Vitamin C in Human Health And Disease is Still A Mystery?

Vitamin C in human health and disease is still a mystery?

Ascorbic acid is one of the important water-soluble vitamins. It is essential for collagen, carnitine, and neurotransmitters biosynthesis. Most plants and animals synthesize ascorbic acid for their requirement. However, apes and humans can not synthesize ascorbic acid due to the lack of an enzyme gluconolactone oxidase. Hence, ascorbic acid has to be supplemented mainly through fruits, vegetables, and tablets.

The current US recommended daily allowance (RDA) for ascorbic acid ranges between 100–120 mg/per day for adults. Many health benefits have been attributed to ascorbic acid such as antioxidant, anti-atherogenic, anti-carcinogenic, immunomodulatory, and prevent cold, etc. Visit here;

However, lately, the health benefits of ascorbic acid have been the subject of debate and controversies viz., Danger of mega doses of ascorbic acid? Does ascorbic acid act as an antioxidant or pro-oxidant? Does ascorbic acid cause cancer or may interfere with cancer therapy?

However, the Panel on dietary antioxidants and related compounds stated that the in vivo data do not clearly show a relationship between excess ascorbic acid intake and kidney stone formation, pro-oxidant effects, excess iron absorption. 

Several clinical and epidemiological studies on the anti-carcinogenic effects of ascorbic acid in humans did not show any conclusive beneficial effects on various types of cancer except gastric cancer. Recently, a few derivatives of ascorbic acid were tested on cancer cells, among them, ascorbic acid esters showed promising anticancer activity compared to ascorbic acid.

Ascorbyl stearate was found to inhibit the proliferation of human cancer cells by interfering with cell cycle progression, induced apoptosis by modulation of signal transduction pathways. However, more mechanistic and human in vivo studies are needed to understand and elucidate the molecular mechanism underlying the anti-carcinogenic property of ascorbic acid.

Thus, though ascorbic acid was discovered in the 17th century, the exact role of this vitamin/nutraceutical in human biology and health is still a mystery given many beneficial claims and controversies.

Historical perspective

The sea voyager/sailors developed a peculiar disease called scurvy when they were on the sea. This was found to be due to eating non-perishable items and a lack of fresh fruits and vegetables in their diet. A British naval Physician, Lind documented that there was some substance in citrus fruits that can cure scurvy. He developed a method to concentrate and preserve citrus juice for use by sailors.

British Navy was given a daily ration of lime or lemon juice to overcome the ascorbic acid deficiency. Ascorbic acid was first isolated from natural sources and structurally characterized by Szent-Gyorgyi, Waugh, and King. This vitamin was first synthesized by Haworth and Hirst. Currently ascorbic acid is the most widely used vitamin supplement throughout the world.

Sources of Ascorbic acid

Ascorbic acid is widely distributed in fresh fruits and vegetables. It is present in fruits like orange, lemons, grapefruit, watermelon, papaya, strawberries, cantaloupe, mango, pineapple, raspberries, and cherries. It is also found in green leafy vegetables, tomatoes, broccoli, green and red peppers, cauliflower, and cabbage.

Most plants and animals synthesize ascorbic acid from D-glucose or D-galactose. A majority of animals produce relatively high levels of ascorbic acid from glucose in the liver.

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