Can Vitamin C Really Help Fight Off the Common Cold?

Does Vitamin C Help with Colds?

It is a commonly held belief that vitamin C can help to treat and prevent colds. In other words, taking vitamin C supplements during cold and flu season may potentially reduce the frequency of upper respiratory tract infections and/or the severity and duration of a common cold.

However, experts say there is little evidence to support the usefulness of vitamin C in preventing colds. Taking vitamin C regularly may be slightly useful in treating colds. It could potentially reduce the duration of the illness slightly and may result in a less severe illness. On the other hand, very high doses of vitamin C can be harmful.

Common Beliefs and Myths

Myth: Vitamin C can cure common colds.

Fact: Experts say this isn’t true. Taking vitamin C supplements or eating vitamin C-rich foods won’t make your cold go away before the illness has run its course.

Myth: Vitamin C can prevent colds.

Fact: Research has shown that taking vitamin C every day does not lower your likelihood of getting a common cold. But vitamin C may help reduce how long your cold symptoms last.

What Is Vitamin C?

Vitamin C, also called L-ascorbic acid, is an essential micronutrient. This water-soluble vitamin is not made in the human body, so we must obtain it from dietary sources. 

Vitamin C plays many essential roles in the body, including the biosynthesis of natural chemicals and proteins such as neurotransmitters, L-carnitine, and collagen. In addition, the body needs vitamin C for protein metabolism. It is present in connective tissue and plays a role in wound healing, iron absorption, and immune system function. 

Vitamin C is an antioxidant, and it protects the body from harmful free radicals that cause oxidative stress. Research has shown that oxidative stress is responsible for causing cardiovascular disease, certain cancers, and other health conditions. 

Vitamin C deficiency causes a condition called scurvy with symptoms such as weakness, fatigue, gum disease, and bleeding. 

Sources of Vitamin C (Ascorbic Acid)

Fresh fruits and vegetables are the best natural sources of vitamin C. Some of the foods rich in vitamin C include citrus fruits, kiwi, strawberries, cantaloupe, tomatoes, red bell peppers, broccoli, Brussels sprouts, and potatoes. 

Vitamin C in food is destroyed by high heat. Cooking methods such as steaming and microwaving can help to preserve the vitamin C in foods. The richest dietary sources of vitamin C (fruits and vegetables) are best consumed raw.

In addition, vitamin C is added to certain foods, such as fortified breakfast cereals. You can also take vitamin C supplements which are available in the form of a tablet, capsule, lozenge, chewable, liquid, and other forms. However, most people can get enough vitamin C from their daily diet and don’t need to take supplements if they eat a healthy, well-balanced diet.

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Can Vitamin C Prevent or Treat Cold Symptoms?

• Taking vitamin C every day does not protect most people from common colds. 

• Vitamin C can slightly shorten the length of time a common cold lasts. 

• You may experience a slightly milder illness during a common cold if you take vitamin C regularly.

• Starting vitamin C once cold symptoms start does not have any effect on the severity or duration of the illness. 

• Vitamin C may protect elite athletes who engage in extreme physical activity from getting infectious diseases such as common colds and other upper respiratory infections.

Research Insights and Studies

Meta-analysis and systematic reviews of 29 studies that enrolled more than 11,000 people of all ages have been done. These studies evaluated whether regular intake of vitamin C supplements at doses of at least 200 mg and up to 1,000 mg or more of vitamin C could prevent common colds. Some of the study participants took vitamin C daily for many years. 

The results of these studies show that taking vitamin C every day for long periods of time does not prevent colds. However, it can slightly shorten the duration of cold symptoms by about 8% in adults and 14% in children. In other words, if symptoms would have lasted 7 days without vitamin C, they might last about 6.5 days with vitamin C supplementation in an adult. The severity of cold symptoms was also slightly less in people who took vitamin C compared to placebo (inactive ingredient).

Interestingly, sub-group analysis has shown that by taking vitamin C regularly, people under high physical stress (for example, soldiers, marathon runners, or skiers doing winter exercises in mountainous regions) can decrease the incidence of common colds, which are common in this population group. Such individuals have about half the risk of getting common colds if they start taking vitamin C supplements two to three weeks before strenuous activities in extreme cold weather.

In summary, the authors concluded that doses of 1 gram daily or more decrease the duration and alleviate the symptoms of common colds; however, the study results vary significantly. Furthermore, another study showed that vitamin C doses of 2g or more daily show greater benefit than 1g daily, suggesting dose dependence.   

How Much Vitamin C Do You Need?

According to the National Institutes of Health (NIH), the recommended daily allowance (RDA) for vitamin C varies by age and is as follows:

Note: Eating five servings of varied fruits and vegetables every day can give you an adequate intake (more than 200 milligrams) of vitamin C.

Read more: Can You Overdose On Vitamin C?

Side Effects

Vitamin C intake in supplement form does not usually cause any side effects. However, taking large doses of vitamin C can cause stomach upset, abdominal cramps, nausea, and diarrhea.

Other potential risks of vitamin C supplementation include:

• An increased risk of death due to cardiovascular disease in postmenopausal women with diabetes who take 300 mg or more of vitamin C daily.

• An increased risk of kidney stones due to increased urinary oxalate and uric acid excretion, especially in people with kidney problems and hyperoxaluria (high oxalate levels in urine).

• Excess iron absorption and iron overload in people with a hereditary condition called hemochromatosis. 

• Potential increase in cancer risk due to vitamin C acting as a pro-oxidant in certain circumstances.

Note: The upper intake level (the highest daily vitamin C intake that poses no risk of adverse health effects in the general population) is 2,000 mg per day in adults.

Safety Precautions for Dietary Supplements

• Consult a healthcare professional before taking a dietary supplement, including vitamin C. Your health care provider can tell you whether a particular supplement is right for you keeping in mind your medical conditions, the proper dose, how long to take it, and whether it's safe for you to take it with your other medications and supplements. 

• Read the label carefully and don’t exceed the recommended dose.

• Don't assume dietary supplements are natural and safe. Some supplements can be harmful, especially if taken at high doses, for a long time, or in combination with certain drugs or foods. 

• Don't use dietary supplements as a replacement for prescribed medications to treat health conditions. 

• Dietary supplements are not a substitute for a healthy, balanced diet. 

• If you develop a bad reaction after taking a dietary supplement, stop taking it and seek immediate medical care.

What Vitamins Are Good for Fighting a Cold?

Some of the nutrients and supplements that play a role in immune system health and may help in fighting a cold include:

• Vitamin D: Found in eggs, fatty fish, and fortified milk and fruit juices.

• Beta carotene (pro-vitamin A): Found in spinach, broccoli, carrots, sweet potatoes, tomatoes, and mangoes. 

• Zinc: Found in beef, seafood, nuts, tofu, beans, and wheat germ. Learn more about zinc for colds.

• Probiotics: Found in fermented foods like yogurt, sauerkraut, kimchi, and kefir.

• Protein: Found in dairy products, eggs, beans, lentils, seafood, chicken, and beef.

• Echinacea: A dietary supplement that can slightly lower your chances of catching a cold, but will not shorten the duration of the illness. Get your free BuzzRx Echinacea coupon.

Lifestyle Tips for Cold Prevention

The following tips can help to strengthen immunity and protect you against common colds and other respiratory and lung infections. They can also prevent you from getting severely ill if you catch infections like the common cold, flu, COVID-19, and others.

• Eat a healthy, balanced diet with at least 5 servings of fresh fruit and vegetables every day. One serving of fresh fruit is one medium fruit or half a cup of chopped fruit.

• Stay well hydrated.

• Get enough sleep.

• Practice good hygiene with regular hand-washing.

• Wear a face mask in public places during cold and flu season.

• Avoid contact with people who are sick, and stay home if you have a common cold or flu.