McLeay a small study, but interesting as it really evaluates the response after a strenuous running trial. There are clear indications that the effects of blueberries are direct and not indirect effect of other vitamins (Sánchez-Moreno et al. Effect of a blueberry nutritional supplement on macronutrients, food group intake, and plasma vitamin E and vitamin C in US athletes. Int J Food Sci Nutr. 2008; 59 :327).



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