Can a sweet potato help your baby sleep through the night?

A study in New Zealand examined the effects of kūmara (a type of sweet potato) on infants’ sleep. Researchers found that infants who were fed standard kūmara experienced less nocturnal wakefulness. A separate group that received kūmara with added resistant starch showed a small increase in daytime sleep, but also experienced trends toward more problematic nighttime sleep. The paper was published in Nutritional Neuroscience.

Kūmara is the Māori name commonly used in New Zealand for the sweet potato, a root crop scientifically known as Ipomoea batatas. It is an edible plant in the morning glory family and is grown for its swollen, starchy roots. In New Zealand, kūmara is an important food with deep historical and cultural significance for the Māori people.

The Polynesian ancestors of the Māori brought kūmara to New Zealand around the 13th century as a cultivated food plant. Because New Zealand is cooler than tropical Polynesia, growing kūmara required careful agricultural techniques. Over time, kūmara became one of the most important traditional crops in Māori horticulture. Today, it is also a common food in the modern New Zealand diet. Kūmara can be baked, boiled, roasted, mashed, or used in soups, stews, chips, and salads.

Study author Xiaoxi Fu and colleagues note that, in New Zealand, kūmara is a common and acceptable first food for infants. It is recognized for its prebiotic effect—the ability to stimulate the growth and activity of beneficial gut bacteria. Kūmara naturally contains resistant starch, a substance that can be fermented and utilized by an infant’s gut microorganisms. A healthy gut microbiome has been shown to produce chemicals that regulate sleep hormones, leading researchers to wonder if prebiotic foods could improve an infant’s rest.

The authors conducted a study examining the effects of standard kūmara and kūmara supplemented with resistant starch (extracted from green bananas) on infant sleep during the early complementary feeding phase (6–10 months of age). The study looked at how the daily consumption of kūmara impacted caregiver-reported infant sleep patterns, as well as the caregivers’ own sleep quality.

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The study participants consisted of 281 healthy infants residing in Auckland, New Zealand. To be included in the study, they needed to be 3–6 months of age at the start, born after at least 32 weeks of gestation, and weighing at least 2.5 kg at birth.

The participants were randomly divided into three groups: two intervention groups and a control group. The control group infants received no intervention and were simply introduced to solid foods according to New Zealand Dietary Guidelines. One of the intervention groups received a standard freeze-dried kūmara powder, while the other received a kūmara powder with added resistant starch. Both intervention groups were also introduced to standard solid foods.

The study was double-blinded, meaning the caregivers in the two intervention groups did not know which specific product they were receiving. The intervention products were given to the caregivers in 5-gram sachets to be consumed daily for four months, starting from the introduction of solid foods until the infants reached approximately 10 months of age. The study authors tracked adherence to this intervention through a consumption log completed by the caregivers, along with a monthly questionnaire.

Information regarding the infants’ and caregivers’ sleep was collected at the start of the study (before the introduction of solids), in the second month of complementary feeding, and in the fourth month. Caregivers completed an assessment of their infants’ sleep (the Brief Infant Sleep Questionnaire) and assessments of their own sleep quality (the PROMIS Sleep Disturbance and Sleep-Related Impairment scales).

Results showed that, compared to the control group, infants fed standard kūmara had significantly less nocturnal wakefulness by the end of the four months. They did not necessarily wake up fewer times, but they settled back to sleep much faster.

Conversely, the group of infants fed kūmara powder with added resistant starch showed a small increase in daytime sleep at the two-month mark. However, caregivers in this group also reported a trend toward more problematic nighttime sleep, with infants more likely to stay awake for more than an hour at a time during the night. The researchers suspect this may be because the longer daytime naps ruined the babies’ nighttime sleep drives, or because the heavy dose of concentrated starch caused mild gastrointestinal discomfort.

Caregiver sleep outcomes did not differ significantly between any of the three groups.

“Kūmara consumption may reduce nocturnal wakefulness in infants, but further research incorporating objective sleep measures and exploring underlying mechanisms is needed,” the study authors concluded.

The study contributes to the scientific understanding of the effects of kūmara consumption in infants. However, the infants’ sleep assessment was based on subjective caregiver reports rather than objective data (like electronic sleep trackers), leaving room for reporting bias to have affected the results. Furthermore, because the study started with generally healthy infants without severe sleep problems, massive improvements were unlikely to be seen.

The paper, “The effect of prebiotic intervention foods on caregiver-reported infant sleep and caregiver sleep quality during complementary feeding-secondary analysis of a randomized control trial,” was authored by Xiaoxi Fu, Amy L. Lovell, Clare R. Wall, Teresa Gontijo De Castro, Yannan Jiang, Robyn L. Lawrence, Nisha Mahawar, and Barbara C. Galland.