5 Ways to Increase Vitamin C Levels

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vitamin c levels

5 Ways to Increase Your Vitamin C Levels

Vitamin C is made naturally in almost all living animals except humans, primates and guinea pigs.  Dogs and cats produce their own vitamin C from ingested food that have metabolized into glucose.  This mechanism keeps their vitamin C levels up without the need to consume vitamin C rich foods.

Humans must consume vitamin C from its food sources or they risk severe health problems.  There is an intimate relationship between glucose and vitamin C that has a dramatic impact on immunity and overall cellular health.  In this article, you will discover 5 keys to increasing your vitamin C levels.

Most animals and plants are able to synthesize their own vitamin C.  This is done through a biochemical pathway that depends on 4 key enzymes which convert glucose to vitamin C.  In mammals, the glucose is extracted from stored sugar (glycogen) and the transformation into vitamin C is produced in the liver (1, 2).

Glutathione Recycles Vitamin C

Humans lack the L-gulonolactone oxidase enzyme that is critical for the last step of vitamin C synthesis.  Humans require a good amount of vitamin C in order to build healthy tissue collagen and promote strong immune function (3, 4).

When vitamin C levels are low the body recycles the oxidized version of vitamin C.  This redox cycling is performed by the master antioxidant glutathione.  As long as enough glutathione is present the vitamin C redox cycle can continue (5).

The Nobel prize winning chemist Linus Pauling discovered that white blood cells need very high doses of vitamin C in order to function effectively.  In the late 1960’s, he developed the understanding of using high dose vitamin C to combat the common cold.  This technique has worked effectively for many individuals; however, there is more to the story when it comes to vitamin C (6).

The GAA Theory

In the 1970’s, Dr. John Ely discovered the Glucose-Ascorbate-Antagonism (GAA) theory.  Glucose and vitamin C (ascorbate) have a very similar chemical makeup.  This theory proposes that elevated glucose levels compete and effectively restrict vitamin C from entering cells.  Both glucose and vitamin C depend upon the pancreatic hormone insulin and its signaling effects in order to get into cells (7).

There is an important protein transporter called the GLUT-1 that activates in response to insulin interacting with the insulin receptor to allow both glucose and vitamin C to enter the cell.  However, glucose has a greater affinity for the insulin receptor.  This means that the greater the content of circulating blood sugar the less vitamin C will enter the cell (8, 9).

White Blood Cells and Insulin Pumps

White blood cells have more insulin pumps than any other type of cell and may contain 20 times the amount of vitamin C as other cells.  They also need 50 times more vitamin C inside the cell than in the blood plasma in order to handle the oxidative stress that occurs when they encounter a pathogenic substance (10, 11).

When white blood cells encounter pathogenic bacteria and viruses they must ingest or phagocytize these organisms in order to neutralize them.  The phagocytic index measures how effective a particular white blood cell is at destroying viruses, bacteria & cancer cells.  Elevated blood sugar impairs this phagocytic index.  In fact, a blood sugar of 120 reduces the phagocytic index by 75% (12).

Vitamin C and the HMP Shunt

Glucose and ascorbic acid also work on the hexose monophosphate (HMP) shunt.  The HMP is a biochemical pathway that produces NADPH.  White blood cells need NADPH to create superoxide and other reactive oxygen species that oxidize and destroy pathogens (13).

Vitamin C not only helps produce NADPH but also regulates quantities so the white blood cell does not create too much oxidative stress in its attempt to protect the body.

Vitamin C activates this important shunt while glucose inhibits it.   This HMP shunt also produces ribose and deoxyribose which provide important raw materials for the formation of new white blood cell RNA/DNA (14).

When the immune system is under attack it needs to quickly produce new immune cells.  If blood sugar is high enough to turn off the HMP shunt it will reduce the quantity of RNA/DNA and the amount of new immune cells formed.

Best Food Sources of Vitamin C:

The current adult RDA for vitamin C is 60 mg, however, as a practicing clinician, I recommend my clients get at least 200 mg from food and ideally supplement with another 500mg -1 gram daily.  In cases of chronic health conditions, I will recommend much higher dosages.

Here are the best food sources to consume to boost your vitamin C levels.  Eating some of these on a daily basis is recommended.  If you are doing a fast and not consuming food, I wouldn’t worry about it as your body will not have as great a need for vitamin C during the fast.  But when you return to consuming food, be sure to include these vitamin C rich foods.

vitamin c levels

5 Ways to Increase Your Vitamin C Levels

Vitamin C is obviously extremely important for our overall health and there are 5 key things you can do to improve your levels.

Avoid Sugar:  

Avoid sugar as much as possible and stick to a lower carbohydrate diet to improve your vitamin C levels.  This includes processed sugars but also high starch foods such as potatoes, rice, high sugar fruits like bananas, watermelon, etc.

I recommend following a lower carbohydrate diet that is rich in non-starchy vegetables such as broccoli, cauliflower, kale, celery, asparagus, garlic, onions, mushrooms, cucumbers, etc.  Consume grass-fed and organic animal products and lots of healthy fats from avocados, olives and olive oil and coconut oil.  These foods will stabilize your blood sugar and insulin and improve your immune health.

vitamin c levels

Vitamin C Rich Foods:

Use low sugar whole food forms of vitamin C such as bell peppers, broccoli, lemon, lime, & green leafy veggies as much as possible to support your vitamin C levels.  These foods sources should be included in most of your meals and you can also drink warm lemon water which not only provides vitamin C but is also a great support for healthy digestion.

You can also add in foods that are rich in quercetin which is a bioflavonoid that works in tandem with vitamin C to support the immune system.  This would include onions, elderberries, cranberries, peppers and kale.

vitamin c levels

Use Vitamin C Supplements:

Vitamin C is an important component in controlling inflammatory responses to damaged tissues.  Vitamin C also acts as an anti-histamine and helps to control hyperinflammatory responses to infections and allergies (151617).

I recommend our Super C, which has a 1:1 ratio of vitamin C to citrus bioflavonoids which are also called Vitamin P.  This combination of Vitamin C and Vitamin P synergizes to uniquely improve immunity, supports adrenal health and this synergy helps to improve capillary permeability to deliver more oxygen to cells.  I personally use 1 gram (2 caps) in the morning upon rising and 1 gram at night before bed to support my adrenal health, circulation and immune system function.

vitamin c levels

Intermittent Fasting:  

Combining intermittent fasting with vitamin C supplementation and lemon water can be of great benefit for improving blood sugar regulation and immunity.  Fasting will improve your blood sugar levels and take stress off of your digestive system, which frees up more energy for immune function, healing and repair.

Intermittent fasting is a strategy that involves fasting (not eating) for a period of time followed by a period of feasting (eating). Intermittent fasting increases autophagy, cellular rejuvenation, immune system function, and genetic repair. It reduces inflammation and the risk of disease.  For more info on how to practice intermittent fasting, read this article.

vitamin c levels

Boost Glutathione:

Glutathione, commonly referred to as “the master antioxidant,” is a powerful force for our immune health. It helps to improve the inflammatory response and has the essential role of maintaining exogenous antioxidants such as vitamins C and E in their active form. Glutathione protects cells from free radicals and repairs free radical damage that does occur.

Many people are deficient in glutathione and may benefit from supplementation.  For supplemental forms, look for reduced glutathione, acetylated glutathione and liposomal forms of glutathione.  Additionally, precursers like N-Acetyl Cysteine (NAC) help the body to produce glutathione.  Discuss dosages with your health care practitioner.

Glutathione Supplements

I have many of my clients boost their glutathione levels through natural strategies and key supplements such as Super Glutathione.  Glutathione helps to recycle vitamin C and it may be more important as a supplement than vitamin C, although vitamin C can be of great benefit.

For optimal glutathione absorption and utilization within the cell, you want to use an acetylated form of glutathione that bypasses the gut and is easily absorbed into the cell.  This is the form used in Super Glutathione.  You can also use liposomal glutathione which also bypasses the gut and fuses into the cell membranes for optimal absorption.

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Sources For This Article Include:

1. Drouin G, Godin J-R, Pagé B. The Genetics of Vitamin C Loss in Vertebrates. Current Genomics. 2011;12(5):371-378.
2. Nishikimi M, Yagi K. Molecular basis for the deficiency in humans of gulonolactone oxidase, a key enzyme for ascorbic acid biosynthesis. Am J Clin Nutr. 1991 Dec;54(6 Suppl):1203S-1208S. PMID: 1962571
3. Nishikimi M, Yagi K. Biochemistry and molecular biology of ascorbic acid biosynthesis. Subcell Biochem. 1996;25:17-39. PMID: 8821967
4. Boyera N, Galey I, Bernard BA. Effect of vitamin C and its derivatives on collagen synthesis and cross-linking by normal human fibroblasts. Int J Cosmet Sci. 1998 Jun;20(3):151-8. PMID: 18505499
5. Winkler BS, Orselli SM, Rex TS. The redox couple between glutathione and ascorbic acid: a chemical and physiological perspective. Free Radic Biol Med. 1994 Oct;17(4):333-49. PMID: 8001837
6. Linus Pauling – Biographical Link Here
7. Ascorbic Acid and Other Modern Analogs of the Germ Theory Link Here
8. Cunningham JJ. The glucose/insulin system and vitamin C: implications in insulin-dependent diabetes mellitus. J Am Coll Nutr. 1998 Apr;17(2):105-8. PMID: 9550452
9. Afkhami-Ardekani M, Shojaoddiny-Ardekani A. Effect of vitamin C on blood glucose, serum lipids & serum insulin in type 2 diabetes patients. Indian J Med Res. 2007 Nov;126(5):471-4. PMID: 18160753
10. Qutob S, Dixon SJ, Wilson JX. Insulin stimulates vitamin C recycling and ascorbate accumulation in osteoblastic cells. Endocrinology. 1998 Jan;139(1):51-6. PMID: 9421397
11. Wilson JX. Regulation of vitamin C transport. Annu Rev Nutr. 2005;25:105-25. PMID: 16011461
12. Role of sugars in human neutrophilic phagocytosis Link Here
13. Varma SD, Bauer SA, Richards RD. Hexose monophosphate shunt in rat lens: stimulation by vitamin C. Invest Ophthalmol Vis Sci. 1987 Jul;28(7):1164-9. PMID: 3110091
14. Glucose-6-phosphate in Metabolic Processes Link Here
15. Shaik-Dasthagirisaheb YB, Varvara G, Murmura G, Saggini A, Caraffa A, Antinolfi P, Tete’ S, Tripodi D, Conti F, Cianchetti E, Toniato E, Rosati M, Speranza L, Pantalone A, Saggini R, Tei M, Speziali A, Conti P, Theoharides TC, Pandolfi F. Role of vitamins D, E and C in immunity and inflammation. J Biol Regul Homeost Agents. 2013 Apr-Jun;27(2):291-5. PMID: 23830380
16. Banerjee D, Kaul D. Combined inhalational and oral supplementation of ascorbic acid may prevent influenza pandemic emergency: a hypothesis. Nutrition. 2010 Jan;26(1):128-32. PMID: 20005468
17. Conway FJ, Talwar D, McMillan DC. The relationship between acute changes in the systemic inflammatory response and plasma ascorbic acid, alpha-tocopherol and lipid peroxidation after elective hip arthroplasty. Clin Nutr. 2014 Jul 10. PMID: 25048713

glymphatic system, Glymphatic System: Critical for Brain and Immune Health

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  1. I read your “helpful article” and was wondering if you knew how much more Vitamin C is absorbed by including bioflavonoids with vitamin C and more importantly, for a type 2 diabetic why you would not suggest maybe 10 times more Vitamin C that you recommend in your article,since perhaps only 30% is absorbed since the cells prefer glucose instead?

    Let me know.


    Richard Iacino

    1. Richard, bioflavonoids do not improve Vitamin C absorption. No evidence demonstrates this. But there are studies that the two may be synergistic in supporting the immune and circulatory systems.

    2. I read somewhere that including bioflavonoids kept the vitamin C around for longer. Sorry don’t have the reference handy.

  2. Does taking glutathione supplement take away or decrease a body’s ability to produce it? You are supplementing so it stops producing since it is being supplied or will body continue to produce? If u stop supplements with u be at a greater deficit?

    1. Good question Liss, this is a common concern. If done for long-term, it is possible that your body will lower endogenous production. The key is to cycle. Something like 5 days on, 2 days off or even 2-3 weeks on, 1 week off would be a good strategy!

    1. A number of factors like your exposure to certain chemicals, chronic infection, nutrition, etc. can inhibit or deplete glutathione stores faster than they can replenish. This makes supplementation helpful in certain situations! Something like an organic acids test or a micronutrient analysis could give you insight into this! Both can be found here: https://drjockers.com/lab-testing/

      1. Glutathione is important in removing brain fog and neuroinflammation after brain injury or severe concussion. Some genes turn from on to off (epigenetics) after a trauma like a brain injury. Also, some people have genetic issues with detoxification and need extra support with NAC or/and L-glutathione. Dr. Jockers have you thought of becoming a Chiropractic Neurologist (DACNB) or Functional Neurologist or have you taken the Neuro Chemistry and Nutrition course offered by the Carrick Institute?

  3. Hello, Dr. David Jockers. My body loves when I take either supplement or food high in Vitamin C. However I passed calcium oxalate kidney stones three times & Vitamin C is promoting it (same as for my late father). Any suggestions?
    Thank you for your time. Leon

    1. Hi Leon, here’s my 2¢ worth. Limit supplementation to ½ gram of true vitamin-c/d. With Dysbiosis you don’t have the normal gut bacteria that metabolize the oxalic acids, thus your hyperoxaluria has also overrode sulfation. Since many excellent foods also have oxalates, you can address those issues by consuming some magnesium citrate with each meal assuming that your kidneys are otherwise healthy.
      Your remark about vitamin-c promoting kidney stones is misleading. It would be the same if I said that fire wood is promoting fires. The problem is the damage to your gut microbiome, which is usually the result of taking antibiotics. Your don’t get calcium oxalate kidney stones from vitamin-c, you get them from Dysbiosis. And you normally get Dysbiosis from taking antibiotics.

      1. Hello, Louise; Thank you for your detail explanation. Because my late father passed kidneys stones many times in his life, I think not only Dysbiosis but genetic weakness plays role as well. Best wishes. Leon

  4. Hi Leon, if you’re interested in the genetic aspects of oxalates, you should consider the Organic Acid Test (OAT), which is offered by Dr. Jockers. It tests for two different genetic oxalic markers plus your urine concentration. Whereas, Dysbiosis will usually consist of a fungal overgrowth (also on the OAT), a low or absent Oxalobacter formigenes count, plus other idiosyncrasies, which can elevate oxalates. Your concern should not be limited to the kidney stones and it would be wise to seek professional guidance. Note also that with oxalates the genetics may only be an issue subsequent to Dysbiosis.

  5. Dr. Jockers: Don’t stomach acid and digestive enzymes render oral glutathione useless unless it is presented in the liposomal state or as NAC which is one of the three amino acid precursors?

  6. i have also found from other sources that both leafy vegetables can be combined with fruits listed for higher content of vitamin c that can also help absorb iron (spinach and strawberries).

  7. “Of equal importance was the recognition about twenty years ago that the optimum intakes of several of the vitamins, far larger than the usually recommended intakes, lead to further improvement in health, greater protection against many diseases, and great value as an adjunct to the appropriate conventional therapy in the treatment of diseases.”

    “Limit your mineral intake to the recommended amounts.”

    Dr. Linus Pauling — HOW TO LIVE LONGER AND FEEL BETTER. (1986, p 11 f.)

  8. Dr. Jockers,
    I find your articles on various health reviews very helpful because you write them so clearly and also include scientific basis. If possible, could you please write a review on Alzheimer’s disease and proven over-the-counter products?

  9. I was told that all Vitamin C was fermented and therefore unacceptable for use by people having Mast cell/high oxalate/histamine issues. Camu camu and a vitamin C by Metabolic Maintenance were the only ones acceptable. Dr. Jockers, do you have anything to suggest that might be helpful in addition to those, except for foods, many of which are not on the diets of those with the above issues?

  10. Awesome articles Dr. Jockers! Can I ask what your Vitamin C is derived from? Allergic to corn and heard that some Vitamin C is derived from corn. Looking at purchasing your Super C Powder and wanted to make sure it wouldn’t bother me.
    Thanks in advance!

  11. There is now evidence that too much synthetic Vitamin C (even only 500mg/day – see below) can have negative effects on the body, but food Vitamin C is fine in any amount. Would you recommend sticking to 200mg/day of synthetic maximum and getting the rest from food sources? I did see a study showing that this dose is effective for antioxidant effects. Thanks.

    “A second study presented to the American Heart Association showed a link between consumption of only 500 mg of vitamin C per day and a greater propensity toward thickening of the arteries (Los Angeles Times, March 3, 2000). More recently, athletes taking 1000 mg of isolated ascorbic acid per day showed reduced endurance capacity from interference with antioxidant enzymes (American Journal of Clinical Nutrition, Jan 2008).” https://www.thehealthyhomeeconomist.com/beware-of-ascorbic-acid-synthetic/

  12. What does a person do who has bladder sensitivity and cannot tolerate high doses of supplemental vitamin C, yet also has anxiety and depression issues and needs the high doses of C?

      1. Dr. Jockers, I find your reply/response to D’s question a “little” short or could be termed “wanting”! Is there a reason for this?

  13. Dr Jockers – just wondering about the different forms of Vit. C – e.g ascorbic acid, ascorbate etc. is ascorbic acid the way to go?

  14. I find your articles very helpful They are clearly written and illustrated. Thank you for all the guidance you offer. Most Vitamin C supplements are Ascorbic Acid based and put my oral mucosa into ulceration overdrive. (Oral Lichen Planus). What do you recommend for folks who cannot tolerate Ascorbic Acid?

    1. I cannot stand ascorbic acid (stomach will complain!!!), so I take a little sodium ascorbate with some camu camu, acerola and NAC (since my Dutch Test showed very low glutathione).

  15. Hello Dr. Jockers, Thanks for giving a lot of information on the importance of Vitamin C uptake and its functioning in the cell metabolism. After reading this I will definitely add Vitamin C foods daily in my diet.

  16. Thank you Dr Jockers@, you are God sent. I have been recently diagnosed with low white cells and was put on vitamin C 1000mg for 6months. Is this enough and what is your advise? I am worried about my immunity and health.

  17. Hi, can somebody, who has metastatik lung cancer treated with Osimertinib, a Kind of targeted drug, take glutathione?

  18. Another really fantastic and educative article by Dr Jockers gifting “the ordinary person who doesn’t read the latest medical and scientific journals” with really life empowering information. Thanks Dr J.

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