Why High Dose Vitamin C Can Be Bad For Your Health (and alternatives!)

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Vitamin C, also known as ascorbic acid, is an essential water-soluble vitamin that supports the immune system, skin health, and wound healing. It acts as a powerful antioxidant, helping to protect cells from damage caused by free radicals. Citrus fruits, strawberries, bell peppers, and leafy greens are common sources of vitamin C in the diet.

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What is Vitamin C?

Vitamin C, also known as ascorbic acid, is a water-soluble vitamin found in fruits and vegetables. It can also be obtained through dietary supplements. Vitamin C is an essential nutritional element that our bodies cannot produce naturally, making it important to include it in our daily diets.

Tangerines a creat source of vitamin c

Why do we need vitamin C?

Vitamin C serves several roles in maintaining human health. First, it plays a pivotal role in keeping our skin healthy by preventing the inactivation of two key enzymes:

Which are essential for collagen production. Collagen, in turn, helps accelerate wound healing and skin elasticity.

skin

Second, vitamin C acts as a cofactor in the synthesis of L-carnitine, a molecule necessary for fatty acid metabolism. It also contributes to the production of neurotransmitters like catecholamines, facilitating various physiological functions. These processes involve hydroxylation steps, where vitamin C optimizes enzyme activity.

Various vitamin c rich fruits

Third, vitamin C exhibits potent antioxidant properties. It functions as a scavenger, neutralizing harmful free radicals and oxygen-derived species, safeguarding our cells from oxidative stress-induced damage. This protective quality is particularly significant in potentially preventing conditions like atherosclerosis and cancer, which can result from tissue damage caused by oxidative stress. Vitamin C's antioxidant capabilities also help shield against UV-induced skin damage.

Vitamin C is a major player in bolstering the immune system, helping the body fend off infections. It also facilitates the absorption of nonheme iron, helping the body's iron utilization.

A deficiency in vitamin C leads to a condition known as scurvy, characterized by symptoms such as:

  • Fragile skin, 

  • Bleeding gums, 

  • Fatigue, and 

  • Weakened connective tissues. 

Therefore, ensuring an adequate intake of vitamin C is essential for overall health and well-being.

a fatigued woman

Interestingly, however, people who have been following a Carnivore Way of Eating for many decades seem to have no problem with lacking daily Vitamin C in their diet. We don't know exactly why this is, though I speculate that when the dietary intake is so low in carbs, the body's need for Vitamin C diminishes.


Why Opt for a Salad Over Vitamin C Supplements?

Based on what we have covered so far, vitamin C is great. You probably want more of it in your diet. Hold that thought. When you’re consuming 500 mg or more of vitamin C on a daily basis, there are  potential risks involved. Excessive intake of vitamin C can transform it from a beneficial nutrient into a potential toxin, leading to issues like:

While we've long been advised about the benefits of vitamin C, such as its potential to ward off colds, it's crucial to recognize that excessive intake can have unintended consequences. Recent research has cast doubt on the once-held belief that vitamin C supplements effectively prevent colds, with effectiveness limited to those engaging in physically demanding work or endurance sports.

From Vitamin C to Oxalic Acid

a woman in EXCRUCIATING pain, similar to passing a kidney stone

The human body has a tendency to metabolize excess vitamin C into a corrosive substance known as oxalic acid. You can find out more about oxalates in your diet in this blog post. This acid readily binds to essential minerals like calcium, forming oxalate. As the kidneys work to remove oxalate from the bloodstream, calcium oxalate crystals can develop. These crystals have sharp edges and can cause damage in tissues in the body, including organs, muscles, blood, etc. Oxalates in the body can also lead to painful stones, not only in the kidneys but potentially anywhere in the urinary tract. Over time, if the kidneys are continually burdened with excessive oxalates, it can lead to kidney failure, emphasizing the potential danger of high vitamin C intake. This phenomenon raises concerns that the modern trend of taking excessive vitamin C supplements may be contributing to the increasing incidence of kidney stones and other chronic symptoms, with one estimate suggesting that half of the population will experience kidney stones during their lifetime.


When these unprocessed oxalates escape the kidneys or become lodged in other tissues throughout the body they can create additional health complications. Oxalate crystals have been identified in various human tissues, including;

  • Bones, 

  • Joints, 

  • Glands (especially the thyroid), 

  • Blood vessels, 

  • Arterial plaque, 

  • Eyes,

  • Lungs,

  • Skin. 

These crystals are sharp and irritating, capable of triggering immune responses and inflammation. They may also generate free radicals, which can damage cell membranes and organelles, particularly the critical energy-producing mitochondria.

When cells attempt to dissolve oxalate crystal deposits, oxalate molecules or ions may shift within the body, potentially leading to episodic pain and impairing brain and nerve functions. This can affect various aspects of daily life, including:

  • Sleep, 

  • Concentration, 

  • Memory, and 

  • Cognitive abilities. 

Excessive vitamin C intake may also heighten the risk of calcium oxalate deposits, contributing to bone issues and joint pain.

What's the Safe Amount of Vitamin C?

When it comes to vitamin C, determining a safe intake level is very important. The Recommended Dietary Allowance (RDA) for ascorbic acid, or vitamin C, stands at 75 mg for adult females and 90 mg for adult males. While these numbers might seem small, even a mere 10 mg is sufficient to prevent scurvy, the dreaded Vitamin C deficiency disease. Most individuals can safely consume 150-200 mg of vitamin C daily without crossing the threshold that leads to excess oxalate production in the body. This level of intake can typically be achieved through a balanced diet that includes fruits and vegetables.

vitamin c SUPPLEMENT

Let's consider two hypothetical diets: one abundant in healthy, fresh foods and another predominantly composed of fast food. 

On the healthy diet side, there will be an abundance of fresh low-carb veggies. For instance, a lunch consisting of chicken stew and a salad featuring romaine lettuce and a quarter of a red bell pepper can provide 60-70% of the RDA for vitamin C. If the salad dressing includes lemon juice, it adds another 5 mg, bringing the vitamin C content to approximately 59-66 mg. Including 2 sliced radishes (about 4 mg of vitamin C) can elevate the vitamin C content of lunch to nearly 70 mg, which is 78-93% of the RDA. However, many people opt for convenience foods, as seen in most fast-food diets.

a healthy food platTer

Let’s take a look at a typical fast food diet, which, without additional fruits or vegetables, supplies only about 25% of the RDA for vitamin C. Incorporating just a quarter of a fresh bell pepper (38 mg of vitamin C) and half a cup of raw cantaloupe (23 mg of vitamin C) would bring this fast-food diet up to the RDA for vitamin C. Nonetheless, it's crucial to note that adding bell peppers and cantaloupe cannot address the myriad other nutritional deficiencies and health issues associated with a fast-food diet.

junk food with a side of fresh veGGies


These examples underscore the importance of including fresh vegetables in your diet to meet vitamin C requirements. Daily consumption of fresh vegetables, like broccoli with dinner or a simple salad, can easily help you achieve your vitamin C goals. Remember, vitamin C is not stored in the body, so daily intake is important if you are eating carbs. Always opt for obtaining your regular daily Vitamin C through your foods rather than a high dose supplement.

The one caveat here is that if you are starting to have symptoms of an acute infection, high doses of Vitamin C are helpful to stave off the infection, along with other measures. Only for acute infections, though, so you'd only be taking it for a few days, not for weeks or months (or years for some!).

DISCLAIMER: The information offered is for informational and educational purposes only. It is not intended as a substitute for medical or psychological care or advice. Consult your physician or other health care provider regarding your symptoms and medical and psychological needs.

References
Curhan, G. C., Willett, W. C., Speizer, F. E., & Stampfer, M. J. (1999). Intake of Vitamins B6 and C and the Risk of Kidney Stones in Women. Journal of the American Society of Nephrology, 10(4), 840–845.

Canavese, C., Petrarulo, M., Massarenti, P., Berutti, S., Fenoglio, R., Pauletto, D., … Marangella, M. (2005). Long-term, low-dose, intravenous vitamin C leads to plasma calcium oxalate supersaturation in hemodialysis patients. American Journal of Kidney Diseases: The Official Journal of the National Kidney Foundation, 45(3), 540–549. http://doi.org/10.1053/j.ajkd.2004.10.025

Padayatty, S. J., Sun, A. Y., Chen, Q., Espey, M. G., Drisko, J., & Levine, M. (2010). Vitamin C: intravenous use by complementary and alternative medicine practitioners and adverse effects. PloS One, 5(7), e11414. http://doi.org/10.1371/journal.pone.0011414

Parasuraman, R., & Venkat, K. K. (2010). Crystal-Induced Kidney Disease in 2 Kidney Transplant Recipients. American Journal of Kidney Diseases, 55(1), 192–197. http://doi.org/10.1053/j.ajkd.2009.08.012

Rosenthal, A., Ryan, L. M., & McCarty, D. J. (1988). Arthritis associated with calcium oxalate crystals in an anephric patient treated with peritoneal dialysis. JAMA, 260(9), 1280–1282.