Ultra-processed foods enter babies’ diets early. What comes with them?

As infants move beyond milk and encounter a wider range of foods, researchers examined how the degree of food processing relates to nutrient intake, dietary diversity and early growth.

Study: Ultra-Processed Food Intake Is Associated with High Consumption of Added Sugar and Sodium in U.S. Infants. Image Credit: Vladimir Sukhachev / Shutterstock

A recent study published in the journal Nutrients found that ultra-processed food (UPF) intake during complementary feeding was associated with higher consumption of added sugar and sodium among infants in a Denver, Colorado cohort. But UPF intake was not consistently associated with infant growth between 5 and 12 months.

Background

Complementary feeding is the transition period when infants shift from a predominantly milk-based diet to a wider range of foods.

The increasing use of prepackaged infant and toddler foods has raised concerns about the nutritional quality of foods offered during this period. In the US, it is estimated that about 70% of complementary foods marketed to infants and toddlers are UPFs, and contribute 45% of daily energy intake between 6 and 23 months of age.

In addition, infants are also offered adult foods during this period. US adults obtain 55% of their daily energy intake from UPFs, which are often high in sodium and sugar.

UPFs are typically highly palatable but relatively low in nutrient density and often contain high levels of sugar, sodium, and trans fats. Little is known about UPF intake during complementary feeding or its relationship with infant growth trajectories.

Study characteristics

The researchers conducted a secondary analysis of dietary intake and growth data from 114 healthy, full-term infants who were part of observational reference groups in two randomized controlled trials in the Denver metropolitan area of Colorado. Infants in these reference groups received no dietary counseling or intervention and ate an unrestricted diet. Their diets were recorded using three-day food records, and weight and length were measured repeatedly by trained research personnel. The infants were assessed at approximately 5, 9, and 12 months of age.

The researchers classified foods using the NOVA system, which divides foods into four categories based on their degree of processing.

UPFs had higher energy density

Of 1,912 unique foods identified across the three time points, 41% were classified as UPFs, 30% as minimally processed, 1% as processed culinary ingredients, and 28% as processed foods. Among the complementary foods analyzed, UPFs accounted for an average of 32% of energy intake, which is lower than the 45% estimate reported in prior NHANES data for infants aged 6-11 months.

UPFs were more energy-dense than minimally processed foods, providing an average of 282 kcal per 100 g compared with 128 kcal per 100 g. They also contained more sodium and less fiber.

UPFs contained more added sugar on average, but the difference did not remain statistically significant after correction for multiple comparisons. The researchers said the difference may still be clinically relevant.

Time-dependent UPF intake

Infant consumption of UPFs increased over time, with the adjusted UPF intake increasing from about 4 kcal/kg/day at 5 months to 20 kcal/kg/day at 12 months. At 9 months, there was no significant difference compared with 5 months, although intake increased from 4 kcal/kg/day to 9 kcal/kg/day.

UPFs continued to contribute a similar proportion of energy intake from complementary foods over time. The rise in absolute UPF intake reflected infants consuming more complementary foods as they moved away from a predominantly liquid diet.

UPFs, added sugar, and sodium

The researchers found that UPF intake was associated with higher added sugar consumption at both 9 and 12 months. The authors note that this is the first reported association between UPF consumption and added sugar intake among US infants, consistent with patterns seen in other age groups.

Sodium intake also followed a similar pattern. At 9 months, each additional 10 kcal/kg/day from UPFs was associated with about 161 mg/day more sodium; at 12 months, the corresponding estimate was about 124 mg/day.

UPF consumption was not associated with macronutrient intake at any time point.

Higher intake of minimally processed foods and of processed culinary ingredients and processed foods was associated with lower added sugar intake, but not with sodium intake. This suggests that, compared with minimally processed and processed foods, UPFs, in particular, were associated with higher levels of added sugar and sodium.

The dietary sources of added sugar in this study included snack bars, instant oatmeal, yogurt melts, and infant mixed meals. The main sources of sodium in the infants’ diets included family foods prepared with salt, cured meats, cheese and cheese dishes, and toddler products. Infant-specific products contributed relatively little sodium.

This suggests that toddler products and family foods, including UPFs, may be important sources of sodium when offered to infants.

Dietary diversity

The study found no evidence that higher UPF intake reduced dietary diversity. Dietary diversity was assessed both by the number of food groups consumed and by whether infants met the WHO/UNICEF minimum dietary diversity (MDD) criterion of at least five of eight food groups. Infants meeting MDD tended to consume more UPF at 9 months, but this association did not meet the study’s corrected threshold for statistical significance; the 12-month association was also not significant.

At 9 months, infants who received breastmilk without formula consumed foods from more food groups than those who consumed formula, either alone or with breastmilk. This difference was not significant at 12 months.

Growth trajectories

The researchers also examined infant growth using weight-for-age, length-for-age, and weight-for-length z-scores. Overall, UPF intake was not consistently associated with growth.

The association between weight-for-age z-scores and UPF intake varied over time. In the longitudinal model, at 5 months, higher UPF energy intake was associated with a lower weight-for-age z-score, but not at 9 or 12 months. There were no significant associations with length-for-age or weight-for-length. Cross-sectional analyses at each time point found no significant associations between UPF intake and any of the three growth measures.

The researchers suggest that the isolated finding at 5 months could reflect the transitional nature of complementary feeding, reverse causality, or chance, particularly because only 45 infants had baseline data on complementary feeding. They also note that infants with lower weight-for-age might have been introduced to complementary foods earlier or given different foods in an attempt to boost their growth.

Limitations

The study has several limitations. The sample was relatively small and consisted of healthy infants from the Denver metropolitan area, limiting generalizability. The cohort was also predominantly White and included a high proportion of families with higher income and maternal education levels. Breastmilk and formula were not included in the dietary analysis, nor was total energy intake quantified. The researchers adjusted for feeding mode, but the liquid diet may still have influenced the findings. The observational secondary analysis cannot establish causation, and the authors noted that some infant and baby foods do not fit neatly within Nova categories.

Study 1 was supported by the National Pork Board, while Study 2 received support from the National Institutes of Health (NIH), the National Dairy Council, and Mead Johnson Nutrition. Both studies also received NIH/NCATS support. The authors reported that funders had no role in the study design, analysis, interpretation, writing or publication decision.

Conclusions

The findings suggest that greater UPF consumption during complementary feeding was associated with higher intake of added sugar and sodium at 9 and 12 months. The study found no consistent relationship between UPF intake and infant growth, and it did not show that higher UPF intake reduced dietary diversity.

Larger and longer-term studies are needed to determine whether dietary patterns established during complementary feeding influence long-term food preferences, diet qualit,y or obesity risk.