14.2: Vitamin C

Chemically, vitamin C (ascorbic acid) is the simplest of vitamins. In fact, it’s a close chemical relative of the simple sugar glucose. Not only do pharmaceutical companies make their vitamin C from glucose, so also do most animals, birds, and insects. Humans are among the very few in the animal kingdom that can’t make vitamin C, but must take it from food. Others that can’t make this vitamin include monkeys, guinea pigs, a few fish, and an obscure Indian fruit-eating bat.

It’s been speculated that it was because the regular diets of the vitamin-C-requiring species included enough of the vitamin, that their cells surrendered vitamin-C-making as a needless function. This makes a nice evolutionary theory, but it’s open to question. First, we don’t know that humans ever had the ability to make vitamin C. Second, some species that make their own vitamin C also seem to get plenty in their usual food.

The vitamin-C-deficiency disease, scurvy, was described as long ago as 1500 B.C. Most of us know that scurvy was once the bane of seafaring men on long voyages, and that the disease was attributable to the lack of C-rich fruits and vegetables. But many of us don’t realize just how devastating scurvy was. It was so devastating that it seems amazing—or else tells something of living conditions in those times—that anyone would volunteer for a long sea voyage, knowing full well that so many wouldn’t make it back alive.

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General characteristics of water-soluble vitamins

• excreted in urine
• limited body stores
• less toxic than fat-soluble vitamins

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Consider Richard Walter’s account of the round-the-world voyage of the British ship Centurion in the early 1740s¹:

…the scurvy began to make its appearance amongst us…at the latter end of April there were but few on board who were not in some degree afflicted with it…and in that month no less than forty-three died of it…In the month of May we lost nearly double that number…The mortality went on increasing…so prodigiously that after the loss of above two hundred men, we could not at last muster more than six foremast men in a watch capable of duty.

This isn’t to say that no one knew of ways to combat the disease. Long before this time, there had been knowledge of anti-scurvy substances. The Chinese had found that while neither beans nor grains had an anti-scurvy effect, the sprouts that formed as they germinated did. The sea captains of England had found that the sprouting barley that went into beer could offer some protection against scurvy, and they sought passengers who could make the brew.

We can’t expect to find vitamin C in today’s beer—a far different brew. The beer of the ships was a kind of fresh brew made from a mash of the sprouting barley, briefly fermented, low in alcohol, and served without aging, heating, or filtering. Like an uncooked soup, it carried some of the nutrients leached from the green sprouts. It probably was just enough to delay the symptoms of scurvy before arrival at land.

Vitamin	Function	Source	Deficiency	Adverse effects of high dose
Vitamin C (ascorbic acid, ascorbate)	Antioxidant, synthesis of connective tissue	Citrus fruits, berries, potatoes, red/green peppers, broccoli, brussels sprouts	Scurvy, loose teeth, bleeding gums	Diarrhea
Thiamin (vitamin B1, aneurin)	Coenzyme in carbohydrate metabolism	Pork, legumes, whole and enriched grains, liver, nuts, squash	Beriberi, impaired nervous system	None reported
Riboflavin (vitamin B2)	Coenzyme in energy and protein metabolism	Liver, meat, dairy products, enriched grains, eggs, mushrooms, greens	Sore, red tongue, inflamed skin, eye disorders	None reported
Niacin (nicotinic acid, nicotinamide)	Coenzyme in energy metabolism	Liver, meat, fish, whole and enriched grains, legumes, mushrooms	Pellagra (diarrhea, inflamed skin, dementia)	Flushing of face and hands, liver damage
Vitamin B6 (pyridoxine)	Coenzyme in amino acid metabolism	Liver, meat, fortified foods, enriched grains, legumes, potatoes	Inflamed skin, convulsions in infants	Weak and numb muscles, nerve damage
Folate (folic acid, folacin)	Coenzyme in cell division	Legumes, green leafy vegetables, whole grains	Anemia	None reported
Vitamin B12 (cobalamin)	Coenzyme in amino acid/fatty acid metabolism, cell division	Animal products (meats, eggs, milk)	Anemia, nerve damage	None reported
Biotin	Coenzyme in carbohydrate and fat metabolism	Liver, yeast, whole grains, egg yolk, fish, nuts, legumes	Dermatitis, depression	None reported
Pantothenic Acid	Coenzyme in metabolism	Liver, yeast, eggs, whole grains, legumes	Fatigue, headache, nausea	None reported

Table 14-1: Water-Soluble Vitamins.

We’re reminded again that in looking at the nutrient value of any food, if the quantity consumed is large enough, even foods with low values can be protective. From all accounts, the seafarers had lusty thirsts.

The fact that scurvy continued to ravage so many, in the face of all the reports of successful means of a cure, is rather surprising. Part of the problem was that objective evidence was lacking. Looking back with today’s knowledge, we can see why certain regimens worked. But at the time, there were only theories and anecdotal evidence.

Seafarers were often cured of scurvy upon arrival at land, but they weren’t sure why. Was scurvy caused by the crowded conditions on board (an infection perhaps), or was it “sea air,” or was it something missing in the diet, or was it something contaminating the diet?

Captain James Lind of the British Royal Navy is recognized as one of the first to provide objective evidence. In 1747, he performed the classic experiment in which he took 12 sailors with scurvy, divided them into 6 pairs, and gave each pair a different dietary supplement of either sea water, vinegar, sulfuric acid, hard apple cider, a medicinal paste, or oranges and lemons. Only the pair of sailors given oranges and lemons were cured of scurvy.

Fruits and vegetables had been found over and again to be effective. Yet even in the American Civil War, scurvy was still a problem for both sides. Scourges of scurvy persisted into the early 1900s. But until the discovery of vitamins in the early 1900s, it wasn’t generally accepted that the lack of a substance in food could be the cause of a disease. The idea persisted that scurvy was a contagious disease.

Part of the problem also may have been that (as discussed in Chap. 6) plant foods were often disdained as the food of the poor. The famed explorer of the South Seas, Captain James Cook, kept his men from scurvy by stocking his ship with vegetables and fruits. But it wasn’t so easy to get his men to eat them. He succeeded in doing so by insisting that his officers eat them with zest, in front of the men. As Captain Cook related in his journal, “…the moment they see their superiors place a value on it, it becomes the finest stuff in the world…”²

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Albert Szent-Gyorgyi discovered that vitamin C was the substance which cured and prevented scurvy. For this, he received the Nobel Prize in 1937.

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In 1796, daily supplements of lemon or lime juice became standard issue in the British navy, and the sailors were nicknamed limeys. Preventing scurvy with citrus juice and fresh fruits and vegetables is thought to have contributed to the superiority of the British navy at that time.

In 1932, vitamin C was identified as the substance which cured and prevented scurvy, and was named ascorbic (anti-scorbutic) acid.

Vitamin C and Body Chemistry

There‘s a huge body of research on vitamin C. The presence and influence of vitamin C are seen in a wide variety of bodily processes—including the formation of connective tissue and the matrix of bone, the body’s use of calcium and iron, the integrity of the capillaries and the prevention of hemorrhage, the immune response, the making of key hormones and brain chemicals, and a host of other bodily work.

One of vitamin C’s functions is to serve as an antioxidant, both in the food and in the body. The iron in plant foods, for example, is more readily absorbed from the intestine when the iron is in an unoxidized form. Vitamin C enhances iron absorption by keeping the iron in this form. For those with borderline iron intake or those whose primary source of iron is plant foods, this is good reason to include vitamin-C-rich foods in a meal.

We don’t yet understand all the details of how vitamin C functions in some of its roles. This fact, together with the vitamin’s broad range of functions, leaves the door wide open to much guesswork and fanciful claims. But the basic functions of vitamin C are not, as some enthusiasts claim, open to anyone’s guess.

Figure 14-1: Vitamin C helps link collagen molecules together to form strong, stable connective tissue

Just because certain symptoms are associated with a vitamin deficiency, this doesn’t mean that extra amounts of the vitamin will alleviate similar symptoms where there is no deficiency. People with scurvy are easily fatigued and more susceptible to stress. This has led to a popular idea that extra vitamin C will make one more energetic or better protected against stress. Studies indicate that when various stresses do induce a fall of vitamin C in the blood, that fall is brief and minor— too small to have an appreciable effect on anyone not at a scurvy level of vitamin deficiency

Vitamin C Intake

The vitamin C content of the “typical American diet” far exceeds the RDA. Add to this the large numbers of people who eat or drink foods fortified with vitamin C and take vitamin supplements. Vitamin C deficiency is uncommon indeed. Most cases of vitamin C deficiency in this country are associated with poverty, alcoholism, and peculiar diets—such as a “tea and toast” diet or the brown-rice-based macrobiotic diet mentioned in the beginning chapter.

Those taking huge doses of C are at the other extreme. Excess vitamin C is readily excreted in the urine, but, as discussed in the previous chapter, massive amounts—particularly doses of 2 grams (2000 milligrams) or more—can be risky.

The adult RDA for vitamin C is 60-75 mg (see Appendix A), with an added 35 mg for smokers.