In this rare clinical cohort of adolescents with a history of CMA and atopic eczema in infancy, we found no difference in dairy product consumption or vitamin D status compared with those with a negative CMA challenge in infancy and controls. Dietary intake of vitamin D was similar across groups, and no differences in HEI or prevalence of special diets were observed. The consumption of liquid dairy products was below the current national recommendation of a minimum of 500 g/d in 56.7% of all participants. (20) However, the majority (93.1%) were vitamin D sufficient.
Infants with CMA, at a mean age of 7 months, in comparison with healthy controls, have been shorter and thinner. (21) A reduction in height has also been described in young adults (median age 19.5 years) with symptomatic CMA compared with controls. (22) In children diagnosed with CMA at the mean age of 5.8 years, height data 1 year from diagnosis showed a significantly increased height SDS compared with at diagnosis among participants who had become tolerant. (23) This indicates that cessation of an elimination diet allows for catch-up growth. In our study, at the time of CMA diagnosis, prior to any elimination diet, infants were similar in weight and height compared to those with a negative DBPCFC. Similarly, in adolescence, our study found no difference between groups in height SDS or BMI-for-age.
In Finland, the reintroduction of milk into the diet, after CMA resolution, was studied from food records from 215 children that had received a special infant formula reimbursement, and were followed up to 3 years of age (24). At this age, 120 children had begun to use dairy products. The daily consumption of dairy products, after adherence to a milk elimination diet, was small as only 17% of children consumed three glasses of milk, and 23% used at least two slices of cheese, which are the national recommendations to ensure adequate intake of calcium (20). In our study, the median intake of milk among adolescents with a history of CMA during infancy was less than one glass. However, this intake did not differ from that of nonallergic peers. After a negative cow’s milk oral food challenge, at the median age of 4.6 years (n = 41), introduction failure has been reported in 9.8%. (25) In our study, no milk-tolerant participants with a history of CMA during infancy or a negative DBPCFC during infancy had a failed cow’s milk reintroduction in adolescence. This suggests that current clinical management of CMA successfully advances the discontinuation of unwarranted elimination diets. In addition, it may reflect the positive outcomes of the Finnish Allergy Program 2008–2018 (26). After a two–year implementation only, an intervention based on the principles of the Finnish Allergy Program reduced allergy diet prevalence by 43% in a daycare setting. (27)
The majority of participants did not meet the national recommendation for liquid dairy product consumption. One plausible explanation is a notable increase, over the past two decades, in the consumption of plant-based beverages, which serve as a substitute for traditional bovine milk. This consumption has exponentially grown in Western Europe throughout the 21st century, while, simultaneously, the consumption of liquid dairy has consistently declined. (28) This increase in consumption of plant-based alternatives could have attenuated the differences between our study groups. Notably, the updated Nordic Nutrition Recommendations 2023 for the intake of milk and dairy products is 350–500 g/d, whereas the previous national recommendation from 2014 was 500–600 g/d (20, 29). While children aged 8 to 27 months on a milk elimination diet ate more healthily compared with controls (11), our study on adolescents found no difference in diet healthiness as the HEI was similar across groups.
Interestingly, although only 57% of participants reported regular vitamin D supplementation, the prevalence of vitamin D insufficiency was only 6.9%. This is explained by the median vitamin D intake from food 6.6 µg/d, which is 66% of the adolescent daily recommended intake in Finland (10 µg/d)(20), and in line with previous findings among children (3). Recommended daily supplementation is 7.5 µg/d all-year round for 2- to 17-year-olds. (20) Combining intake from food with intake from supplements raised the median intake among our participants to 13.7 µg/d, which is above the daily recommended intake. A previous study from Finland observed vitamin D insufficiency among 16% of 10-year-olds, concluding that, in these children, the vitamin D status was sufficient. (6) Our results support this finding, which is attributable to the national vitamin D fortification of liquid dairy products and fat spreads. (30) This study reaffirms the success of this fortification strategy in reducing vitamin D insufficiency. Our study found no difference in the 25(OH)D concentration between participants with a history of CMA during infancy compared with nonallergic peers. In contrast, in a previous report, children with a history of CMA (parental reported) showed a significantly lower mean 25(OH)D concentration (65.0 nmol/l) compared with children without CMA (74.0 nmol/l). (6) An explanation could be that 19% of the children with CMA reported ongoing symptoms, whereas our analysis mostly included DBPCFC proven CMA participants who later had become milk tolerant. Another study found no differences in 25(OH)D levels between children aged 0.5 to 17 years with CMA, those with other food allergies, and controls. (31)
The strength of our study is that CMA during infancy was either confirmed or refuted by DBPCFC, which for diagnosis of food allergy is the gold standard diagnostic test. (32) Also, children that develop tolerance are likely to do so by age 15 (7), thus, to study the reintroduction of dairy products, adolescence is an optimal period in life.
Limitations of this study include some of the control group traits, namely a high proportion of female participants and special diets. A report on special diets among 12- to 18-year-olds in Finland in 2013 found that the prevalence of special diets was 22.5% and that this prevalence was significantly higher in girls (28.4%) compared with boys (16.3%). (33) The prevalence in our control group was 45%. Thus, the generalizability of our results may be compromised. Our data is also limited in terms of total milk intake from composite dishes. The applied FFQs were designed to evaluate the dietary intake of vitamin D and to calculate HEI; however, this limitation affects all groups equally and is unlikely to impact the results. Due to its cross-sectional nature, our study does not provide information on the timing of the reintroduction of cow’s milk or the span of the milk elimination diet in childhood. Even though no differences in vitamin D concentration or milk consumption were found in this population with a CMA history, other effects on health, such as bone strength or proneness to fractures, regardless of the cessation of an elimination diet, may persist. This warrants further research.
All participants in our cohort, with a history of CMA and developed milk tolerance, had successfully reintroduced dairy products into their diet. The nationwide fortification with vitamin D of liquid dairy and fat spreads has proven successful as almost all participants were vitamin D sufficient. Current management of children with CMA appears sufficient; additional monitoring of diet and vitamin D concentration, once milk tolerance has been attained, remains uncalled-for. Concerns regarding persisting with dietary restrictions that have surfaced in clinical contexts appear unwarranted.