Vitamin C is getting a lot of buzz these days as an immune-boosting supplement for protecting against, and treating, COVID-19.
To be perfectly clear, there is no evidence that vitamin C—or any supplement or drug, for that matter—can prevent or cure this viral infection. However, vitamin C is essential for optional immune function, and high doses are being tested as a treatment for severe COVID-19.
How Does Vitamin C Help Your Immune System?
Vitamin C is your body’s premier water-soluble antioxidant. In addition to protecting proteins, lipids, DNA, and other molecules by neutralizing harmful free radicals, it also regenerates vitamin E and other antioxidants.
Specific to the immune system, vitamin C:
- Stimulates the production of several types of white blood cells, as well as interferons and other signaling proteins that enhance antimicrobial defenses.
- Protects immune cells against oxidative damage incurred as they fight viruses and other pathogens.
- Counterbalances oxidative stress, which occurs as antioxidants are depleted during the body’s immune response to infections and other illnesses.
In fact, supplemental vitamin C has been used to enhance immune function since 1949, when Fred Klenner, MD, got excellent results injecting polio patients with 1–2 g of vitamin C every few hours. He also reported good outcomes treating flu, chicken pox, measles, and other infections.
But it was two-time Nobel Prize winner Linus Pauling, PhD, who put vitamin C supplements on the map with his 1970 book Vitamin C and the Common Cold. Since then, multiple studies have shown that it reduces the duration and severity of colds, and at least five controlled clinical trials have demonstrated significant effects against pneumonia.
IV Vitamin C for Severe COVID-19 Infections?
Although supplemental vitamin C is at best ignored—and more often than not discouraged—by conventional doctors, high-dose intravenous vitamin C is gaining support as one promising treatment for severe COVID-19.
Most of the deaths associated with the coronavirus are caused by what is referred to as a “cytokine storm.” Cytokines are proteins that help to orchestrate the body’s immune response. In very serious infections, the immune system sometimes overreacts, releasing massive amounts of cytokines and setting off a storm of oxidative stress and inflammation that overwhelms healthy tissues.
IV vitamin C rapidly replenishes depleted antioxidant stores, reducing oxidative stress, curbing tissue-damaging inflammation, and reactivating multiple biochemical pathways critical for recovery.
This therapy has saved the lives of hundreds of patients with sepsis, a deadly complication of serious infections characterized by cytokine storms. It has also been used in China to successfully treat advanced COVID-19 infections. Clinical trials are now underway, and early research suggests that IV vitamin C may be one of the most effective treatments for COVID-19.
What Are the Benefits of Vitamin C Besides Immune Support?
Quenching free radicals isn’t vitamin C’s only claim to fame. It is also an indispensable cofactor in multiple enzymatic reactions and is required for the synthesis of collagen, carnitine, and norepinephrine and other neurotransmitters. Therefore, its benefits extend far beyond the immune system.
Diabetes: Vitamin C protects against oxidative stress, which is a significant contributor to diabetic complications. It also enhances blood sugar control. Study participants with type 2 diabetes who took 500 mg of vitamin C twice a day for four months had significant improvements in postprandial (post meal) blood sugar levels, and blood pressure declined by an average of 7/5 mm Hg.
Cardiovascular disease: Population studies have found strong links between higher dietary vitamin C intake and lower heart disease risk. Although the clinical trials evaluating vitamin C supplements have had inconsistent results, many of these studies were of notoriously poor quality. In any case, oxidative damage is a known cause of arterial endothelial dysfunction and atherosclerosis.
Gout: Vitamin C is inversely associated with the prevalence of gout—the higher the intake and blood level, the lower the risk. This suggests that supplemental vitamin C may play a role in gout prevention in susceptible individuals.
Eyes: Low vitamin C levels have been linked with an increased likelihood of cataracts and glaucoma. Plus, a daily dose of 500 mg is part of the Age-Related Eye Disease Study 2 protocol shown to protect against advanced age-related macular degeneration.
Skin Care: In addition to protecting against free radical damage from UV radiation, vitamin C is necessary for the production of collagen, the primary structural protein in the skin. Many products for aging skin, both oral and topical, contain vitamin C.
Are You Getting Enough Vitamin C?
Every mammal on Earth, except for primates, guinea pigs, and fruit-eating bats, produces vitamin C. So, we humans must get this essential vitamin from outside sources.
Diet is a good start. If you eat five or six servings of fruits and vegetables per day—especially foods with lots of vitamin C like citrus, kiwi, strawberries, red bell peppers, and broccoli—you’ll get about 150–200 mg of vitamin C. Even a mediocre diet likely contains the meager recommended vitamin C dosage for adults of 75–90 mg.
That’s enough to prevent scurvy, which is a clear sign of vitamin C deficiency. But to maintain an optimal blood level to help protect against multiple health challenges, you also want to supplement with vitamin C.
How Much Vitamin C Should You Take?
I’ve always gone with Dr. Linus Pauling’s recommended dose of 1,000–2,000 mg of vitamin C per day, increasing to 500 mg every couple of waking hours at the first signs of a cold or other viral illness. It is best taken in divided doses since the intestinal tract cannot absorb more than 500 mg at a time—the rest will be excreted.
Taking up to 10,000 mg a day is safe and nontoxic. However, there is an effect of too much vitamin C you should be aware of: loose stools. If you find it affects you in this way, back off on your daily dose. It’s also always important to work with your doctor.
What form of vitamin C should you take? Some people argue that acerola cherry, rose hips, and other natural sources of vitamin C are superior to synthetic ascorbic acid, but the two are chemically identical. There is also no evidence supporting claims that ascorbate or liposomal forms are better. Good old inexpensive regular vitamin C, preferably with citrus bioflavonoids for increased bioavailability, is just fine.