The importance of vitamin C for health and mood

Vitamin C plays a role in connective tissue, the immune system, the brain, hormone balance, the circulatory system, and iron absorption. In addition, it functions as a unique antioxidant that protects cells and tissues from damage caused by oxidative stress. Official recommendations have primarily focused on preventing the classical deficiency disease scurvy, but evidence suggests that even mild deficiencies make the body more vulnerable. In a review article published in Molecules, the authors examined vitamin C’s therapeutic role in supporting quality of life and in the prevention of infections and various chronic diseases such as atherosclerosis, diabetes, and cancer.

Albert Szent-Györgyi received the Nobel Prize in 1937 for his discovery of vitamin C. Ever since it was found that the vitamin could be used to treat scurvy, it has been a focus of scientific research.
Vitamin C is involved in numerous biological processes, especially as a cofactor in enzymes, regulation of genes, formation of hormones, iron absorption, cholesterol balance, and metabolism of folic acid, tryptophan, and tyrosine. It also works as a highly important antioxidant.
Vitamin C is water-soluble and appears in two main forms. The first is called ascorbic acid (AA) and is the primary active form. The second, dehydroascorbic acid (DHA), is formed when ascorbic acid has been used as an antioxidant or a coenzyme. Dehydroascorbic acid also functions as an important metabolite and is regenerated into ascorbic acid inside the cells. This interplay between the two forms is crucial for vitamin C’s effect and for maintaining cellular vitamin C levels.
Most animals can synthesize vitamin C endogenously, with the synthesis multiplying during infections and stress conditions. Humans, however, have lost the ability to produce vitamin C to evolution and must therefore obtain the vitamin daily. Evidence indicates that our need for the vitamin increases significantly during infections and other stressful states. The review article discusses vitamin C’s many roles and our real requirements, which can be summarized as follows:

Collagen synthesis and wound healing

Vitamin C is essential for the production of collagen that make tissues strong and elastic. Collagen is also important for a variety of cellular activities. It is found in blood vessels, muscle fascia, tendons, skin, and bones. The classic deficiency disease, scurvy, leads to fragile connective tissue and internal bleeding, and if untreated, death. While scurvy is rare today, subclinical scurvy is common, typically characterized by easy bruising, bleeding gums, nosebleeds, poor wound healing, low stress tolerance, poor mood, frequent infections, and other symptoms.
The review article also discusses several studies where high doses of vitamin C were given in cases of complicated wounds, showing how it can support collagen production and different stages of wound healing.

Antioxidant

Most chronic diseases are associated with oxidative stress, where free radicals outnumber protective antioxidants. Free radicals are involved in many physiological processes but must be kept under control to avoid damaging healthy cells and tissues. Aging, stress, infections, chronic inflammation, heavy metals, tobacco smoke, medication, and radiation all increase free radical activity. Here, vitamin C plays a decisive role by donating electrons to neutralize free radicals. It also has a synergy with vitamin E, as vitamin C can regenerate oxidized vitamin E, thereby increasing overall antioxidant capacity.

Infections and inflammation

The immune system is designed to protect against harmful microorganisms (viruses, bacteria, fungi, parasites) and toxins. Vitamin C is particularly important for the innate immune system’s white blood cells, including neutrophils and macrophages. It is also crucial for the adaptive immune system, consisting of T cells, B cells, and antibodies.
When an infection occurs, innate immune cells absorb large amounts of oxygen and generate free radicals in a process known as the “respiratory burst.” This requires high amounts of vitamin C, and neutrophils contain vitamin C in concentrations that are 10 times higher than normal, indicating an increased demand.
Vitamin C also acts as a powerful antioxidant, protecting surrounding tissues from free radical damage, while counteracting harmful inflammation.
The review cites numerous studies where vitamin C supplements were given for colds, flu, pneumonia, COVID-19, staphylococcal infections, and others, with mixed results. Evidence suggests the best preventive effect comes from maintaining sufficient daily intake. Higher doses taken several times a day at the first signs of infection may also support the innate immune system’s rapid and efficient response.

Cardiovascular disease

Cardiovascular disease remains the leading cause of premature death, with high blood pressure and atherosclerosis as major risk factors.
As mentioned, free radicals are highly reactive molecules that, under oxidative stress, can attack cholesterol. Cholesterol is essential for cell membranes, vitamin D, steroid hormones, and more. In the bloodstream, cholesterol is transported as LDL. But when LDL becomes oxidized, it turns rancid and can no longer fulfill its functions. White blood cells engulf oxidized LDL, migrate into vessel walls, and form foam cells. The later stages of atherosclerosis include fibrin and calcium deposits around these foam cells.
Thus, oxidative stress combined with foam cell and calcium buildup in vessel walls promotes atherosclerosis, regardless of whether cholesterol levels are high or low.
Chronic inflammation further increases the risk by aggravating oxidative stress and vascular damage.
The review highlights vitamin C’s cardiovascular role: regulating inflammatory processes, strengthening connective tissue in vessel walls, maintaining cholesterol balance, and participating in several related mechanisms.

The brain, nervous system, and mood

The brain contains billions of neurons and glial cells in a complex network. Due to its high energy turnover and blood flow, the brain is particularly vulnerable to oxidative stress. This is also because it contains cholesterol, omega-3 fatty acids, and other lipids that are highly susceptible to free radical attacks. Oxidative stress in the brain can damage cell membranes, triggering chain reactions that disrupt cellular functions. This can contribute to neurodegenerative diseases such as Alzheimer’s - the leading cause of dementia - and Parkinson’s disease, which is characterized by involuntary tremors.
Vitamin C plays a vital antioxidant role here, and large concentrations of the vitamin are found in the brain and adrenal glands, suggesting that these tissues have a high demand.
Vitamin C is also important for collagen formation in the brain’s connective tissues, which supports blood vessel integrity and cerebral blood flow.
It contributes to the formation of neurons and neurotransmitters such as glutamate, dopamine, noradrenaline, and adrenaline, which are crucial for cognitive functions, stress management, and mental balance. Research also suggests that the DHA (dehydroascorbic acid) form of vitamin C may protect nerve cells.
Patients with Alzheimer’s disease have been observed to have low vitamin C levels in blood and cerebrospinal fluid. This is associated with oxidative stress and disease progression.
Supplementation has shown mixed results in neurological diseases. Still, early symptoms of scurvy include fatigue, mood swings, and depression, highlighting vitamin C’s importance for mood and the nervous system.

Cancer and redox therapy

Chemist Linus Pauling and physician Ewan Cameron pioneered the use of high intravenous vitamin C doses (10-100 grams daily) in terminal cancer patients and have reported significant improvements in survival.
Intravenous high-dose vitamin C therapy, also known as redox therapy, relies on its dual role as antioxidant and pro-oxidant, as well as its influence on gene regulation.
Unlike chemotherapy, which damages both cancer cells and healthy cells, redox therapy exploits biological differences between the two types of cells. Intravenous administration raises blood vitamin C levels 100-500 times more than oral intake, enabling it to generate hydrogen peroxide (a free radical) that selectively kills cancer cells. Healthy cells neutralize these radicals with the enzyme catalase, but cancer cells, with their lower catalase levels, are particularly vulnerable, enabling vitamin C to work like a natural form of chemotherapy without side effects.
Some cancer types with higher catalase activity are less sensitive, but the review cites several studies where high-dose intravenous vitamin C had promising results in both animals and humans. It may also reduce side effects from conventional treatments (chemotherapy and radiation). More studies are needed to determine optimal dosages and effectiveness in cancer care. Many orthomolecular physicians also recommend specific diets and additional supplements to enhance results.

Prevention of chronic diseases

Chronic inflammation and oxidative stress contribute to the development of type 2 diabetes, cardiovascular disease, neurological and psychiatric disorders, lung diseases, and many other chronic conditions.
Vitamin C may help prevent these by serving as an antioxidant and anti-inflammatory agent.
Studies show that patients with metabolic syndrome, a precursor to type 2 diabetes, often have low blood levels of vitamin C. Supplementation has been shown to improve blood sugar control, cholesterol balance, blood pressure, and weight by supporting different mechanisms.
Vitamin C also helps prevent and manage osteoarthritis by supporting cartilage collagen synthesis and protecting cells from oxidative damage.

Sources, official recommendations, and real needs

Vitamin C is found mainly in fruits, vegetables, berries, and herbs. Interestingly, an estimated four billion people worldwide are deficient in the nutrient. Excess sugar intake can also inhibit vitamin C absorption in cells.
Official recommendations in most countries range from 75-90 mg daily. According to the review article, around 200 mg is needed to saturate blood levels at 70 µmol/L. Levels below 23 µmol/L indicate deficiency, and levels below 11 µmol/L indicate scurvy.
Healthy individuals are generally advised not to exceed 1,000-2,000 mg daily, as higher intakes may increase the risk of kidney stones, although experts disagree on this.
Smokers and patients with infections or chronic illnesses usually have lower vitamin C levels and therefore need more of the nutrient.
Vitamin C supplements should preferably be buffered (non-acidic) to avoid stomach irritation.

References

Adina Alberts et al. Vitamin C: A Comprehensive Review of Its Role in Health, Disease Prevention, and Therapeutic Potential. Molecules 2025

Simone Passarelli et al. Global estimation of dietary micronutrient inadequacies: a modeling analysis. The Lancet Global Health 2024

Claire M Doskey et al. Why high-dose vitamin C kills cancer cells. ScienceDaily. 2017