Will a bedtime snack help treat hyperglycaemia in type 2 diabetes?

There is no convincing benefit to consuming a bedtime snack for glycaemic control in individuals with type 2 diabetes (T2D) or prediabetes, according to the results of a systematic review.

“Current advice to consume a bedtime snack is based on a limited number of intervention studies that often do not include a no-snack control, nor have used a feasible bedtime snack option that could be translated into everyday clinical practice,” the researchers said.

The databases of PubMed, Medline (EBSCO), Cochrane Library, and CINAHL Plus (EBSCO) were searched until 20 July 2022. Prospective studies in people with T2D or prediabetes that included the intervention of a bedtime snack, consumed >30 min after dinner and <2 h before bed, and reported glycaemic outcomes were included.

Sixteen studies met the eligibility criteria. No consistent association was noted between consumption of a bedtime snack and improved glycaemic control, particularly when a no-snack control was included. [Am J Clin Nutr 2022;116:1251-1264]

In four studies that included the use of corn starch, a low-dose compared with high-dose corn starch appeared to provide benefits in terms of improved nocturnal and fasting glucose concentrations.

“Overall, findings indicate no benefit of consuming a bedtime snack over a no-snack control for improving measures of glycaemic control, including fasting and nocturnal glucose concentrations,” the researchers said. [Diabetes Care 1990;13:748-755; Diabetes Res Clin Pract 2001;53:137-139; Diabetes Metab 2018;44:226-234; Am J Clin Nutr 2000;71:1108-1114]

“Studies that compared different bedtime snack compositions found that a resistant starch snack or a low-carbohydrate bedtime snack resulted in better glycaemic profiles than higher carbohydrate snack comparators,” they added. [Diabetes Res Clin Pract 2001;53:137-139; Clin Nutr 2020;39:3601-3606]

Carbohydrates and dietary fibre

Food items that are rich in carbohydrates are usually preferred for snacks before bedtime since it is traditionally recommended to distribute carbohydrates over the day to control blood glucose concentrations. [Nutr Diet 2006;63:36-47]

The most common bedtime snack analysed was that of corn starch due to its complex carbohydrate with a drawn-out digestibility of ≤6–9 h, releasing glucose slowly into the bloodstream and increasing insulin moderately to reduce hepatic glucose production. [N Engl J Med 1984;310:171-175; Am J Clin Nutr 1990;52:667-670]

“However, our findings have shown that the higher doses of corn starch often resulted in increased nocturnal glucose compared with a sandwich or a placebo and resulted in no improvement in fasting glucose concentrations compared with sandwiches or placebo,” the researchers noted. [Eur J Clin Invest 1997;27:157-163; Eur J Clin Nutr 1999;53:706-710; Am J Clin Nutr 2000;71:1108-1114]

On the other hand, consumption of dietary fibre has been shown to provide benefits to people with T2D, including lower HbA1c and fasting plasma glucose. Therefore, eating fibre-rich foods as a bedtime snack may help reduce hyperglycaemia through slow gastric emptying. [Nutr Rev 2013;71:790-801]

Moreover, a dietary fibre-enriched versus a standard cereal consumed at dinner, as a bedtime snack, and for breakfast the next day could improve glycaemic response to breakfast. [J Korean Med Sci 2016;31:222]

“More high-quality long-term randomized control trials … are warranted to provide further evidence,” the researchers said.