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The results of a network meta-analysis, which evaluated the use of various nutritional supplements for chronic obstructive pulmonary disease (COPD), were published in BMC Pulmonary Medicine. This analysis included 37 randomized and controlled trials, a total of nearly 2,000 participants with COPD, and 21 nutritional interventions. Network analysis allows for a rough comparison between interventions that have not necessarily been compared directly. COPD was defined in these studies as a Forced Expiratory Volume in One Second to Forced Vital Capacity (FEV1/FVC) ratio <70% of the predicted value. This review provides a useful source of recent nutritional trials for COPD, though it had a number of inaccuracies and limitations.
The supplements associated with improved lung function included nanocurcumin, butyrate, and probiotics, with nanocurcumin associated with the largest overall improvement in lung function, including an improvement in FEV1 and a slowed decline in FEV1/FVC. It should be noted that this benefit of nanocurcumin was based on a recent single study published in Phytotherapy Research, which enrolled 60 participants with COPD in Iran, who received either nanocurcumin or a placebo for 3 months. This double-blind and randomized trial reported a significant increase not only in FEV1 and FEV1/FVC compared to placebo, but also a significant drop in the inflammatory cytokine IL-6, and systolic blood pressure. The only previously published study evaluating the use of a bioavailable form of curcumin among people with COPD (not included in this meta-analysis) did not find a change in FEV1 compared to placebo (it may not have been adequately powered to do so), but did see a decrease in the inflammatory marker AT-LD (α1-antitrypsin–low-density lipoprotein), known for its pro-atherosclerotic effects. Certainly, larger and longer trials with nanocurcumin would be helpful.
Similarly, the research cited around butyrate in this review is less than helpful for measuring lung function (the citation provided for the use of 300mg butyrate per day was for vitamin D supplementation). The presumed trial referred to (and the only published clinical trial for COPD) suggests that butyrate may improve intestinal permeability among people with COPD, with a resulting reduction in sarcopenia and several improved markers of physical function. Despite these encouraging signs, no assessment of lung function was mentioned in this study.
Similarly, the probiotic study cited in this review was also associated with reduced intestinal permeability (e.g., reduced plasma zonulin, claudin-3), as well as improved handgrip strength and other markers of physical performance. Yet, no measures of lung function were included in this study, raising another red flag about the accuracy of the meta-analysis. A previous meta-analysis of 3 randomized trials did find an improvement in FEV1, as well as a reduction in some inflammatory biomarkers.
This recent meta-analysis also reported on exercise endurance, marked by the 6-minute walk distance (6MWD). Coenzyme Q10 combined with creatine emerged as having the largest benefit. At least two clinical trials have been performed with this combination of 320mg CoQ10 and 340mg creatine per day, which found benefits including an increase in 6MWD, dyspnea index, activities of daily living questionnaire, and exercise tolerance. Creatine alone did not seem to enhance the benefits of pulmonary rehabilitation in a previously published clinical trial, so perhaps the combination of CoQ10 and creatine has an additive effect.
Lastly, the meta-analysis included results for the effects of nutritional supplements on dyspnea and quality of life, with the largest benefits attributed to melatonin and yam‑epimedium (a mixture of Chinese yam and epimedium, also known as horny goat weed). A single study was included for each; in one, melatonin (3mg per day) or a placebo was given to 39 participants with COPD for 12 weeks, with melatonin associated with improved 6MWD and quality of life. A previous study with melatonin found improved dyspnea and oxidative stress, despite no change in lung function. The single study evaluating yam-epimedium included 49 participants with moderate to severe COPD who received either the mixture or a placebo twice daily for 3 months. The yam mixture was associated with improvements in St. George's respiratory questionnaire (SGRQ) and the BODE index (used to assess COPD severity), including scores related to dyspnea and respiratory symptoms, exercise tolerance, and the 6MWD.
It's also worth noting that a number of relevant nutrients were not included in this meta-analysis, and only a limited number of studies for specific nutrients. For example, only one study related to vitamin D appears to have been included, which had a total of 50 participants randomized to either 1,200 IU vitamin D per day or placebo, with no observed benefits after 6 months. However, a much larger study previously published in The Lancet, Respiratory Medicine found that among people with a serum 25-hydroxyvitamin D level of less than 50 nmol/L, vitamin D protected against moderate and severe exacerbations (nearly ½ the risk), though here too the results have been mixed. Similarly, N-acetylcysteine was found to significantly reduce the incidence of exacerbations among people with COPD and chronic bronchitis in a meta-analysis of twenty studies, yet was not mentioned in this recent meta-analysis. Despite its limitations, this meta-analysis does point to several promising therapies with complementary mechanisms of action to support lung function, exercise endurance, and quality of life among people with COPD.
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