1.1. Fatty acids
In relation to lung conditions, especially COPD, dietary intake of n‐3 polyunsaturated fatty acid (FUFA) has been suggested to improve the lung function due to anti‐inflammatory and antioxidative stress effects (Rawal & Yadav, 2015). Results from two large cohort studies in the United States of 120,175 participants showed a significantly reduced risk of newly diagnosed COPD among subjects more frequent fish intake (hazard ratio [HR] = 0.71, 95% CI = 0.54–0.94) (Varraso, Barr, Willett, Speizer, & Camargo Jr., 2015). However, the effect of fatty acids as well as n‐3 FUFAs was found to be nonsignificant (Varraso et al., 2015). Like n‐3 FUFAs, epidemiological evidence for the effect of n‐6 FUFAs on COPD prevention was inconsistently reported (Hirayama et al., 2010; McKeever et al., 2008; Varraso et al., 2015). In addition, data from the National Health and Nutritional Examination Survey of 11,180 participants did not show any significant association between dietary saturated fatty acids (SFA) and lung function (Cornell et al., 2019).
Regarding CVD risk, a recent meta‐analysis of cohort studies found the borderline effect of dietary total fat, saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), and FUFA, with HRs (95% CIs) of 0.97 (0.93–1.01) (N = 45), 0.97 (0.93–1.02) (N = 56), 0.97 (0.93–1.01) (N = 43), and 0.97 (0.93–1.00) (N = 45) (Zhu, Bo, & Liu, 2019). Among FUFAs, n‐3 FUFA was found to significantly reduce the risk of CVD, with RRs (95% CIs) ranging between 0.89 (0.82–0.98) to 0.90 (0.85–0.96), whereas findings for n‐6 FUFA and total FUFAs did not reach the consistency in the umbrella review (Chareonrungrueangchai, Wongkawinwoot, Anothaisintawee, & Reutrakul, 2020). Pooled estimates from another meta‐analysis found that n‐3 FUFA supplementation was associated with lower risks of coronary heart disease (RR = 0.90, 95% CI = 0.85–0.96) and myocardial infarction (RR = 0.89, 95% CI = 0.80–0.99), but not for total CVD (RR = 0.98, 95% CI = 0.95–1.01) and stroke (RR = 0.88, 95% CI = 0.71–1.10) (Hoang & Kim, 2020).
Furthermore, data of 28,100 women reported that dietary intake of n‐3, n‐6, total PUFAs, MUFA, and SFA were not associated with incident hypertension, with RRs (95% CIs) of 1.01 (0.96–1.07), 0.99 (0.94–1.05), 1.03 (0.98–1.10), 1.05 (0.99–1.12), and 1.04 (0.97–1.11), respectively (Wang et al., 2010). Besides, dietary intake of fish and marine n‐3 FUFAs in Asian populations and regular‐fat dairy foods in Western populations was shown to related to a reduced risk of diabetes (Rice Bradley, 2018).
Nonalcoholic fatty liver disease has been the leading cause of chronic liver disease. A high dietary intake of MUFAs or PUFAs was found to be beneficial for the prevention of nonalcoholic fatty liver disease, whereas a possible harmful effect was observed for a high dietary intake of SFAs (Perdomo, Fruhbeck, & Escalada, 2019; Ullah et al., 2019). Despite the lack of evidence from different populations, dietary PUFA intake from the Southern Community Cohort Study of 1,074 cases and 3,230 controls was shown to be not associated with end‐stage renal disease, with RRs (95% CIs) of 0.93 (0.71–1.21), 0.81 (0.61–1.06), and 0.79 (0.60–1.05) for n‐3, n‐6, and total PUFAs, respectively (Malhotra et al., 2016). In terms of cancer risk, a recent umbrella review of 57 meta‐analyses reported nonsignificant or weak associations between n‐3 PUFAs and different cancer types (Lee et al., 2020).
Overlapping mechanisms for the effect of resveratrol on both lung and muscle might suggest the potential benefit of resveratrol in COPD patients (Beijers, Gosker, & Schols, 2018). Several inflammatory cytokines such as nuclear factor kappa B, tumor necrosis factor, and matrix metalloprotease‐9 protein expression in lymphocytes were observed to be higher in COPD patients than in healthy controls and were reduced after treatment with resveratrol (Beijers et al., 2018). Additionally, antioxidant properties of resveratrol on both lung and muscle would be beneficial to reduce the lung injury in COPD (Beijers et al., 2018).
Dyck et al. recently reviewed the effect of resveratrol on different conditions related to CVD (Dyck, Raj, Zieroth, Dyck, & Ezekowitz, 2019). Since the evidence from randomized controlled trials for the endothelial improvement and plasma low‐density lipoprotein cholesterol lowering effects has still been contradictory, further studies were suggested to confirm the effect of resveratrol on CVD prevention (Dyck et al., 2019). In terms of hypertension, meta‐analyses revealed that resveratrol supplementation might have the blood pressure lowering effect at high doses (Dyck et al., 2019). Regarding diabetes, a meta‐analysis of 11 individual studies showed that resveratrol consumption significantly reduced fasting glucose, insulin, glycated hemoglobin, and insulin resistance levels in the subgroup of diabetes patients (Dyck et al., 2019; Ma et al., 2017). However, these significant findings were not observed in the subgroup of nondiabetes subjects (Ma et al., 2017).
Furthermore, the evidence for the beneficial effect of resveratrol on other comorbidities including chronic liver diseases (Ma et al., 2017), chronic kidney diseases (Den Hartogh & Tsiani, 2019; Kitada & Koya, 2013), and cancer prevention has still limited, as most evidences from preclinical studies were available only (Ko et al., 2017; Vervandier‐Fasseur & Latruffe, 2019; Xiao et al., 2018).