Low Dietary Protein Linked to Growth Deficits in Taiwan

A study suggests lower intake of dietary protein is associated with more severe growth deficits in Taiwanese children with Rett syndrome.

While dystonia — uncontrolled movements due to muscle contractions — increased with age, it did not affect growth, the scientists said. 

The study, “Dietary intake and growth deficits in Rett syndrome—A cross‐section study,” was published in the journal Autism Research. 

Growth defects are a common feature in people with Rett syndrome, a condition caused mainly by mutations in the MECP2 gene. Other symptoms include deficits in cognitive, emotional, sensory, and motor function. 

Insufficient caloric intake may contribute to growth defects due to difficulties in chewing and swallowing, gastroesophageal reflux (acid reflux), delayed stomach emptying, and impaired breathing.

Dystonia, a common symptom in Rett patients, may affect oral function and mobility, also affecting growth.

How dystonia affects different growth patterns in Rett, however, has not been thoroughly investigated. Also, growth studies have focused mainly on Rett patients in Western countries, with limited available data from Asian countries.

Notably, as dietary intake varies among different ethnic groups and countries, the growth patterns of Rett patients in Asian countries may be different.

Researchers based at the National Taiwan University College of Medicine led a study to investigate growth patterns, dystonia, clinical characteristics, and their correlation in a group of Taiwanese people with Rett. 

“To the best of our knowledge, this is the first study focusing on dietary intakes and growth patterns of RTT [Rett] individuals in Asia,” the researchers wrote. 

The study included 44 participants with confirmed MECP2 mutations, 11 of whom were younger than 8, 13 between 8 and 18, and 20 patients were 18 or older. 

Clinical Severity Score was used to assess disease severity with scores ranging from 0 to 58, in which higher scores reflected greater severity. The Burke-Fahn-Marsden-movement scale (BFMMS) assessed the severity of dystonia, with higher scores indicating more dystonia. 

Caregivers or parents of participants recorded dietary intake in a diary over 72 hours, and from these, dieticians estimated the amount of daily energy and nutrient intake, including protein and fiber. 

Growth measurements included height, weight, head circumference, and body-mass index (BMI), a standard measure of body fat. 

Initial analysis found a significant relationship between age and total dystonia scores, in which every year increase in age was linked with a 1.76-point rise in dystonia severity score. Higher dystonia with age was found in the mouth area as well as the neck, arms, legs, and trunk. 

Compared to an international Rett growth chart of mainly Caucasian children, more Taiwanese children with Rett showed a significantly lower BMI, but not a smaller head circumference. A non-significant trend toward a greater height and lower weight was found in Taiwanese children. 

In adults, the mean BMI in the Taiwan group was similar to international adults with Rett, but was mostly underweight and normal, compared to a broader range in the international group.

Growth patterns

Taiwanese patients showed three distinct growth patterns, including 13 with severe growth deficit, 16 with moderate growth deficit, and 14 with mild growth deficits. 

Most of the study group had adequate protein (97.37%) and energy (58.97%) intake, but fiber intake was generally low, with 38 (97.4%) individuals not meeting daily reference intake (DRI).  

Carbohydrate intake was adequate in the majority, with 33 (84.62%) individuals exceeding the recommended dietary allowance. Excessive fat intake was reported for 26 (66.67%), and saturated fat intake was found in 19 (52.78%).

In participants 18 and younger, the team found statistically significant differences in protein intake among different growth deficit groups. Those with mild growth deficits had a mean protein intake of 14.89% DRI, whereas patients with moderate deficits had 10.75% DRI and 5.42% DRI for severe growth deficits. 

Statistical analysis showed protein intake was significantly lower in young Rett individuals with severe growth deficit than those with mild growth deficit. Although not statistically significant, energy intake tended to be lower in the severe growth group than the mild and moderate growth groups. The team saw no differences between growth groups in respect to carbohydrate, fat, and fiber intake.

In adults with Rett, the results showed no difference in protein, energy, carbohydrate, fat, and fiber intake among the different growth deficit groups.

The overall dystonia score was not associated with the degree of growth deficit. However, dystonia in the trunk region was linked to the degree of growth deficit. Further analysis found hand-use impairment to be significantly associated with a more severe growth deficit. 

“Although all individuals had dystonia at certain variable degrees and the dystonia worsened with age, but it did not have significant impact on growth deficit,” the investigators wrote.

Overall disease severity, age of regression, walking ability and language skills all correlated with the degree of growth deficit.

A final examination of mutations and growth deficits found that Rett patients who carry an A131D mutation generally showed mild growth deficits, whereas R133C, R294X, and C-terminal deletions (shorter protein) were associated with mild and moderate growth deficit and clinical severity. 

Patients with R255X and R168X mutations showed variable degrees of growth deficit, ranging from mild to severe, while T158M and R106W mutations correlated with moderate-to-severe growth impairment, and had moderate-to-severe clinical severity. 

“This indicates that individuals with genotypes [genetic profiles] of milder clinical severities were associated with milder growth deficit, while genotypes with more severities were associated with more pronounced growth deficit,” the team wrote. 

“Nutritional intakes may partially affect growth,” the scientists added. “Furthermore, ethnicity should be considered when comparing RTT individuals’ growth pattern to the RTT‐specific growth chart.”

“Intervention strategy to improve growth should be individualized in terms of nutrition intake and treatment of comorbidity [co-existing conditions] such as dystonia,” the team concluded.