Metabolic Medical Newsletter #8 | February 2026 | "But You'll Get Scurvy!"

When I tell people my diet is exclusively animal based, the conversation often turns to curiosity about two issues. First we navigate the waters of cholesterol, saturated fat and heart disease. Then we dive into the perceived nutritional Achilles heel of a carnivore diet: ascorbic acid, also known as vitamin C. In the world of micronutrients, Vitamin C has achieved celebrity status. And among micronutrient deficiencies, scurvy has all the swashbuckling notoriety of an 18th century pirate: scurvy is better known than all the other deficiencies like pellagra, beri beri and rickets combined. So what is the metabolic story of vitamin C and do people who eat only animal based have a higher risk of scurvy?  

Among mammals, Homo sapiens are in a rare class. Only humans, higher primates, guinea pigs, capybaras and bats don’t make vitamin C- use that bit of trivia for a conversation starter! We may have lost the ability to make vitamin C, perhaps as a trade off for better immunity against vitamin C dependent parasites.¹ Since we no longer make vitamin C, it is by definition an essential nutrient. We find vitamin C most commonly in fresh produce such as citrus, bell peppers, strawberries and kiwis. It is also a water soluble vitamin, meaning we do not store excesses: we excrete them in our urine as regulated by our kidneys. We need vitamin C for a long list of functions from production of collagen, connective tissue, carnitine, wound healing and is required for the creation of neuropeptides such as dopamine and B-endorphin for pain relief.²  Vitamin C is also an antioxidant, mitigating against oxidative stress. Vitamin C helps absorb non-heme iron, plant sources of iron which are more difficult to absorb.² Although many believe in vitamin C to fight off viral infections, studies demonstrating an immune boosting role have been inconclusive.³ 

A deficiency of vitamin C over several months results in scurvy.⁴ But how much vitamin C do we need? The vitamin C recommended daily allowance, the RDA, varies based on age, gender and smoking status, as smoking increases anti-oxidant demand by 35mg more of vitamin C per day. Even though humans can’t make vitamin C, breast milk contains vitamin C depending upon the mother’s diet. Interestingly, the RDA has been a moving goal post over the last 50 years from 45mg in 1974 to 90mg in 2000. But what changed over a matter of decades to require a 100% increase in vitamin C requirements? We can’t assign blame to genetics for this increase in need. However, the carbohydrate heavy diet that emerged globally in the 1980’s created an often unappreciated side effect: competition for vitamin C uptake by the cells. This is where a little chemistry is handy.

Glucose and vitamin C are small, simple molecules with a lot in common. Animals that make their own vitamin C synthesize it from glucose: we humans are missing the final enzyme needed for this conversion. Both glucose and vitamin C need to be let into cells by specific insulin dependent receptors. These GLUT 4 receptors are found in our skeletal muscles, heart and adipose tissue and act as a gateway into the cell for both glucose and vitamin C. But because of their chemical similarity, vitamin C and glucose compete for this absorption: high glucose blocks vitamin C’s entry into the cells. Eating more carbohydrates over the last five decades has created more uptake competition for vitamin C, pushing the requirements higher. For those that eat a diet with very little glucose, such as keto or carnivore, there is less competition for the vitamin C to enter. A little goes a long way. 

Carnivore and whole food ketogenic diets also create less inflammation and oxidative stress. A carbohydrate heavy diet overworks the mitochondria and produces a metabolic exhaust called reactive oxygen species (ROS). These ROS can accumulate and harm the mitochondria; the body tries to counteract these harms by producing anti-oxidants. Vitamin C is a powerful antioxidant, donating electrons to the ROS to neutralize their damage. But all this changes with ketosis. In a ketogenic, fat burning state, the body uses ketones and fatty acids for energy, much cleaner burning fuels creating fewer ROS, lowering vitamin C demand. The most common ketone in the blood, B-hydroxybutyrate, reduces the generation of ROS, improves mitochondrial function, and stimulates antioxidant production.⁵  With the right diet, vitamin C deficiency can be prevented with as little as 10mg of vitamin C daily. 

Sadly, scurvy is on the rise in Canada, but it isn’t among those eating an animal based diet. Poverty is often accompanied by a diet devoid of fresh produce, seafood and organ meats, leaving millions at risk. As many as 1 in 5 are now living with food insecurity.⁶  Among lower socioeconomic income groups, vitamin C deficiency can be as high as 25%.⁷ As vitamin C supports a wide range of functions, deficiency can manifest with a wide range of symptoms, from lethargy and low mood to anemia, bruising, bleeding, skin, hair and dental abnormalities. The non-specific nature of scurvy can make diagnosis difficult, leaving many suffering despite a cheap and accessible remedy. Scurvy responds quickly to either dietary replacement or supplementation with 500-1000mg of vitamin C daily. 

In the 1970s, Linus Pauling advocated for megadoses of oral vitamin C, as high as 5-10g daily. Although this approach to help terminal cancer patients was unable to achieve reproducible results, some have tried to resurrect vitamin C through intravenous administration for cancer to sepsis to COVID 19, still with inconsistent or even harmful results.⁸ Some choose to supplement with vitamin C to optimize their health or to achieve certain health benefits, such as wound healing, cardiovascular protection and chronic pain management. High doses of vitamin C supplements greater than 1000mg can result in diarrhea and increase endogenous oxalate production, increasing the risk of kidney stones especially in men.⁹  

Vitamin C is an essential micronutrient that can be obtained on a carnivore diet through organ meats and seafood. Those that eat ferments for the health of their microbiome also enjoy added vitamin C from the process of fermentation. Thankfully, we need not worry about the vitamin C levels of the health conscious carnivore’s among us. Perhaps society would be better served if we turned our attention to supporting those living in poverty. 

References

1. Chen G, Jun JH, Wijshake T, Li Y, Yuan M, Rose J 3rd, Li S, Cobb S, Serpa W, Li Y, Li L, Chen W, Collins JJ 3rd, Wang J, Agathocleous M. Loss of vitamin C biosynthesis protects from a parasitic infection. bioRxiv [Preprint]. 2025 Jul 26:2025.07.22.666193. doi: 10.1101/2025.07.22.666193. Update in: Proc Natl Acad Sci U S A. 2025 Dec 30;122(52):e2517730122. doi: 10.1073/pnas.2517730122. PMID: 40777373; PMCID: PMC12330480.

   
   

2. National Institutes of Health Vitamin C Fact Sheet for Health Professionals https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

   
   

3. Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2007

   
   

4. Crandon J. H., Lund C. C. & Dill D. B. Experimental Human Scurvy. N Engl J Med 223, 353–369 (1940).

   
   

5. Salman A. Alhamzah, Othman M. Gatar, Nawaf W. Alruwaili,Effects of ketogenic diet on oxidative stress and cancer: A literature review Advances in Cancer Biology - Metastasis, Volume 7, 2023. 100093

   
   

6. Li T, Fafard St-Germain A-A, Tarasuk V. Household food insecurity in Canada, 2022. Toronto: Research to identify policy options to reduce food insecurity (PROOF); 2023:1–67.

   
   

7. Scurvy in a 65-year-old woman with severely limited function and social supports Kevin R. Murray, Diana Cagliero, Thomas Kiebalo, Sarah Engelhart CMAJ Oct 2024, 196 (33)

   
   

8. François Lamontagne, Marie-Hélène Masse, Julie Menard, Sheila Sprague, Ruxandra Pinto, Daren K. Heyland, Deborah J Cook, Intravenous Vitamin C in Adults with Sepsis in the Intensive Care Unit June 15, 2022N Engl J Med 2022;386:2387-2398

   
   

9. Ferraro PM, Curhan GC, Gambaro G, Taylor EN. Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. Am J Kidney Dis. 2016 Mar;67(3):400-7.