by Nick Lane
Pauling, then, was a colossus of twentieth-century science, whose work laid the foundations of modern chemistry. He could be insufferably self-assured, but was far from infallible, as Watson and Crick were delighted to discover. His methods were unorthodox. In The Double Helix, written before Pauling’s conversion to orthomolecular medicine, Watson described Pauling’s approach to chemistry as intuitive rather than mathematical; and Pauling referred to his own application of intuitive guesses as the ‘stochastic method’. Always the maverick, Pauling felt betrayed by the establishment and was quick to fight his corner, sometimes with barbed personal attacks. His experiences no doubt coloured his attitude to the pharmaceutical industry and the medical profession, which he termed the ‘sickness industry’, accusing them of misleading the public to bolster drug sales. For their part, doctors dismissed Pauling’s claims for vitamin C
as quackery and fraudulence. Journals became reluctant to publish his papers, and the dispute degenerated into a public slanging match. So began a stand-off that continues to this day. Pauling died in 1994, at the age of 93, an embittered man. If he was right, he had solved one of the world’s greatest problems — how to age gracefully — and we would be fools to turn our backs on his simple solution. On the other hand, the woes of old age have hardly been vanquished, even among those who follow Pauling’s example. One might be forgiven for assuming that he must have been mistaken. Was there any truth in his claims?
Vitamin C acquired its status as a vitamin — an essential trace constituent in the diet — for a curious reason. With the exception of higher primates, guinea-pigs and fruit bats, almost all other plants and animals manufacture their own vitamin C. In contrast, we must eat ours, because a common ancestor of the higher primates once lost the gene coding for an
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enzyme called gulonolactone oxidase, which catalyses the final step in the synthesis of vitamin C. As a result, the entire human race suffers from what amounts to an inborn error of metabolism. Pauling was fond of drawing attention to this deficit in his talks; he would hold up a test tube containing the amount of vitamin C produced by a goat in a single day and say, conciliatory to the end, “I would trust the biochemistry of a goat over the advice of a doctor”.1
This apparently strong argument must be flawed. Loss of the gene for gulonolactone oxidase could not have been counterproductive for our primate ancestors, or they would have been eliminated by natural selection. Indeed, the fact that the individuals that lost the gene eventually prevailed among the primates suggests that there may even have been some benefit in its loss. In their authoritative text Free Radicals in Biology and Medicine, Halliwell and Gutteridge suggest one possibility. They note that gulonolactone oxidase produces hydrogen peroxide as a by-product of vitamin C synthesis. This means that high rates of vitamin C synthesis in animals such as the rat could, ironically, impose an oxidative stress.
Given an adequate diet of fruit, which is rich in vitamin C, it might indeed be beneficial to consume, rather than synthesize, vitamin C. Of course, this is only true if we do eat enough. One of Pauling’s arguments was based on the observation that gorillas consume nearly 5 grams of vitamin C daily in their normal diet. Our own Palaeolithic forebears are thought to have consumed about 400 milligrams daily.
Failure to eat enough vitamin C causes the once-dreaded deficiency disease scurvy. Scurvy is no longer a familiar sight, but once devastated the lives of sailors, who were deprived of fresh foods on long voyages. Scurvy was also endemic among soldiers on military campaigns from the Cru-sades to the First World War. The disease was a liability for global explorers, who were sometimes at sea for months or years at a time. One outbreak in 1536 afflicted all but 10 of the 110 men wintering aboard the ships of the French explorer Jacques Cartier, founder of Montreal, in the frozen St Lawrence river in Canada. Cartier wrote that “the victims’ weakened limbs became swollen and discoloured whilst their putrid gums bled profusely.” Other symptoms of scurvy include anaemia, spontaneous bruising, fatigue, heart failure and finally death. Thirty years after Cartier’s 1 This quantity (5–10 grams) was based on extrapolations made from measurements in homogenized liver samples, and may bear little resemblance to the amount actually produced by a goat each day.
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winter of sorrows, the Dutch physician Ronsseus advised sailors to eat oranges to prevent scurvy, and in 1639 the English physician John Woodall recommended lemon juice. With characteristic phlegm, the British Admiralty disregarded this advice, standing firm even after the crew of Lord Anson’s round-the-world expedition of 1740 was cut down by scurvy. Of the 1955 men who set sail, 320 died from fevers and dysen-tery and 997 from scurvy before Anson returned to England in 1744.
Protesting against the appalling conditions faced by sailors, James Lind, a Scottish naval surgeon, produced a Treatise on Scurvy in 1753, in which he, too, recommended citrus fruits. Unlike his predecessors, however, he had actually proved his theory in the world’s first controlled clinical trial, on board HMS Salisbury in 1747. Lind tested a variety of reputed remedies on 12 members of the crew who had succumbed to scurvy. Two of them received a quart of cider each day; two had oil of vitriol; two received vinegar; two drank sea water; two had oranges and lemons; and the final pair took a medicament prepared from garlic, radish, Peru bal-sam and myrrh. The two seamen who received oranges and lemons made a speedy recovery and were put to nurse the others. Of the rest, only those receiving cider showed any signs of recovery. Curiously, despite the practicality of his conclusions, Lind did not regard scurvy as a deficiency disease, but rather as the result of a contagion in moist air. He thought of lemon juice as a detergent that could break down toxic particles.
Lind’s recommendations were acted on by Captain Cook on his two circumnavigations of the globe between 1768 and 1775. Cook had exacting standards, and emphasized the importance of good diet, cleanliness, ventilation and high morale. He supplied his sailors with fresh lemons, limes, oranges, onions, cabbage, sauerkraut and malt. Only one seaman died from scurvy in a total of nearly six years at sea. Even so, the British Admiralty did not capitulate to Lind’s demands until 1795, when it finally agreed to issue lemon juice on British ships. Thanks to the publicizing efforts of Sir Gilbert Blane, physician to the navy, the effect was dramatic.
From an average of over 1000 patients with scurvy admitted to the Haslar naval hospital each year, the number dwindled to a mere two between 1806 and 1810. As the late social historian Roy Porter observed wryly, lemons might have done as much as Nelson to defeat Napoleon. The situation did not last long. In a cost-cutting measure typical of the British over the ages, the Admiralty replaced lemons with cheaper limes, which contain barely a quarter as much vitamin C. Scurvy soon reappeared. To add insult to injury, British sailors acquired the nickname ‘limeys’.
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The idea that scurvy might be a deficiency disease, rather than an infection, was advanced in the 1840s by George Budd, professor of medicine at Kings College in London, earning him the grand Victorian epithet
‘the prophet Budd’. In a series of articles published in the London Medical Gazette, entitled “Disorders Resulting from Defective Nutriment”, Budd prophesied that scurvy was due to the “lack of an essential element, which it is hardly too sanguine to state will be discovered by organic chemistry or the experiments of physiologists in a not too distant future”.
In the event, fulfilment of Budd’s prophesy had to wait another 93
years, in part because the concept of deficiency diseases was set back by Pasteur’s germ theory of disease, which was then applied with indiscriminate enthusiasm to almost any condition. By the late 1920s, though, a number of researchers were racing to isolate the ‘antiscorbutic factor’
from oranges, lemons, cabbages and adrenal glands. Several workers, notably the Hungarian biochemist Albert Szent-Györgyi, succeeded in isola
ting white crystals of an acidic sugar, whose properties corresponded to vitamin C, but whose chemical identity remained a mystery. A bit of a joker, Szent-Györgyi proposed the name ‘ignose’, the - ose ending signifying its relationship to sugars, and the ign- prefix his ignorance of its nature. When this name was rejected, he proposed ‘godnose’; and finally, in a single sentence in Nature in 1933, the term ascorbic acid, in reference to its antiscorbutic properties. Progress was fast. The same year, ascorbic acid was synthesized independently by the Polish émigré Tadeus Reichstein in Switzerland and Sir Walter Haworth in Birmingham, UK, making it not only the first vitamin to be assigned a chemical formula, but also the first to be synthesized by purely chemical means.
Ironically, the concept of vitamin C as the dietary element that prevents scurvy has hampered our understanding of its positive role in the body.
The general approach to how much vitamin C we need to eat each day (the recommended daily allowance or RDA) is derived from this negative stance — the prevention of scurvy — rather than any positive criterion.
The amount of vitamin C required to prevent clinical scurvy, in other words to hide any obvious signs of disease, is surprisingly small. A series of studies on the inmates of Iowa jails in the 1960s showed that only about 10 milligrams a day are required to abolish the signs and symptoms of scurvy. When the dose is raised to about 60 milligrams a day, we begin to excrete vitamin C in our urine, implying that the excess is superfluous to requirements. The notion that our body pool is saturated by about 60
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milligrams a day is supported by the rate of breakdown of vitamin C: the Iowa studies suggested that breakdown products are excreted in the urine at a rate of about 60 milligrams each day. These three factors, then — prevention of scurvy with a margin for error, excretion of vitamin C, and excretion of breakdown products — form the basis of the long-standing RDA of 60 milligrams vitamin C daily.
Although this analysis sounds like a closed case, it is in reality misleadingly simplistic. The case is confounded by both practical and conceptual difficulties. These were scrutinized during the 1990s by Mark Levine, of the NIH. Levine had been a member of the panel convened by the NIH to review Cameron’s 25 case studies in 1989, and has since done more than anyone to bridge the gap between mainstream medicine and the advocates of vitamin C.
Besides querying the accuracy of the early measurements of vitamin C and its breakdown products, which were carried out using insensitive and non-specific tests, Levine questioned the assumptions underlying each of the three factors used to estimate the RDA. First, he said, the amount of vitamin C required to prevent scurvy may be much less than the ideal intake for maintaining bodily functions. We do not know how much less. Second, the threshold of urinary secretion may or may not correspond to the saturation of body pools — it does for some substances and doesn’t for others. For vitamin C, we do not know. Third, the rate of breakdown of vitamin C depends on a variety of factors, including the size of the dose consumed. High doses are broken down faster than low doses, perhaps because the body has less need to conserve a precious resource. This means that estimates of breakdown based on low doses (such as 30 or 60 milligrams) may be misleading. Thus, Levine stripped away the conceptual basis underpinning the current RDA of vitamin C.
Far from being merely critical, Levine worked up his own recommendations for a rational daily dose of vitamin C, based on the ideal amount required for known reactions, and the saturation of blood levels and other body pools. For the impatient, let me say immediately that he recommends 200 milligrams daily for healthy individuals; that doses above 400
milligrams have no evident value; and that doses of more than 1 gram may not be safe, as they can provoke diarrhoea and induce the growth of kidney stones. Five portions of fruit and vegetables each day corresponds to a daily intake of between 200 and 400 milligrams of vitamin C, so given a sensible diet there is no need for supplementary vitamin C. We shall see that there are other good reasons for not relying on supple-
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mental vitamins. On the other hand, the RDA of 60 milligrams (raised to 90 milligrams in the United States in April 2000) is, according to Levine, too low. To understand his reasoning, and especially the wider ramifica-tions in terms of antioxidant function, we need to look in more detail at what vitamin C actually does in the body.
Quite apart from its antioxidant effects, we need vitamin C for a wide variety of biochemical reactions that help to maintain our normal physiological function. The best known requirement for vitamin C is as a cofactor (a necessary accessory for enzyme function) in collagen synthesis.
Collagen fibres make up about 25 per cent of the total protein content of our bodies, and are familiar to all of us in a melted form as gelatine. In their normal bodily environment, collagen fibres are the most important structural and shock-absorbing component of connective tissues, including bone, teeth, cartilage, ligament, skin and blood vessels.
In the absence of vitamin C, collagen fibres do not form properly. Many of the symptoms of scurvy can be attributed to defects in collagen production and maturation. As a result, blood vessels become fragile and wounds heal slowly, if at all. Such vascular degeneration probably accounts for the putrid bleeding gums, swollen joints, spontaneous bruising and, ultimately, as fluids seep out of leaky blood vessels and blood pressure falls, heart failure.
Other symptoms are characteristic of scurvy but not specific to it, including general malaise, fatigue and anaemia. Fatigue affects many millions of people. In some cases, fatigue might be a form of ‘sub-clinical’
scurvy; in other cases it is not. In his Treatise on Scurvy, Lind reported lassitude as an early and invariable symptom. While it is possible that errors in collagen synthesis may contribute to lassitude, such vague symptoms are more likely to relate to the synthesis of a small amino acid called carnitine
— which requires vitamin C. We need carnitine to burn fats. When fats are broken down, the component fatty acids must be transported into the mitochondria where they are oxidized to produce energy. The problem is that fatty acids cannot get into the mitochondria by themselves, but must be ferried in attached to carnitine. Carnitine is also responsible for removing left-over organic acids from the mitochondria en route back to the cytoplasm. Without vitamin C, we cannot make enough carnitine to generate energy from fats, and the mitochondria eventually pollute them-
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selves with toxic organic acids, reducing their ability even to generate energy from glucose. Fatigue might seem a small price to pay.
Vitamin C also has a variety of neuronal and endocrine functions, which are crucial to our physiological and psychological well-being. For example, we need vitamin C to make noradrenaline (norepinephrine), a cousin of adrenaline (epinephrine) which has an important role in modulating our response to stress. We also need it for the correct function of an enzyme called PAM (peptidyl alpha-amidating mono-oxygenase), which is found in many parts of the body, but especially in the pituitary gland.
PAM bites the end off a large number of immature peptide hormones and neurotransmitters, and in so doing activates them. Without activation by PAM, the hormones remain inert. If only to downplay the perception of vitamin C as just a water-soluble antioxidant and cofactor in collagen synthesis let me list a few of the peptides that are activated by PAM. They include: corticotrophin-releasing hormone, which stimulates production of steroid hormones; growth hormone-releasing hormone, which promotes growth and influences energy metabolism; calcitonin, which promotes calcium phosphate absorption and distribution in the bones; gastrin, the most powerful stimulant of gastric acid secretion; oxytocin, which stimulates milk ejection and uterine contraction; vasopressin, which regulates water balance and stimulates intestinal contraction; secretin, which stimulates pancreatic and bile secretions; and substance P, a potent vasodilator and sensory neurotransmitter, which me
diates our sense of pain, touch and temperature. Given this wide range of actions, the extent to which our normal physiology is fine-tuned by vitamin C is virtually anybody’s guess.
Nor is this all. Vitamin C is also taken up by white blood cells. When we are infected with bacteria, white blood cells called neutrophils mount the first defence. In the course of this defence, neutrophils vacuum up vitamin C from their surroundings, using miniature protein pumps in their membranes. The level of vitamin C inside the neutrophils increases tenfold within minutes, and if the infection persists, may reach 30 times the level of resting neutrophils, or 100 times that in plasma, even in someone taking massive oral supplements.
Here, finally, we see an action of vitamin C that seems to be an antioxidant effect, along the lines of that described by Tom Kirkwood at the start of this chapter. Neutrophils need this extra protection to survive the wrath of their own assault, as they turn their immediate environment into a battlefield. The effect is a little like soldiers strapping on their gas
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masks before releasing chlorine gas onto the enemy. Instead of chlorine gas, neutrophils produce a burst of free radicals and other powerful oxidants (including hypochlorous acid, derived from chlorine), which are responsible for bacterial killing.2 Vitamin C prevents or delays the demise of neutrophils in a chemical cesspool of their own making, and hastens the death of bacteria, which cannot take up vitamin C or continue to benefit from its presence in their locally denuded surroundings. Levine, among others, sees the uptake of vitamin C by neutrophils as a promising avenue for pharmaceutical development in the emerging era of antibiotic resistance.
Finally, what of anaemia? This, too, is a symptom of scurvy, but is not a physiological failure in the sense of those discussed above. In this case, vitamin C acts on the inorganic iron in food in the stomach and intestines, converting it from the insoluble form usually found in food (Fe3+) to the soluble form (Fe2+) that we can absorb in our intestines. (This is the reverse of the reaction that took place on a huge scale in the Precambrian oceans, leading to the precipitation of insoluble iron into banded iron formations, discussed in Chapter 3). Without adequate supplies of vitamin C, we cannot absorb enough iron to stock red blood cells with haemoglobin (which contains iron), and so we develop anaemia.