Do Humans Need Vitamin C?

Do Humans Need Vitamin C?

Do Humans Need Vitamin C?

Do humans need Vitamin C?” I wondered…

When I first decided to experiment with the Carnivore Diet, I had some concerns.

I was going from Keto to Carnivore and worried about the lack of fiber and the elimination of many “healthy” plant-based antioxidants. I was curious about its associations with cancer and correlations with disease. I wondered about what a carnivore’s carbon footprint must look like.

But what concerned me the most was vitamin C.

Vitamin C

Vitamin C is a powerful antioxidant and Linus Pauling, one of my favorite scientists in history, believed it was the solution to all diseases of civilization. Together with vitamin E it reduces lipid peroxidation. It’s a cofactor in many enzymatic reactions – including those in the making of collagen and carnitine.

But what I was most concerned about was that inadequate vitamin C can result in scurvy.


Vitamin C is essential in the synthesis of collagen. Many animals can synthesize vitamin C out of glucose. But humans as well as primates like monkeys and apes lost this ability about 60 million years ago. We lack the enzyme (L-gulonolactone oxidase – GULO) that is required in the last step in the synthesis of Vitamin C from glucose. [r]

Because of this, we must consume our vitamin C or risk the consequences of scurvy – fatigue, weakness, gum disease, poor wound healing, and potentially death from infection or bleeding.


Looking through the lens of evolution has influenced my nutrition views as much as looking through the lens of microscopes. Evolution doesn’t tend to just drop things because they are no longer useful. It selects for advantages.

But what’s the advantage of not synthesizing an essential vitamin?

Uric Acid

In our evolutionary history, we also loss the ability to break down uric acid. And there is a striking parallel between the loss of the ability to synthesize vitamin C and the loss of the ability to break down uric acid.

Uric acid is a major antioxidant, more potent than Vitamin C.

Losing the ability to break down uric acid resulted in higher levels of uric acid in primates. These high levels are thought to explain the relatively long lifespans of apes.

It’s entirely possible, if not likely, that increased uric acid took over many of the antioxidant functions of vitamin C.

Glucose-Ascorbate Antagonism Theory (GAA Theory)

When we look at animals that make their own vitamin C, we find they make less of it when carbohydrates are low.

Which is interesting – low carbohydrates would indicate a lower vitamin C intake from the diet and presumably a higher need to make it endogenously.

Yet we see the opposite.

The more carbohydrates/glucose an animal eats, the more vitamin C it gets from its food, AND the more it makes endogenously.

This suggests that more vitamin C is needed in a glucose-based metabolism.

It also suggests that Vitamin C requirements may be less in low-carbohydrate conditions. [r]

This makes sense though.

Glucose and vitamin C look very similar. There molecules are nearly identical. They even use the same pathways for absorption into cells. Because of this they directly compete with each other for uptake into cells. And glucose wins out preferentially.

Orange Juice

orange juice and vitamin cThis is why drinking orange juice doesn’t make sense (at least for vitamin C purposes). It may have a lot of vitamin C, but it’s high sugar content blocks that vitamin C from getting used.

This is also why diabetics with high blood sugar have strikingly similar symptoms that are seen with scurvy. They are vitamin C deficient even though they may be getting “adequate” intake from their diet or supplements. The glucose blocks out the vitamin C.

In fact, the benefit of vitamin C in disease may not have anything to do with its antioxidant properties. Rather, high dose vitamin C could sometimes compensate for the glucose overload and insulin resistance that is characteristic of many of the diseases of modern man.

Linus Pauling was on to something after-all.

Meat, Vitamin C, and Scurvy

Our food labeling would lead us to believe that meat doesn’t contain vitamin C. But it does. Sailors prevented and cured scurvy with fresh meat. (r)

And in the absence of carbohydrates far less vitamin c is needed. It doesn’t have to constantly compete with glucose for uptake.

The amount of vitamin C to prevent scurvy is just 10 mg/day in the context of a high carb diet.

In a low/no carb diet, even less is needed.

On the Carnivore Diet, the meat content plus the absence of carbs creates an environment that doesn’t result in scurvy.

Vitamin C’s role as a cofactor in hydroxylation reactions (transferring a hydroxl group to the amino acids lysine and proline), is what helps make the building blocks of collagen. But meat comes “pre-packaged” with hydroxylysine and hydroxyproline – further bypassing much of the requirement for vitamin C.

So even though the amount of dietary vitamin C consumed on a meat-based diet may be lower compared to that of a plant-based diets with fruits and vegetables, the former has a lower need for vitamin C with higher bioavailability.

Antioxidant Properties

Well if we don’t need Vitamin C to prevent scurvy on a meat-based diet, surely we need its antioxidant properties, right?

Well, no.

Endogenously synthesized uric acid and glutathione (natural human antioxidants) are much more powerful and take over much of the roles that vitamin C would play. Plus, in a low carb diet these powerhouses are up-regulated.

In essence, we “turn on” more of our most powerful antioxidants. In addition glutathione and uric acid spare vitamin C by recycling it.

So Do Humans Need Vitamin C?

Yep we do.

But how much is entirely dependent on the context of one’s diet. If you eat a high carb diet, you need a lot more vitamin C to compete with those carbs for uptake.

Contrary to popular belief, meat does contain vitamin C, and in the context of a low/no carb diet like the Carnivore Diet, very little vitamin C is actually needed to prevent scurvy. This environment also up-regulates our naturally produced antioxidants. It’s likely the loss of endogenously synthesized vitamin C was not detrimental to our hominid ancestors but rather conferred a competitive advantage (perhaps from the uptick of the likes of uric acid and glutathione) that coincides with our remarkable ability to recycle the vitamin c.

However, a mismatch, the “discordance theory,” between our current diet and ancestral physiology is likely the cause of vitamin C deficiencies and their association with disease.

As is seen time-and-again in research, the clinical manifestation (vitamin C deficiency for example) is the consequence, not the cause, that can only be understood in the proper context.

If you’d like to learn more about micronutrients and avoiding deficiencies, and how to make a meat-based / carnivore diet work, I’d highly recommend watching the Meat Health Masterclass:

56 Replies to “Do Humans Need Vitamin C?”

  1. Dr.Stock,  This is a fantastic article. Paulings findings of reduced LPa on high VC/lysine are so enlightening.  Could it be that the same results would be observed on a keto diet without supplements? Or would supplementing on a keto diet provide more powerful benefits. My worry would be the biological mismatch.


  2. It has been two years on Carnivore, cannot get over loose stools and fatigue. Any advice?

  3. With low carbohydrate intake, blood glucose levels can still be high.
    Your text:
    “Although a blood glucose of 89 falls within the “normal” range, and I’m clearly not diabetic based on the other values, my blood glucose is higher than most would anticipate given this data”.
    So vitamin C can still compete with glucose.
    Do I think right?

      1. I have not found any direct information about this issue.
        Could you give me some direct links to scientific publications?

      2. Hi, Kevin,
        I appreciate your content; however, you could use a proofreader. I’m a teacher, and I’d be happy to offer my services at a reasonable rate.
        C. Cocco

  4. Having fairly recently read up on orthomolecular medicine and high dose vitamin C, this is a very interesting article from the flip side. My question is; if the big cats and other carnivores are eating fresh meat after their kill and presumably getting some VC from this, why then do their bodies continue to make VC? Is it simply down to them breaking down uric acid, as not doing so would hinder their ‘chase to capture prey’ methodology? And hence the need for vit C in the relative absence of uric acid? Or does glutathione come into it, or what? That old axiom of the more you know, the less you know… I sure am feeling it!

  5. Thanks for this observation, Dr. Stock: it confirms my findings over the past 5 years of following a carnivorous regimen. This is partly in reply to Rita Patel’s question concerning gout. I only experienced it whilst I ate plant material and carbohydrates. Since becoming carnivore, I have discovered that I also no longer experience leg and foot cramps; indigestion; diarrhoea or constipation or flatulence. I no longer burp and, surprisingly perhaps, my blood pressure became normal after years of being too low. Strangely, as an aside, I no longer stink up the loo when I pay it a visit, and my B.O. has also disappeared.
    After having diagnosed angina pectoris from the symptoms I presented about fifteen years ago, the doctor who attended me put me onto a strict, low-fat, high plant-matter diet and prescribed medication. The symptoms were not alleviated, but instead I experienced two to three angina “events” a week for two weeks, accompanied by splitting headaches I’d never had before.
    Subsequent investigation revealed that the headaches were probably a side-effect of the medication. A return to the doctor resulted in a prescription for paracetamol and the assurance that the medication would work, but that “these things take time”(!) Two more weeks elapsed, with the paracetamol doing very little to help with the headaches, the angina events not subsiding, but with the added discomfort of indigestion. On the third visit to the doctor, I was offered antacids. I had had enough, so upon returning home, I told my wife that I was abandoning the doctor’s treatment and that I wanted a lot more meat and plenty of animal fat in my meals.
    My wife does not argue with me, as all my alternative treatments for medical issues have delivered astounding results, so she complied, including no longer using vegetable oils in the preparation of my food. I had one “event” about a week later, a mild one after a month and then – nothing: my ticker has been behaving itself ever since. Upon seeing the improvement in my condition, I slowly began eliminating plant material from my diet and about five years ago went full carnivore, meaning that I eat only animals products, including poultry, cheese, eggs, some fish and either liver, heart or tongue at least once a week each. This is accompanied by a lot of animal fat: I consume upwards of eight kilogrammes per month.
    Although she did not criticise my diet, six months down the line my wife nevertheless thought that I should, at least, add a little vegetable matter to my diet, to which I reluctantly agreed (only fools argue with well-meaning women), upon which she put some cooked green beans on my plate. Within fifteen minutes of eating them I felt a dull ache stretching from my left shoulder to the bottom of my rib cage. Then my right side decided that it would no longer play ball with me: my mouth drooped so that I could no longer form words properly, my right hand refused to co-operate and my right leg dragged, so that I kept tripping over obstacles that were not there. Poor V wanted to whisk me off to the hospital, at eight at night, at a distance of some one hundred kilometres away. I assured her that I would be fine if she simply put more fat on my plate. Of course I was not certain about anything at the time, but I don’t like to see her in such a state. Once again she accepted my decision. Friends thought I was mad not to get treatment, but slowly, over the course of a month, all mobility returned and although I tire more quickly now, I have not lost any of my former physical or mental abilities.
    About two years ago V showed me her hands: her knuckles were swollen and painful and were becoming claw-like. I suggested she cut out the plant-based oils she was still using for her meals and replace them with animal fats and butter, as she was using for my meals. The swelling subsided, the pain went away, her hands regained their former dexterity and she has not experienced any of the symptoms of arthritis ever since.
    I am in no way suggesting that carnivory is the answer to all ills, but am a firm proponent of the notion that there is no “one size fits all” diet. Just as our fingerprints, facial features, mannerisms and characters differ, so may it be that our dietary requirements are also varied. The veracity or fallacy of this idea can only be decided by a long-term experiment involving a large number of people.

  6. Thank you so much for this article Dr Stock! I was just wondering with the high uric acid levels would that make us more prone other diseases like gout?

    Thank you for your time and all of this information!


  7. Hi Kevin, and truly thank you for such an incredible article. I’ve had automimmune issues for years, primarily with gluten, but after getting a nasty viral infection and having a huge immune reaction to a large amount of natural antivirals (chaga mushroom) I was taking, along with large dose Vit C, my adapative immune system seems to have deregulated to somehow develop antibodies for Vitamin C. I know it sounds ridiculous, but over the past two months, every few days I eat something with more than 2-3mg of Vitamin C in it I have terrible autoimmune reactions, especially around the heart and lungs that take me another day or two to recover from. I’ve been very worried about scurvy, and have found the 10mg required of Vit C simply impossible to consume without horrible consequences, but, equally, I notice I hardly have any symptoms more than two months on. Interestingly, I’ve been strict keto for two years, and while I had to stop all the low-carb/high Vit C veggies I was consuming, I’ve since been living on meat and mushrooms and doing OK. My question to you is how few daily mgs do you think I can get away with on keto? And how do I ensure my collagen production is up to scratch, sans-Vit C, as this is a big issue for me. Thanks again, Dave

    1. Hi Dave it’s hard to say and definite a minimum as people will require different amounts (especially if we look at metabolic dysfunction / diabetes / prediabetes – for example – it’s likely they need more). But things like weakness/fatigue and bleeding gums are signs someone might have a deficiency.

  8. Kevin, how long have you been on the carnivore diet? I was just diagnosed with RA and have been on carnivore for about 10-days now. My symptoms are already better. Thanks for the info on Vit C

  9. So to sum up your write up in vitamin C on Carnivore….should we supplement? If yes, how many mg per day? We eat very little beef liver. Typical protein is eggs, bacon, ground beef & pork, beef & pork shoulder steaks, occasional shrimp, escargot, chicken, butter, bacon grease and minimal cheeses.

    1. For most people I’d say there is no need; however, some people (like those with diabetes / pre-diabetes) it may not be a bad idea to supplement a bit until metabolically healthy.

      In the years of eating this way and talking with thousands and thousands of people, I have not heard of one person who developed scurvy.
      The people I’d caution are those who primarily eat dried meats (i.e. beef jerky, etc…) and more processed meat (i.e. hot dogs, sausages, ham) instead of focusing on more fresh meats (which I recommend).

Leave a Reply