Heat and type 2 diabetes: a hopeful title, a thin result
A review pooled five studies of heat therapy in people with type 2 diabetes. Blood sugar measures moved a little in the right direction, but not clearly enough to call it an effect.
Worth knowing: A review is a snapshot: its search ended in August 2021.
The short version
This review pooled five studies in which people with type 2 diabetes had regular heat therapy. Long-term blood sugar (HbA1c) was about half a point lower afterwards on average, and fasting blood sugar slightly lower, but neither result was clear enough to rule out no change. Blood fats did not change. The title says heat therapy shows benefit; the numbers say the question is open. The studies were few and small, compared people before and after, and the reviewers call for proper randomized trials.
Keep in mind
Five small studies, measured before and after. The average changes could also be no change at all.
What they found
HbA1c was 0.55 points lower after heat therapy on average, but the 95% confidence interval ran from 1.26 lower to 0.16 higher, so it includes no change.
Fasting blood sugar was 0.29 mmol/L lower (from 0.90 lower to 0.32 higher), again including no change. Triglycerides did not change.
The reviewers conclude that heat may be beneficial and that randomized trials with longer follow-up are needed.
What this means for your practice
Heat is not a way to manage diabetes on this evidence. If you have diabetes, keep to the treatment you have agreed with your doctor, and ask before using a hot sauna.
This does not establish a sauna routine to follow.
Methods and limitations
What the researchers did
The reviewers searched three databases up to August 2021 for studies in which people with type 2 diabetes were treated with passive heat, such as hot baths or sauna.
They compared long-term blood sugar (HbA1c), fasting blood sugar and blood fats (triglycerides) before and after the heat program. Five studies qualified.
How much can this tell us?
This review is useful mainly for what it shows is missing. Five studies is very few, and before-and-after comparisons cannot separate heat from other changes over the same weeks.
The small average improvements point in a hopeful direction, but the ranges are wide enough to include no effect.
It sits alongside a 2024 trial in this library that found one infrared sauna session did not improve blood sugar after a meal.
What makes it useful
- A focused question in people with diabetes
- Reports its uncertainty ranges in full
What limits it
- Only five studies
- Before-and-after comparisons, not randomized trials
- Different kinds of heat across studies
Where this study fits
Where this study fits
We score claims, not single studies. This one is part of the evidence for:
Heat helps control blood sugar. Not supported
Low certaintyNo effect foundBody signals
Read the original
Sebők J, Édel Z, Váncsa S, Farkas N, Kiss S, Erőss B, et al. Heat therapy shows benefit in patients with type 2 diabetes mellitus: a systematic review and meta-analysis. Int J Hyperthermia. 2021;38(1):1650-1659.
DOI 10.1080/02656736.2021.2003445 · PubMed 34808071