Although previous studies have demonstrated the beneficial effects of some components of whole grains on premenstrual syndrome (PMS), our literature review shows that no clinical trial has studied the effect of whole grain consumption on PMS so far. Therefore, the present study was designed to study the effect of diets rich in whole grains on PMS among nurses. This study is a parallel controlled clinical trial with a 3-month intervention period in which, after following two menstrual cycles among nurses, 100 nurses diagnosed with PMS were randomly divided into two groups of intervention and control, with fifty individuals in each. Those in the intervention group replaced at least four servings of refined grains in their daily diets with whole grains. To supply four servings, 120 g of bread made with whole flour was given to the intervention group on a daily basis. Those in the control group, however, continued their regular daily consumption of grains. The two groups were compared regarding PMS symptoms after adjusting the confounding variables. The repeated measurement test showed that the interaction between the time factor and the experimental group on the mean score of PMS symptoms was significant. That is, the intervention group showed a significant decrease in the general, mood, physical and behavioural symptoms of PMS compared with the controls (P<0·001, P=0·01, P<0·001 and P=0·003, respectively). Therefore, daily consumption of whole grains in place of refined grains can contribute to improvement in PMS symptoms. Further studies are needed to confirm our findings.

The aim of this study was to perform a systematic review and meta‐analysis of randomized clinical trials (RCTs) to examine the effect of grapes/grape products supplementation on glycemic indices in adults. Our systematic search to find relevant RCTs was performed up to February 2020 using PubMed, Scopus, ISI Web of Science, Cochrane Library, and Google Scholar. Based on the heterogeneity between included studies, a random effects or a fixed model was applied in the meta‐analysis, and results were expressed as weighted mean differences (WMD) with 95% confidence intervals (CI). Twenty‐nine clinical trials (1,297 participants) fulfilled the eligibility criteria of the present meta‐analysis. Overall, the grapes/grape products supplementation significantly reduced homeostatic model assessment of insulin resistance (HOMA‐IR) (WMD: −0.54, 95% CI: −0.91, −0.17, p = . 004) but did not affect fasting insulin levels (WMD: −0.90 μIU/ml, 95% CI: −1.04, 2.84, p = .362) and hemoglobin A1C (Hb1Ac) percentage (WMD: 0.00%, 95% CI: −0.10, 0.11, p = . 916) in the main analyses. In addition, changes to fasting blood glucose (FBG) levels were in favor of the control group (WMD: 1.19 mg/dl, 95% CI: 0.05, 2.34, p = .041). We found that giving grapes/grape products to adults might have beneficial effects on the HOMA‐IR. Further, large‐scale RCTs with longer duration are required to confirm these results.