Vitamin C (ascorbic acid)

Vitamin C (ascorbic acid)

During the Age of Exploration, when human beings started making long journeys on sailing ships, the sailors were plagued by a potentially deadly disease called scurvy. People with scurvy bruised easily and often lost their teeth. If the disease is allowed to progress, the poor victim will eventually die of internal bleeding. The prevention and cure seemed to be fresh fruit and vegetables, which were hard to keep on long voyages.

One of the great landmarks in the history of medicine was the discovery of the cure for scurvy. In 1747, while serving as surgeon on the British Royal Navy ship HMS Salisbury, James Lind carried out an experiment to find the best treatment for scurvy in sailors. He selected 12 scurvy victims and divided them into 6 pairs. Each group received a different treatment in addition to their ordinary rations. Some were given cider, others a mixture of garlic, mustard and horseradish. Some were given seawater. Some were given spoonfuls of vinegar or dilute sulfuric acid. Two men were given oranges and lemons. Unlike the other men, the ones who had received the oranges and lemons rapidly recovered.

By the early 20th century, it was clear that no animal could survive on a mixture of purified protein, carbohydrate, fat, and minerals. They all needed trace amounts of several organic compounds that could only be found in plant or animal tissue. There were several different syndromes that each seemed to result from deficiency of a particular compound. At first, chemists suspected that all of these compounds were amines, so they called them “vitamines,” which was short for vital amines. After they realized that some of the compounds weren’t amines, the name was changed to vitamins.

Scientists suspected that there were at least four vitamins, called A, B, C, and D. Vitamin A was fat-soluble and found in the butterfat of cow’s milk. Vitamin B was water-soluble and found in the watery portion of cow’s milk. Later on, it was discovered that cow’s milk contains several water-soluble vitamins, so they were named B1, B2, and so on. Vitamin C was the compound found in fresh fruits and vegetables that prevented and cured scurvy. Vitamin D was whatever it was in cod-liver oil that cured rickets. Later on, nutrition researchers discovered vitamin E and vitamin K (from the German “Koagulations-Vitamin,” because it was involved in coagulation or clotting of the blood).

At first, scientists believed that you had to eat some fruit or vegetable in order to prevent or cure scurvy, In 1928, however, an Arctic explorer named Vilhjalmur Stefansson showed that the Eskimos avoided scurvy on their essentially plant-free diet, while Europeans got scurvy from eating those same foods, because the Eskimos ate their meat virtually raw. In the late 1920s, a Hungarian chemist named Albert Szent-Györgyi had isolated a compound he called hexuronic acid, which he suspected was responsible for vitamin C activity. When his theory was proved correct, hexuronic acid was renamed ascorbic acid, and Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine or Physiology. In 1933, several chemists independently figured out how to synthesize ascorbic acid. Vitamin C, along with the other vitamins, quickly became available cheaply in pill form.

The discovery of ascorbic acid cleared up a mystery that had dated from the Age of Exploration. Why did the human beings on long sea voyages fall prey to scurvy, while the ship’s rats and the ship’s cat stayed in perfect health? The answer is that nearly all animals, the notable exceptions being human beings and other primates as well as guinea pigs, can make their own supply of ascorbic acid. Thus, vitamin C is a vitamin for human beings and a few other species but is not an essential nutrient for rats or cats or most other animals.

Ascorbic acid performs many important functions in the body. It is an electron donor for eight important enzymes, three of which are essential for building and repairing collagen. This explains why vitamin C deficiency causes problems with the connective tissue. Two of the enzymes are essential for the production of carnitine, which cells need in order to transport fatty acids into the mitochondria (the powerhouses of the cell), so that they can be burned in order the release the energy needed to produce ATP, which is the main form of energy used in the cell.

The fact that ascorbic acid acts as an electron donor means that it is an antioxidant. It can therefore help to protect the body against the damaging effects of highly reactive molecules called free radicals, which can be produced by normal metabolism and the immune system. Free radicals are considered to be a major cause of aging.

Since ascorbic acid is so important to so many basic life functions, it’s hardly surprising that most animals can make their own supply. Our inability to make our own vitamin C could be viewed as a genetic defect, albeit one that we share with our close relatives (primates such as apes and monkeys) and that is also found in some unrelated species, such as guinea pigs, bats, and some species of birds and fish. We can survive despite this genetic defect because the food we are supposed to eat contains plenty of vitamin C. Thus, scurvy happens only when people eat an abnormal diet.

Vitamin C is clearly essential to prevent scurvy, and a health-optimizing diet that contains lots of fresh fruits and vegetables is certainly rich in vitamin C. Yet for years some people have claimed that people need much larger amounts of vitamin C than they could get from eating ordinary food. Linus Pauling, who had won two unshared Nobel Prizes, one for chemistry and one for peace, was a prominent advocate of “megadoses” of vitamin C, for everything from the common cold to cancer. Unfortunately, there’s little or no evidence that these doses of vitamin C can do anyone any good, and they can cause problems such as kidney stones.