Optimal Health and the Synthesis of Vitamin C

Diary entry by Linus Pauling, 1980. The text reads: “L[inus] P[auling] / Found enzymes enthralling / He was filled with glee / By Vitamin C”

[Reading Cameron and Pauling’s Cancer and Vitamin C, part 4 of 9]

In their ambitious 1979 book, Cancer and Vitamin C, Ewan Cameron and Linus Pauling argued that vitamin C possessed the ability to cure cancer. As remarkable as this suggestion was, in some respects it was almost secondary to the broader biological role that Pauling and Cameron assigned to the vitamin. As they made clear in their book, much of vitamin C’s importance could be attributed to the special way that it is made by most animals…not including ourselves.


As animals, including humans, have evolved, they have lost the ability to internally synthesize certain vital nutrients, which must now be obtained through diet alone. That said, nearly every being in the animal kingdom has retained the ability to synthesize its own vitamin C. In fact, humans are among a very small subset of animals who have lost this ability over evolutionary time, such that all of our vitamin C needs must now be met through diet. If a person does not meet this dietary need, they will develop scurvy, grow sick and eventually die. Therefore, it is paramount that humans regularly consume a baseline amount of vitamin C.

In addition to vitamin C, humans also cannot synthesize vitamins A, B1, B2, B6, and niacin, all of which are also essential for life. A deficiency in niacin, for example, can lead to pellagra, a primary disease of the skin which can result in death. Likewise, a deficiency in vitamin B1 can manifest as beriberi, a potentially fatal disease of the nervous system. But even though the absence of these nutrients will usher in dire consequences, humans have lost their ability to produce them internally.

Why is this so? The basic prevailing theory is that even though these nutrients are vital for life, food-based sources have historically been so plentiful that there was no need for the nutrients to be produced “in house.” Moreover, from an evolutionary perspective, obtaining a nutrient from a food source, rather than through self-synthesis, offers significant advantages, since it can require a lot of energy to internally produce nutrition. Once freed from the burden of self-synthesis, an organism becomes capable of applying that store of energy toward other activities.

But vitamin C seems to be a special case. Despite the evolutionary advantages of obtaining nutrition from food sources, every studied animal on Earth continues to synthesize it internally except for the following: humans, primates, guinea pigs, one species of fruit eating bat, a South Asian bird called the red vented bulbul, some grasshoppers, and fish in the trout family. For Pauling and Cameron, the tenacity with which animals have held on to the ability to produce their own vitamin C was further proof of its importance.


So again, why not humans too? Why have we lost this ability? Pauling and Cameron believed it was due to an evolutionary quirk.

As we have noted, there are evolutionary advantages to losing the ability to synthesize vitamin C. If two animals are competing for resources, the animal that is not also preoccupied with the internal process of generating its own nutrition will theoretically outcompete an opponent that is hamstrung with that energy burden. Pauling and Cameron believed that, at some point in the past, a mutant human ancestor who could not synthesize its own vitamin C successfully outcompeted other human ancestors, and was able to do so because, at that time – around 50 million years ago – its environment was abundant in vitamin C-rich foods. As the mutant bred and passed along its genetics to its progeny, its traits continued to outcompete, out-mate, and eventually eliminate vitamin C-synthesizing humans altogether. Pauling and Cameron posited that a similar situation arose with other animals, including primates, who have also lost their ability to synthesize vitamin C.

And while that idea makes intuitive sense, one still wonders why nearly all other animals have retained their capacity for vitamin C synthesis, even while losing the ability to internally produce other nutrients. The answer, according to Pauling and Cameron, is two-fold. Point one is that vitamin C is objectively important, and this special importance meant that animals tended to retain the ability to synthesize it. Crucially for humans, point two is that animals’ true need for vitamin C is far greater than what can be obtained through diet alone. In this sense, even though the human mutants were able to outcompete their synthesizing foes for a time by obtaining vitamin C through diet, maintaining that diet was not sustainable for a growing population, and perhaps the mutants never truly obtained enough vitamin C after all.


Pauling and Cameron were convinced that humans were underdosing their vitamin C, and doing so in part because of the guidance being provided by the very agency charged with providing accurate information on nutritional needs. The Recommended Daily Allowance (RDA) provided by the United States Food and Drug Administration (FDA) serves as a standard for the amount of a given nutrient that one should consume per day to maintain their health. Pauling and Cameron believed that the RDA chronically underestimated the true daily needs for specific nutrients; the recommendation for vitamin B1, for example, was about 1.5 times below optimum in their minds. In the case of vitamin C however, Pauling and Cameron believed the RDA to have been grossly underestimated at about 200 times below optimum daily need. Where once the FDA was recommending 60 mg of the nutrient per day, (bumped up to 90 mg in the year 2000) Pauling and Cameron pushed for 12,000 mg.

To determine the optimal dose of vitamin C for humans, Pauling and Cameron looked at how much vitamin C other animals synthesize, and how much dietary C the mutant human ancestor might have been expected to consume on a daily basis. For this second supposition, the researchers used data on how much vitamin C is present in specific foods and what types of foods were likely predominant when the mutant edged out its competition. The outcomes of this analysis connected with observations of contemporary primates who live in climates similar to the mutant and who ingest large amounts of vitamin C daily through their diets — volumes close to the 12,000 mg that Pauling and Cameron believed to be ideal. Finally, when analyzing the amount of vitamin C that other animals synthesize, a conjecture can be drawn about the optimal quantity for humans. A 154 pound goat, for example, could be expected to synthesize 13,000 mg per day, and other animals generated quantities that were roughly proportional to the goat by body weight.


For Pauling and Cameron, the evidence from the animal kingdom further compounded the idea that vitamin C is vital for life and that large amounts of the substance are crucial for maximizing health. But because we have lost our ability to produce our own vitamin C, most humans are living in states of suboptimal health and are exposing themselves to greater risk of affliction with serious disease. And because – as we saw in our previous post – the symptoms of scurvy closely mimic those of cancer, one might draw a connection between the two, and posit that biologically insufficient vitamin C levels are a source for increasing rates of cancer.

Chris Hables Gray, Resident Scholar

Dr. Chris Hables Gray

Dr. Chris Hables Gray, professor at the Union Institute and University and lecturer at the University of California, Santa Cruz, is the fourth individual this year to complete a term as Resident Scholar in the Special Collections & Archives Research Center.  Dr. Gray is a self-described “anarchist, feminist, post-modernist” who has written widely on a number of subjects, with a particular emphasis on cyborgs and evolution.

Gray visited Corvallis to examine the Paul Lawrence Farber Papers and the Ava Helen and Linus Pauling Papers, spurred by a keen interest in tracing the development of Pauling’s thinking on evolution.  His provocative Resident Scholar presentation, titled “Linus Pauling and the Temptation of Evolutionary Ethics,” generated a great deal of thoughtful discussion among those who gathered to hear him speak.

Gray’s thesis was that, in at least two instances, Linus Pauling gave in to what Paul Farber termed “the temptations of evolutionary ethics.”  Farber, a historian of science and emeritus chair of the OSU History Department, defined this temptation as the impulse to use science as a basis for a full system of normative ethics.  Gray is sympathetic to Farber’s warnings against this impulse as, in his view,

Culture is not different from nature.  Human culture is natural.  It is evolved, as much as the behavior of mockingbirds or ants.  All of life is evolved.  The natural/biological vs. cultural distinction is not only wrong, it is dangerous.  [On the same token], humans are not rational.

As an extension of this postulate, Gray offered this thought, which was fundamental to his presentation

I don’t think evolutionary science will ever provide a base for a system of ethics.  The ideas and actions behind the Holocaust are as natural as those behind the Civil Rights movement.  All that humans do is natural….Farber is right that evolutionary science cannot give us a normative ethics, a complete system of ethics.  It cannot show what should be ethical, but it can show what is possible and what is impossible.  It can help us in our ethical reasoning.

During his stay in Corvallis, Gray traced Pauling’s thinking on evolution from his earliest documented years, noting a particularly optimistic Junior Class Oration in which the future scientific great “makes of evolution a religion.”  As time moved on, Pauling’s thoughts on the topic changed somewhat, his optimism tempered by the realities of the atomic age.  Instead of a religion, evolution became a morality.  Likewise, man was no longer destined to evolve into a superman, but rather was part of a superorganism, “humankind,” whose greatest attributes – as Pauling noted in 1959 – were “sanity (reason), and morality (ethical principles.)”

For Pauling the concept of morality was firmly rooted in Albert Schweitzer’s principle of “minimization of suffering,” and it is here that he began to fall prey to the temptations of evolutionary ethics. Most glaring was Pauling’s advocacy of negative eugenics in the mid- to late-1960s.  As Gray noted

Pauling saw reality as based on molecules, and so diseases were molecular….His work on sickle-cell anemia was framed in this way. Once he realized that it was a genetic disease he put forward some startling solutions… [including the tattooing of phenotype information on people’s foreheads] enforced genetic testing and abortions…even though dietary and other treatments for sickle cell anemia were known and effective. Eventually he stopped raising this issue. We don’t know why for sure, but we can assume he realized it was not a popular approach to the problem of genetic disease.

Gray also submitted Pauling’s interest in vitamin C, especially as a possible treatment for cancer, as another example in which his evolutionary thinking went astray.

The reasoning behind Pauling’s belief that humans did not consume enough Vitamin C was based on evolutionary science. Roughly half the primates, including humans and our closest cousins, cannot synthesize vitamin C, an ability that all plants and almost all animals have. His theory was that the ancestral primate lost the ability to synthesize C when in an environment with plentiful dietary C. Then, as humans moved into other environments with less dietary C, deficiency diseases and conditions, such as a degraded immune system…resulted – and not just scurvy, but long term conditions and even cancer.

While Gray conceded that there is some validity to this argument, he found Pauling’s larger thesis to be “less than convincing.”

…numerous studies have failed to show that all, or even most, humans have a massive Vitamin C deficit. It is true that C can help limit the severity of colds, that it helps in some healing, and has other benefits. But the massive positive effects of massive doses of C have not proven to be as helpful as Pauling claimed.

Gray concluded that

we have to be more careful that Pauling in applying evolutionary thinking to ethics….if we take evolution seriously we have to let go of totalizing schemes for perfecting humanity, as much as the dream of perfection appeals to young chemistry students and profoundly moral famous scientists alike. But evolutionary science can be useful in our quest for a better, more moral, world.

Because of the great diversity of humans…especially as evolved culture allows for such a wide range of variation, and “conscious” evolution, no totalistic ethical system based on human altruism or any other quality is viable. Altruism has certainly evolved in humans, as has selfishness, cruelty, and social pathology. Inherited traits are often not universal, which makes sense in that variation is the key to evolution’s power. But this also means that any ethical system will have to be imposed on some people, even if it is a “biological” fit for the majority. And since all of us have many layers of moral reasoning and ethical impulses, often contradictory, and that humans continue to evolve and a very fast rate thanks to the Lamarkian power of culture, we will never have a perfect ethics.

For more on the Resident Scholar Program, please visit this page, which, among other details, includes links to the profiles that we have written of all past scholarship recipients.

Vitamin C Deficiency in Humans: An Issue of Evolution?

Linus Pauling and Irwin Stone, 1977.

[Part 3 of 4 in a series on Vitamin C and the Common Cold]

In the chapter “Vitamin C and Evolution” from his book Vitamin C and the Common Cold, Pauling wondered about the reasons why the rest of the animal world can synthesize vitamin C, while human beings, along with a very small group of mammals, cannot. His answer was gene mutation, using the instance of thiamine as evidence.

All animals need thiamine as an essential vitamin; in its absence they develop a disease similar to beriberi. Pauling theorized that over 500 million years ago, when the common ancestor to present-day birds and mammals lived, there existed an environment imbued with an abundance of green plants containing thiamine. By way of gene mutation, one of the animals living during that era must have lost the mechanism which allowed it to synthesize thiamine. This was advantageous to the animal – which was probably plant-eating – because it could obtain the thiamine it needed from the plants it ingested while simultaneously conserving the energy that it would have used to manufacture the vitamin.

Pauling pointed out that possessing this extra energy would have caused the animal to flourish and to have more offspring than others of its kind. The advantageous mutation would be passed on to certain of the progeny, who would in turn pass it on to their own offspring, and so on. Eventually the mutation would spread, and a few million years later all mammals and birds would possess the mutation.

Pauling believed that in the same way that all animals lost the biochemical machinery to produce thiamine, so too did human beings, primates, guinea pigs and a particular Indian fruit-eating bat lose the ability to synthesize vitamin C. A mutation that results in the inability to synthesize a substance is simple and occurs often; it only requires a single gene to be damaged or deleted. The reverse process is more complex and takes much longer. The mutation that removed the ability to synthesize vitamin C probably took place about 25 million years ago, in the ancestor of modern primates and humans.

In his book, Pauling next asked the question, why didn’t all mammals and birds lose the ability to synthesize vitamin C the way that they lost the ability to synthesize thiamine? Pauling theorized that the change likely occurred in the guinea pig and the Indian fruit-eating bat independently of the common precursor of the primates, due to an abundance of vitamin C in their diets. The fact that the majority of animals possess the ability to synthesize vitamin C indicates that there is not sufficient vitamin C in their dietary environment for them to obtain the vitamin solely from their nutrition intake.  To Pauling, this also suggested the existence of a deficiency of ascorbic acid in the human diet.

Dr. Irwin Stone, a biochemist in Staten Island, New York, was the person responsible for sparking Linus Pauling’s interest in vitamin C. Dr. Stone, a leader in the ascorbic acid field at the time, sent a letter to Pauling in 1966 informing him of a high-level ascorbic acid regimen that he had been developing over the past three decades, which Pauling and his wife began to follow. Stone believed that humans need between 3 and 5 grams of vitamin C per day, reinforcing this claim by citing the British researcher G. H. Bourne’s evidence that gorillas ingest about 4.5 g of ascorbic acid per day.

Gorillas, like humans, do not synthesize vitamin C, and so need to obtain it from their diet. In 1949 Bourne pointed out that before the development of agriculture, humans lived mainly off of raw, green plants with little meat; a diet similar to that of the modern gorilla. Bourne concluded that

it may be possible, therefore, that when we are arguing whether 7 or 30 mg of vitamin C a day is an adequate intake we may be very wide of the mark. Perhaps we should be arguing whether 1 g or 2 g a day is the correct amount.

Irwin Stone also took into consideration the amount of ascorbic acid that other animals, such as rats, manufacture. The rat synthesizes vitamin C at a rate of between 26 mg and 58 mg per day per kilogram of body weight. If the same rate of manufacture were applied to humans, a person weighing 70 kg (154 lbs) would need to ingest between 1.8 g and 4.1 g of ascorbic acid per day.

From there, Pauling verified the amounts of various vitamins contained in 110 different raw fruits and vegetables corresponding to a diet of 2,500 kilocalories per day, and found that “for most vitamins this amount is about three times the daily allowance recommended by the Food and Nutrition Board.” For ascorbic acid, the difference was much more drastic: the average amount of ascorbic acid in a day’s ration of the 110 raw foods was 2.3 g, which was about 42 times the recommended amount. Pauling argued that

If the need for ascorbic acid were really as small as the daily allowance recommended by the Food and Nutrition Board the mutation would surely have occurred 500 million years ago, and dogs, cows, pigs, horses, and other animals would be obtaining ascorbic acid from their food, instead of manufacturing it in their own liver cells.

Pauling found that the average ascorbic acid content for the fourteen most vitamin C-rich plant foods is 9.4 g per 2,500 kilocalories, leading him to the conclusion that the optimum daily vitamin C intake for an adult human being is between 2.3 g and 9 g – quantities in line with what he saw as existing in the natural diet of the human lineage and numbers far beyond the recommendations issued government nutritional authorities, then or now.