Leila Azadbakht - Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran
Hadis Mozaffari - Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran

Background and Aim: Acid-base status which can be affected by dietary acid load (DAL) has been associated with chronic disease including cardiovascular disease (CVD), metabolic syndrome (MetS), diabetes, gestational diabetes mellitus, obesity and even psychological disorders. However, published studies revealed conflicting findings regarding the association of DAL and chronic diseases. Therefore, the current study was conducted to determine the health outcomes of DAL. Methods: PubMed, ISI Web of Science, Scopus and Google Scholar were used to conduct a comprehensive search for articles published on this topic until August 2018. All the observational studies which assessed the association between risk factors of chronic disease including CVD, MetS, diabetes, obesity and psychological disorders in relation to DAL were included. We have also focused on our epidemiologic studies in Iran. Thirty five studies were included in the current review.Totally 9 studies showed a significant or marginally significant positive association between DAL and BMI. Also, 13 of included studies had no significant association between DAL and BMI. In addition, 1 study had no significant relationship between weight and DAL. Two studies showed a significant positive relationship between WC and DAL (Pvalue: 0.01; Pvalue: 0.0001); however, others did not find a significant association. With regard to BP, six studies indicated a positive significant relationship between SBP and DAL, whereas 5 studies had no significant association between SBP and DAL. In addition, 3 studies showed a positive significant association between DBP and DAL, whilst 5 studies had no significant relationship. Five studies found no significant relationship between FBS and DAL, as well insulin, HOMA-IR and HbA1c with DAL. However, one study found a significant positive relationship between FBS (Pvalue: <0.001), HbA1c (Pvalue: 0.006) and DAL. Akter et al. found a significant positive relationship between insulin, HOMA-IR and DAL. With regard to lipid profiles, 3 studies found no significant relationship between TG and DAL; however, other studies indicated a significant positive association. Three studies indicated no significant association between TC and DAL, but Murakami et al. and Berg et al. indicated a significant association. Several studies had no significant relationship between LDL and DAL, however, 2 studies indicated a significant association. Murakami et al., Berg et al. and Han et al. did not show a significant relationship between HDL and DAL, but one study showed a marginally significant positive association between DAL and HDL. Moreover, our case-control study on pregnant women in Iran showed that high DAL was associated with increased serum level of FBS (Pvalue: <0.001), HbA1C (Pvalue: 0.006), LDL (Pvalue:0.008), and TC (Pvalue: 0.01). There was also a strong positive association between high DAL and risk of gestational diabetes (ORPro/k: 7.60 95%CI: 3.43, 16.84; Ptrend<0.001) (ORPRAL: 9.27 95%CI:4.00, 21.46; Ptrend <0.001) in this study. Another epidemiologic study in Iran regarding the association of DAL with CVD risk factors in patients with diabetic nephropathy showed that high DAL was associated with higher HbA1c (Pvalue:0.01) , SBP (Pvalue:0.03), but lower serum level of FBS (Pvalue:0.01), LDL-C (Pvalue:0.0001), and WC (Pvalue:0.01). Another cross-sectional study in Iran reported a positive association between DAL and depression (ORPRAL: 3.57 95%CI:2.18, 5.84; Ptrend= 0.0001), anxiety (ORPRAL: 3.41 95%CI: 2.13, 5.47; Ptrend= 0.0001), and psychological distress(ORPRAL: 3.56 95%CI: 2.22, 5.70; Ptrend= 0.0001). Moreover, another cross-sectional on Iranian healthy women reported a significant positive link between DAL and obesity (OR: 3.07 95%CI: 1.92, 4.93; pvalue: 0.0001), WC (OR: 2.27 95%CI: 1.37, 3.75; pvalue: 0.001), serum level of TG (ORPRAL: 4.28 95%CI: 1.67, 10.99; pvalue: 0.002) (ORNEAP: 4.92 95%CI: 1.87, 12.92; pvalue: 0.001). Conclusion: Most well-designed studies showed a positive association between high DAL with BP, and BMI. Based on the results from studies in Iran, DAL was associated with CVD risk factors in our society. There was a significant relationship between high DAL and risk of depression, anxiety, and psychological distress in Iranian epidemiologic study. Moreover, a positive link between DAL and risk of gestational diabetes was reported in Iran. In addition, DAL was positively associated with CVD risk factors in Iranian patients with diabetic nephropathy.

dietary acid load, cardio-metabolic risk factors, psycological disorder, diabetes, obesity, Observational studies