16 Vitamin C Benefits And Side Effects

There are so many people who take Vitamin C every day but do you know what is Vitamin C benefits and side effects?

Vitamin C also known as ascorbic acid is a carbohydrate converted from glucose. The appearance is white crystalline. It is weakly acidic and has a sour taste. It is the most important water-soluble vitamin in the human body.

Most mammals can be Synthesized from the body by itself, only humans can’t make it by themselves due to genetic variation, and must be ingested from food

In the human body, Vitamin C has a variety of functions, among which the most important ones include antioxidant, anti-inflammatory, anti-viral, antibacterial, and collagen production. These are also the basic conditions for maintaining health because fighting diseases are all related to these factors Closely related.

The reason why Vitamin C is so popular all over the world comes from the strong promotion of two-time Nobel Prize winner Linus Pauling, in his best-selling book: Vitamin C and the Common Cold), began to change the world’s view of Vitamin C, from now on Vitamin C is often used to treat colds and daily health care, becoming an essential health care product for American families

The two medical doctors in the United States: Vitamin C: The Real Story also mentioned that Vitamin C is an excellent molecule, which has a key impact on health.

Table of Contents

When is Vitamin C most effective?

The human body does not naturally produce or store water-soluble Vitamins. Therefore, these Vitamins need to be taken from dietary sources or supplement sources.

Water-soluble Vitamins are best absorbed on an empty stomach. This represents the most suitable time to take 30 minutes before a meal or two hours after a meal.

However, for groups with poor gastrointestinal tract function, do not supplement multiVitamin C (especially ascorbic acid form) on an empty stomach. Excessive amounts may cause gastrointestinal irritation.

People with poor gastrointestinal tract function or acid-fearing groups can switch to acid-free Vitamin C. Related forms include Liposomal Vitamin C, sodium ascorbate, calcium ascorbate, and ascorbyl palmitate.

Which absorption rate of natural and synthetic Vitamin C is better?

In the increasingly robust supplement market, Vitamin C supplements come in many different forms but can be roughly divided into natural extraction and artificial synthesis.

In terms of chemical structure, natural and synthetic Vitamin C (ascorbic acid) is the same, and there is no known difference in biological activity.

In at least two human trials, the bioavailability difference between natural sources and synthetic L-ascorbic acid was studied, and it was found that there was no clinically significant difference between the two.

In addition, because the nutrients in natural foods are not single, the study pointed out that if ingested with other nutrients, such as bioflavonoids, Vitamin E, etc., they can produce a synergistic effect that enhances each other’s bioavailability.

What are the benefits recommended by Vitamin C?

1. Vitamin C reduces C-reactive protein

C-reactive protein is an acute-phase protein that is a biomarker of the inflammatory process.

During inflammation or stress reactions such as coronary heart disease, trauma, arthritis, and surgical injuries, their serum levels increase.

Existing clinical studies have shown that C-reactive protein levels are associated with early stages of coronary artery disease and are considered potential predictors of future cardiovascular disease.

A systematic literature review and meta-analysis (including 12 randomized controlled trials with a total of 446 participants) pointed out that Vitamin C supplementation significantly reduced the level of C-reactive protein.

In addition, the related effect of reducing hs-CRP (high-sensitivity C-reactive protein) is particularly significant in the following subjects, such as CRP baseline level ≥3, age <60 years, or intravenous Vitamin C.

*Conclusion: Vitamin C supplementation has a positive effect on reducing the inflammation index C-reactive protein, but it is limited by the heterogeneity between studies, and more trials are needed to corroborate.

2. Vitamin C helps exercise bronchospasm

Exercise-induced bronchoconstriction is defined as acute airway stenosis (transient and reversible) that occurs during or after exercise and can be observed in patients with or without chronic asthma (reportedly, usually It occurs within 2 to 5 minutes after exercise, peaks after 10 minutes, and subsides after about 60 minutes)

Typical symptoms include difficulty breathing, wheezing, coughing, chest tightness, increased mucus, or feeling sick when the body is in good condition

A systematic literature review and meta-analysis (including 3 double-blind placebo-controlled randomized trials with a total of 40 participants) pointed out that taking Vitamin C (dose 0.5 to 2 g) before exercise can reduce forced breathing after exercise The value of one second of gas (FEV1) (the amplitude is about 50%).

*Conclusion: Taking Vitamin C before exercise may have a positive effect on exercise bronchospasm, but more large-scale trials are still needed to confirm its clinical benefit.

3. Vitamin C is beneficial to essential hypertension

Essential hypertension is characterized by a chronic increase in blood pressure due to unknown reasons, which affects nearly 95% of patients with hypertension.

Various environmental factors, such as smoking, socioeconomic status, stress, high-salt diet, obesity, and Vitamin D deficiency, have been shown to play a role in the onset.

These factors cause primary hypertension through epigenetic and gene interaction, or by inducing specific gene expression.

A systematic literature review and meta-analysis (including 8 randomized controlled trials, a total of 614 participants with primary hypertension) pointed out that oral Vitamin C (daily dose between 300 mg and 1000 mg, intervention time from 4 weeks to 24 weeks) helps reduce systolic and diastolic blood pressure.

In addition, subgroup analysis showed that the effect of related blood pressure regulation is especially significant for subjects who are older than 60 years old, whose dose is greater than 500 mg, and whose intervention period is greater than 6 weeks.

*Conclusion: For patients with essential hypertension, oral Vitamin C has a positive effect on blood pressure regulation, but it is limited to a small number of samples, and more large-scale trials are still needed to corroborate.

4. Vitamin C is good for the common cold

Common Cold, also known as respiratory viral infection, is a spontaneous remission type upper respiratory tract infection characterized by a runny nose, nasal obstruction, headache, sneezing, coughing, and fever (usually <37.8°C). The total symptoms last for Between 7 – 14 days.

About 30% to 50% of cold symptoms are caused by rhinoviruses, and bacterial infections are rare.

According to the World Health Organization, in the United States, there are 100 million visits to the common cold every year, and the related cost is 7.7 billion US dollars (mostly used to purchase non-prescription drugs).

A literature meta-analysis (including 9 randomized placebo-controlled trials) pointed out that under the premise of regular daily supplementation of small doses of Vitamin C (1 g per day or less), if you take extra High doses of Vitamin C (3 to 4 grams per day) can help shorten the duration of illness and stay indoors, and can relieve common cold symptoms, including chest pain, fever, and chills.

For ethnic groups who do not have regular supplements on weekdays, the sudden increase of high-dose Vitamins when they have a cold does not significantly help.

Another meta-analysis (including 9 randomized controlled trials, a total of 3135 children from 3 months to 18 years) pointed out that compared with placebo, although oral Vitamin C has no obvious effect on preventing upper respiratory tract infections, But it helps to reduce the duration of upper respiratory tract infection (about 1.6 days).

The underlying mechanism may be related to the activation of the immune system with Vitamin C, such as natural killer cell activity, lymphocyte proliferation, chemotaxis, and delayed hypersensitivity, and can increase the secretion of the sympathetic nervous system and epinephrine under stress.

*Conclusion: The effect of oral Vitamin C on the prevention of colds is still controversial, but the use of a therapeutic dose of Vitamin C (3 to 4 grams per day) at the beginning of a cold may help shorten the course of the disease and the severity of symptoms.

5. Vitamin C is beneficial for blood sugar control

Diabetes is a chronic disease caused by an absolute or relative lack of insulin due to impaired insulin secretion and action. Related risk factors include family history, obesity, long-term lack of exercise, race, history of impaired fasting blood sugar, sugar Impaired tolerance, glycated hemoglobin, high blood pressure, abnormal HDL cholesterol, or elevated triglyceride levels.

In the long run, these metabolic abnormalities can lead to complications such as cardiovascular disease, retinopathy, nephropathy, and neuropathy.

A systematic literature review and meta-analysis (including 24 randomized controlled trials with a total of 937 participants) pointed out that, overall, oral Vitamin C does not change the concentration of glucose, glycated hemoglobin, and insulin.

However, the stratified analysis showed that the effect of Vitamin C in reducing blood glucose concentration can be seen in patients with type 2 diabetes, lasting more than 30 days, and older participants.

*Conclusion: The effect of Vitamin C supplementation on blood glucose regulation is very different depending on the study design and the characteristics of the participants. The related improvement effect is most significant in the studies of diabetes, seniors, and long duration.

6. Vitamin C helps improve hyperlipidemia

In the United States, more than 100 million people (approximately 53% of adults) have abnormal cholesterol levels. However, less than 50% of patients receive treatment, and less than 35% of patients receiving treatment have achieved adequate control.

Modifiable risk factors for hyperlipidemia include high saturated or trans-fat diet, lack of exercise, smoking, and obesity, secondary causes include biliary obstruction, chronic kidney disease, type 2 diabetes, hypertension, hypothyroidism, etc. disease.

A systematic literature review and meta-analysis (including 40 randomized controlled trials with a total of 1981 participants) pointed out that overall, Vitamin C supplementation had no significant effect on blood lipids.

However, further subgroup and sensitivity analysis showed that for subjects with dyslipidemia or low Vitamin C levels, there was a significant effect of improving blood lipids after supplementation (to reduce total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides, and increase high-density lipoprotein cholesterol (HDL-C)).

*Conclusion: Extra Vitamin C supplementation may have a positive effect on improving blood lipids, especially those with abnormal blood lipids or low Vitamin C levels

7. Vitamin C anti-anxiety

Anxiety is a psychological, physical, and behavioral state triggered by events that threaten overall well-being or survival, whether actual or potential.

However, persistent excessive anxiety (and avoidance) is generally referred to as anxiety disorders, especially when there is no real danger. According to recent epidemiological studies, the lifetime prevalence of any form of anxiety disorder can reach 28.8%.

A randomized, double-blind, placebo-controlled trial (142 students) pointed out that for high-trait anxiety subjects, taking Vitamin C (1000 mg) has an anti-anxiety effect in the short term.

*Conclusion: For high trait anxiety subjects, the use of Vitamin C may have the effect of regulating emotions and alleviating anxiety, but it is limited by the number of samples, and a broader population study is still needed to comment on clinical relevance.

8. Vitamin C beneficial cognitive function

Due to the advancement of medicine and the improvement of medical quality, the life expectancy of human beings has been greatly improved, but it is accompanied by many diseases related to aging.

One of them is the deterioration of cognitive function. According to the US research survey, the prevalence of dementia in elderly people over 71 years old is about 13.9%, of which 69.9% is Alzheimer’s disease, and vascular dementia accounts for 17.4%.

A Cohort Study pointed out that subjects with the highest concentration of Vitamin C in the blood had a lower incidence of cognitive impairment (even after adjusting for gender, race, and smoking factors).

In addition, more standard weight, BMI, waist circumference, and metabolic values ​​that meet the standard, such as glycated hemoglobin, insulin, and triglycerides are also observed in this group.

*Conclusion: The concentration of Vitamin C in the blood is related to cognitive function, but more studies need to confirm the association with dietary intake.

9. Vitamin C is beneficial to cardiovascular health

Cardiovascular disease, generally called heart disease, is a disease caused by a lack of blood flow to the heart tissue, which often includes angina pectoris, myocardial infarction, and heart failure. But with a mortality rate of up to 30%, it is a big killer in an instant.

A prospective survey pointed out (the follow-up period was 12.8 years and the number of samples was 20299). The person with the highest concentration of Vitamin C in the blood (compared to the lowest) can reduce the risk of heart failure by 24%. The increase in the concentration of Vitamin C in the blood by 20 μmol/L can reduce the risk value by 9% (range value is between 23-82 μmol/L).

Another meta-analysis (including 44 clinical trials) also found that intake of Vitamin C can help improve endothelial function. Abnormal endothelial function is considered to be an important factor that causes cardiovascular disease.

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10. Vitamin C prevents atrial fibrillation

Atrial fibrillation is a common postoperative complication after cardiac surgery. The prevalence rate ranges from 25% of coronary artery bypass grafting to 65% of valve replacement surgery, which may cause acute myocardial infarction, ischemic stroke, and acute renal failure. Increase the patient’s medical burden, hospital stay, and mortality.

A systematic literature review and meta-analysis (including 15 studies with 2,050 participants) pointed out that Vitamin C (oral or intravenous) can reduce the incidence of atrial fibrillation after cardiac surgery or cardiac rhythm conversion by 27%. And reduce hospital stay by 10%.

*Conclusion: Vitamin C may have the effect of reducing the incidence of atrial fibrillation in high-risk groups, and due to the high heterogeneity between studies, the results still need more confirmation.

11. Vitamin C reduces the incidence of hip fractures

Hip fractures are one of the most serious bone problems in seniors over 65 years of age, with multiple post-bed complications such as pressure ulcers, deep vein thrombosis, pneumonia, and urinary tract infections. Compared with the average person, the hip fracture will increase the risk of death by 3 to 8 times in the first 3 months.

A meta-analysis (6 studies, a total of more than 10,000 participants) pointed out that compared with the group that took the least amount of Vitamin C, those who took the most from food can reduce the incidence of hip fracture by 27%.

In addition, the same analysis also found that for every 50 mg increase in daily Vitamin C intake, the risk of hip fracture can be reduced by 5%.

The underlying mechanism is related to the collagen synthesis that Vitamin C has, scavenging free radicals, and regulating bone formation and erosion of cell metabolism.

*Conclusion: Higher intake of Vitamin C from natural foods can reduce the incidence of hip fractures.

12. Vitamin C reduces the incidence of cancer

Traditionally, Vitamin C has been regarded as a potential cancer chemopreventive factor due to its free radical scavenging, reducing Vitamin E, and reducing DNA oxidative damage properties.

Several Meta-analysis has found that taking more Vitamin C from the natural diet helps reduce the risk of various cancers (including gastric cancer, pancreatic cancer, esophageal cancer, prostate cancer, lung cancer, breast cancer, etc.), And even the survival rate.

The intravenous Vitamin C therapy for cancer was proposed by Linus Pauling, a Nobel laureate in the 1970s, and is still used in natural medicine and integrative therapy to this day (the underlying mechanism is related to the high-concentration co-oxidation and anti-inflammatory effects. Can reduce tumor cell growth, proliferation, and migration).

According to a systematic analysis, intravenous Vitamin C combined with chemotherapy may help to improve the treatment effect (such as cancer recurrence time, survival period, quality of life) and the side effects of chemotherapy (including fatigue, nausea, insomnia, constipation, and depression) Among them, several cases of cancer remission were reported.

However, the author believes that because the relevant evidence is still insufficient, more evidence is needed to confirm the safety and effectiveness of intravenous Vitamin C in the future.

13. Vitamin C is beneficial to hyperuricemia and gout

Gout is a type of chronic osteoarthritis. Hyperuricemia is the main risk factor. When the blood urate level is greater than 9 mg/dL, the chance of attack will increase tenfold.

Hyperuricemia is also associated with various diseases, such as hypertension, obesity, kidney disease, metabolic syndrome, sleep apnea syndrome, stroke, vascular dementia, etc.

A meta-analysis (including 13 randomized controlled trials with 556 samples) pointed out that supplementation with Vitamin C (average dose and duration of 500 mg per day for 30 days) helps to lower blood uric acid value and average decrease Up to 0.35 mg/dL (compared to placebo).

The underlying mechanism is related to Vitamin C promoting kidney excretion of uric acid and reducing free radical formation. Although lowering uric acid helps prevent gout attacks or relapses, more research is still needed to further confirm its feasibility.

14. Vitamin C reduces the risk of cervical precancerous lesions

Cervical cancer ranks third among common cancers in women, second only to breast cancer and colorectal cancer. According to statistics, there are about 500,000 new cases worldwide each year.

Cervical neoplasia is a type of cervical precancerous lesion. Among them, grade 3 cervical intraepithelial neoplasia (CIN), if not properly treated, the risk of developing into cancer within 10 years is as high as 40%.

A systematic analysis study (including 12 population studies) pointed out that Vitamin C intake is inversely related to the incidence of cervical neoplasia, especially every 50 mg increase in daily intake can help reduce 8 % Of cervical tumors are at risk.

The underlying mechanism may be related to the antioxidant properties of Vitamin C, the inhibition of free radicals and the reduction of DNA damage, the inhibition of matrix metalloproteinases (MMPs) and the prevention of cancer cell invasion (but the author believes that more research is still needed to further verify).

*Conclusion: Population observation found that a higher intake of Vitamin C can reduce the risk of cervical cancer precancerous lesions.

15. Vitamin C reduces the risk of cataract

Cataracts related to aging are one of the main causes of blindness. Every year, millions of blind and severely impaired vision patients worldwide are associated with the occurrence of cataracts.

Under the threat of an aging population, cataracts are almost inevitable. Elderly people over 75 years old have a high incidence of about 40%. In addition to age, the occurrence of cataracts is also significantly related to oxidative stress, smoking, and nutritional intake.

A prospective cohort study (targeting 2054 twins) pointed out that higher intake of Vitamin C from the diet can reduce the incidence of nuclear cataracts by 19% (compared to those with the least intake) and by 33% The possibility of developing into cataracts in the next 10 years (the underlying mechanism is related to the reduction of the oxidative stress of water crystals).

16. Vitamin C is beneficial for sepsis

Sepsis is a life-threatening clinical symptom (often causing multiple organ dysfunction), mainly caused by uncontrolled body infections.

Any infectious disease may progress to sepsis, but the elderly and patients with immune dysfunction have the highest incidence.

The main clinical symptoms are, for example, hypoxemia, oliguria, lactic acidosis, increased liver index, and abnormal brain function. If sepsis worsens to septic shock, it may cause a sudden drop in blood pressure and even life-threatening.

A double-blind controlled study (targeting 28 patients with septic shock in the intensive care unit), intravenous Vitamin C (ascorbic acid/ascorbic acid) can help reduce the dose of norepinephrine and duration.

The same experiment also found that the 28-day mortality rate in the Vitamin C group was also significantly lower, at 14.28%, compared with 64.28% in the placebo group (but there was no significant difference in the length of stay in the Intensive Care Unit).

Are there any side effects of Vitamin C?

Vitamin C is very safe and has no side effects by oral administration at an appropriate dose (it is water-soluble and the body will exclude unwanted amounts), but high doses (greater than 2,000 mg) may cause diarrhea, exhaust gas, heartburn, and gastrointestinal discomfort if it occurs In the above cases, please lower the dose.

Safety precautions

1. Vitamin C has a diuretic effect, which accelerates the body’s discharge of water, so be sure to take in more water when taking it.

2. Vitamin C will increase the absorption of iron, so people with genetic diseases such as hemochromatosis should avoid additional supplements.

3. Those suffering from thalassemia, sickle cell anemia, or G6PD deficiency (broad bean disease), please do not consume large amounts of Vitamin C, which may cause serious side effects.

4. People who have suffered from kidney stones or poor oxalate metabolism should limit the number of additional supplements. It is best not to exceed the recommended daily dietary allowance (recommended dietary allowance) or 250mg per day (overdose may cause kidney stones).

5. Do not use in combination with aluminum-containing acid (antacids), because Vitamin C will increase the amount of aluminum absorbed by the body (there are potential doubts), it is recommended to be between 2 and 4 hours.

6. Do not use in combination with estrogen, because Vitamin C will reduce the speed of the body to eliminate estrogen, which may enhance the effects and side effects of estrogen.

7. Do not use with psychiatric drugs: Fluphenazine, because Vitamin C will reduce the effect of drugs.

8. Do not use in combination with chemotherapy drugs, because Vitamin C may reduce the effectiveness of drugs.

9. Do not use in combination with HIV/AIDS drugs, such as protease inhibitors, because Vitamin C may reduce the effectiveness of drugs. The names of related drugs are amprenavir, nelfinavir, ritonavir, saquinavir.

10. Do not use it in combination with cholesterol-lowering drugs (Statins), because Vitamin C may reduce the effectiveness of the drugs. The names of the related drugs are atorvastatin, fluvastatin, lovastatin, pravastatin.

11. Do not use in combination with anticoagulant drugs (Warfarin). Large amounts of Vitamin C may reduce the efficacy of the drugs and may cause blood clotting problems.

12. Do not use in combination with anti-inflammatory and analgesic drugs, because a large amount of Vitamin C may reduce the speed of the body’s decomposition of drugs, and may increase the occurrence of adverse reactions. The names of related drugs are Acetaminophen, Aspirin, III Choline Magnesium Trisalicylate, Salicylic Acid (Salsalate).

13. Do not use in combination with calcium ion blockers (Nicardipine, Nifedipine), because taking it at the same time may reduce the amount of Vitamin C absorbed by the cells.

Do Vitamin C supplements cause tooth erosion?

The tooth erosion is mainly caused by the erosion of the hard tissue of the tooth body (enamel) by acidic substances. Serious acid erosion may even cause caries, loose teeth, shaking, and collapse.

A meta-analysis of literature (including 9 studies) pointed out that Vitamin C chewable tablets will significantly increase the chance of tooth etching (others such as foaming tablets and soft candy have similar effects).

Etching of teeth generally occurs when the pH of the tooth surface is below 5.5, and the pH of Vitamin C chewable tablets is about 2.3. With the increase of contact time and dose, the probability of acid etching will increase significantly.

There are two ways to avoid acid etching

1. use Vitamin C in capsule or non-acid forms, such as mineral ascorbate or Liposomal Vitamin C

2. Rinse your mouth immediately after taking it to reduce enamel damage

What are the foods rich in Vitamin C?

Unlike plants and most animals, humans do not have the ability to synthesize Vitamin C endogenously, so there are basic dietary requirements for this Vitamin.

The content of Vitamin C in food will be reduced due to cooking and long-term storage. Sufficient fruits and vegetables, equivalent to 5 or more different fruits and vegetables per day, usually provide the required Vitamin C.

Symptoms of Vitamin C deficiency or deficiency include bleeding gums, frequent bruising and infections, poor wound healing, anemia, and scurvy.