Vitamin C is one of the safest and most effective nutrients, experts say. Though it may not be the cure for the common cold, the benefits of vitamin C may include protection against immune system deficiencies, cardiovascular disease, prenatal health problems, eye disease, and even skin wrinkling. The tolerable upper intake level (or the maximum amount you can take in a day that likely won’t cause harm) is 2000 mg a day for adults.
"Vitamin C has received a great deal of attention, and with good reason. Higher blood levels of vitamin C may be the ideal nutrition marker for overall health," says study researcher Mark Moyad, MD, MPH, of the University of Michigan. "The more we study vitamin C, the better our understanding of how diverse it is in protecting our health, from cardiovascular, cancer, stroke, eye health [and] immunity to living longer."
"But," Moyad notes, "the ideal dosage may be higher than the recommended dietary allowance."
How Much Vitamin C Is Enough?
Most of the studies Moyad and his colleagues examined used 500 daily milligrams of vitamin C to achieve health results. That's much higher than the RDA of 75-90 milligrams a day for adults. So unless you can eat plenty of fruits and vegetables, you may need to take a dietary supplement of vitamin C to gain all the benefits, Moyad says. He suggests taking 500 milligrams a day, in addition to eating five servings of fruits and vegetables.
"It is just not practical for most people to consume the required servings of fruits and vegetables needed on a consistent basis, whereas taking a once- daily supplement is safe, effective, and easy to do," Moyad says. He also notes that only 10% to 20% of adults get the recommended nine servings of fruits and vegetables daily.
Moyad says there is no real downside to taking a 500-milligram supplement, except that some types may irritate the stomach. That's why he recommends taking a non-acidic, buffered form of the vitamin. "The safe upper limit for vitamin C is 2,000 milligrams a day, and there is a great track record with strong evidence that taking 500 milligrams daily is safe," he says.
Vitamin C's Role in the Body
Vitamin C, also known as ascorbic acid, is necessary for the growth, development and repair of all body tissues. It's involved in many body functions, including formation of collagen, absorption of iron, the proper functioning of the immune system, wound healing, and the maintenance of cartilage, bones, and teeth.
Vitamin C is one of many antioxidants that can protect against damage caused by harmful molecules called free radicals, as well as toxic chemicals and pollutants like cigarette smoke. Free radicals can build up and contribute to the development of health conditions such as cancer, heart disease, and arthritis.
Vitamin C is not stored in the body (excess amounts are excreted), so overdose is not a concern. But it's still important not to exceed the safe upper limit of 2,000 milligrams a day to avoid stomach upset and diarrhea.
Water-soluble vitamins must be continuously supplied in the diet to maintain healthy levels. Eat vitamin-C-rich fruits and vegetables raw, or cook them with minimal water so you don't lose some of the water-soluble vitamin in the cooking water.
Vitamin C is easily absorbed both in food and in pill form, and it can enhance the absorption of iron when the two are eaten together.
Deficiency of vitamin C is relatively rare, and primarily seen in malnourished adults. In extreme cases, it can lead to scurvy -- characterized by weakness, anemia, bruising, bleeding, and loose teeth.
The Health Benefits of Vitamin C
According to recent research, vitamin C may offer health benefits in these areas:
1. Stress. A deficiency in vitamin C is associated with many stress related disease. It is the first nutrient to be depleted in alcoholics, smokers, and obese individuals. And because vitamin C is one of the nutrients sensitive to stress, Moyad says naintaining levels of vitamin C can be an ideal marker for overall health.
2. Colds. When it comes to the common cold, vitamin C is not a cure, but some studies show that it may help prevent more serious complications. "There is good evidence taking vitamin C for colds and flu can reduce the risk of developing further complications, such as pneumonia and lung infections," says Moyad.
3. Stroke. Although research has been conflicting, one study in the American Journal of Clinical Nutrition found that those with the highest concentrations of vitamin C in their blood were associated with 42% lower stroke risk than those with the lowest concentrations. The reasons for this are not completely clear. But what is clear is that people who eat plenty of fruits and vegetables have higher blood levels of vitamin C.
"People who consume more fruit and vegetables will not only have higher [blood] levels of vitamin C, but higher intake of other nutrients potentially beneficial to health, such as fiber and other vitamins and minerals," study researcher Phyo K. Myint said in an email interview.
- Improve macular degeneration.
- Reduce inflammation.
- Reduce the risk of cancer and cardiovascular disease.
How to Get More Vitamin C in Your Diet
This antioxidant super-nutrient is found in a variety of fruits and vegetables. Yet, according to dietary intake data and the 2020 U.S. Dietary Guidelines, many adults don't get enough vitamin C in their diets. This is especially true of smokers and non-Hispanic black males, according to research done by Jeff Hampl, PhD, RD, and colleagues at the University of Arizona.
The foods richest in vitamin C are citrus fruits, green peppers, strawberries, tomatoes, broccoli, white potatoes, and sweet potatoes. Other good sources include dark leafy greens, cantaloupe, papaya, mango, watermelon, brussels sprouts, cauliflower, cabbage, red peppers, raspberries, blueberries, winter squash, and pineapples.
Here are eight easy ways to work more fruits and veggies into your diet each day:
- Add pureed or grated fruits and veggies to recipes for muffins, meatloaf, and soups.
- Keep cut-up fruits and veggies on hand so they are ready for a quick snack.
- Frozen fruit slices make a cool summer treat.
- Include dark lettuce, tomatoes, and shredded broccoli slaw on all your sandwiches and wraps.
- Eat raw veggies with hummus, low-fat dips, and salsas.
- Add fresh or frozen berries to muffins, pancakes, cereal, and salads.
- Throw a handful of dried fruit on top of your cereal or in a baggie with nuts for an easy snack.
- Enjoy a glass of vegetable juice as a filling and low-calorie mid-afternoon snack.
The bottom line? "There is no one silver bullet vitamin, mineral, or nutrient," says Sandquist. "It is all about the big picture. And eating a varied diet rich in all the nutrients is the best strategy for good health."
Her advice: Take a daily multivitamin, because most people don't get enough of several nutrients. And if you want to combat colds and flu, wash your hands more often.