Taking vitamin C every day to try to prevent colds won't protect most people from colds. It only slightly shortens the amount of time that they're ill. Starting to take vitamin C once you already have cold symptoms won't have any effect on your cold.
You need a certain amount of vitamin C to stay healthy and well, and most people get enough in their daily diet. Vitamin C (ascorbic acid) can be found in fruits and vegetables, and citrus fruits and berries have especially high levels of vitamin C. Medical conditions that are caused by vitamin C deficiency, such as scurvy, are practically non-existent in countries like Germany.
Despite this, many people take vitamin C supplements every day in order to prevent a number of different illnesses, particularly colds. Some of these products have more than one gram of vitamin C, which is more than ten times the recommended daily amount, which is about 100 milligrams (mg). Because the body can't store vitamin C, the excess vitamins are usually flushed out of the body in urine within a few hours, so they end up in the toilet.
Studies on vitamin C
Researchers from the Cochrane Collaboration – an international network of researchers – looked into the question of whether taking large doses of vitamin C can protect against colds or relieve the symptoms. To find out, they analyzed studies comparing vitamin C with a product that didn't contain any active ingredients (a placebo).
29 studies, involving more than 11,000 children and adults, tested whether the regular use of supplements containing at least 200 mg of vitamin C prevented colds. Most of the studies tested a dose of 1,000 or more mg of vitamin C per day. Some of the participants took the vitamin C over a period of several years.
Research results
The studies showed that it wasn't possible to prevent colds by taking vitamin C every day over a longer period of time. But doing so did shorten the amount of time that people were ill by about 10 percent. In other words, a cold that would have lasted ten days was over in nine days. The cold symptoms were also a bit milder in people who always took vitamin C.
Other studies show that taking vitamin C only after becoming ill didn’t shorten the length of colds in men and women. It didn’t relieve their symptoms, either.
Some of the studies looked at whether vitamin C can prevent colds in people exposed to short periods of very strenuous physical activity, often in extremely cold temperatures. Examples include marathon runners or soldiers doing winter exercises in a mountainous region. The study participants started taking vitamin C two to three weeks before the activities, with the aim of preventing colds. It was found that doing so reduced their risk of developing a cold by about half.
Taking very high doses of vitamin C regularly may cause diarrhea, but the study participants who took vitamin C didn’t report having more side effects than those who used a placebo.
Sources
IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.
Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.
Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.
FAQs
Taking vitamin C every day to try to prevent colds won't protect most people from colds. It only slightly shortens the amount of time that they're ill. Starting to take vitamin C once you already have cold symptoms won't have any effect on your cold.
Is vitamin C not proven to fight colds many people still use it? ›
"Overall, though, vitamin C taken in extra doses to prevent common colds hasn't proven true." While it doesn't prevent you from getting a cold, Dr. Bracamonte says there is some limited research that additional vitamin C might speed up the recovery process slightly in some people.
Can we conclude that vitamin C has a strong effect in preventing colds? ›
No, we cannot conclude that vitamin C has a strong effect in preventing colds. Although the P-value is lower than a = 0.05, P is not significant at the a = 0.01 significance level.
Is the vitamin C you are taking will cure your cold or you will get better on your own either way you should feel better next week? ›
Vitamin C. It appears that taking vitamin C won't usually help the average person prevent colds. However, some studies have found that taking vitamin C before cold symptoms start may shorten the length of time you have symptoms.
Does vitamin C actually help the immune system? ›
In addition to directly affecting immune cells, vitamin C also acts as an important antioxidant to the cells of the immune system. It can help protect cells from both endogenously and exogenously produced reactive oxygen species (ROS) during an immune response [24].
Is there evidence that vitamin C helps colds? ›
The studies showed that it wasn't possible to prevent colds by taking vitamin C every day over a longer period of time. But doing so did shorten the amount of time that people were ill by about 10 percent. In other words, a cold that would have lasted ten days was over in nine days.
Is vitamin C good to prevent getting sick? ›
But taking vitamin C won't prevent you from getting the flu or a cold — or from getting COVID-19. If you take vitamin C regularly and catch a cold or the flu, your symptoms may not be so bad. But if you take vitamin C when you already have a cold or flu, it won't affect how long you're sick or how sick you get.
How much vitamin C to stop a cold? ›
How much vitamin C can you take when you're sick? The average dose of vitamin C for colds is anywhere from 1,000 mg to 2,000 mg. This is based on the dose range in the studies that looked at the safety and effectiveness of vitamin C for treating colds.
Does emergen C prevent colds? ›
Although they're intended to help boost your immune system, there's not a lot of evidence that they're effective at preventing illness. However, some of their ingredients, like Vitamin C and zinc, may help you feel better faster or lessen the severity of your cold symptoms.
Do vitamin C and zinc prevent colds? ›
It's an antioxidant that helps your body battle against illness by taking on cell-damaging free radicals. But the nutrient isn't magical, cautions Dr. Ford. Studies evaluating the effectiveness of therapeutic vitamin C show that it doesn't reduce the incidence of colds.
The best ways to avoid catching a cold are:
- washing your hands with warm water and soap.
- not sharing towels or household items (like cups or children's toys) with someone who has a cold.
- not touching your eyes or nose in case you've come into contact with the virus.
- staying fit and healthy.
The bottom line. You can catch a cold anytime of the year, but steering clear of crowded places and people who are sick may reduce your chances. Getting plenty of rest, eating healthy, and reducing stress may also reduce your risk of getting sick if you're exposed to a cold.
What's the best thing for a cold? ›
In general, remember that getting plenty of rest and fluids is the best way to help you deal with your cold symptoms. Eventually, your cold symptoms usually go away, probably in about a week. If you still feel sick after a week, see your doctor to rule out a sinus infection, allergies, or any other medical problem.
Why avoid taking vitamin C at night? ›
Do not add too much vitamin C at the same time but should be divided into 3-4 times Drink/day at different times Avoid taking vitamin C at night before going to bed, because it can cause stimulation, excitement leading to insomnia.
What is the latest research on vitamin C? ›
Recent research hints that vitamin C could be a key player in reducing the risk of some chronic diseases. This is attributed to it's antioxidant properties which reduces inflammation and keeps the heart in good shape, which may reduce the risk of heart disease.
Is 500mg of vitamin C per day too much? ›
The recommended daily amount for vitamin C is 75 milligrams (mg) a day for women and 90 mg a day for men. During pregnancy, 120 mg a day are recommended. The upper limit for all adults is 2,000 mg a day.
Does vitamin C actually work? ›
Vitamin C is an antioxidant that helps protect your cells against the effects of free radicals — molecules produced when your body breaks down food or is exposed to tobacco smoke and radiation from the sun, X-rays or other sources. Free radicals might play a role in heart disease, cancer and other diseases.
Does vitamin C and zinc actually help with colds? ›
Both vitamin C and zinc are effective at boosting the immune system. However, you can't boost your immune system enough with these two nutrients while battling a cold. Instead, you need to be using these supplements year-round to avoid the common cold in the first place.
How much vitamin C stops a cold? ›
Vitamin C might help to treat your cold, but it's probably not enough to notice. Research shows that regularly taking 1,000 mg to 2,000 mg of vitamin C may reduce how long cold symptoms last and how severe they are. But this decrease in time is less than 10%. And most people probably won't notice the difference.
Is emergen C actually good for you? ›
While there aren't any proven health benefits of taking Emergen-C products, both doctors say it is generally regarded as safe to take. That said, there are dangers in getting too much of some vitamins and nutrients.
