Association of Dietary Acid Load with Insulin Sensitivity Index among Apparently Healthy Nigerians

cardiovascular diseases, malignancies and other The possible role of regular consumption of diets chronic metabolic disorders. It is a multi-with high acid forming potential in decreasing factorial disorder influenced by both genetic and cellular sensitivity to insulin and its associated environmental factors 2001; Pankow complications has been investigated. However, al. Abel al. , 2012). The rapid rise in findings across different study groups are the prevalence of type 2 diabetes mellitus, in conflicting. It is likely that the association is combination with earlier disease onset, affected by genetic and environmental factors especially in developing countries including that differ among different populations. We Nigeria has led to increased public health investigated the impact of diet-induced acidosis concern and a more focus on the delineation of on the degree of insulin sensitivity among strategies that may prevent or delay its onset apparently healthy adult Nigerians. Assessment (Uloko al., 2018; al. Recently of dietary intake was done using a semi-there is mounting evidence to suggest that quantitative food frequency questionnaire and regular consumption of diet with high acid load the Nigerian Food Composition Table. Acid increases body acidity and impairs glucose forming potential of our local diets were metabolism in humans by reducing cellular estimated as Potential Renal Acid Load (PRAL) sensitivity to insulin and predicts type 2 diabetes scores. Fasting plasma glucose and insulin were mellitus ., measured. Degree of insulin sensitivity was 2016; and 2020). calculated as Quantitative Insulin Sensitivity Check Index (QUICKI). About 35 (16.2%) of the The crucial role of dietary acid load in decreasing study subjects were observed to have insulin cellular sensitivity to insulin and predicting the resistance. Across the study groups, there was a risk of type 2 diabetes mellitus has been statistically significant trend with higher intake investigated; but findings across different study of dietary acid associated with decreased insulin groups are inconsistent or even conflicting sensitivity ( p for trend < 0.05 ). We conclude that (Schwalfenberg, among apparently healthy adult subjects in this study, regular consumption of diets with high acid forming potential might be linked with It worsening of insulin sensitivity.

evidence from studies in our setting with measured to the nearest 0.1kg, were obtained different dietary habits is clinically relevant to with each subject standing erect without shoes or enhance the generalizability of the findings and headgear. Body mass index was calculated as s u b s t a n t i a t e p r e v e n t i v e d i e t a r y weight in kilogram (kg) divided by height in 2 2 recommendations and also contribute to the meters squared (m ) and expressed as kg/m . identification of therapeutic targets.
Systolic and diastolic blood pressures were taken at rest in a sitting position using a mercury The aim of this present study was to evaluate the sphygmomanometer. effect of regular dietary acid intake on the risk of insulin resistance in a cohort of apparently Dietary assessment healthy Nigerian adult men and women.
Assessment of dietary intake was based on a semiquantitative food frequency questionnaire (FFQ).

Materials and Methods
The FFQ was administered to each of the subjects Study subjects and included all the local food items as identified by Two hundred and sixteen (216) apparently healthy their local names. Subjects were asked to recall all adult Nigerians, who gave informed consent, were foods and drinks they had consumed over the past included in this cross-sectional analytical hospitalweek and to estimate portion size and frequency of based study and comprised of 123 males and 93 consumption. Food items that are not initially part of females aged greater than 18 years. All the study the FFQ but are consumed by a study subject were subjects were enrolled from among individuals added to the list. For seasonal foods and foods not who presented to the general outpatient clinic of consumed by a subject during the past week but the Gombe State Specialist Hospital, Gombe, were part of their usual diet, monthly consumption Nigeria, for pre-marital screening, routine medical frequencies were determined and converted to check-up and blood donors.
weekly consumption frequencies. The consumption frequencies were then converted to daily and the The subjects were categorized in to four quartiles portion sizes were converted to grams using according to their median dietary acid load household measures. We used the Nigerian food scores. The study subjects were further composition table to determine the energy and categorized into two groups according to their nutrient content of all the food items. degree of insulin sensitivity and include thirtyfive (35) subjects who were insulin resistant Estimation of Dietary Acid Load (defined as QUICKI < 0.324) and one hundred Dietary acid intake was estimated using the and eighty-one (181) subjects with normal Potential Renal Acid Load (PRAL) score; The PRAL score was calculated based on nutrient insulin sensitivity (QUICKI 0.324) (Udenze, intakes using the following equation (Remer, 2003 subjects were collected into lithium heparin bottles. Each blood sample was immediately Data collection centrifuged for 15 minutes and the separated Each of the study subjects was assessed in the 0 plasma was stored in aliquots at -20 C until morning following 10-12 hours of overnight analysis. Plasma Insulin was assayed using a fasting. Basic demographic data and selfcommercially available human insulin enzymereported information on dietary intake were linked immunosorbent assay (ELISA) kit obtained and recorded. Body height, measured to (Monobind Inc. USA). Glucose was measured the nearest centimeter, and body weight, using glucose oxidase method (Agappe mean age and BMI of 26.2 ± 5.3 years and 24.5 ± 2 Diagnostics Limited, India). All laboratory 4.4 kg/m respectively, were included in the analyses were done at the Chemical Pathology study. No significant differences were observed laboratory of Gombe State University/Federal in the age and BMI statuses across the male and Teaching Hospital, Gombe.
The subjects were categorized in to four quartiles Fasting Plasma Insulin in µU/mL according to their PRAL scores ( Table 2). The Fasting Plasma Glucose in mg/dL median dietary PRAL scores in the first (Q1), second (Q2), third (Q3) and fourth (Q4) quartiles Definition of Insulin Resistance w e r e -2 2 . 5 m E q / d a y, + 6 . 5 m E q / d a y, Insulin Resistance was defined as QUICKI +12.0mEq/day and 41.5mEq/day respectively. values < 0.324 (Udenze, 2019).
The distributions of the subjects in terms of age and body mass index were not significantly Statistical analysis different across the quartiles of the PRAL scores Statistical analysis of data was done using (p for all > 0.05). Higher dietary acid intake was Statistical package for social sciences (SPSS) statistically significantly associated with lower version 20.0. Shapiro-Wilk test was used to test intakes of energy and potassium and higher for normality of distribution of data and intakes of magnesium, calcium, protein and logarithmic transformation was used to improve phosphorus (p for all < 0.05). the normality of distribution of skewed data. Quantitative variables were presented using Prevalence of insulin resistance among the study proportions and measures of central tendency subjects were presented in Table 3. About 35 and dispersion. Mean differences of the study (16.2%) of the study subjects were observed to have variables between the groups were compared insulin resistance, with higher prevalence among using t-test and ANOVA. Partial correlation male than female subjects (22.6% vs. 11.4%). analysis was used to determine relationship between the PRAL score and the QUICKI and to Higher intake of dietary acid was significantly adjust for confounders. All p-values were twoassociated with decreased insulin sensitivity sided and considered significant if less than 0.05. regardless of gender and independent of age, energy intake and body mass index as shown in Table 4 and Figure 1. Across the quartiles, there Results was a statistically significant trend with higher The basic characteristics study subjects were intake of dietary acid associated with decreased given in Table 1. A total of two hundred and insulin sensitivity (p for trend < 0.05). sixteen (216) subjects; including 123 males (56.9%) and 93 females (43.1%), with an overall      et al., 2016). Circulating level of adiponectin, an Nigerians. We found that consumption of foods insulin sensitizing adipocytokine, is lower in a with high acid-forming potential, as determined state of chronic acidosis because of the inhibitory by high PRAL scores, was significantly effect of acidosis on the adiponectin gene associated with decreased insulin sensitivity expression (Disthabanchong et al., 2010). The among apparently healthy individuals. The resulting hypoadiponectinemia has been overall prevalence of insulin resistance among suggested to be positively associated with the study subjects was observed to be 16.2%.
insulin resistance (Hanley et al., 2003;Yamamoto et al., 2004; Ziemke and Mantzoros, Our findings are in agreement with those from 2009). other investigators that reported positive relationship between consumption of diets with Limitations high acid load and risks of insulin resistance 1. The study is cross-sectional in nature; (Akter et al., 2016;Moghadam et al., 2016; therefore, we cannot be certain of causality. Gaede et al., 2018). Furthermore, it was reported 2. It was an observational study; and therefore, that regular consumption of food items with high residual confounders are still possible and alkalizing potential as fruits and vegetables is could influence the relationships. associated with decreased risk of type 2 diabetes 3. Quantitative insulin sensitivity check index mellitus (Schwalfenberg, 2012;Muraki et al., (QUICKI) was used to assess the degree of 2013; Wang et al., 2016).
insulin resistance, rather than the gold standard hyperglycemic clamp technique. However, in contrast to our findings, no 4. The study subjects were predominantly significant association was found between young and from Fulani ethnic group living in dietary acid load scores and insulin sensitivity in Gombe State, so the findings may not be a prospective study conducted among Swedish generalizable to other ethnic groups living in elderly men (Xu et al, 2014). Heterogeneity of other geographical regions with different the study subjects, including differences in dietary habits. d i e t a r y p a t t e r n s , s o c i o -d e m o g r a p h i c characteristics, mean ages, gender proportion Conclusion and body weight status might partially explain In summary, consumption of a diet loaded with high the discrepancies in the findings from the acid forming potential food items was associated p r e v i o u s s t u d i e s . S t u d i e s i n v o l v i n g with a decreased cellular sensitivity to insulin in a predominantly elderly subjects reported no group of apparently healthy adult Nigerians in this significant associations. study. We recommend further prospective studies to validate the findings. Interventional studies Mechanisms by which diet induced acidosis modifying the dietary acid intake are especially could contribute to the decreased cellular recommended to confirm the impacts on acid base sensitivity to insulin have been proposed.
balance and insulin sensitivity as well as its role in Decreased in blood pH could disrupt the binding the initiation and progression of type 2 diabetes of insulin to its receptors, by decreasing the mellitus in our setting. binding affinity of insulin to the insulin receptors, thereby inhibiting the early step in the Acknowledgement insulin signaling pathway; resulting in the We would like to express our appreciation to all possible decreased cellular glucose uptake and the study participants. There was no external insulin resistance (Igarashi et al.,1993; Hayata et funding source. The study was funded by al., 2014 Baldini and Avnet, 2018). Also, personal financial contributions from the sustained elevation of circulating cortisol, whose authors.