This study was designed to assess the relationship between dietary insulin index (DII) and dietary insulin load (DIL) and rheumatoid arthritis (RA) risk in a case–control study. This study enrolled ninety-five newly diagnosed RA patients and 200 age- and sex-matched healthy controls. Dietary intakes were assessed using a validated 168-item semi-quantitative FFQ. DII and DIL were calculated using food insulin index values from previously published data. In the unadjusted model, individuals in the highest DIL tertile had the significantly higher odds of RA than those in the lowest tertile of the DIL scores (OR = 1·32, 95 % CI (1·15, 1·78), Pfor trend = 0·009). After adjusting for confounders, the risk of RA was 2·73 times higher for participants in the highest tertile of DIL than for those in the lowest tertile (OR = 2·73, 95 % CI (1·22, 3·95), Pfor trend < 0·001). In addition, patients in the highest DII tertile had higher risk of RA than those in the first tertile (OR = 2·22, 95 % CI (1·48, 3·95), Pfor trend = 0·008). This association persisted after adjusting for potential confounders (OR = 3·75, 95 % CI (3·18, 6·78), Pfor trend = 0·002). Our findings suggest that diets high in DII and DIL may increase the risk of developing RA, independent of other potential confounders. These findings can be verified by more research, particularly with a prospective design.

The progression of cardiometabolic diseases is determined by both genetic and environmental factors. Gene–diet interactions may therefore be important in modulating the risks of developing metabolic diseases. The objectives were to investigate the effect of the interaction between brain-derived neurotrophic factor (BDNF) Val66Met polymorphisms and dietary insulin index (DII) and dietary insulin load (DIL) on cardiometabolic markers among diabetic patients. In this cross-sectional study, blood samples were collected from 667 patients. DIL and DII were defined using a validated FFQ. Genotyping the BDNF Val66Met polymorphism was conducted by the PCR-Restriction fragment length polymorphism (RFLP) method. Interactions between dietary indices and gene variants were evaluated using a generalised linear model. PGF2a concentrations were significantly higher among Val homozygotes than Met-allele carrier. This study revealed that, compared with individuals with the Val/Val genotype, those with the Met/Val or Met/Met genotype had lower BMI (Pinteraction = 0·04), TAG (Pinteraction = 0·04), leptin (Pinteraction = 0·01), LDL (Pinteraction = 0·04) and total cholesterol (Pinteraction = 0·01) when they consumed diets higher on the DIL index. Moreover, the highest quartile of the DIL, compared with the lowest, showed increase in waist circumference (Pinteraction = 0·02) and LDL/HDL (Pinteraction = 0·04) for Val/Val homozygotes compared with Met-allele carriers. BDNF Val66Met variants may interact with DIL and DII, thus be involved in the development of cardiometabolic risk factors. If diabetic patients with Met alleles regulate dietary intakes, they have a protective opportunity to regulate their cardiometabolic markers.

The dietary insulin index directly estimates the postprandial insulin secretion potential of foods, whereas the empirical dietary index for hyperinsulinaemia (EDIH) assesses the insulinaemic potential of usual diets based on fasting plasma C-peptide, and is primarily reflective of insulin resistance. It is unknown whether these insulin-related indices are predictive of an integrated measure of insulin secretion. We conducted a cross-sectional analysis that included 293 non-diabetic men with 24-h urinary C-peptide data from the Men’s Lifestyle Validation Study. EDIH, dietary insulin index and dietary insulin load were calculated using validated FFQ. We conducted multivariable-adjusted linear regression to estimate relative and absolute concentrations of 24-h urinary C-peptide. In multivariable-adjusted models, we found a significant positive association between all three insulin-related dietary indices and 24-h urinary C-peptide (P < 0·05). Relative concentrations of 24-h urinary C-peptide per 1-sd increase in insulin-related dietary indices were 1·12 (95 % CI 1·02, 1·23) for EDIH, 1·18 (95 % CI 1·07, 1·29) for dietary insulin index and 1·16 (95 % CI 1·06, 1·27) for dietary insulin load. When we further adjusted for BMI, the association was attenuated for EDIH, to 1·07 (95 % CI 0·98, 1·16), and remained unchanged for dietary insulin index and dietary insulin load. In conclusion, EDIH, dietary insulin index and dietary insulin load were predictive of integrated insulin secretion assessed by 24-h urinary C-peptide. Findings after adjustment for BMI appear to confirm the relation of EDIH to insulin resistance and dietary insulin index/load to insulin secretion; the respective constructs of the two dietary indices.

The present study was carried out to determine whether the dietary insulin index (DII) and dietary insulin load (DIL) are related to psychological disorders in a cross-sectional study among adults. A total of 3172 Iranian adults (age range of 18–55 years) were included. Data on dietary intakes were collected using a validated dish-based 106-item semi-quantitative FFQ. DII and DIL were calculated using food insulin index values published earlier. To assess depression and anxiety, an Iranian validated version of the Hospital Anxiety and Depression Scale was used. Furthermore, psychological distress was examined using the General Health Questionnaire. Among women, a significant positive association was seen; such that women in the highest quartile of DIL had higher odds of depression than those in the lowest quartile (OR 1·84; 95 % CI 1·14, 2·96). In terms of DII, in the fully adjusted model, women in the top quartile of DII were more likely to be depressed compared with those in the bottom quartile (OR 1·65; 95 % CI 1·05, 2·58). In conclusion, we found a significant positive association between DIL and DII and odds of depression among women, but not in men. However, such findings were not seen for anxiety and psychological distress.

Given the limited research on dietary insulin load (DIL), we examined DIL in relation to cardiovascular risk factors and inflammatory biomarkers in elderly men. For the present cross-sectional study, we recruited 357 elderly men. Dietary intake was assessed using FFQ. DIL was estimated by multiplying the insulin index of each food by its energy content and frequency of consumption and then summing the final value of all food items. After adjustment for covariates, a significant positive association was observed between high DIL with fasting blood sugar (FBS) levels (OR: 7·52; 95 % CI 3·38, 16·75; P=0·0001) and high-sensitive C-reactive protein (hs-CRP) (OR: 3·03; 95 % CI 1·54, 5·94; P=0·001). However, there was no association between high DIL and BMI (OR: 1·43; 95 % CI 0·75, 2·75; P=0·27), serum TAG level (OR: 0·82; 95 % CI 0·26, 2·59; P=0·73), HDL-cholesterol (OR: 2·03; 95 % CI 0·79, 5·23; P=0·13) and fibrinogen (OR: 1·57; 95 % CI 0·80, 3·06; P=0·18). Overall, elderly men with high DIL had higher FBS and hs-CRP levels than those with low DIL. Future studies are needed to clarify the association between DIL and other cardiovascular risk factors in both men and women.