To our knowledge this is one of the first studies in the Middle East to examine the relationship between food consumption and nutritional status in children and adolescents with PKU, to our knowledge. The findings reveal that PKU patients who consumed the most phe had a higher probability of having a high BMI than those who consumed the least amount of phe, but that there is no direct association between BMI and calorie, protein, carbohydrate, or fat intake.
Although various studies have revealed growth retardation in children and adolescents with PKU (17, 24), the incidence of obesity in phenylketonuria patients was one of the assumptions in this investigation. This hypothesis was tested using the BMI z-score. According to their BMI z-score values, about 44% of patients in this study were overweight or obese, with females having higher BMI z-score values. In a study conducted by Almeida et al. (33) in Brazil, the prevalence of obesity and overweight was 28.5%. Also, in the studies of Camatta et al. (12) and Mazzola et al. (34), the prevalence of obesity and overweight was lower than our study (19.13% and 22%, respectively). In the Ogden et al. study of 2 to 19-year-olds in the United States, the prevalence of overweight and obesity was 31.8% (35). Therefore, Brazilian and United States data have a lower prevalence of overweight and obesity than Iran. As a result, the prevalence of overweight and obesity in Brazil and the United States is lower than in Iran. Because of the poor protein consumption of these patients and the high cost of special low protein foods (SLPF) in Iran, carbs, sugars, and fats constitute the majority of the patients' calories, which may explain the increased prevalence of overweight and obesity in this study.
Almeida et al., who supported the findings of this investigation, found that 88.1 percent of the sample was sufficient in terms of the H/A z-score (33).
The majority of patients exhibited normal serum levels of albumin, ferritin, iron, calcium, zinc, and tyrosine, according to biochemical studies. In 35% of patients, vitamin D insufficiency was found, and high plasma phenylalanine levels indicated poor disease control. Vitamin B12 and folic acid serum levels were high in 45 percent and 35 percent of patients, respectively. There was no significant difference between the two BMI groups except for serum calcium levels.
In opposition to our findings, in the Barretto et al. study (36), zinc levels were below normal in 37.5% of people, and one possible reason is that the bioavailability of zinc may be affected by excess fiber, phytates, and other minerals. It also seems that due to the limited diet of natural protein in these patients and the intake of vegetarian diets, zinc absorption has decreased (37), however, in our study, zinc deficiency was seen in 10% of patients, which is consistent with the results of some previous studies (26, 33, 38).
Iron, vitamin B12, and folate are important for oxygen transport for optimal cognitive function, and their deficiency can affect brain function (3). In the present study, vitamin B12 and folic acid deficiency were negligible, with 45% and 35% of patients having high serum concentrations, respectively, similar to that seen in the Crujeiras et al. (25), and Kose et al. study (38). Similar to the present study, the results of Evans et al. (39) and Almeida et al. (33) studies showed that more than 90% of the subjects had adequate and normal ferritin levels.
Compared with the averages of the Demirdasa et al. study (26), the apparent lack of vitamin D was observed. While the prevalence of vitamin D deficiency was higher (53.57%) in Kose et al. study (38). Because vitamin D is involved in neurotransmission, calcium balance maintenance, signaling, and synaptic plasticity, a vitamin D deficit can increase the effects of inadequate phenylketonuria control (22). As a result, its deficit must be addressed in order to avoid neurological problems.
The current study also has a number of limitations. One of the study's major flaws is that it was cross-sectional and conducted in a single center with a small number of patients, making it impossible to extrapolate the findings to other patients. Because of the small sample size, no causal association between dietary intake and BMI can be deduced as a pilot hypothesis-generating study. Of course, our study had a higher sample size than other earlier studies (17, 24, 26, 34).
Finally, this study looked into the nutritional status of phenylketonuria patients. The implementation of this method has aided in the regulation of blood phenylalanine levels and the prevention of neurological diseases in phenylketonuria patients. According to the findings, nearly one-third of the patients were vitamin D deficient and had a BMI/A index of overweight/obese. Furthermore, the majority of the individuals showed elevated phenylalanine levels in their blood. Evidence suggests that patients with phenylketonuria may experience neurological and psychiatric issues as a result of hyperphenylalaninemia. On the other hand, several micronutrient deficiencies, such as iron, vitamin D, B12, and folic acid, can lead to neurological problems. As a result, we believe that nutritional inadequacies may exacerbate the disease's severity. PKU patients should follow a phenylalanine-restricted diet with a balanced intake of macronutrients and micronutrients, and be monitored for plasma phenylalanine levels and nutritional intake on a regular basis. More research is needed on the impact of dietary inadequacies and micronutrient intake on phenylketonuria, as well as evaluating overweight and obesity in these patients as they get older, as well as other obesity-related concerns in this population.