Wevers A. et al. - Photobiomodulation and metabolic outcomes in type 2 diabetes: a systematic review and meta-analysis

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This systematic review with meta-analysis concludes that photobiomodulation has inconsistent and largely short-term effects on glycemic control, inflammation, and neurological function in type 2 diabetes. Only modest periodontal benefits could be aggregated, with the certainty of the evidence rated as low.

What this study measured

In late 2025, Anne Wevers and her colleagues published a systematic review and meta-analysis of randomized controlled trials in the *International Journal of Molecular Sciences*, focusing on the metabolic, inflammatory, and neurological effects of photobiomodulation in adults with type 2 diabetes.

Five databases were searched through June 2025, according to a protocol pre-registered on PROSPERO (CRD420251083550). Metabolic, inflammatory, and neurological criteria were defined a priori as primary. Periodontal criteria, which were not predefined, were added as secondary outcomes, as several trials reported them with sufficient consistency. The abstract does not specify the number of trials, the number of participants, or the irradiation parameters. It does not state whether photobiomodulation was combined with physical exercise, information that is necessary to determine whether the effects could be attributed to light alone.

Key Findings

A key methodological issue: the main criteria could not be statistically aggregated.

Key metabolic, inflammatory, and neurological criteria: narrative synthesis only; heterogeneity and incomplete reporting prevented any quantitative pooling
Blood Glucose Control, Systemic Inflammation, and Neurological Function: Inconsistent and Largely Short-Term Effects
Clinical attachment level (periodontal, secondary): -0.21 mm, significant improvement
Probing depth: -0.25 mm, significant improvement
Plaque index: no effect
Overall certainty of the evidence: low

The authors consider these gains to be modest and unlikely to be clinically significant when viewed in isolation. No confidence intervals are reported.

How Photobiomodulation Affects Metabolism

The most commonly cited mechanism remains hypothetical: red and near-infrared light is thought to be absorbed by cytochrome c oxidase, the final link in the mitochondrial respiratory chain, which could promote the production of adenosine triphosphate and improve mitochondrial function in skeletal muscle—the primary site of glucose uptake. An effect on oxidative stress and low-grade inflammation has also been proposed. This review does not validate any of these mechanisms: the clinical effects measured on metabolic and inflammatory markers are inconsistent.

Limits You Should Know

The most significant limitation is also the main finding: no meta-analysis could be conducted on metabolism, inflammation, or neurological function, as the heterogeneity among trials and the incompleteness of the data made this impossible. The narrative synthesis shows inconsistent and short-lived effects. The only aggregated results pertain to periodontal endpoints not specified in the protocol, which weakens their evidential value, and their magnitude remains small given the variability in periodontal measurements. The authors rate the certainty of the evidence as low. The abstract provides neither the number of trials, nor sample sizes, nor confidence intervals, and does not indicate whether physical exercise was involved.

What This Means in Practice

This study calls for caution: the journal does not support the idea that photobiomodulation provides a reliable glycemic benefit in adults with type 2 diabetes. It is in no way a substitute for antidiabetic treatment, and treatment should never be reduced or discontinued based on these data. Any changes to treatment are the sole responsibility of the physician, and self-monitoring of blood glucose remains necessary. The only quantified benefit relates to periodontal health, as a supplement to conventional treatment and not as a substitute for it.

Frequently Asked Questions

Does photobiomodulation lower blood sugar levels in people with type 2 diabetes?

This review does not support such a claim. The effects on glycemic control are described as inconsistent and largely short-term, and the heterogeneity of the trials precluded any meta-analysis on this outcome. No favorable conclusions can be taken for granted.

Why were the authors unable to conduct a meta-analysis on the primary endpoints?

There are two reasons: substantial heterogeneity among the trials and incomplete reporting of results. Combining data that is too disparate or incomplete would yield a misleading estimate. The authors therefore opted for a narrative review, which has a lower level of evidence.

How reliable are the reported periodontal results?

These changes are significant but of modest magnitude: -0.21 mm in clinical attachment level and -0.25 mm in probing depth, with no effect on the plaque index. These outcomes were not specified in the protocol, and the certainty of the evidence remains low.

Reference

Wevers A, San Roman-Mata S, Navarro-Ledesma S, Pruimboom L. Effects of Photobiomodulation on Metabolic, Inflammatory, and Neurological Outcomes in Type 2 Diabetes: A Systematic Review and Meta-Analysis. International Journal of Molecular Sciences, 2025;27(1):440. PMID 41516314. DOI 10.3390/ijms27010440. https://pubmed.ncbi.nlm.nih.gov/41516314/

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.