Ultraprocessed Food Adversely Impacts Metabolome in Kids

Becky McCall

May 14, 2021

High consumption of ultraprocessed foods in childhood alters the metabolome and is associated with an increased risk of obesity, according to a large study of UK children and adolescents.

Presented at this year's virtual European Congress on Obesity (ECO), the researchers, led by Evangelos Handakas, PhD, and coauthor Oliver Robinson, PhD, both from Imperial College London, UK, found a "pretty dramatic overall effect on the metabolome, especially in childhood," said Robinson.

"Delving into the metabolic changes, both analyses [one in children aged 7.5 years, and the other in adolescents] showed changes in fatty acid profiles, characterized by reduced levels of omega-3 fatty acids, and a shift in the lipoprotein profile from HDL [high-density lipoproteins] to VLDL [very low-density lipoproteins]," Robinson told Medscape Medical News.  

"These changes are consistent with established metabolic risk factors for later development of cardiometabolic disease," he emphasized.

Handakas added that the altered metabolomic profiles "increase the risk for children to become overweight [or develop] obesity, and the findings reveal the significant role of nutrient-poor diets and lifestyle behaviors in metabolic dysfunction in children and adolescents."

In particular, branched chain amino acids (BCAAs) were negatively associated with ultraprocessed food consumption. "BCAA levels may influence later propensity for overweight through mechanisms such as control of food intake," explained Handakas.

Also, phenylalanine and tyrosine were found to be negatively associated with ultraprocessed foods. "These are indispensable amino acids essential to our diet," he added.

Asked to comment, session comoderator Maria Bryant, PhD, reader in public health nutrition at the University of York, said: "The first thing that struck me was the finding that over 60% of daily consumption was reported to be ultraprocessed food in this population."  

"Children who consume more ultraprocessed foods have more fatty acids linked to poor metabolic health and less linked to strong metabolic health," she observed.

However, "Whether these associations are a direct result of the consumption of ultraprocessed foods or a consequence of consumption of less healthy foods remain unclear," she stressed. "We might hypothesize, for example, that adolescents who consume very high amounts of ultraprocessed food are less likely to consume foods high in omega-3 fatty acids, such as oily fish." 

Molecular Metabolite Associations With Ultraprocessed Food

There is growing evidence that ultraprocessed foods are linked with weight gain and overweight, noted Handakas, but what has been unclear is what is happening at a molecular level.

With this in mind, the researchers aimed to investigate the associations between ultraprocessed food consumption and the metabolome, and their roles in overweight and obesity risk in early childhood (average age of 7.5 years) and adolescence.

Data were drawn from the Avon Longitudinal Study of Parents and Children (ALSPAC study) and involved dietary intake assessed by a 3-day food diary at 7 and 13 years of age, supplemented with interview material by a nutritionist, and metabolomic data at 7 and 16 years of age. Socioeconomic and sedentary/physical activity levels were determined via questionnaire, and anthropometric data at 7, 9, and 16 years of age were also incorporated into the analyses.

The level of ultraprocessed food consumption was calculated as the calorie (kcal) proportion of total daily calorie consumption. The degree of processing involved in the preparation of various foods was determined using the NOVA classification, which categorizes foods into one of four groups based on the degree of processing: 1) unprocessed or minimally processed foods, for example, fruit or eggs; 2) processed culinary ingredients, such as salt, sugar, and vegetable oils; 3) processed foods, for example most freshly baked bread; and 4) ultraprocessed foods that are formulations of ingredients, mostly mass produced packaged goods such as cookies, which are low in essential nutrients and high in sugar substitutes and likely to be over-consumed.

The relationship between the consumption of ultraprocessed food intake and plasma metabolites was determined using multiple linear regression adjusted for child age, sex, and body mass index (BMI); maternal age; maternal education level; pre-pregnancy BMI; family income; average time spent watching TV; presence of smokers at home; and physical activity.

Nuclear magnetic resonance spectroscopy was used to analyze the metabolomic profile of blood plasma samples from over 4500 children.

Ultraprocessed Foods Linked to Poor Molecular Metabolic Profiles

The analysis showed that the ultraprocessed food proportion of total daily consumed food (in kcal) was a mean 61.1% at age 7.5 years (midchildhood) and 57.8% at 13 years (adolescence).

In midchildhood, 128 of the initial 232 metabolic traits showed a significant association with ultraprocessed food intake consumption, and 98 of these associations remained after adjustments.

A diet with a higher proportion of ultraprocessed food was negatively associated with metabolites including docosahexaenoic acid (DHA) and omega-3 fatty acids (generally considered biomarkers of fish consumption), tyrosine, and BCAAs (leucine, valine, and isoleucine), as well as small, medium, and large HDL ("good" cholesterol). 

Additionally, in middle childhood the results showed that citrate as well as small, medium, and large VLDL were positively associated with ultraprocessed food consumption. VLDL particles are mainly made up of triglycerides and increased levels are associated with cardiometabolic diseases and usually indicate a lower quality diet.

Handakas pointed out that intestinal levels of BCAAs are dependent on the gut microbiota and gut metabolism. "They may offer a potential mechanism by which the gut microbiota could directly influence childhood adiposity."

Robinson provided further comment on the changes in smaller, nonlipid molecules in the midchildhood analysis: "The decrease in BCAAs is particularly interesting. [Many studies] show that their levels regulate appetite and have positive effects on metabolic parameters."

"In a recent randomized control trial on ultraprocessed foods, the latter were found to be associated with greater food intake, and therefore, these metabolites may present a mechanism whereby ultraprocessed foods have effects on appetite regulation," he postulated.

In adolescence, 79 metabolic traits showed a statistically significant association with ultraprocessed food consumption, and 19 of them remained significant after further analysis.

Diets with a higher proportion of ultraprocessed food at the age of 13 years were negatively associated with such ratios as DHA to total fatty acids, and ratio of omega-3 fatty acids to total fatty acids. Additionally, higher ultraprocessed food consumption in adolescence was associated with increased triglycerides in total lipids.

Preliminary data from the study show BMI increased significantly by an additional 0.33 kg/m2 per 2 years in childhood for each 1% increase in the proportion of ultraprocessed food in the diet.

Finally, researchers conducted an analysis to find out if any particular metabolite mediated the effect of high ultraprocessed food consumption at age 7 years on BMI at age 9 years. They found about 20 that provided some evidence of mediation. Further analyses are ongoing.

Bryant also remarked that more research is needed to better understand mechanisms involved.

"However, I'm left wondering whether it matters that the consumption of ultraprocessed foods impacts on metabolites directly or indirectly. Either way, this study adds to a growing evidence base which advocates for a substantial reduction in the availability of ultraprocessed foods."

ECO 2021. Presented May 11, 2021. Abstract AD06.04. 

Handakas and Robinson have reported no relevant financial relationships.

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