In a recent study published in The Journal of Nutrition, researchers investigate the associations between avocado consumption and diabetes risk.

Study: Associations between Metabolomic Biomarkers of Avocado Intake and Glycemia in the Multi-Ethnic Study of Atherosclerosis. Image Credit: Krasula / Shutterstock.com

Do we need patient-specific biomarkers for predicting T2D risk?

Type 2 diabetes (T2D) affects 10.5% of the world's adult population, over 50% of whom remain unaware that they are living with the condition. In recent decades, T2D prevalence has increased significantly, especially in developing countries. The International Diabetes Federation (IDF) predicts that the global prevalence of T2D will increase by 46% by 2045, thus projected to affect approximately 783 million adults worldwide.

Living with T2D increases an individual's risk of several comorbidities, including overweight and obesity, heart and cardiovascular disease, sleep disruptions, dyslipidemia, hypertension, and cancer. Comorbidities often arise from poor glycemic control and occur together, severely affecting individual quality of life and daily functioning.

Recent research has aimed to prevent or delay the onset and progression of T2D and has identified diet, sleep, and exercise as the best non-pharmacological interventions. Weight management and dietary interventions have received particular attention due to their direct impacts on glycemic regulation, thus allowing these interventions to manage T2D and its most common comorbidities.

Most dietary research has explored the effects of 'healthier diets' and their nutritional components, either as food components consumed individually or as meals comprising multiple food items. Studies on the metabolomic and gut microbiota modulators of nutritional uptake remain lacking.

Previous work by the current research group revealed that avocado-glycemic interactions were sensitive to participant-specific metabolic health, suggesting that dietary results may vary significantly from person to person. Avocados are rich in fiber and monounsaturated fatty acids (MUFAs), which allude to the fruit's benefits in aiding glucose homeostasis, thereby managing T2D.

Metabolomic studies would likely reveal individual-specific responses to dietary components and elucidate the mechanisms underlying nutrient digestion, processing, and absorption. Therefore, these studies are vital tools in investigating the beneficial impacts of food items toward clinically desirable outcomes.

About the study

In the present study, researchers evaluate the association between avocado consumption and T2D risk. Several metabolomic examinations were used to determine whether habitual avocado intake and its associated metabolites may reduce fasting glucose and insulin levels, thereby lowering T2D risk.

The study population was derived from the ongoing Multi-Ethnic Study of Atherosclerosis (MESA), which comprised 6,814 adults aged 45-84 years recruited between 2000 and 2002 from six locations across the United States. Inclusion criteria included a lack of cardiovascular disease (CVD) at recruitment-measured baseline and self-reported ancestry (white, black, Asian, or Hispanic). Participants were followed up at 18-month intervals since recruitment, with the most recent follow-up conducted in 2018.

Of the total MESA sample cohort, 557 participants were allergic to avocado, and 37 lacked baseline dysglycemia data, thus resulting in their exclusion from the study. Metabolomic data was available for 3,438 randomly subsampled participants.

Dietary data collection was conducted using the MESA FFQ questionnaire, which includes intake frequency and quantity of 120 food items that were subsequently categorized into 47 food groups. Intake data was dichotomized into nonconsumers and consumers. Previous research on the Mediterranean-style diet was used to score the nutrient content and overall 'healthiness' of participant diets.

Fasting serum samples collected during baseline assessment were used for untargeted metabolomic profile generation using a standard proton nuclear magnetic resonance (NMR) analyzer. Obtained spectra and their chemical shifts were baseline-corrected and calibrated to standard glucose signals.

Metabolite annotation involved additional spectral data generated from 2D NMR, 2D J-resolved, correlation spectroscopy, total correlation spectroscopy, heteronuclear single quantum correlation spectroscopy, and statical correlation. Subset optimization by reference matching (STORM) analyses were used for the final annotation, which was then compared to the Human Metabolome Database.

Fasting serum collected during baseline assessment was used to measure fasting insulin and glucose levels. Dysglycemia status was derived from the American Diabetes Association (ADA) 2003 criteria, defining T2D as fasting glucose levels of 126 mg/dL or greater. Demographic, physical activity, and anthropometric measurements were collected through questionnaires during baseline and follow-up examinations.

Study findings

Modest associations were observed between participant-reported avocado consumption and fasting insulin; however, these associations were not statistically significant when controlling for participant body mass index (BMI). Three metabolomic spectral features strongly and significantly correlated with reduced fasting glucose and insulin rates. Since these features were highly intra-correlated, they were combined into a single avocado biomarker.

The derived avocado biomarker showed a strong and significant association with reduced T2D risk, even after accounting for sociodemographic factors, anthropometric measurements, health behaviors, including smoking and alcohol consumption, and measures of adiposity, including BMI. Despite lower analytical power intrinsic to the current study design, subgroup-level differences were observed in participants with- and without dysglycemia, corroborating previous work.

Participants with normoglycemia exhibited weaker associations with reduced glucose and insulin levels and T2D risk than those with dysglycemia. Taken together, these findings suggest gut microbiome differences between cohorts, which could alter food item processing and nutrient uptake.

Our analyses contribute to a growing body of work demonstrating that diet-health investigations benefit from metabolomic data, which serve as individualized biomarkers of food intake after digestion, metabolism, and absorption."

Journal reference:

• Wood, A. C., Goodarzi, M. O., Senn, M. K., et al. (2023). Associations between Metabolomic Biomarkers of Avocado Intake and Glycemia in the Multi-Ethnic Study of Atherosclerosis. The Journal of Nutrition 153(10); 2797-2807. doi:10.1016/j.tjnut.2023.07.013