Introduction. Becker Muscular Dystrophy (BMD) is a rare X-linked genetic condition characterised by reduced dystrophin expression, causing progressive skeletal muscle and functional decline, and ultimately poor quality of life (QoL). With no current pharmacological cure, practical easy-to-implement strategies are needed to improve QoL in BMD. Elevated dietary protein intake is known to be beneficial in muscle-wasting conditions such as sarcopenia [1] and cachexia [2], and can improve lean body mass [3] and reduce pain [4] in certain conditions. However, little is known about habitual dietary practices and their relationship with muscle size, strength, physical function and QoL specifically in BMD.
Aim. To characterise habitual dietary practices in adults with BMD and examine associations with muscle size, strength, physical function and self-reported QoL.
Methods. Adult males with BMD (n = 20; 46 ± 12 years) and age-matched controls (n = 12; 47 ± 13 years) completed two weighed food diaries ~6 weeks apart. In addition, participants completed a battery of physical testing including assessments of body composition and muscle size, strength and function as well as validated questionnaires on perceived physical function, pain/fatigue, QoL, and nutritional knowledge. Between-group differences were assessed using independent t-tests or Mann-Whitney U tests and correlations with Pearson’s R or Spearman’s Rho depending on normality (p value threshold < 0.05). Ethical approval was obtained from institutional level research ethics committee and all procedures conformed to Declaration of Helsinki.
Results. Adults with BMD reported 29% lower daily energy intake compared with controls (1602 vs. 2229kcal, p<0.001), with 25-30% lower carbohydrate and fat ingestions (p<0.01). Protein intake (relative to bodyweight) was 21% lower in BMD (0.86±0.28 vs. 1.08±0.24g/kg/day, p=0.028) with only 10% of individuals meeting The European Society for Clinical Nutrition and Metabolism (ESPEN) recommendations for protein intake in those with disease-related protein catabolism (1.2g/kg/day). Despite reduced energy intake, adults with BMD exhibited greater body fat percentage (31.1±4.7 vs. 22.9±6.9%, p=0.002) and 40% of the cohort were classified obese (BMI >30kg/m2). BMD also exhibited lower tibialis anterior muscle thickness, strength and physical function, reported reduced QoL, lower limb function and activities of daily living, and higher pain and fatigue compared to controls (all p<0.05).
In the BMD cohort specifically, relative protein intake was positively correlated to lean mass percentage (r=0.619; p=0.018) and QoL (r=0.596; p=0.006) and negatively associated with BMI (r=-0.571, p=0.009). Lean mass (%) was negatively associated with self-reported fatigue (r=-0.591, p=0.026) whilst BMI correlated positively with pain (r=0.689, p<0.001).
Conclusion. Here, we show that adults with BMD report lower energy consumption, compared to non-dystrophic individuals, yet display unfavourable body composition. Moreover, relative protein intake was substantially lower than guidelines for similar clinical conditions, suggesting habitual dietary practices are not sufficient to offset muscle deterioration in this condition. Importantly, we observed protein intake to be moderately-to-strongly correlated with lean mass and QoL in BMD indicating interventions which elevate protein consumption could positively affect these outcomes. Together, this highlights the need for further research to inform potential future dietary guidance for those living with BMD.