Carbohydrate-free diet: a panacea for asthma and other conditions

Editorial note: this article was previously published and has been updated according to scientific rigor and popularization criteria. The information collected here is for informational purposes only and does not replace the advice of your treating physician. For clinical or therapeutic decisions, consult a healthcare professional.

IN BRIEF

• Preclinical studies indicate that a diet that restricts carbohydrates and increases ketones can reduce the activation of specific immune cells linked to airway inflammation.
• The ketone body β‑hydroxybutyrate (BHB) exerts anti‑inflammatory effects on known molecular pathways; however, most evidence in asthma is still experimental.
• Human results on ketogenic diet and asthma control are scarce: some studies show effects on the immune system, but do not replace validated therapies.
• For people with obesity and asthma, weight loss often improves disease control; the specific contribution of ketosis remains a subject of research.

Abstract: what does science say?

Recent research shows that carbohydrate restriction and the consequent production of ketone bodies (ketosis state) modify cellular metabolism and can attenuate some inflammatory responses associated with asthma. In murine models, the ketogenic diet reduced the proliferation and function of type 2 innate lymphoid cells (ILC2s), which are important in promoting mucus production and eosinophil recruitment in the airways; similarly, the ketone body β-hydroxybutyrate (BHB) was found to modulate inflammatory pathways and mast cell activity. However, this evidence largely comes from experimental models and small studies or interventions on healthy volunteers; therefore, generalizability to asthmatic patients is limited. The effects depend on the context (presence of obesity, type of asthma, duration of intervention), the extent of ketosis, and the overall energy balance. In summary: biological plausibility and preclinical results support an immunometabolic role of ketosis in airway inflammation, but robust clinical evidence is still lacking to recommend the ketogenic diet as a therapeutic strategy for asthma.

Plausible Biological Mechanisms: How Ketosis Can Affect Airways

In recent years, an integrated view of metabolism and immunity has emerged: nutrients and metabolites (such as ketones) are not just energy sources but also signals that modulate the behavior of immune cells. In experimental models, ILC2s — innate immune cells involved in type 2 responses and mucus production — increase lipid and glucose uptake to support proliferation and the formation of new cell membranes. Limiting dietary glucose and promoting fat utilization can reduce this metabolic activity, hindering the accumulation of lipid droplets necessary for ILC2 proliferation; this effect has been observed in murine models of airway inflammation [1].

In parallel, the ketone body β-hydroxybutyrate (BHB) has shown the ability to modulate known inflammatory pathways: in cellular and animal studies, BHB can inhibit the activation of the NLRP3 complex (a pathway that promotes IL-1β production) and influence cytokine production and mast cell function, elements that contribute to airway hyperreactivity [3][2]. BHB's properties include its role as an energy substrate, an epigenetic modulator, and a ligand for metabolic receptors, all elements consistent with a systemic immunomodulatory effect [6][7].

Key experimental evidence (animal and cellular models)

In mice with allergic airway inflammation, a ketogenic diet reduced ILC2 proliferation and activity, as well as the set of tissue responses typical of asthma (mucus, eosinophil recruitment, hyperreactivity) [1]. Subsequent studies showed that BHB supplementation or administration attenuates IL-2 production from mast cells and, indirectly, ILC2 proliferation, resulting in reduced pulmonary inflammation in experimental models [2]. These experiments provide biological plausibility but remain not directly transferable to humans without clinical confirmation.

What human data exists and what we can infer

Direct clinical evidence on the use of the ketogenic diet for asthma is limited. Some human studies show that low carb interventions or exposure to increased ketone levels modify the immune profile: for example, a trial on healthy volunteers documented transcriptional and functional changes in T lymphocytes after a brief ketogenic intervention, with an improvement in some parameters of immune capacity [4]. However, these studies are not equivalent to clinical trials in subjects with asthma and do not directly measure clinically relevant respiratory outcomes (exacerbations, symptom control, long-term lung function).

Furthermore, weight loss in obese people with asthma is associated with improved disease control and respiratory function in several studies and systematic reviews; this point is relevant because ketosis is often accompanied by weight reduction and metabolic changes that can contribute to the observed benefit [8]. Consequently, distinguishing the specific effect of ketosis from the general effect of weight loss requires ad hoc controlled studies.

Limitations of available human studies

The main limitations are: small sample sizes, short intervention durations, healthy populations or those not selected for asthma, absence of primary clinical measures of asthmatic outcome, and difficulty in separating the effects of weight loss from the specific metabolic effects of ketosis. Furthermore, there are currently no guidelines recommending the ketogenic diet for the treatment of asthma based on robust clinical trials.

What this means in practice

For the general public, the main message is one of caution: laboratory research indicates that limiting carbohydrates and increasing lipids can modify specific immunometabolic pathways involved in airway inflammation, but there is insufficient clinical evidence to recommend the ketogenic diet as a therapy for asthma. People with asthma considering dietary modifications should discuss them with their doctor or a clinical nutritionist. In particular, those with concomitant medical conditions (type 1 diabetes, kidney failure, pregnancy, eating disorders) should avoid radical dietary changes without specialist supervision.

For patients with obesity and asthma, structured and supervised weight loss programs often improve symptom control and quality of life: this remains an approach based on consolidated evidence, regardless of the dietary strategy chosen [8]. Nutritional interventions aimed at a balanced diet and progressive weight loss are established and safe practices.

Key points to remember

• The ketogenic diet modifies cellular metabolism and can reduce the activation of cells involved in asthma in animal models [1].
• The ketone body BHB shows anti-inflammatory activity on known molecular pathways, including the inhibition of the NLRP3 inflammasome [3].
• There are human data documenting immunometabolic changes after carbohydrate restriction, but no robust clinical evidence in asthmatic patients [4].
• Weight loss in obese subjects with asthma is associated with improved control: the benefit could derive from multiple mechanisms, not just ketosis [8].
• Currently, the ketogenic diet cannot replace validated pharmacological therapies for asthma; any modification should be discussed with a doctor.

Limitations of the Evidence

It is important to distinguish between different types of studies: observational studies describe associations, animal models allow for causal analysis at a molecular level but do not always replicate the human context, and randomized clinical trials provide the highest level of evidence for therapeutic interventions. Many of the current claims regarding the ketogenic diet and asthma are based on experimental data in animals or immunological measurements in small groups of volunteers; clinical generalization requires controlled trials in asthma patients, with relevant clinical outcome measures (exacerbations, pulmonary function, corticosteroid use, quality of life) and adequate follow-up.

Other methodological limitations include: variability in the composition of diets defined as "ketogenic," differences in the duration and depth of ketosis, and the potential confounding role of weight loss and gut microbiota composition. The heterogeneity of asthma phenotypes (e.g., type 2 vs. non-type 2 asthma) makes it probable that the effect of metabolic interventions will differ among patients.

Editorial Conclusion

Immunometabolic research has opened up interesting perspectives: ketosis and ketone bodies are biochemical signals capable of modulating immune responses relevant to airway inflammation. Relevant preclinical studies identify plausible mechanisms and molecular targets for future interventions [1][2][3]. However, clinical evidence supporting the use of the ketogenic diet as asthma therapy is currently insufficient. In the meantime, for patients with asthma and obesity, weight reduction remains an evidence-based strategy to improve disease control. Well-designed clinical trials are needed to separate the specific effect of ketosis from the effect of weight loss and to evaluate safety, tolerability, and long-term respiratory outcomes.

Editorial Note

The article has been updated with recent and verifiable scientific references to provide a clear and balanced picture. Therapeutic choices should always be discussed with healthcare professionals. For more information or specific references, consult the bibliography below.

SCIENTIFIC RESEARCH

1. Fotios Karagiannis et al., "Lipid‑Droplet Formation Drives Pathogenic Group 2 Innate Lymphoid Cells in Airway Inflammation". Immunity. 2020. https://doi.org/10.1016/j.immuni.2020.03.003. [Experimental study showing the effect of ketogenic diet on ILC2s in murine models]
2. Ya‑Jen Chang et al., "The ketone body β‑hydroxybutyrate mitigates ILC2‑driven airway inflammation by regulating mast cell function". Cell Reports. 2022. https://doi.org/10.1016/j.celrep.2022.111437. [Study on BHB and mast cell/ILC2 regulation]
3. Yun‑Hee Youm et al., "The ketone metabolite β‑hydroxybutyrate blocks NLRP3 inflammasome–mediated inflammatory disease". Nature Medicine. 2015. https://doi.org/10.1038/nm.3804. [Molecular mechanism: inhibition of NLRP3 inflammasome by BHB]
4. Very‑low‑carbohydrate diet enhances human T‑cell immunity through immunometabolic reprogramming. EMBO Molecular Medicine. 2021. https://doi.org/10.15252/emmm.202114323. [Human intervention on low carb diet and effects on T lymphocytes]
5. Shafiei‑Jahani et al., "Dietary Fiber‑Induced Microbial Short Chain Fatty Acids Suppress ILC2‑Dependent Airway Inflammation". Frontiers in Immunology. 2019. https://doi.org/10.3389/fimmu.2019.02051. [Role of SCFAs (butyrate) in modulating ILC2]
6. P. Puchalska & P.A. Crawford, "Multi‑dimensional roles of ketone bodies in fuel metabolism, signaling, and therapeutics". Cell Metabolism. 2017. https://doi.org/10.1016/j.cmet.2016.12.022. [Review on the metabolic and signaling roles of ketones]
7. J.C. Newman & E. Verdin, "β‑Hydroxybutyrate: A signaling metabolite". Annual Review of Nutrition. 2017. https://doi.org/10.1146/annurev-nutr-071816-064916. [Review on the role of BHB as a signaling molecule]
8. Doggett et al. (systematic review), "Weight Loss for Children and Adults with Obesity and Asthma". Annals of the American Thoracic Society. 2019. https://doi.org/10.1513/AnnalsATS.201810-651SR. [Evidence that weight loss improves asthma control in obese subjects]
9. Study: "Blocking the HIF‑1α/glycolysis axis inhibits allergic airway inflammation by reducing ILC2 metabolism and function". Allergy. 2023. https://doi.org/10.1111/all.16361. [Example of metabolic target of ILC2s]

Authors cited in the text: Christoph Wilhelm (Institute for Clinical Chemistry and Clinical Pharmacology, University of Bonn), Fotios Karagiannis (author of the study cited above). [ORCID data not present in the original input]