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 it risks 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 makes due by recycling the oxidized version of vitamin C. This redox cycling is performed by the master anti-oxidant 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 receptor called the Glut-1 receptor that activates in response to insulin 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/DNAand 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 disease, I will recommend much higher dosages.
5 Ways to Increase Your Vitamin C Levels
1) Avoid Sugar: Avoid sugar as much as possible and stick to a lower carbohydrate diet to improve your vitamin C levels
2) Use Vitamin C: Load up on high quality vitamin C that also contains bioflavonoids with it to prevent illness – 1-2 grams per day is great for supplementation.
3) 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.
4) Intermittent Fasting: Combining intermittent fasting with vitamin C supplementation and lemon water can be of great benefit for improving blood sugar regulation and immunity.
5) Boost Glutathione: I have many of my clients boost their glutathione levels through natural stategies 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.
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