natural? synthesis? neutrality?
Two criteria for choosing good vitamin C
01 Synthetic vitamin C or natural vitamin C
02 neutral vitamin C

Whether it is natural or synthetic
Vitamin C is both natural and synthetic. Each supports a different position. Groups emphasizing synthetic vitamin C emphasize studies showing that there is no difference in efficacy, including bioavailability, between synthetic and natural vitamin C. It is clearly different from vitamins A and E, which emphasize naturalness. The story that vitamin C is synthesized from coal tar, a by-product of oil production, is always wrong. This is related to the manufacturing process of some vitamins, such as B vitamins, and has nothing to do with vitamin C. Today, vitamin C is usually synthesized by fermenting glucose from corn or potatoes. So, those who emphasize synthesis emphasize that even synthetic vitamin C is made from plants.
However, the side that emphasizes nature criticizes the claim that 'vitamin C = ascorbic acid'. The logic is that vitamin C, which is consumed in food, is effective only when various types of plant components such as flavonoids and coenzymes are combined in addition to ascorbic acid. Vitamin C is also a natural vitamin that is close to the form of food, if possible. Natural vitamin C preparations are extracted from real fruits, such as acerola and lemon, and are formulated into pills. Not surprisingly, the cost is high, and the pills are large and difficult to swallow. First of all, natural vitamin C is too low in actual vitamin C content in a single tablet. Low purity is one of the disadvantages of natural vitamins.
What do I think...
When it comes to vitamin C, I don't think it's necessary to be as sensitive as vitamins A or E to whether it's synthetic or natural. However, when a large amount of high-purity vitamin C is injected intravenously at once, synthesis is advantageous in all aspects, including cost and administration process. However, for small daily use, I would recommend natural vitamin C, assuming you can afford it.
Neutral vitamin C is also good to know
Regarding vitamin C preparations, it is also good to know the neutral vitamin C that has recently been on the market. As you know, vitamin C has a low acidity and tastes sour and can cause stomach upset in people with stomach aches or sensitive stomachs. In this case, the so-called neutral vitamin C, which reduces acidity in combination with calcium minerals, helps. It does not irritate the stomach, so it can be taken before meals or on an empty stomach. The downside is that it is more expensive than regular vitamin C preparations. Neutral vitamin C and general vitamin C preparations do not differ in blood concentration or urine excretion. However, studies have shown that neutral vitamin C preparations are advantageous in terms of increasing the concentration of vitamin C in white blood cells. If you have a sensitive stomach, it is better to choose a neutral vitamin C formulation.

Esther Lyuh, Doctor of Preventive Medicine, Seoul National University