The goal of this study is to learn whether eating a small serving of almonds before meals can improve blood sugar control in adults who have early signs of problems with blood sugar regulation. The main questions it aims to answer are:
1. Does eating almonds before a meal reduce the rise in blood sugar after eating? 2. Do some people consistently benefit more than others from eating almonds before meals?
Adults aged 25-50 years
Females over 40 years must have had a cycle in the last 6 months
Body mass index (BMI) at least 18.5 and at most 55.0 kg/m2
Fasting blood glucose at least 100 mg/dL (5.6 mmol/L) and less than 125 mg/dL (6.9 mmol/L)
Weight change ≥5% in past 6 months, actively trying to lose weight, or unwilling to remain weight stable throughout the study based on self-report
Recent history within past 12 months of medical provider-diagnosed cardiovascular, renal, or liver disease that required treatment
Current or past diagnosis of cancer (except skin cancer) in the last 5 years
Current or past diagnosis of type 1 or type 2 diabetes
Crossover
Premeal almond ingestion
Dietary supplementPremeal almond ingestion (18 g; \~100 kcal) 30 minutes prior to meal
8
Treatment groupsSee each treatment group below.
Postprandial glucose assessed during acute meal test
The primary endpoint will be the difference in plasma glucose incremental area under the curve (iAUC) assessed via intravenous blood sampling over three hours following a standardized mixed meal tolerance test (MMTT) with premeal ingestion of 18 g of almonds 30 minutes prior (MMTT+) compared to without (MMTT-). This effect will be averaged across the replicated acute challenge visits in the repeated crossover design.
Interindividual variability in the postprandial glucose assessed during acute meal test
Variability in response to the single-dose, acute premeal almond supplementation prior to the MMTT will be characterized according to previously established procedures using Pearson's correlation between the first and second replicate of the control-adjusted treatment effect (i.e., MMTT+ vs MMTT-). That is, the correlation between the difference in iAUC during the first crossover trial (i.e., iAUC during MMTT+ minus iAUC during MMTT-) and the difference in iAUC during the second crossover trial (i.e., iAUC during MMTT+ minus iAUC during MMTT-).
Consistency between acute glycemic response and longer-term glycemic control
Whether the individual glucose-lowering effect of the almond preload observed during the acute, repeated crossover, controlled in-laboratory MMTT predicts an individual's glycemic control during the 10-day, free-living, controlled-feeding phase in which almonds will be consumed thrice daily prior to each main meal on the background of a Standard American diet. We will evaluate this via the regression coefficient derived from a linear regression with the magnitude of the acute treatment effect in Days 1-4 (i.e., the difference in iAUC between MMTT+ and MMTT- averaged between both crossover trials) as the predictor and the magnitude of the treatment effect in Days 5-25 (i.e., the difference in average iAUC across the 10-day controlled feeding diet periods between MMTT+ and MMTT-) as the outcome.
Acute postprandial glucose
The difference in plasma glucose assessed via intravenous blood sampling over three hours following a standardized mixed meal tolerance test (MMTT) with premeal ingestion of 18 g of almonds 30 minutes prior (MMTT+) compared to without (MMTT-). This effect will be averaged across the replicated acute challenge visits in the repeated crossover design.
Acute postprandial gastric emptying
The difference in acetaminophen appearance (gastric emptying) assessed via intravenous blood sampling over three hours following a standardized mixed meal tolerance test (MMTT) with premeal ingestion of 18 g of almonds 30 minutes prior (MMTT+) compared to without (MMTT-). This effect will be averaged across the replicated acute challenge visits in the repeated crossover design.
Acute postprandial insulin
The difference in plasma insulin assessed via intravenous blood sampling over three hours following a standardized mixed meal tolerance test (MMTT) with premeal ingestion of 18 g of almonds 30 minutes prior (MMTT+) compared to without (MMTT-). This effect will be averaged across the replicated acute challenge visits in the repeated crossover design.
Acute postprandial glucagon-like peptide 1
The difference in plasma glucagon-like peptide 1 assessed via intravenous blood sampling over three hours following a standardized mixed meal tolerance test (MMTT) with premeal ingestion of 18 g of almonds 30 minutes prior (MMTT+) compared to without (MMTT-). This effect will be averaged across the replicated acute challenge visits in the repeated crossover design.
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