Vitamin C is a popular vitamin that people supplement to improve their overall health. Megadosing vitamin C is recommended in the alternative health community for relieving influenza and the common cold. You do need adequate amounts of vitamin C for proper health. Vitamin C is essential for innate immunity, collagen synthesis, carnitine synthesis, and catecholamine (dopamine, noradrenaline, and adrenaline) production. However, health issues may arise when people take vitamin C supplements, even natural sourced vitamin C supplements, not just synthetic isolated ascorbic acid. What are some reasons that supplementing vitamin C may harm your health, and why should some people only get adequate amounts of vitamin C from dietary sources instead of supplements?1

Health Issues That May Be Caused By Vitamin C Supplementation

Specific health issues caused by vitamin C supplementation include:

  • Both natural and artificially sourced vitamin C ingestion may cause oxalic acid accumulation within the human body. Oxalic acid can crystallize within our joints and skin and cause various symptoms, including pain, inflammation, and itching. For some people (possibly if they are heavy metal cadmium toxic, cadmium might oxidize vitamin C to form oxalic acid), excess consumption of vitamin C supplemental ingestion might produce oxalic acid within the human body. If vitamin C supplementation does cause you to accumulate oxalic acid, when the oxalic acid is dumped into our bloodstream from detoxification and binds with minerals including calcium within our kidneys, calcium oxalate stones are formed. Kidney and/or bladder stones form and may pass (if they do not pass and block the kidneys ability to excrete waste, it may become a medical emergency,) causing health issues and sometimes severe pain.2 3
  • Diarrhea may occur from megadosing vitamin C (more than a few thousand milligrams) within a short time period (within one to two hours). Excessive vitamin C supplemental ingestion can irritate your intestinal lining, open up your gut junctions further (cause or worsen leaky gut,) and flush water and electrolytes into the intestinal tract as an osmotic laxative, causing diarrhea.4  
  • Taking naturally and artificially sourced vitamin C supplements increases iron absorption from supplements or iron-containing food. In addition, when supplementing with iron, megadosing vitamin C may increase iron oxidation and create excess oxidative stress within our cells. If you suffer from hemochromatosis, you want to avoid iron supplementation and possibly even take vitamin C for hours around the time you eat iron-rich foods, including meat, spinach, or animal liver supplements.5 6 7 8 9
  • Supplementing with non-buffered ascorbic acid may cause/worsen gastritis and stomach ulcerations. Non-buffered ascorbic acid supplements, especially taken on an empty stomach, may irritate or inflame gastritis and stomach ulcerations because ascorbic acid is quite acidic (less than a pH of 3).10
  • Supplementing with non-buffered ascorbic acid in a powdered form mixed with a beverage may worsen reflux disorder symptoms by irritating and/or inflaming the throat and esophagus because ascorbic acid is quite acidic. People suffering from silent reflux should avoid powered non-buffered ascorbic acid or even natural sourced vitamin C powders, for example, acerola cherry powder because their acidity reactivates the protein-digesting enzyme pepsin embedded in tissue triggering inflammation and/or irritation.11

Vitamin C supplementation DOES NOT affect the microbiome of the jejunum, ileum, or colon when ingested orally. Non-buffered ascorbic acid might reduce upper gut dysbiosis because it is quite acidic, and numerous microbes cannot survive in an acidic environment like our stomach (our stomach is supposed to be acidic).

Here’s another Fix Your Gut blog for you to read on the dangers of vitamin C supplementation.

My above blog post was to bring awareness to potential issues vitamin C supplementation may cause but should not disparage proper vitamin C supplementation when necessary. Ingesting adequate amounts of vitamin C is crucial for our health to prevent scurvy (vitamin C deficiency). Megadosing vitamin C is sometimes essential for cancer therapy, as an antihistamine, recovery from surgery, and/or recovery from viral infections including Covid, Influenza, or common cold.12

Are you having issues from supplementing Vitamin C, or any other related health issues?

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