[Vitamin C Episode 1] Praise and Criticism of Vitamin C | Dr. Esther Lyuh

Why are opinions on vitamin C different?

A mysterious disease that hit the navy... What is the cause?

The greatest scourge of the 18th-century British navy was a mysterious disease prevalent among sailors. His gums bleed, his joints ached, and he died. For more than a few years, grains and meat were the main sources of food for those away from land and fighting at sea. In other words, not eating vegetables and fruits caused vitamin C deficiency.

The solution to the problem is lemon... Vitamin C!

Scurvy is a disease that occurs when vitamin C deficiency progresses for more than several months. Scurvy has been the leading cause of death among sailors for hundreds of years. In 1499, 116 of the 170 sailors of Vasco da Gama's fleet died, and in 1520, 208 of the 230 sailors of Magellan's fleet died of scurvy. Then, in 1747, James Lind, a British surgeon, supplied lemons to sailors, and the problem was solved.  But at the time, I didn't know that lemons contain vitamin C and that vitamin C works as a cure for scurvy. In 1937, Hungarian scientist Albert Gyorgyi, who discovered the physiological action of vitamin C, was awarded the Nobel Prize in Physiology or Medicine. And in 1934, the Swiss pharmaceutical company Hofmann Laroche succeeded in mass-producing vitamin C for the first time in history.

Praise vs Criticism

Vitamin C is one of the most widely known nutritional supplements in Korea. However, reviews of this nutrient vary widely.

First, let's take a look at the theory...

Let's look at the precepts first. Usually 6-10g a day, it is said that it is good to eat 6-10 pills in 1g thick pills 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 urine. Currently, 100mg, the daily recommended amount used in the academic world, is the minimum dose to prevent symptoms of vitamin C deficiency such as scurvy, but it is said that you should consume much more than this for actual health. The background of the dose of 6 to 10 g per day is that it is converted by comparing animal and human body weight. Most animals, such as dogs, cats, and mice, synthesize vitamin C within the body, while primates, such as humans, cannot make vitamin C on their own and must consume it daily through food. The logic is that an animal weighing 70kg synthesizes 6-10g in the body, so humans should eat that much too.

Very safe vitamin with no side effects

I agree with the claim that vitamin C is safe as far as side effects are concerned. At most, it can cause watery stools and stomach upset, but it is mostly safe even when taken in excess.  However, there is disagreement among scientists as to capacity. This is because there is still a lack of papers proving the effect of vitamin C in large doses on disease prevention through long-term, large-scale epidemiologic studies. 

Voices of criticism as high as praise

Critics are also vocal about vitamin C. Absorption of more than 1 g of vitamin C per day is less than half in the small intestine, and the remaining vitamin C is excreted in the urine, so excessive intake is useless.  In case-control studies, there are many results that vitamin C is beneficial to health, such as anti-cancer effects, but most of the effects have not been proven in randomized clinical studies that can more clearly demonstrate the causal relationship.

Looking at case-control studies...

A case-control study compares past intakes of vitamin C between patients with a particular disease and a control group who do not. It is a way to put the effect first and then the cause. Many of these studies have found vitamin C to be helpful. It turns out that the control group consumed more vitamin C than the patients.


However, the problem with case-control studies is that they rely on memory to determine whether vitamin C was consumed or not. On the other hand, in a randomized clinical study, two groups of people were initially given vitamin C, and the other was given a placebo of the same shape but made from wheat flour. Then, after observing them for years or more, they compare how much a particular condition develops on both sides. Because it is a method of providing a cause first and examining the result later, it is advantageous in inferring an accurate causal relationship because it fits the time flow and allows the researcher to proceed with the researcher's intention rather than the participant's memory.

Do not expect too much

Unfortunately, randomized clinical trials of vitamin C are mostly disappointing. There was no preventive effect in most diseases such as cancer, heart disease, high blood pressure, and diabetes.  In the case of multivitamins and vitamin D preparations, this contrast with the positive results of several important randomized clinical trials showing reductions in morbidity and mortality. I don't think it's right to have too many expectations regarding the prevention and treatment of diseases, especially cancer.

Esther Lyuh, Doctor of Preventive Medicine, Seoul National University