Is taking 1000mg of vitamin C (ascorbic acid) at nighttime excessive?

Vitamin C Supplementation at Nighttime: Safety of 1000mg Dose

Taking 1000mg of vitamin C at nighttime is generally excessive for most healthy individuals and may cause sleep disturbances, gastrointestinal upset, and increased risk of kidney stones in susceptible individuals.

Safety and Recommended Dosages

The recommended daily intake of vitamin C varies by authority, with significantly lower amounts than 1000mg considered sufficient for most people:

• US Recommended Dietary Allowance (RDA): 75mg/day for women and 90mg/day for men 1
• European recommendations: 95mg/day for women and 110mg/day for men 1

Potential Concerns with 1000mg Dosing

1. Kidney Stone Risk: Vitamin C can be metabolized to oxalate, increasing the risk of calcium oxalate stone formation. A metabolic trial demonstrated that 1000mg of supplemental vitamin C consumed twice daily increased urinary oxalate excretion by 22%, and men consuming ≥1000mg/day had a 40% higher risk of kidney stone formation compared to those consuming less than 90mg/day 2

2. Gastrointestinal Effects: High doses of vitamin C (>2g) can cause gastrointestinal upset, including diarrhea, nausea, and abdominal cramps 3, 4

3. Sleep Disruption: While moderate vitamin C intake may help prevent sleep disorders 5, high doses taken at night might interfere with sleep quality due to its stimulating properties

Special Considerations for Nighttime Dosing

Taking vitamin C at nighttime specifically may be problematic for several reasons:

1. Nighttime Noise Sensitivity: Research suggests that vitamin C supplementation can affect vascular function and potentially increase sensitivity to nighttime noise disturbances, which could impact sleep quality 2

2. Pro-oxidant Effects: Under certain conditions (especially at night when metabolism slows), high-dose vitamin C can act as a pro-oxidant rather than an antioxidant 2, 4

3. Stimulating Properties: Vitamin C is involved in the biosynthesis of neurotransmitters like noradrenaline and serotonin 2, which could potentially interfere with normal sleep patterns when taken at night

Recommendations for Vitamin C Supplementation

For Healthy Individuals:

• Aim for the RDA (75-90mg/day) through diet or supplements
• If supplementing, consider taking vitamin C in the morning rather than at night
• Split higher doses throughout the day rather than taking all at once

For Special Populations:

• Dialysis patients: 200-500mg/day 1
• Critical illness: Higher doses may be warranted under medical supervision 2, 1

Conclusion

While vitamin C is generally safe, a 1000mg dose at nighttime exceeds daily requirements by 10-fold and may cause adverse effects, particularly related to sleep quality, gastrointestinal comfort, and kidney stone risk in susceptible individuals. For most people, lower doses distributed throughout the day or taken in the morning would be more appropriate and just as effective for maintaining vitamin C status.