Wednesday April 2 2008
The participants completed a 12-week course
Researchers say “traditional Chinese martial arts exercises could help diabetics control their blood sugar levels”, the Daily Mail reports today. It says that a 12-week programme of tai chi caused the blood sugar levels of people with type 2 diabetes to drop "significantly" by 8% and bolstered their immune systems.
The Daily Mirror also covers the story, saying that the practice of tai chi could cut blood glucose or improve how the body processes it. It adds that tai chi could boost the immune system through increasing fitness and “the feeling of wellbeing”.
The stories are based on a study of people with and without diabetes in Taiwan. It has some design flaws and as a result it cannot establish that tai chi was responsible for any improvements in the diabetes group. Importantly the researchers did not compare the effects of tai chi between the two groups (those with diabetes and those without), neither did they look at the effects of tai chi compared with no tai chi in people with diabetes.
The study found changes in certain immune markers before and after practising tai chi. However, the clinical significance of this, i.e. whether it would make a difference in susceptibility to infection, is unclear for any individual, diabetic or otherwise, as these are unrelated to the diabetes disease.
As the insulin resistance that develops with type 2 diabetes is associated with weight gain, it seems plausible that taking part in regular exercise, of any form, would be of some benefit to people with the disease. In any case, any form of exercise that the individual finds increases their health, fitness and energy levels can only be a good thing.
Where did the story come from?
S-H Yeh and colleagues from the Chang Gung Memorial Hospital-Kaohsiung Medical Center, Taiwan, carried out the research. The study was funded by grants from Chang Gung Memorial Hospital and the National Science Council, Taiwan. It was published in the British Journal of Sports Medicine, a peer-reviewed medical journal.
What kind of scientific study was this?
The aim of the study was to investigate the effects of a 12-week programme of tai chi on the immune systems of people with diabetes.
The research paper described this as a case-control study, but it was actually an uncontrolled study in people with diabetes. The ‘control group’ without diabetes that the researchers included was unnecessary for the question of the study, i.e. is tai chi beneficial for diabetes. Furthermore, the researchers did not compare any changes between the groups that happened over the study period. The exception to this was a comparison of the change in the groups’ BMI, though this was not a primary outcome of their study Essentially, they have studied the effect of tai chi in people with diabetes and separately in people without diabetes.
The researchers posted a recruitment notice in diabetic clinics and community culture centres in Kaohsiung County, Taiwan. From those who responded, they excluded people who had cancer and were being treated with chemotherapy, people with autoimmune disease on immunosuppressant drugs, or those on steroids, as these things could all affect the body’s immune system. They selected 30 people with type 2 diabetes and 30 age-matched controls without the disease.
Before starting the study, all participants had fasting blood sugar taken, as well as HbA1C (a more reliable marker of stability of blood sugar levels over time), and levels of various substances in the body which reflect the function of the immune system. All participants then completed a 12-week exercise programme, during which they learned to perform 37 standardised exercises from ”an expert [tai chi] master with 31 years of experience who conducted all treatment sessions” three times per week. At completion of the 12 weeks, the researchers took more blood samples and, in each of the groups, compared the fasting glucose, HbA1C and immune parameters with levels at the beginning of the study.
What were the results of the study?
At the beginning of the study, both groups were similar (matched) in terms of age, sex, education and BMI. However, as could be expected, people with diabetes had higher blood glucose and HbA1c levels than controls.
After the tai chi course, the group with diabetes showed a barely significant reduction in HbA1c levels and a non-significant reduction in fasting blood sugar levels. The research paper does not say that the researchers compared the effect of tai chi in the diabetic group with the control group.
When the researchers looked at the levels of the immune markers that were tested, the marker IL-12 (involved in the body’s resistance against infections) was found to have increased significantly in diabetics but not in non-diabetics after tai chi.
The researchers also found that levels of a certain transcription factor (involved in the transfer of genetic material) increased following exercise in diabetics. The clinical significance of this is unclear.
What interpretations did the researchers draw from these results?
The authors conclude that a 12-week exercise programme of tai chi decreased HbA1C levels and caused an increase in a certain immune reaction. They say: ”A combination of [tai chi]with medication may provide an even better improvement in both metabolism and immunity of patients with type 2 diabetes.”
What does the NHS Knowledge Service make of this study?
This study cannot prove that tai chi benefits diabetics. It has several important limitations.
- The study design is not a reliable one. The best way to answer this question would be to randomise diabetics to tai chi training or a control condition and compare the effects in both groups. If this was not possible for these researchers, i.e. randomisation was too expensive, they could have compared people with diabetes who practised tai chi with diabetics who did not. As it stands, the use of a control group seems superfluous as they were not actually compared to the diabetic group for anything other than BMI.
- The study did not show any significant benefits of tai chi on the blood sugar levels of diabetics. The differences found in certain immune markers are not related to the diabetes disease process. Therefore, it is also not possible to say whether this slight increase in levels would cause any meaningful change in immunity, in those with diabetes or without.
- The study was carried out in Taiwan and the results may not be applicable to different populations in other countries. Possible psychosocial influences include differences in the practice of tai chi between practitioners in different countries, particularly as the sessions were guided by an expert in the field. Also, the belief that relaxing martial arts exercises and meditation can be of benefit to health may be different between Taiwanese people and people from other countries, which could have an effect on success. As the participants responded to recruitment posters for a tai chi programme to improve immunity, they would have been aware of the nature of the study so may have been more likely to believe that the exercise programme would help them.
- All the people with diabetes were taking their prescribed medication during the study so it is impossible to distinguish between the effects of these drugs and the tai chi through a study designed in this way.
This study does not demonstrate that tai chi is beneficial to diabetics. However, any form of exercise that the individual finds increases their health, fitness and energy levels can only be a good thing.
Sir Muir Gray adds...
Any form of exercise is beneficial for people with diabetes; a daily dose of tai chi is likely to do much more good than harm.