Nutcracker: Can Almond Nut Consumption Improve Nocturnal Glycaemic Control in Women With Gestational Diabetes Mellitus?

Gestational diabetes mellitus (GDM) is a significant and increasingly prevalent public health concern, affecting over one-sixth of births globally. A key challenge in its management is fasting hyperglycaemia, which may result from elevated nocturnal glucose concentrations. Nocturnal hyperglycaemia has been linked to an increased risk of large-for-gestational-age infants in women with GDM. These women are also more likely to snack at night, a behaviour associated with higher fasting glucose concentrations; however, the impact of snack quality on overnight glucose regulation remains unclear.

Almond consumption has been shown to improve glycaemia in individuals with prediabetes or type 2 diabetes, potentially through mechanisms such as carbohydrate displacement and the beneficial effects of their nutrient profile, particularly magnesium and monounsaturated fats. Despite this, research in pregnant populations-especially those with GDM-is limited.

This study will investigate whether consuming almonds as an evening snack for four weeks improves overnight glucose regulation in women with GDM. Participants will be randomised to receive either almonds or a nut-free, energy-matched control snack. Changes in glucose metabolism will be assessed to determine the potential role of almonds in dietary management of GDM.

• Almond Snack Intervention for Gestational Diabetes (Other): This intervention involves daily consumption of 43 g of whole almonds, split into two portions (afternoon and evening), for 28 days in pregnant women diagnosed with gestational diabetes who habitually consume evening snacks.
• Control (placebo) group (Other): This control involves the daily consumption of a nut-free snack (2 portions) that reflects a 'typical snack' choice among pregnant women with gestational diabetes. It serves as a comparison to assess the specific impact of almond-based evening snacking on overnight glucose regulation.

Primary outcomes

• Mean nocturnal blood glucose (22.00-07.00h) [The primary endpoint will be assessed on day 14 and day 28 of the intervention.]

Secondary outcomes

• Mean daytime glucose 07.00-22.00h [Assessed on day 14 and day 28 of the intervention.]: Recommended glucose control target 3.5-7.8mmol/L, AUC <6.7mmol/L, AUC <7.8mmol/L
• Postprandial blood glucose [Assessed on day 14 and day 28 of the intervention.]: Mean postprandial blood glucose for 1, 2 \& 4 hours after dinner.
• Glucose variability [Assessed on day 14 and 28 of the intervention.]: Glucose SD, glucose CV
• Blood glucose indices [Assessed on day 14 and 28 of the intervention.]: High and low blood glucose indices (HBGI \& LBGI)
• HbA1c [Assessed on day 0 and day 28 of the intervention.]: Biochemical analysis of maternal blood
• Liver function [Assessed on day 0 and day 28 of the intervention.]: Biochemical analysis of maternal blood: gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), aspartate aminotransferase (AST)
• Maternal metabolome (blood) [Assessed on day 0 and day 28 of the intervention.]: Lipid measures, including lipoprotein particles (VLDL subdivided into six subclasses, IDL, LDL subdivided into three subclasses, and HDL subdivided into four subclasses), constituents within each lipoprotein particle type (triglycerides, total cholesterol, free cholesterol and cholesterol ester levels and phospholipid concentrations), fatty acids, amino acids, glycolysis related metabolites, ketone bodies and inflammatory markers.
• Maternal weight in kg [Assessed on day 0 and day 28 of the intervention.]: Maternal weight and height will be combined to report BMI in kg/m\^2
• Dietary intake using questionnaire [Assessed on or around day 0 (x2), day 14 (x 2) and day 28 (x2) of the intervention.]: Assessment of dietary intake using Intake24, a validated digital dietary recall system based on the multiple-pass 24-hour recall
• Assessment of appetite on a Likert scale [Assessed on day 0, day 14, and day 28 of the intervention.]: Assessment of appetite on a 1-7 Likert scale (i.e., 1 = Not at all hungry, 7 = Extremely hungry)
• Physical activity using accelerometer [Assessed on days 0-28 of the intervention.]: The accelerometer will record physical activity, such as average time spent in moderate, low, and sedentary activity
• Stool [May be assessed on days 0, 14 and 28 of the intervention.]: (Optional) may be collected and stored for microbiome analysis
• Sleep quality using accelerometer [Assessed on days 0-28 of the intervention.]: The accelerometer will measure sleep quality, such as sleep duration
• Course of GDM [Assessed on days 0-28 of the intervention.]: If medication is required for glucose control, such as metformin or insulin (dose, time of initiation)
• Mode of delivery [Assessed at delivery.]
• Acceptability of the intervention using questionnaire [Assessed on day 28 of the intervention.]: A dietary intervention acceptability questionnaire will be used to assess enjoyment, sensory aspects, gastrointestinal effects, palatability, and appetite sensations.
• Birthweight [Assessed at delivery.]
• Neonatal head circumference [Assessed at delivery.]
• Neonatal sex [Assessed at delivery.]
• Gestational age [Assessed at delivery.]
• Neonatal complications [Assessed at delivery.]
• Maternal complications [Assessed at delivery.]
• Labour onset checklist [Assessed at delivery.]

Sex: Female, ages: 16 Years to 55 Years

Inclusion Criteria:

1. Age over 16 years
2. Singleton pregnancy
3. 25 to 31+6 weeks' gestation diagnosed with GDM using a standard clinical 75g oral glucose tolerance test (OGTT), as per the guidelines of the National Institute of Health and Care Excellence (NICE), and had their first post-diagnosis consultation (approx. 7-10 days later). The NICE criteria state that the diagnosis of GDM will be made with one or more glucose concentrations during the OGTT of >5.6 mmol/l in the fasting state; >7.8 mmol/l 2 hours after 75g glucose
4. Planned antenatal care at the same centre
5. GDm-Health (a digital app for the management of diabetes in pregnancy) used as part of their management for GDM
6. Willing and able to give informed consent

Exclusion Criteria:

1. Age under 16 years or over 55 years
2. Multiple pregnancy
3. Non-snack consumers
4. Smokers
5. Women who would work night shifts over the study period
6. Women who have already commenced insulin for the treatment of GDM
7. Allergy or intolerance to nuts
8. Pre-existing medical conditions, including Type 1 or Type 2 diabetes, chronic coronary, renal or bowel disease or history of cholestatic liver disease or pancreatitis. Presence of gastrointestinal disorder or use of a drug which is likely to alter gastrointestinal motility or nutrient absorption, previous bariatric surgery
9. Unwilling or unable to give informed consent

• Sara L White, Principal investigator, King's College London