Let us take a deeper look at the wisdom of the Donguibogam through the eyes of modern medicine. Many people turn to high-dose products seeking relief from fatigue. Regrettably, excessive intake of vitamin C—especially high-dose regimens known as a megadose—can trigger unexpected adverse effects on our kidneys. The hidden culprit behind this is oxalic acid.
Vitamin C is a water-soluble vitamin, commonly understood to be absorbed only as much as the body requires while the remainder is excreted in the urine. However, there is a crucial point here. Vitamin C absorbed into our body undergoes various metabolic pathways, and a portion of it is converted into oxalic acid in the liver. The problem is that when this oxalic acid is excreted in urine, it can combine with calcium inside the kidney to form calcium oxalate crystals. In fact, over 80% of kidney stones are calcium oxalate stones.
In particular, when high doses of vitamin C exceeding 1,000 mg daily are consumed over a long period, the amount of oxalic acid excreted in urine increases sharply. As the concentration of oxalic acid in urine rises, the urine becomes supersaturated. At this point, minute crystals form and clump together, gradually growing into a larger kidney stone. This follows a principle similar to sugar crystals settling at the bottom of a glass when too much sugar is added past the saturation point.
A kidney stone may present with no symptoms whatsoever in its early stages. However, as the calculus grows or travels from the kidney down into the ureter, it induces symptoms such as severe flank pain, hematuria, nausea, vomiting, and dysuria. This pain is counted among the most excruciating pains a person can experience. Furthermore, once a kidney stone forms, its recurrence rate is high, and in severe cases, it can impair kidney function or lead to chronic kidney disease.
Does everyone who takes a vitamin C megadose develop a calculus? Fortunately, that is not the case. A kidney stone arises from a combination of multiple factors. Risk factors include genetic predisposition, urine concentration resulting from inadequate hydration, dietary habits centered on salty foods or animal protein, consumption of high-oxalate foods like spinach, chocolate, and nuts, and preexisting kidney conditions. When high-dose vitamin C is added on top of these, the risk of calculus development rises substantially.
The daily recommended intake of vitamin C for adults suggested by the World Health Organization is approximately 100 mg. The daily recommended intake established by Korea's Ministry of Food and Drug Safety is also 100 mg. While the tolerable upper intake level is set at 2,000 mg, this applies to general scenarios; individuals with concerns regarding kidney health must exercise caution even with far smaller amounts. It is essential to understand your body's condition and consume an appropriate quantity. If you have been taking a vitamin C megadose for an extended period and have experienced symptoms such as flank pain or a sensation of residual urine, do not hesitate to consult a doctor. Making informed choices to consume vitamin C safely is an important first step.
