Vitamin C is an antioxidant you can get easily from a variety of foods or from supplements. Because vitamin C is water soluble, your body can't store it, and you need the correct daily amount to prevent deficiency, according to the National Institutes of Health (NIH).
For adults, the recommended daily vitamin C dosage depends on your gender, whether you're pregnant or nursing and whether you smoke. A higher dosage isn't toxic but may result in gastrointestinal side effects.
So, What Does Vitamin C Do?
Your body needs vitamin C to form collagen, which makes up the connective tissues in the body and helps heal wounds. Vitamin C also contributes to the overall health of your bones, cartilage and teeth.
This nutrient plays a role, too, in your body's absorption of non-heme iron, which comes from plant sources. When eating iron-rich foods like spinach, for example, it's best to also eat some vitamin C-rich food, like tomatoes or berries.
Because it's an antioxidant, vitamin C supports your overall immune function, according to a 2017 article in Nutrients. Antioxidants like vitamin C scavenge for free radicals — those wayward molecules that can cause DNA damage in the body and lead to chronic illness. The NIH notes that those who regularly consume fruits and vegetables high in vitamin C enjoy greater natural protection against cancer and a reduced risk of heart disease.
The recommended daily allowance for vitamin C — that it, the intake sufficient to meet the body's nutrient needs — varies according to several factors, according to the NIH:
- Adults ages 19 and older: 75 milligrams for women; 90 milligrams for men
- Teenagers ages 14 to 18: 65 milligrams for girls; 75 milligrams for boys
- Pregnant women ages 19 and older: 85 milligrams
- Nursing women ages 19 and older: 120 milligrams
- Active smokers: Additional 35 milligrams
Deficiency of vitamin C, which presents in a condition called scurvy, is rare in developed countries but can occur in those with poor diets. Signs of deficiency can appear within a month of consistently low intake of this vitamin. Scurvy symptoms include fatigue, swelling of the gums and tooth loss.
Smoking, in addition to its well-known connections to lung cancer and heart disease, depletes the body of vitamin C. Active smokers need at least 35 extra milligrams of vitamin C per day. Cigarette smoke produces free radicals in the body, which the vitamin works to neutralize.
Other adults may need a higher vitamin C dosage, too. Those with substance-abuse issues and people with malabsorption conditions may be at risk for vitamin C deficiency. Ask your doctor if you're getting enough vitamin C or if you need to boost your intake.
Consuming more than 2,000 milligrams of vitamin C daily may cause side effects such as diarrhea, nausea, abdominal cramps, headaches and insomnia.
Food vs. Supplements
The Linus Pauling Institute of Oregon State University undertook a review of studies and found that natural vitamin C from food and synthetic vitamin C in supplements demonstrate the same bioavailability; that is, the body seems to absorb both forms of the nutrient equally well.
According to Harvard Health Publishing, though, it's better to get vitamin C from foods than to follow a nutrient-poor diet and then take supplements to make up for vitamin shortfalls. Through a healthy, well-rounded diet, you get the benefits of other nutrients and phytochemicals working in conjunction with vitamin C.
Besides, as Harvard Health Publishing also notes, research on the benefits of multivitamins has had mixed findings, and, as a result, the U.S. Preventive Services Task Force does not recommend vitamin supplements to prevent disease. By including more fresh fruits and vegetables in your diet, you'll get all the nutrients you need on a daily basis, which leads to overall good health and disease prevention.
Hitting High C
The National Academies of Science, Engineering, and Medicine set the upper limit (UL) for vitamin C — the most you should get in a day — at 2,000 milligrams for all adults ages 19 and older. While it's not toxic to ingest more than that amount, a higher vitamin C dosage may result in gastrointestinal issues, such as diarrhea, nausea and cramps, as well as headaches and insomnia, according to the Mayo Clinic.
Your body may not even absorb the extra amount. The NIH reports that the body absorbs less than 50 percent of a vitamin C dosage over 1,000 milligrams a day. What your body doesn't need it excretes in urine, so you're literally flushing away those excess milligrams.
In contrast, at a more modest vitamin C dosage of 180 milligrams or less, the body will absorb 70 to 90 percent.
C and the Common Cold
In the midst of cold and flu season, you may start popping vitamin C pills in an attempt to ward off respiratory illness. It's a common response, but does it really work? A summary of evidence from 45 studies, published by Medwave in July 2018, concluded that vitamin C does not prevent the common cold.
However, the nutrient may help some people reduce their symptoms. A study published in the Journal of Health Care and Prevention in 2017 found that 480 milligrams of vitamin C taken with 800 milligrams of aspirin did reduce early symptoms of a cold compared to placebo.
A meta-analysis of nine clinical trials, published in BioMed Research International in July 2018, also found that a higher dosage of vitamin C, taken at the onset of a cold, helped reduce the duration of the illness and lessen its symptoms. The extra amount, though, only benefited people who had already been taking vitamin C supplements on a daily basis.
Vitamin C and Your Skin
The collagen that vitamin C helps to form is a major component of your tissues. Collagen in the skin tends to break down as you get older, causing wrinkles and sagging, so vitamin C may be an effective preventive against aging skin.
Aging can also make skin appear duller. A study published in the Journal of Food and Nutrition Research in November 2018 concluded that a mixture of citrus peel extract, vitamin C and l-cysteine, taken orally, brightened healthy women's skin after four weeks and carried no side effects.
In addition, the antioxidant powers of vitamin C help strengthen the epithelium — the thin outer tissue that protects the skin — against bacteria and environmental damage, according to the 2017 article in Nutrients.
Read more: How to Take Vitamins C and E for Skin
Tips on Types
If you do decide to take vitamin C pills, be aware that there are many varieties and not all of them are created equal. The Linus Pauling Institute reviewed different types of vitamin C supplements, looking at ease of absorption, among other factors. The institute concluded that three different kinds of vitamin C pills — liquid, tablets and chewable tablets — all appear to have equally good absorption. However, studies present conflicting evidence on the efficacy of timed-release vitamin C.
What about the brands of vitamin C that tout their inclusion of bioflavonoids or rose hips? The Institute could find only one small study in which vitamin C with bioflavonoids positively affected the nutrient's absorption.
Vitamin C From Food
Getting vitamin C from foods is easy, as long as you consume plenty of fruits and vegetables. ChooseMyPlate.gov, the U.S. government's guide to healthy eating, recommends filling half of your plate at each meal with fruits and vegetables. Opt for whole fruits instead of juices and vary the kinds of fruits and veggies you select each day.
You may automatically think of oranges and other citrus as the fruits highest in vitamin C, but in fact, guavas, kiwis and strawberries all contain more of the nutrient than oranges, according to MyFoodData. Papaya offers just slightly less than an orange. Raspberries, blackberries and blueberries supply ample amounts of vitamin C, too.
Among veggies, broccoli, cauliflower, Brussels sprouts and cabbage all contain more than 60 percent of the daily value for vitamin C, if you follow a 2,000-calorie diet. Tomatoes and bell peppers also supply an excellent amount, as do leafy greens such as kale, Swiss chard and spinach.
Read more: The Best Natural Sources of Vitamin C
Eat vitamin C-rich foods at every meal to get the milligrams you need daily and replenish your store of this nutrient.
- Slice a half-cup of strawberries onto your morning oatmeal (49 milligrams)
- Add half of a medium-sized grapefruit alongside your eggs and toast (44 milligrams)
- Sweeten up your Greek yogurt with a half-cup of blackberries (30 milligrams) or a half-cup of pineapple chunks (40 milligrams)
- Construct a salad from a base of leafy green; choose one cup of baby kale (19 milligrams) or Swiss chard (nearly 11 milligrams)
- Along with your protein of choice, top your greens with a half-cup of cherry tomatoes (10 milligrams) and the same amount of sweet bell peppers (59 milligrams)
- Add a small orange on the side (51 milligrams)
By dinner, you've likely exceeded your vitamin C needs for the day. In case you skimped at your earlier meals, though, enjoy a side dish of:
- A half-cup of steamed broccoli with a clove of garlic (42 milligrams)
- A medium baked sweet potato (22 milligrams)
- National Institutes of Health Office of Dietary Supplements: "Vitamin C"
- Tobacco-Free Families: "The Connection Between Smoking and Vitamin C Deficiency"
- Mayo Clinic: "Is It Possible to Take Too Much Vitamin C?"
- Harvard Health Publishing: "Should You Get Your Nutrients From Food or From Supplements?"
- BioMed Research International: "Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials"
- Medwave: "Does Vitamin C Prevent the Common Cold?"
- Journal of Food and Nutrition Research: "Effect of Oral Intake of a Mixture Containing Natural Citrus Peel Extract, Vitamin C, and L-Cystine on Skin Brightness in Healthy Women"
- Nutrients: "Vitamin C and Immune Function"
- Linus Pauling Institute: "Supplemental Forms: The Bioavailability of Different Forms of Vitamin C (Ascorbic Acid)"
- MyFoodData: "The Top 10 Foods Highest in Vitamin C"
- ChooseMyPlate.gov: "What Is MyPlate?"
- National Academies of Science, Engineering, and Medicine: "Dietary Reference Intakes (DRIs): Vitamins"
- MyFoodData: "Nutrition Facts Comparison Tool"