Tart Cherry Juice: Protector and Pain-Reliever
Kuehl et al., Efficacy of tart cherry juice in reducing muscle pain during running; a randomized controlled trial. Journal of the International Society of Sports Nutrition 2010, 7:17
Long distance running is known to cause muscle damage thereby causing inflammation. Tart cherries are a source of phenol compounds that are known for being full of anti-oxidants and useful as an anti-inflammatory. Previous studies have been conducted that show reduced inflammation in healthy men and women with an intake of approximately 45 cherries per day. The objective of this study was to test the effectiveness of tart cherry juice on long distance runners to see if it lessens muscle pain.
This was a randomized, double-blind, placebo-controlled study. 54 healthy runners (36 male, 18 female) ages 35.8 +/- 9.6 years, volunteered to participate in the study and run the Oregon Hood to Coast Relay Race. Subjects were placed on teams, where each would run 3 segments of the relay race. The race included steep ascents and descents, and each subject averaged 26.3km +-2.5km (approx. 16.3mi total) over a 24 hour time period. The subjects agreed not to use any anti-inflammatory drugs or other pain relieving practices such as acupuncture, steroids, or topical medications. Frozen tart Cultivar Montmorency cherries, and apple juice were used to make the “juice”. It was packaged in 10.5oz bottles, which contained 600mg phenol compounds, equivalent to 45-50 cherries. The placebo was unsweetened fruit punch soft drink mixed with water and sugar to match the concentration of the tart cherry juice. For the study, data was collected at 3 different times. Day 1 (baseline) was 7 days prior to the race. Day 7 was Race Start, and Day 8 was Race End. On day 1 (baseline), the subjects participated in a health screening, and were asked to assess their pain intensity on the 100mm Visual Analog Scale, where 0 was ”no pain”, and 100 was ”most severe pain”. The subjects were given 16-355mL bottles of juice. They were instructed to drink 2 bottles daily before the race (14 bottles over 7 days) and 2 bottles during the race itself. On day 7 there was a physician screening and pain assessment prior to the race starting. On day 8, at the race’s conclusion, the subjects were screened and asked to assess their pain, as well as a satisfaction/willingness to use drink again survey (Likert Scale).
Out of the 54 subjects starting the trial, 3 withdrew, 26 people were assigned the tart cherry juice, and 25 drank the placebo. After day 1 assessments, the cherry group had higher pain scores, despite participants being in randomly assigned groups. (16.1 vs. 6.1) Day 7 (Race Start) assessments showed the placebo group 8.0 versus 10.6 for the tart cherry juice group. At Race’s End (Day 8), the placebo group was 45.3 versus 22.6 for the tart cherry group. The tart cherry juice group showed less pain at the race’s end than the placebo group. And the tart cherry group had a higher satisfaction and willingness to use the drink again.
Running does cause muscle damage & inflammation. All the participants showed an increase in pain after the race. The tart cherry juice group showed a smaller increase in pain after the race than the placebo group. The results of the study indicate there is a protective benefit for the muscles from the tart cherry juice, and it is effective in reducing muscle pain during an endurance event.
One of the strengths of this trial was that it was randomized, double-blind, and placebo controlled. The participants were randomly placed in groups that were unknown to both the participants and the researchers. This type of study is much more convincing, and less likely to be influenced by any bias’ the researchers may have. A second strength of this trial was the race that was chosen. The Hood to Coast Relay is the largest relay in the world. The 197 mile course took runners from Mt. Hood (6000 ft elevation at the start) to the Pacific Ocean. The course had varying terrain with many steep ascents and descents. It was surely a challenging course for the participants and was definitely the needed stimulus for muscle damage.
One limitation of this study was the use of the 100mm Visual Analog Scale in assessing the subject’s pain. The scale was marked at one end 0”no pain”, and the other end, 100 “most severe pain”. I believe that this scale is too difficult to accurately define the amount of pain a subject is feeling. Pain tolerances vary widely, and what may be severe pain to one person, may not be the same for another. There are no other markers or descriptors on the scale, such as “pain can be ignored”, or “pain interferes with tasks”, or “pain interferes with concentration”. These descriptors would have added information so the subjects could have better assessed how much pain they were feeling and then it could have been more easily compared with the other subjects. It is extremely hard to get an accurate picture as to the amount of damage that occurred to the muscles by using pain assessments such as the VAS. Another limiting factor was the possibility of the subjects switching drinks without the researchers knowing. This presents a problem because the data may have become contaminated.
This study was of particular interest to me because I am a runner and deal with muscle aches and pains often. I was curious to find out if the tart cherry juice provided the subjects any protection against muscle damage. The article was extremely easy to read and interpret. As I examined the article, I kept wondering how much experience the subjects had as runners. Being a relatively new runner myself, I did not have a lot of knowledge about training when I first started. I just finished 18 weeks of marathon training and learned a great deal, especially how diet and nutrient timing can play a significant role in recovery. This may have been a factor during the study if some participants ate a diet of carbohydrates and protein right after finishing their workouts, thereby reducing pain and increasing recovery rates. The subjects were asked to refrain from using other methods of pain relief, like acupuncture, topical creams, pain relieving drugs, but there is no mention of any dietary guidelines for the week before the race or during the race itself. The subjects were told to consume 2 bottles of juice during the race, but were not given any specific time. I also wondered what the subjects ate after finishing their legs of the race. This may have helped in their recovery and pain relief by the end of the race. Another question that I had centered on the fact that despite being put into random groups, the cherry group had much high pain scores than the placebo group at Day 1 assessments. If the cherry group already had some sort of low-level pain at the baseline assessment, could they become “used to” the pain and may not have a true assessment of their discomfort? Another question that crossed my mind was how “hard” did each participant race. People vary in their ability to tolerate pain and their intensity levels can vary. A person may feel they are racing their hardest and it may be at 75% of their maximum heart rate, while another person raced their hardest at 85% of their maximum heart rate. The ability to push harder, or intensity, may yield in more acute muscle damage. There are many variables that could affect the amount of muscle injury and recovery, which may not necessarily be attributed to the tart cherry juice. The only recommendation I could make is to find a more objective way to measure muscle damage, possibly using muscle biopsies to obtain data.
Tart cherries are known to have high antioxidant properties and help in reducing inflammation in the body. They are also known for neutralizing free radicals and helping repair and prevent damage done by the free radicals in the body. After analyzing this trial, I think the researchers accomplished their objectives for the study. The trial showed that the tart cherry juice group exhibited less than half the pain than the placebo group at the race’s end. It was also shown that the tart cherry group had the most satisfaction and willingness to try the drink again. Despite the subjective nature of pain assessment used in this study, I would try the cherry juice to see if it effective. I think this study is one that could be applied to many more people. Since the tart cherry juice lessened the pain associated with running, it may be useful in recovery from injuries or general soreness, where other anti-inflammatories would normally be used.