[Vitamin C Episode 1] Arguments and Criticisms of Vitamin C | Dr. Esther Yeo

Vitamin C is one of the most widely known nutritional supplements in our country. However, the evaluation of this nutritional supplement varies widely.

Let's start with the cult theory...

First of all, let's look at the cult theory. It is usually claimed that it is better to take 6~10 pills a day, that is, 6~10 grains in a thick pill of 1g. It's almost a fist. It is said to help fight fatigue and prevent colds. It is also said to be good for diabetes and cancer. Even if you eat a lot, it is water-soluble, so it is said that there is no problem with it escaping in the urine. The current scientific recommendation of 100 mg per day is the minimum dose to prevent vitamin C deficiency such as scurvy, and it is said that much more should be taken for actual health. The background of the dosage of 6~10g per day is the comparison of animal weight and human weight. Most animals, such as dogs, cats, and mice, synthesize vitamin C in their bodies, while primates such as humans cannot make vitamin C on their own and must consume it daily from food. If an animal weighs 70kg, the body synthesizes 6~10g, so humans should eat that much.

Vitamins that are very safe against side effects

I agree with the argument that vitamin C is safe as far as side effects are concerned. At best, it can cause loose stools and heartburn, but it's mostly safe to overdose. However, there is also disagreement among scientists about its dosage. Regarding the effectiveness of large vitamin C intake, there are still not enough papers that prove its effectiveness in preventing disease through large-scale epidemiological studies over a long period of time. 

A voice of criticism as high as praise

Critics of vitamin C are also vocal. It is argued that there is no point in consuming more than 1 gram of vitamin C per day, since the absorption rate drops by less than half in the small intestine, and the remaining vitamin C is excreted in the urine. While many patient-controlled studies have shown that vitamin C has health benefits, such as its anti-cancer effects, most of the randomized clinical studies that can more clearly demonstrate causality have not shown its effectiveness.

If we look at the patient-controlled study...

A patient-controlled study compares how much vitamin C a patient with a particular disease has taken in the past with a control group that does not have a particular disease. It is a method of looking at the effect first and then the cause. Many studies in this way have shown that vitamin C is beneficial. It appears that the control group consumed more vitamin C than the patients.

However, the problem with patient-controlled studies is that they rely on memory to determine whether or not a person is taking vitamin C. Randomized clinical studies, on the other hand, put two groups of people in the first place, with one given vitamin C and the other given a placebo that looks the same but is made from wheat flour. And after more than a few years of observation, they compare how much of a particular disease occurs on both sides. Since it is a method of providing the cause first and weighing the result later, it is advantageous to infer an accurate causal relationship because it fits the flow of time and allows the research to proceed according to the researcher's intention, not the participant's memory.