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A recent study published in Clinical Nutrition adds additional evidence to what we covered in a past blog article: ketogenic diets may be beneficial for people living with McArdle disease (glycogen storage disease type V).
The primary defect in McArdle disease is absence or deficiency of the enzyme myophosphorylase, responsible for muscle glycogen breakdown. This deficit results in intolerance to physical activity, and activity-induced muscle pain and muscle damage (typically indicated by dramatically elevated creatine kinase). Being that individuals with this condition can’t rely on glucose to fuel skeletal muscle, it stands to reason that shifting the muscles to run primarily on fatty acids – as occurs on ketogenic diets – may reduce symptoms and improve physical endurance and quality of life.
The study randomized subjects to follow either a modified ketogenic diet (75-80% fat, 15% protein, 5-10% carbohydrates) or an isocaloric placebo diet (45-50% fat, 15% protein, 35-40% carb) for a period of 3 weeks and then switch to the other diet, separated by a washout period of a minimum of 13 days. If you’re wondering how a “placebo” was created for a ketogenic diet (after all, you know for certain whether you’re following a keto diet or not), the diets are described as follows:
“Participants were instructed to follow a meal plan that was identical for the two diets and included 3 meals and 1-2 snack(s). Each meal consisted of 1 protein, 2-4 carbohydrate, and 2-3 fat choices chosen from an ingredient list. At every meal and snack, the participants had to consume a carefully measured amount of a blinded liquid-supplement, which accounted for approximately 67% of the daily caloric intake.”
Diet compliance was assessed via a food journal. Despite efforts at blinding, ten out of fifteen subjects who completed both diets could tell which diet they were on during the given period.
Compared to the higher-carb diet, subjects experienced significant increases in fat oxidation and plasma β-hydroxybutyrate, and an approximately 20% increase in maximal exercise capacity, along with significant improvements in patient-reported outcomes (fatigue severity and physical functioning). It will be interesting to see what happens in longer-term studies, but this small trial is a start to generate clinical evidence for what many McArdle patients have already discovered for themselves: keto diets improve numerous parameters of overall functioning and wellbeing.
*These statements have not been evaluated by the Food and Drug Administration. This product has not intended to diagnose, treat, cure, or prevent any disease.