Tuesday May 25 2010
Ginger (Zingiber officinale)
“Ginger kills pain”, reported the Daily Express. It said that a study has found that “muscle pain from sport or gardening can be eased by eating ginger”.
This study compared the effect of capsules of raw or heat-treated ginger to a “dummy” capsule on muscle pain. Students were asked to take the capsules for 11 days, and carry out strenuous arm exercises on the eighth day. They then rated their muscle pain over the next three days. The ginger group rated their pain as slightly less than the placebo group in the 24 hours after the exercise.
Although the study used a good design and both researchers and participants were blinded, the study was relatively small (78 participants). This theory should ideally be tested in further, larger studies. It is also not possible to determine from this study whether ginger would have any effects on other kinds of pain or more intense exercise-related muscle pain.
Where did the story come from?
The study was carried out by researchers from Georgia College and State University and the University of Georgia. It was funded by the McCormick Science Institute (MSI), an independent organisation that supports research into the health effects of culinary herbs and spices. MSI receives funding from McCormick & Company, Inc., a manufacturer of culinary herbs and spices. The study was published in the peer-reviewed Journal of Pain.
The study was covered in the Daily Express and Daily Mail, who reported the story relatively accurately.
What kind of research was this?
This study consisted of two randomised controlled experiments looking at the effect of daily ginger supplements on muscle pain. Ginger has been reported to have anti-inflammatory and pain-reducing effects in rodents, but the researchers reported that its effects in humans have not been extensively studied.
The researchers used a type of study design that is good for looking at the effects of treatments. Both experiments were also double blind, meaning that neither the participants nor the researchers knew whether they were receiving ginger or placebo. Blinding is particularly important in cases such as this where the outcome (pain as reported by participants) is subjective, and could be affected by a person’s beliefs about what they were receiving and their preconceptions about its possible effects.
What did the research involve?
The researchers enrolled 78 volunteers for their studies. In the first study, 36 participants were randomly assigned to receive raw ginger capsules or placebo capsules for 11 days. In the second study, 42 participants were randomly assigned to receive capsules containing heat-treated ginger or placebo capsules. The participants took part in strenuous arm exercises on the eighth day, and researchers assessed the pain experienced for the next three days, as well as various measures of inflammation. They then compared these between the groups.
Volunteers were recruited from the university campus, and were eligible to participate if they did not have any medical or orthopaedic conditions that would prevent them from doing the required exercises. People who had done moderate to high-intensity biceps training in the past nine months were excluded, as were people taking psychiatric medication or prescription pain medication.
Participants took six of their assigned capsules every day for 11 days, a total of two grams of ginger or placebo a day. The participants were watched while they took the pills to ensure that they took them. They were asked not to take pain medication during the study. From the second to the final day of the study, the participants were also asked whether they thought they had taken ginger or placebo capsules on the previous day.
The exercises involved the arm muscles that bend the elbow (elbow flexors) of the non-dominant arm (usually the left arm in right-handed people, or vice versa). On day 8 of the study, the range of motion of this elbow was assessed, as well as arm volume and the strength of the elbow flexors. In the strength test, the participant sat down and placed their upper arm on a bench with their arm fully extended, and then performed a single lift with dumbbells of increasing weight to determine the maximum that they could lift.
After this, the participants performed 18 repetitions of an exercise that extended the elbow flexors. This involved placing their upper arm on the bench with their arm bent, and then lowering a dumbbell in a controlled way. The weight used in this exercise was a little heavier (120%) than the maximum they were able to lift in the strength test they had just carried out; but this weight could be reduced by about 5% if this was too heavy.
On days 9 to 11, the participants’ muscle pain, elbow range of motion and arm volume were measured. Participants rated the intensity of their muscle pain on a chart consisting of a line measuring 100mm, ranging from “no pain” on the left to “most intense pain imaginable” on the right. Blood samples were also taken on days 1, 8, and 10, to measure levels of certain indicators of inflammation.
What were the basic results?
The strenuous arm exercises on day 8 of the study were found to induce mild muscle pain 24 hours later. This pain was lower in the ginger groups than in the placebo groups 24 hours after the exercise. The placebo groups rated their pain between 35 and 40mm on the 100mm pain scale. The ginger groups rated their pain at 25 to 30mm. However, the differences between the groups in muscle pain were not statistically significant 48 hours or 72 hours after the exercise.
In the first study, participants in the raw ginger group could correctly guess that they had taken ginger capsules 66% of the time, and the placebo group guessed correctly 58% of the time. Participants in the ginger group who felt more certain that they were taking ginger did not differ in pain levels to those who were uncertain whether they were taking ginger. In the second study, participants in the heat-treated ginger group correctly guessed that they had taken ginger capsules 48% of the time. The placebo group guessed correctly 67% of the time.
How did the researchers interpret the results?
The researchers concluded that their study shows that “daily consumption of raw and heat-treated ginger resulted in moderate-to-large reductions in muscle pain following exercise-induced muscle injury”.
This study did have some good features, including its randomised design and the blinding of both participants and researchers. There are some points to note:
- The study was relatively small and included only young adults (in their twenties). Ideally, the theory that ginger can help to relieve muscle pain would be tested in larger studies and in more mixed age groups.
- This study also cannot tell us whether taking ginger capsules would have any effect on different kinds of pain not caused by exercise, e.g. arthritic pain or non-muscular pain, such as headaches.
- The pain experienced in the placebo group was described as “mild”. It is not possible to say what effect ginger would have on more intense post-exercise pain.
- The pain relief was only greater with ginger in the 24 hours after exercise. After this, the differences were not statistically significant.
Although this study suggests that taking ginger supplements may reduce muscle pain after exercise, this theory should ideally be tested in further, larger studies.