Vitamin C (ascorbic acid) is a nutrient your toàn thân needs to khung blood vessels, cartilage, muscle and collagen in bones. Vitamin C is also vital to your body"s healing process.
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Vitamin C is an antioxidant that helps protect your cells against the effects of miễn phí radicals — molecules produced when your body toàn thân breaks down food or is exposed to lớn tobacco smoke và radiation from the sun, X-rays or other sources. Free radicals might play a role in heart disease, cancer và other diseases. Vi-ta-min C also helps your body toàn thân absorb và store iron.
Because your body doesn"t produce vitamin C, you need khổng lồ get it from your diet. Vi-ta-min C is found in citrus fruits, berries, potatoes, tomatoes, peppers, cabbage, Brussels sprouts, broccoli & spinach. Vi-ta-min C is also available as an oral supplement, typically in the size of capsules và chewable tablets.
Most people get enough vi-ta-min C from a healthy diet. Vitamin C deficiency is more likely in people who:
Smoke or are exposed lớn secondhand smoking Have certain gastrointestinal conditions or certain types of cancer Have a limited diet that doesn"t regularly include fruits & vegetablesSevere vitamin C deficiency can lead lớn a disease called scurvy, which causes anemia, bleeding gums, bruising & poor wound healing.
If you take vitamin C for its antioxidant properties, keep in mind that the supplement might not offer the same benefits as naturally occurring antioxidants in food.
The recommended daily amount of vi-ta-min C is 90 milligrams for adult men & 75 milligrams for adult women.
Evidence
Research on the use of vitamin C for specific conditions shows:
Cancer. Eating a diet rich in fruits và vegetables might lower your risk of many types of cancer, such as breast, colon and lung cancers. However, it"s not clear whether this protective effect is related to the vi-ta-min C content in the food. Taking oral vi-ta-min C supplements doesn"t appear to offer the same benefit. Common cold. Taking oral vitamin C supplements won"t prevent the common cold. Evidence also shows that the benefits of regularly taking vitamin C supplements khổng lồ reduce the duration or severity of a cold are minimal. Eye diseases. Taking oral vi-ta-min C supplements in combination with other vitamins & minerals seems lớn prevent age-related macular degeneration (AMD) from worsening. Some studies also suggest that people who have higher levels of vi-ta-min C in their diets have a lower risk of developing cataracts.Is a glass of OJ or vi-ta-min C tablets your go-to when the sniffles come? Loading up on this vitamin was a practice spurred by Linus Pauling in the 1970s, a double Nobel laureate và self-proclaimed champion of vitamin C who promoted daily megadoses (the amount in 12 to lớn 24 oranges) as a way to lớn prevent colds & some chronic diseases.
Vitamin C, or ascorbic acid, is a water-soluble vitamin. This means that it dissolves in water và is delivered to lớn the body’s tissues but is not well stored, so it must be taken daily through food or supplements. Even before its discovery in 1932, nutrition experts recognized that something in citrus fruits could prevent scurvy, a disease that killed as many as two million sailors between 1500 & 1800. <1>
Vitamin C plays a role in controlling infections và healing wounds, và is a powerful antioxidant that can neutralize harmful không tính phí radicals. It is needed to make collagen, a fibrous protein in connective tissue that is weaved throughout various systems in the body: nervous, immune, bone, cartilage, blood, và others. The vi-ta-min helps make several hormones và chemical messengers used in the brain and nerves. <2>
While megadosing on this vitamin is not uncommon, how much is an optimum amount needed to lớn keep you healthy, & could taking too much be counterproductive?
Recommended Amounts
RDA: The Recommended Dietary Allowance for adults 19 years and older is 90 mg daily for men và 75 mg for women. For pregnancy và lactation, the amount increases lớn 85 mg & 120 mg daily, respectively. Smoking can deplete vi-ta-min C levels in the body, so an additional 35 mg beyond the RDA is suggested for smokers.UL: The Tolerable Upper Intake màn chơi is the maximum daily intake unlikely khổng lồ cause harmful effects on health. The UL for vitamin C is 2000 mg daily; taking beyond this amount may promote gastrointestinal distress and diarrhea. Only in specific scenarios, such as under medical supervision or in controlled clinical trials, amounts higher than the UL are sometimes used. <2>
The intestines have a limited ability khổng lồ absorb vitamin C. Studies have shown that absorption of vitamin C decreases to less than 50% when taking amounts greater than 1000 mg. In generally healthy adults, megadoses of vi-ta-min C are not toxic because once the body’s tissues become saturated with vitamin C, absorption decreases và any excess amount will be excreted in urine. However, adverse effects are possible with intakes greater than 3000 mg daily, including reports of diarrhea, increased formation of kidney stones in those with existing kidney disease or history of stones, increased levels of uric acid (a risk factor for gout), & increased iron absorption & overload in individuals with hemochromatosis, a hereditary condition causing excessive iron in the blood. <2>
Absorption does not differ if obtaining the vitamin from food or supplements. Vitamin C is sometimes given as an injection into a vein (intravenous) so higher amounts can directly enter the bloodstream. This is usually only seen in medically monitored settings, such as lớn improve the quality of life in those with advanced stage cancers or in controlled clinical studies. Though clinical trials have not shown high-dose intravenous vi-ta-min C to produce negative side effects, it should be administered only with close monitoring and avoided in those with kidney disease and hereditary conditions lượt thích hemochromatosis & glucose 6-phosphate dehydrogenase deficiency.
Vitamin C is involved with numerous metabolic reactions in the body, & obtaining the RDA or slightly higher may be protective against certain disease states. However, a health benefit of taking larger amounts has not been found in people who are generally healthy và well-nourished. Cell studies have shown that at very high concentrations, vitamin C can switch roles & act as a tissue-damaging pro-oxidant instead of an antioxidant. <2,3> Its effects in humans at very high doses well beyond the RDA are unclear, and can lead khổng lồ increased risk of kidney stones và digestive upset.
Vitamin C & Health
There is interest in the antioxidant role of vi-ta-min C, as research has found the vitamin khổng lồ neutralize không lấy phí radical molecules, which in excess can damage cells. Vi-ta-min C is also involved in the body’s immune system by stimulating the activity of white blood cells. Does this translate lớn protection from certain diseases?
Chronic diseases
Although some epidemiological studies that follow large groups of people over time have found a protective effect of higher intakes of vi-ta-min C (from food or supplements) from cardiovascular disease and certain cancers, other studies have not. Randomized controlled trials have not found a benefit of vi-ta-min C supplements on the prevalence of cardiovascular disease or cancer. The inconsistency of the data overall prevents the establishment of a specific vi-ta-min C recommendation above the RDA for these conditions. <2>
Age-related vision diseases
Vitamin C has also been theorized khổng lồ protect from eye diseases like cataracts & macular degeneration. Human studies using vitamin C supplements have not shown a consistent benefit, though there appears lớn be a strong association between a high daily intake of fruit và vegetables and decreased risk of cataracts. <4>
The common cold
Despite being a popular fix, vi-ta-min C’s cold-fighting potential hasn’t panned out. Review of several studies show that megadoses (greater than 500 mg daily) of supplemental vi-ta-min C have no significant effect on the common cold, but may provide a moderate benefit in decreasing the duration và severity of colds in some groups of people. <2> Small trials suggest that the amount of vitamin C in a typical multivitamin taken at the start of a cold might ease symptoms, but for the average person, there is no evidence that megadoses make a difference, or that they prevent colds. <5>
Gout
The Physicians’ Health Study II, a randomized, double-blind, placebo-controlled trial of more than 14,000 male physicians, found a modestly reduced risk of new gout cases in men who took vitamin C supplements of 500 mg daily for up lớn 10 years. <6> Other short-term trials have found that vi-ta-min C may lower blood levels of uric acid, a substance that can lead to gout if there is too much in the body.
Food Sources
Fruits và vegetables are the best sources of this vitamin.
Citrus (oranges, kiwi, lemon, grapefruit)Bell peppersStrawberries
Tomatoes
White potatoes
Signs of Deficiency
Vitamin C deficiency is rare in developed countries but may occur with a limited diet that provides less than 10 mg daily for one month or longer. In developed countries, situations at greatest risk for deficiency include eating a diet restricted in fruits & vegetables, smoking or long-term exposure lớn secondhand smoke, & drug and alcohol abuse. The following are the most common signs of a deficiency.
Scurvy, the hallmark disease of severe vi-ta-min C deficiency, displays symptoms resulting from loss of collagen that weakens connective tissues:Skin spots caused by bleeding and bruising from broken blood vesselsSwelling or bleeding of gums, and eventual loss of teeth
Hair loss
Delayed healing of skin wounds
Fatigue, malaise
Did You Know?
Vitamin C can be destroyed by heat and light. High-heat cooking temperatures or prolonged cook times can break down the vitamin. Because it is water-soluble, the vitamin can also seep into cooking liquid và be lost if the liquids are not eaten. Quick heating methods or using as little water as possible when cooking, such as stir-frying or blanching, can preserve the vitamin. Foods at peak ripeness eaten raw contain the most vitamin C.Vitamin C serums & skin creams are popular because normal skin typically contains high concentrations of vitamin C, which stimulates collagen production and protects against damage from UV sunlight. However, research suggests that topical vitamin C may have limited benefits, as very little can penetrate the skin’s surface and will not produce additional benefit if a person obtains adequate vi-ta-min C through food or supplements. <7>Related
Vitamins và Minerals
References
Carpenter KJ. The history of scurvy và vitamin C. Cambridge: Cambridge University Press, 1986.Poljšak B, Ionescu JG. Pro-oxidant vs. Antioxidant effects of vi-ta-min C. Handbook of vi-ta-min C Research: Daily Requirements, Dietary Sources & Adverse Effects (pp.153-183). January 2009. Nova Science Publishers, Inc.
Last reviewed March 2023
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