A Quiet Win for the Soybean: Isoflavones and Living Better With COPD
- Joyce Knieff, ND, LAc
- Jun 1
- 7 min read
If you have COPD, you already know the daily picture. Some mornings the cough is louder than it was the night before. Some afternoons a flight of stairs feels longer than it used to. Most clinical conversations turn on inhalers, exacerbation prevention, and getting through the next winter without a hospital visit. Diet usually gets a passing mention. A small new study out of Johns Hopkins makes a case that one specific piece of the diet, the isoflavones in soy and other legumes, may belong higher up in the conversation than it has been.
TL;DR: A small Johns Hopkins study links higher dietary soy isoflavone intake to milder COPD symptoms, though it's a dietary association, not a prescription.
Key takeaways:
In 99 people with COPD, higher soy isoflavone intake tracked with milder symptoms.
This is observational data, not a trial, so soy isn't a prescribed treatment.
The evidence is for whole foods: tofu, tempeh, edamame, miso, lentils, beans.
Concentrated isoflavone supplements differ; ask a clinician if you have hormone-sensitive history.
What the research found
The study, published in March 2026 in Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation, followed 99 former smokers living with COPD over six months. The team, led by Daniel Belz and Ernesto Quiroz, asked each participant to fill out a detailed food frequency questionnaire, then calculated total isoflavone intake from the five most studied compounds: genistein, daidzein, glycitein, formononetin, and biochanin A. Symptom burden was measured with several standard questionnaires that capture how much COPD is interfering with daily life. Markers of platelet activation, inflammation, and oxidative stress came from spirometry and lab work.
The average isoflavone intake was modest, about 1.8 mg per day, which lines up with a typical American diet where soy is incidental rather than central. Within that range, a one-standard-deviation jump in isoflavone intake (roughly an extra 3 mg per day) was associated with measurably better symptom scores on the COPD Assessment Test, the Clinical COPD Questionnaire, and a metric called the Ease of Cough and Sputum Clearance. Urinary 11-dehydro-thromboxane B2, a marker of platelet activation that runs high in COPD, was 7.4 percent lower in higher-isoflavone consumers. Exacerbation rates and one of the breathlessness scores didn't change in this small cohort.
This is observational data from a cohort study, not a randomized trial. Eating more soy isn't being prescribed as treatment. What it does show is a consistent enough signal across multiple symptom measures and a downstream inflammatory marker to take seriously, especially in a disease where small daily-quality-of-life gains matter.
Where this fits in the broader literature
The Johns Hopkins paper isn't the first time this signal has shown up. A 2010 Japanese case-control study of 278 COPD patients and 340 controls found that COPD patients had significantly lower habitual isoflavone intake than people without the disease, and the highest-intake group had about a 64 percent lower odds of having COPD compared with the lowest-intake group. That study also linked higher intake to better spirometry. The Japanese diet, with regular soy in the form of tofu, edamame, miso, and natto, was offered as part of the explanation for the country's comparatively lower COPD burden.
A 2024 paper in the American Journal of Clinical Nutrition looked at the broader question across nearly 120,000 UK Biobank participants and found that moderate to high intake of dietary flavonoids was associated with up to an 18 percent lower risk of developing COPD, with the strongest effect in current and former smokers. Inflammation appeared to mediate part of that protection.
The story across these studies is reasonably consistent. Higher intake of soy-family compounds and the broader flavonoid family tracks with better respiratory outcomes, particularly in people with smoking exposure. The new cohort study extends the picture from prevention into management, which is the question most people already living with COPD actually want answered.
The naturopathic perspective
COPD is fundamentally an inflammatory disease. The mucus, the cough, the airway remodeling, the breathlessness all sit downstream of a chronic inflammatory state in the lungs that doesn't switch off the way an acute illness does. Whatever lowers the inflammatory tone of the system in a sustained way tends to help. Isoflavones are one of several plant compounds that interact with that tone, with antioxidant activity, anti-inflammatory signaling, and the platelet-activation pathway that the Belz study specifically measured.
This is the kind of finding that fits a whole-person frame well. The lungs aren't an isolated organ. They sit in a body that is also processing food choices, sleep quality, stress load, environmental exposures, and the microbial environment of the gut, which has its own conversation with the immune system that decides how the lungs respond to triggers. Diet quality is one of the few daily inputs a person actually has leverage over. A modest, sustained shift toward more legumes and soy foods, in the context of an otherwise food-as-medicine-friendly diet, is a low-cost, low-risk intervention that lines up with a growing pile of evidence.
The corollary matters too. Isoflavones aren't a pill substitute. The Hopkins data suggest a dietary pathway, not a supplement protocol. The whole-foods version of this story is tofu, tempeh, edamame, miso, soy milk, and the broader legume family (lentils, chickpeas, beans), eaten regularly. Concentrated isoflavone supplements behave differently in the body and have their own considerations, particularly for anyone with hormone-sensitive cancer history or who is on certain medications. The dietary form is the one with the evidence behind it.
How to apply this now
A few practical pieces, if you are living with COPD or know someone who is. Build in a regular serving of soy or other legumes most days of the week. A bowl of lentil soup, a stir-fry with tofu, edamame as a snack, hummus on whole-grain bread, a sprinkle of miso into soups and dressings. Pair it with the broader anti-inflammatory eating pattern that has the most evidence behind it: plenty of colorful vegetables and fruit, olive oil, nuts and seeds, fatty fish a couple of times a week, and a sharp reduction in ultra-processed foods. Hydrate, because mucus clearance depends on it. Keep moving in whatever way your lung function allows, because muscle strength and breathing efficiency both depend on regular use. And work with your pulmonologist on the medications and pulmonary rehab side of your care, because diet sits alongside that work, not instead of it.
If you have a personal or family history of hormone-sensitive cancer, or you are on medications where soy intake could matter (thyroid hormone replacement is the most common example), the conversation about how much soy fits your picture is worth having with a clinician who knows your full history.
References
Belz DC, Quiroz E, Woo H, et al. Isoflavone Intake is Associated With Decreased Chronic Obstructive Pulmonary Disease Morbidity. Chronic Obstr Pulm Dis. 2026;13(2):125-135. PMID: 41738766. DOI. Original AANP digest link: https://journal.copdfoundation.org/jcopdf/id/1583/Isoflavone-Intake-is-Associated-With-Decreased-Chronic-Obstructive-Pulmonary-Disease-Morbidity
Hirayama F, Lee AH, Binns CW, et al. Dietary intake of isoflavones and polyunsaturated fatty acids associated with lung function, breathlessness and the prevalence of chronic obstructive pulmonary disease: possible protective effect of traditional Japanese diet. Mol Nutr Food Res. 2010;54(7):909-917. PMID: 20112297. DOI.
Bondonno NP, Parmenter BH, Thompson AS, et al. Flavonoid intakes, chronic obstructive pulmonary disease, adult asthma, and lung function: a cohort study in the UK Biobank. Am J Clin Nutr. 2024;120(5):1195-1206. PMID: 39222688. DOI.
Gozzi-Silva SC, Teixeira FME, Duarte AJDS, Sato MN, Oliveira LM. Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve? Front Nutr. 2021;8:674258. PMID: 34557509. DOI.
A note before you go
This is for educational purposes and is not a substitute for individualized medical care. If you live with COPD or any chronic respiratory condition, please work with a clinician who can take your full picture into account, including any conditions or medications that interact with dietary changes.
Frequently asked questions
Should I start eating more soy if I have COPD?
There's probably no harm in it, and possibly some benefit. The data here are early and observational, so think of soy and other legumes as one supportive piece of an anti-inflammatory diet, not a treatment that replaces your inhalers or pulmonary rehab. If you tolerate soy and enjoy it, working it in regularly is a reasonable, low-risk move.
How much soy are we talking about?
Less than you'd guess. The people in the study who did better were eating only a few milligrams of isoflavones more per day than average, which is roughly the difference a regular serving of tofu, edamame, or miso makes. You don't need to overhaul your plate. A legume habit most days of the week is the idea, not a soy-heavy diet.
Are soy supplements as good as eating the food?
The evidence here is for food, not pills. Concentrated isoflavone supplements behave differently in the body and carry their own considerations, particularly if you have a hormone-sensitive cancer history or take thyroid medication. The whole-food version, tofu, tempeh, edamame, miso, lentils, and beans, is the one with the research behind it.
Who should be cautious with soy?
If you have a personal or family history of hormone-sensitive cancer, or you take thyroid hormone replacement, it's worth talking through how much soy fits your picture with a clinician who knows your history. For most people, soy as a food is well tolerated and nutritious.
Does this mean diet can replace my COPD medications?
No. Diet sits alongside your medical care, not in place of it. Keep working with your pulmonologist on medications and pulmonary rehab. The soy-and-legumes piece is a low-cost addition that may help with day-to-day symptoms. It isn't a substitute for the rest of your treatment.
Related reading
Reviewed by Joyce Knieff, ND, LAc on 2026-06-01.
If this resonates with what you're experiencing and you'd like to explore a naturopathic approach, book a consultation with our clinic.