Vitamin C, also known as ascorbic acid, is an essential nutrient the body requires to form blood vessels, cartilage, muscle, and bone collagen, in the healing process. Since your body cannot produce vitamin C, you must obtain it from foods such as citrus fruits, berries, and potatoes. There are also vitamin C supplements available in capsule and chewable tablet form.
Vitamin C promotes infection control and wound healing and is a potent antioxidant capable of neutralizing damaging free radicals that destroy DNA. The accumulation of free radicals over time may lead to aging and the development of diseases such as cancer, heart disease, and arthritis.
It works in collagen production, a fibrous protein found in connective tissue woven throughout the body's neurological, immunological, bone, cartilage, blood, and other systems. The vitamin is involved in generating many hormones and chemical messengers that operate in the brain and nerves.
Vitamin C protects against the following:
Despite popular perception, scientific data does not support the claim that vitamin C helps treat the common cold. Taking vitamin C supplements regularly (rather than just at the start of a cold) leads to a minor decline in cold duration (about one day only).
The only other research supporting vitamin C for cold prevention comes from studies on people who exercise in extreme conditions (athletes, like skiers, marathon runners, and soldiers in the Arctic). Vitamin C did appear to lessen the chance of catching a cold in these studies.
Population-based studies have found that individuals who ingest foods high in antioxidants, including vitamin C, have a lower risk of high blood pressure than those with less diverse diets. This underscores the importance of including vitamin C-rich foods in your diet for overall health, especially if you are at risk for hypertension.
The DASH (Dietary Approaches to Stop Hypertension) diet, frequently recommended for treating and preventing high blood pressure, includes a lot of fruits and vegetables, which are excellent antioxidant sources.
Scientific studies have produced mixed results on whether vitamin C can prevent heart attack or stroke. Although it does not lower cholesterol or reduce the overall risk of heart attack, evidence suggests that it can help protect arteries against damage. Some studies imply that vitamin C can hinder the progression of atherosclerosis (hardening of the arteries). It can also prevent damage to LDL ("bad") cholesterol, which is responsible for plaque buildup in the arteries.
In addition, people with low levels of vitamin C may be more prone to a heart attack, stroke, or peripheral artery disease, all possible outcomes of atherosclerosis. While there is no evidence that vitamin C supplements can help with this, it is essential to consume enough vitamin C in your diet, which provides other beneficial nutrients and antioxidants. If you have low levels of vitamin C and struggle to get enough from food, consult with your doctor about taking a supplement.
Many population-based studies suggest that eating vitamin C-rich foods may be connected with lower incidences of cancer, including skin cancer, cervical dysplasia (changes to the cervix that may be malignant or precancerous, detected by pap smear), and possibly breast cancer. However, because these foods include numerous beneficial nutrients and antioxidants in addition to vitamin C, it is impossible to ascertain that vitamin C protects against cancer. On the other hand, taking vitamin C supplements has not been demonstrated to be beneficial.
Vitamin C is essential for collagen production, a part of normal cartilage. Cartilage is ruined in osteoarthritis (OA), putting stress on bones and joints. Some researchers suggest that free radicals, which can damage cells and DNA, may also be involved in cartilage destruction. Antioxidants such as vitamin C appear to limit the harm caused by free radicals. While no evidence suggests that taking vitamin C supplements will help treat or prevent OA, people who eat diets rich in vitamin C are less likely to be diagnosed with arthritis.
Evidence is mixed when it comes to the effect of vitamin C on asthma. Certain studies reveal that low vitamin C levels are more prevalent in people with asthma, prompting some researchers to believe that low vitamin C levels may enhance the risk of this condition. Other research suggests that vitamin C may help lessen the symptoms of exercise-induced asthma. 
Human studies employing vitamin C supplements have not consistently proven a benefit, although there seems to be a clear link between a high daily intake of fruits and vegetables and a lower incidence of cataracts.
The following foods are rich in vitamin C:
For adults 19 years and older, the Recommended Dietary Allowance (RDA) is 90 mg per day for men and 75 mg for women, which increases to 85 mg and 120 mg per day during pregnancy and lactation, respectively. Smokers should aim to consume an additional 35 mg of vitamin C above the RDA because smoking can lower vitamin C levels in the body.
The Tolerable Upper Intake Level (UL) is the highest daily intake unlikely to cause adverse health effects. The UL for vitamin C is 2000 mg a day. Consuming more than the UL may result in gastrointestinal distress and diarrhea. However, in certain circumstances, such as under medical supervision or controlled clinical trials, higher doses of vitamin C may be used.
Oral vitamin C supplements are generally safe in appropriate doses. But excessive intake can lead to side effects such as nausea, vomiting, diarrhea, heartburn, stomach cramps, bloating, fatigue, sleepiness, insomnia, headache, and skin flushing. Long-term use of oral vitamin C supplements exceeding 2,000 milligrams per day can increase the risk of significant side effects, including the formation of kidney stones.
Scurvy is a consequence of acute vitamin C deficiency. The timeline for the development of scurvy depends on the amount of vitamin C stored in the body, and symptoms may appear within a month of little or no vitamin C intake (below 10 mg/day). Initial symptoms can include fatigue, malaise, and gum inflammation. If left untreated, scurvy can be fatal.
As vitamin C deficiency progresses, collagen synthesis is impaired, and connective tissues weaken, leading to symptoms such as petechiae, ecchymoses, purpura, joint pain, poor wound healing, hyperkeratosis, and corkscrew hairs. Swollen, bleeding gums, and tooth loss are also signs of scurvy due to tissue and capillary fragility.
Iron deficiency anemia may occur due to increased bleeding and decreased non-heme iron absorption caused by low vitamin C intake. In children, it may lead to bone disease.
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