What are some of the health effects of vitamin C?
Scientists study vitamin C to determine how it affects health. Here are some examples of the results of these investigations:
Prevention and treatment of cancer
Those who consume a lot of vitamin C by eating fruits and vegetables may have a lower risk of several types of cancer, such as lung, breast, and colon cancer. However, taking vitamin C dietary supplements, with or without other antioxidants, does not appear to help prevent cancer.
It is not known for sure if high intake of vitamin C is beneficial for treating cancer. The effects of vitamin C appear to depend on how it is administered to the patient. Oral doses of vitamin C cannot raise vitamin C levels in the blood nearly to the levels of doses given by intravenous injections. Some studies in animals and test tubes indicate that very high levels of vitamin C in the blood could shrink tumors. However, further studies are required to determine whether high doses of intravenous vitamin C contribute to the treatment of cancer.
Dietary supplements of vitamin C and other antioxidants may interact with chemotherapy and radiation therapy for cancer. People receiving cancer treatment should consult with their oncologist before taking vitamin C supplements or other dietary supplements, especially in high concentrations.
Those who eat plenty of fruits and vegetables appear to have a lower risk of cardiovascular disease. Researchers believe that the antioxidant content of these foods could be partly responsible for this association because oxidative damage is one of the main causes of cardiovascular disease. However, scientists still cannot say for sure whether vitamin C itself, present in food or supplements, helps protect people against cardiovascular disease. It is also not known with certainty whether vitamin C helps prevent the worsening of cardiovascular disease in those who suffer from it.
Age-related macular degeneration and cataracts
Age-related macular degeneration and cataracts are two of the leading causes of vision loss in the elderly. Researchers do not consider that vitamin C and other antioxidants influence the risk of age-related macular degeneration. However, research studies indicate that vitamin C, combined with other nutrients, could slow the progression of age-related macular degeneration.
In a large scientific study of elderly people with age-related macular degeneration who were at high risk of worsening later in life, those who took a daily dietary supplement with 500 mg of vitamin C, 80 mg of zinc, 400 IU of vitamin E, 15 mg of beta-carotene and 2 mg of copper for about 6 years were less likely to progress to the advanced stage of this vision disorder. In addition, they had less vision loss than those who did not take the dietary supplement. However, it is advisable for people who have or are beginning to have this disease to speak with their doctor about the possibility of taking dietary supplements.
The relationship between vitamin C and cataract formation is unclear. Some studies indicate that people who consume more vitamin C present in food have a lower risk of cataracts. However, more studies are required to clarify this association and to determine whether vitamin C supplements influence the risk of cataracts.
While vitamin C has long been a popular remedy for the common cold, research studies show that vitamin C supplements do not reduce the risk of colds for most people. However, those who take vitamin C supplements regularly may experience colds of slightly shorter duration or somewhat milder symptoms when they catch a cold. Taking vitamin C supplements also doesn’t seem to help once cold symptoms start.
Can vitamin C be harmful?
Consuming vitamin C in too high concentrations can cause diarrhea, nausea, and stomach cramps. In people with hemochromatosis, a disorder that causes an excessive accumulation of iron in the body, vitamin C in high doses may worsen excess iron and damage body tissues.
How much vitamin C do I need?
The amount of vitamin C you need each day depends on your age. The average daily amounts of vitamin C, expressed in milligrams (mg), that are recommended for people of different ages are as follows:
Stage of life Recommended amount
Babies up to 6 months of age 40 mg
Babies 7 to 12 months of age 50 mg
Children 1 to 3 years of age 15 mg
Children 4-8 years of age 25 mg
Children 9 to 13 years old 45 mg
Adolescents (males) ages 14 to 18 75 mg
Adolescents (girls) ages 14 to 18 65 mg
Adults (men) 90 mg
Adults (women) 75 mg
Pregnant teens 80 mg
Pregnant women 85 mg
Lactating adolescents 115 mg
Lactating women 120 mg
If you smoke, you should add 35 mg to the above values to calculate the total recommended amount of vitamin C you need each day.
The following are the upper limits for vitamin C:
Stage of life Recommended maximum limit
Babies up to 12 months of age Not determined
Children 1 to 3 years of age 400 mg
Children 4-8 years of age 650 mg
Children 9 to 13 years old 1,200 mg
Adolescents 14 to 18 years of age 1,800 mg
Adults 2,000 mg