Vitamin C, also known as ascorbic acid, is an essential nutrient for the human body. On May 21, the U.S. website "Medscape" published an article by Dr. Sandra Fryhofer, former president of the American College of Physicians and associate professor at Emory University School of Medicine, warning that long-term excessive intake of Vitamin C may cause kidney stones.
Vitamin C is a water-soluble vitamin, and any excess can be excreted through urine. However, this does not mean that it can be supplemented casually. The Swedish Institute for Environmental Medicine and the Department of Nutritional Epidemiology conducted a study that tracked and followed up on data from over 22,000 men, of whom 907 reported taking at least 1000 mg of Vitamin C supplements daily. During the 10-year follow-up period, 3.4% of the Vitamin C supplement users developed kidney stones, compared to 1.8% in the non-supplement group. The risk of developing kidney stones for those taking high-dose Vitamin C supplements was twice that of the general population. The highest risk of kidney stones was found in those who took seven Vitamin C tablets per week (each containing 1000 mg), while this proportion did not increase in those taking multivitamins or frequently consuming foods rich in Vitamin C. Fryhofer explained that Vitamin C absorbed by the body is excreted in urine in the form of oxalate. Oxalate is a primary component of kidney stones, and excessive excretion can increase the burden on the kidneys. Those who already have kidney stones should be even more cautious.
Fryhofer recommends that the daily supplemental intake of Vitamin C should not exceed 1000 mg. If you consume enough fresh vegetables and fruits daily, there is generally no need for extra supplementation. For those who need to take supplements due to an irregular diet, attention should be paid to the dosage. For example, a common Vitamin C effervescent tablet contains 1000 mg of Vitamin C, and only one tablet per day is needed. It is not recommended to take multiple types of vitamin supplements simultaneously. Special attention should be paid to the summer season, as increased sweating can lead to reduced urination if water intake is not timely, increasing urine concentration and the risk of stones. Therefore, when supplementing with Vitamin C in the summer, it is crucial to drink plenty of water.