The research literature on the effect of a low carb or ketogenic diet (KD) in Parkinsons Disease (PD) is fairly small, but quite encouraging.
In a clinical study published in 2005, Vanitallie et al. observed 5 patients with PD who had agreed to adhere to KD rules in their home environments. The observation continued for 28 days. The researchers observed some improvement in the scores of the Unified Parkinson’s Disease Rating Scale (UPDRS), while not excluding the possibility of placebo effects.
VanItallie TB, Nonas C, Di Rocco A, et al. Treatment of Parkinson disease with diet-induced hyperketonemia: a feasibility study. Neurology 2005;64:728–730.
A proof of concept trial that recruited 14 people with PD and mild cognitive impairment, randomized to a standard western diet or a KD (8 weeks in duration, n = 7 in each group), reported a between-group improvement in aspects of cognitive performance in the KD group, without a difference in motor function
Krikorian R, Shidler MD, Summer SS, et al. Nutritional ketosis for mild cognitive impairment in Parkinson’s disease: a controlled pilot trial. Clin Parkinsonism Relat Disord. 2019;1:41–47.
The largest study was performed by Matt Phillips and his group in Hamilton, New Zealand. They conducted a pilot randomized, controlled trial to compare the plausibility, safety, and efficacy of a low-fat, high-carbohydrate diet versus a ketogenic diet in a hospital clinic of PD patients. The trial had 47 patients, of which 44 commenced the diets and 38 completed the study (86% completion rate for patients commencing the diets).
Both diet groups significantly improved their MDS-UPDRS scores over the 8-week diet intervention. Both diet groups improved in Part 1 (nonmotor daily living experiences), but the ketogenic group improved more; every single patient in the ketogenic group improved in Part 1, resulting in a substantial 41% reduction in baseline Part 1 scores (as opposed to 11% in the low-fat group) over the 8-week diet intervention.
This is a potentially important finding, given that non-motor symptoms ultimately represent the most disabling aspect of PD— for example, depression alone may have over twice the impact of motor symptoms on health. Moreover, non-motor symptoms, such as urinary problems, pain, fatigue, daytime sleepiness, and cognitive impairment, are among those least responsive to the most commonly used medication L -dopa, yet these are the non-motor symptoms that improved the most in the ketogenic group compared to the low-fat group in this study. Since the magnitude of weight loss and BMI decrease were similar between groups, and the protocol and assessments were applied equally to both groups excepting the diets, neither weight loss nor a placebo effect explains the between-group differences in non-motor symptom improvements.
Phillips M, Murtagh D, Gilbertson L, et al. Low-fat versus ketogenic diet in Parkinson’s disease: a pilot randomized controlled trial. Mov Disord 2018;33:1306–1314.
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