Hot smoothies for better health? Heat-treated drinks improve polyphenol bioavailability, finds study

Scientists in Spain have found that applying high heat to fruit and vegetable smoothies increases the absorption of beneficial polyphenols in the human gut microbiome. This is in addition to the usual benefits of preservation and increased shelf life.

The findings can help manufacturers improve smoothie processing and advance functional beverage formulation for better absorption of polyphenols, which can protect against heart disease and neurodegenerative disorders.

The WHO recommends consuming at least 400 g, or five portions, of fruits and vegetables per day to achieve health effects. However, the study points out that the estimated daily intake is lower than the recommended values, and smoothies provide an “appealing and practical” strategy to promote fruit and vegetable consumption.

To understand how well smoothies are absorbed in the body, the team prepared smoothies using Granny Smith apples, green celery, green chicory, peppermint, and lemon in three sample groups: untreated, high-pressure processed (HPP) (600 MPa, 6 min), and high-temperature short-time treated (HTST) (82 °C, 2.6 s).

Thermal pasteurization resulted in more than double the polyphenol bioaccessibility compared to untreated or HPP-treated smoothies, from 17% (untreated) to 44% (HTST-treated).

These samples also generated the highest levels of beneficial metabolites, including phenylpropanoic acids and phenylacetic acids, which are known for antidiabetic and anti-inflammatory properties.

The study, published in ACS’ Journal of Agricultural and Food Chemistry, was conducted by the University of Navarra, Navarra Institute for Health Research, National Centre for Food Technology and Safety, Andalusian Institute of Agricultural and Fisheries Research and Training, and Maimonides Institute for Biomedical Research of Córdoba in Spain.

Impact on gut microbiome

The Spanish study mimicked the human digestive process in the lab, and used human feces as a source of gut microbes. The gut microbiota broke down most of the polyphenols into smaller compounds, some of which are known to help fight diabetes, inflammation, and even cancer.

Smoothies pasteurized with pressure (left) or heat (right) have higher amounts of digestible polyphenols than raw smoothies (Image credit: Iziar Ludwig).Previous research has reported that food processing techniques like canning and boiling peppers and artichokes may increase the absorption of polyphenols. However, the researchers note that knowledge “gaps” still exist around other food processing techniques. 

A recent review echoes this gap, stating that studies examining how various food processing methods influence gut microbiota are limited, highlighting a promising area for future investigation. 

In the future, making smoothies more absorbable through high-temperature processing could help gut bacteria create more beneficial compounds, paving the way for healthier, functional beverages with targeted health benefits.