Updated March 10, 2025
As of March 10, 2025 we found no new data to support any changes in our TOE grades.
Key Information
Click on any letter grade below for more info:
Preclinical Trials Grade:
C
Published: Jul 2021
Vitamin C is safe and inexpensive. As an antioxidant, it has a plausible mechanism for influencing the course of neurodegenerative diseases. Two flawed preclinical studies by the same group showed benefits in a mouse model of familial ALS. There are two case reports in which it was associated with improvement. However, there are multiple possible explanations for the improvement in these cases. It is not clear which if any dose of vitamin C might be beneficial for PALS; a small clinical trial using oral vitamin C at 2,000 mg daily was unable to demonstrate benefits in PALS. Based on this negative trial, we currently advise against using vitamin C to treat ALS.
Grade A: Shown in a peer-reviewed publication to act on a relevant mechanism in humans
Grade B: Shown in a peer-reviewed publication to act on a relevant mechanism in pre-clinical model(s)
Grade C: Theoretically and plausibly acts on an ALS-relevant mechanism in humans
Grade D: Acts on a biological mechanism but it is not clear that this mechanism is relevant in ALS
Grade F: Implausible; would violate known principles or laws of biology
Grade U: No useful information was found for this category
Grade A: Two or more peer-reviewed publications reporting benefits in well-designed studies.
Animal studies are assumed to be ‘well designed’ when they follow published guidelines. When they deviate from these they are considered ‘flawed’.
Grade B: One peer-reviewed publication reporting benefits in a well-designed study.
Animal studies are assumed to be ‘well designed’ when they follow published guidelines. When they deviate from these they are considered ‘flawed’.
Grade C: One or more peer-reviewed publication(s) reporting benefits in flawed studies.
Animal studies are assumed to be ‘well designed’ when they follow published guidelines. When they deviate from these they are considered ‘flawed’.
Grade D: One or more non-peer reviewed studies reporting benefits (published on a website or in an abstract)
Grade F: The only studies available show no benefit
Grade U: No useful information was found for this category
Grade A: One or more peer-reviewed publications reporting benefits with validated diagnosis and benefits
Grade B: More than one unpublished report of benefit with validated diagnosis and benefits
Grade C: One unpublished report of benefit with validated diagnosis and benefits
Grade D: Subjective report(s) of benefit without validated diagnoses and/or benefits
Grade F: The only reports available show no benefit
Grade U: No useful information was found for this category
Two or more peer-reviewed publications describing benefits in well-designed randomized, blinded placebo-controlled phase III trials
Grade C: One or more peer-reviewed publications reporting benefits in a well-designed randomized, blinded, placebo-controlled phase I or II trial
Grade D: One or more peer-reviewed publications reporting benefits in a flawed trial.
Flawed trials means those in which there are identifiable problems with patient selection, randomization, blinding, controls or follow-up. These have ‘high or unclear risk of bias’ according to published criteria. Well-designed trials are those that have ‘low risk of bias’.
Grade F: The only trials available show no benefit
Grade U: No useful information was found for this category
Grade A: No exposed patients appear to have experienced harms
Grade B: More than 0% but less than 10% of exposed patients experienced harms (no hospitalizations or deaths)
Grade B (oral): More than 0% but less than10% of exposed patients experienced harms (no hospitalizations or deaths)
Grade D (intravenous): More than 0% but less than 5% of exposed patients experienced death or hospitalizations
Grade C: At least 10% of exposed patients experienced harms (no hospitalizations or deaths)
Grade D: More than 0% but less than 5% of exposed patients experienced death or hospitalizations
Grade D: More than 0% but less than 5% of exposed patients experienced death or hospitalizations
Grade F: At least 5% of exposed patients experienced death or hospitalization
Grade F: At least 5% of exposed patients experienced death or hospitalization
Grade U: No useful information was found for this category
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