Can You Take Too Much Vitamin C?

Check out this answer from Consensus:

While vitamin C is essential for health and offers numerous benefits, particularly in preventing chronic diseases and improving metabolic and cardiovascular health, excessive intake can lead to adverse effects. It is crucial to adhere to recommended dosages and consider individual factors such as body weight when determining the optimal intake. Further research is needed to solidify these findings and provide more precise guidelines for vitamin C consumption.

By understanding the balance between the benefits and risks of vitamin C, individuals can make informed decisions about their supplementation practices to optimize their health outcomes.

Vitamin C, also known as ascorbic acid, is a vital nutrient that plays a crucial role in various bodily functions, including the maintenance of skin, blood vessels, bones, and cartilage, as well as wound healing. While it is essential for health, there is ongoing debate about the optimal intake and potential risks associated with high doses of vitamin C. This article explores the benefits and potential harms of excessive vitamin C consumption.

Benefits of Vitamin C

Antioxidant Properties and Chronic Disease Prevention

Vitamin C is renowned for its antioxidant properties, which help neutralize free radicals and reduce oxidative stress. This function is particularly beneficial in preventing chronic diseases such as cardiovascular disease, stroke, and certain cancers. Research indicates that vitamin C supplementation can lower hypertension, improve endothelial function, and reduce chronic inflammation, all of which are risk factors for cardiovascular diseases and some cancers2.

Metabolic and Cardiovascular Health

In patients with diabetes or metabolic syndrome, vitamin C intake has been shown to improve metabolic parameters and lower total cholesterol levels, thereby reducing the risk of cardiovascular disease. Additionally, vitamin C can reduce markers of inflammation and oxidative stress, such as C-reactive protein and interleukin-6, which are associated with improved endothelial function and increased blood flow5.

Risks of Excessive Vitamin C Intake

Impact on Exercise and Training Efficiency

While vitamin C is beneficial in many aspects, excessive intake can have adverse effects, particularly in the context of physical exercise. A study found that high doses of vitamin C (1 g daily) can hamper endurance capacity by preventing exercise-induced cellular adaptations. This includes the reduced expression of key transcription factors involved in mitochondrial biogenesis and antioxidant enzymes, which are crucial for improving endurance performance1.

Potential Adverse Effects

High doses of vitamin C, especially when administered intravenously, have been associated with several adverse effects. These include oxalate nephropathy, hypernatremia, hemolysis in patients with glucose-6-phosphate dehydrogenase deficiency, and kidney stones. Although there is no consistent evidence that high-dose vitamin C therapy is more harmful than placebo in double-blind randomized controlled trials, these potential risks warrant specific monitoring6.

Safe Dosage Recommendations

Research suggests that the current Recommended Dietary Allowance (RDA) for vitamin C may be insufficient for optimal health benefits. Studies indicate that a daily intake of 200 mg is optimal for most adults, providing maximum health benefits with minimal risk of adverse effects. However, doses above 400 mg daily have no additional value and may increase the risk of adverse effects3. For individuals with higher body weight, an additional intake of 10 mg of vitamin C per day for every 10 kg increase in body weight is recommended to achieve comparable plasma concentrations4.

Can you take too much Vitamin C?

Anitra Carr has answered Extremely Unlikely

An expert from University of Otago in Vitamin C

No – you cannot take too much vitamin C. Firstly, the body has specialised vitamin C transporters in the small intestine that can take up only a certain amount of vitamin C at any one time (the rest is excreted in faeces). Secondly, because vitamin C is water-soluble, it is not stored in the body like the fat soluble vitamins A and D. Therefore, the body takes what it needs from the blood and the rest is excreted in urine. Unless a person has kidney failure, the evidence for the role of vitamin C in kidney stone formation is very equivocal and often does not take confounding factors into consideration [1,2].

References:

1.         Pullar JM, Carr AC, Vissers MC. Vitamin C supplementation and kidney stone risk. N Z Med J. 2013;126(1384):133-4.
2.         Prier M, Carr AC, Baillie N. No reported renal stones with intravenous vitamin C administration: A prospective case series study. Antioxidants. 2018;7(68):1-10.

Can you take too much Vitamin C?

Sofia Marques has answered Likely

An expert from Braga Public Hospital in Nephrology

High-dose intake of vitamin C, either orally or parenterally, can cause hyperoxaluria and oxalosis because vitamin C is oxidized to dehydroascorbic acid, which then breaks down to oxalate. Combined with cations such as calcium, oxalate can form crystals intratubularly (kidney stones) and cause acute tubular injury and nephrolithiasis.

There is no specific cut-off for what dose can cause harm. There are case reports where doses as low as 1g of vitamin C taken daily in association to other risk factors such as high-oxalate diets or gastrointestinal problems lead to oxalosis. In this relatively low doses there are usually other concomitant risk factors all concurring to the disease, it’s not the vitamin C alone. These are just case reports, not clinical trials so it is not possible to quantify the risk, but there is a signal.

Can you take too much Vitamin C?

Margreet Vissers has answered Unlikely

An expert from University of Otago in Vitamin C, Biochemistry, Cancer Immunology

It is difficult to take too much as your body will rapidly clear any excess. You can take more than is necessary though, but this is unlikely to be harmful apart from being a waste of time and money.

Can you take too much Vitamin C?

Jens Lykkesfeldt has answered Unlikely

An expert from University of Copenhagen in Pharmacology, Toxicology, Vitamin C

Probably not. Excess vitamin C is efficiently excreted through the urine. The recommended upper limit is 2 grams/day but the evidence that even higher amounts should be harmful is not convincing.

On the other hand, the evidence that amounts higher than 500mg/day are beneficial for healthy individuals is also not convincing and therefore there seems to be little reason to exceed 500mg/day. Having said that, evidence shows that when you are sick, it takes a considerably higher vitamin C intake to saturate the body – maybe up to 2-4 grams/day or even more. However, it has not been sufficiently investigated if a higher intake during disease actually improves recovery. Several studies are underway e.g. within sepsis and acute infections to figure out if high dose intravenous vitamin C may improve the prognosis of the patients.