Vitamin C is water-soluble, but the human body can not synthesize it and must strictly obtain it through diet. When there is a deficiency in vitamin C, individuals are more susceptible to infectious diseases and scurvy with symptoms such as bleeding and hyperkeratosis. However, the supplementation of vitamin C must be properly prescribed, with correct dosages and consideration of the specific individuals.
1. Indications of Vitamin C
Vitamin C is a water-soluble vitamin, an antioxidant, and also a cofactor essential for the biosynthesis of collagen, carnitine metabolism, catecholamine metabolism, and the absorption of dietary iron.
Humans cannot synthesize vitamin C, so it must be obtained through a diet with fruits and vegetables. Citrus fruits, berries, tomatoes, potatoes, and leafy greens are excellent sources of vitamin C. Although most vitamin C is completely absorbed in the small intestine, this absorption rate decreases as the concentration in the intestinal fluid increases. Proline residues on procollagen require vitamin C for hydroxylation, which is necessary for forming the triple-helix structure of mature collagen. The lack of a stable triple-helix structure affects the integrity of the skin, mucous membranes, blood vessels, and bones. Consequently, vitamin C deficiency leads to scurvy, characterized by symptoms such as bleeding, hyperkeratosis, and hematological abnormalities.
Additionally, vitamin C deficiency often occurs due to poor diet or decreased demand. Those at risk of inadequate vitamin C intake include:
- The elderly;
- Those with alcohol addiction, smoking, anorexia, or cancer;
- People who are susceptible to food allergies;
- Individuals receiving parenteral nutrition without adequate supplementation;
- Those on restrictive diets secondary to inflammatory bowel disease, gastroesophageal reflux, or Whipple's disease;
- Those taking medications such as Aspirin, Indomethacin, contraceptives,
- Tetracycline, and Corticosteroids;
- People with kidney failure, as vitamin C is soluble in water during dialysis;
- Individuals experiencing complications from interleukin-2 treatment for metastatic renal cell carcinoma;
- Liver transplant recipients.
Furthermore, the daily requirement for vitamin C increases in patients with conditions such as gingivitis, asthma, glaucoma, collagen disorders, heatstroke, arthritis, infections, and chronic diseases. Vascular disorders, burns, and delayed wound healing are additional factors that increase daily vitamin C consumption.
2. How to supplement vitamin C?
Vitamin C is typically taken orally, intramuscularly, intravenously, or subcutaneously when malabsorption is suspected. For intravenous administration, it's crucial to minimize adverse reactions by diluting the medication with normal saline or glucose solution.
The average vitamin C supplementation dose for adults is 70 to 150 mg per day; this can be up to 300 mg to 1 g per day in cases of scurvy.
3. Side effects of vitamin C supplementation
Side effects of vitamin C supplementation include headaches, flushing, nausea or vomiting, and dizziness. Additionally, there have been reports of migraines with daily vitamin C doses of 6 grams.
A significant amount of vitamin C can increase the risk of kidney stones, elevated uric acid, and oxalate levels, as it can acidify the urine.
4. Who should not take vitamin C?
Vitamin C supplementation is contraindicated in blood disorders such as thalassemia, G6PD deficiency, sickle cell disease, and hemochromatosis. Avoid using supplements immediately before or after angioplasty. Patients with diabetes should supplement with vitamin C cautiously, as it can increase blood glucose levels.
Vitamin C should be used with caution in patients with oxalate kidney disease or kidney stones, as the acidification process by ascorbic acid increases the precipitation risk of cysteine, urate, and oxalate stones.
5. Drugs may interact with vitamin C
Patients undergoing treatment with any of the following medications should not take vitamin C:
- Aspirin and Nonsteroidal Anti-inflammatory Drugs (NSAIDs): Both aspirin and NSAIDs can reduce vitamin C levels in the body, as they increase the loss of vitamin C through urine. Additionally, high doses of vitamin C can cause these medications to stay in the body longer, increasing their blood levels. Some initial studies suggest that vitamin C may help protect against stomach irritation caused by aspirin and NSAIDs. If you regularly take aspirin or NSAIDs, consult your doctor before taking more than the recommended daily amount of vitamin C.
- Acetaminophen: High doses of vitamin C can decrease the amount of acetaminophen excreted in urine, potentially increasing its blood levels.
Antacids containing aluminum: Vitamin C can increase the absorption of aluminum, worsening the side effects of these medications.
Sedatives: Sedatives can reduce the effectiveness of vitamin C. These medications include phenobarbital, pentobarbital, and secobarbital.
Chemotherapy Drugs: As an antioxidant, vitamin C may interfere with the effects of certain chemotherapy drugs. However, some researchers hypothesize that vitamin C may enhance the effectiveness of chemotherapy. - Nitrate Medications for Heart Disease: The combination of vitamin C with nitroglycerin, isosorbide dinitrate, or isosorbide mononitrate can reduce the tolerance to these medications. If you take nitrate medications, consult your doctor about whether you should supplement with vitamin C.
- Oral Contraceptives and Hormone Replacement Therapy: Vitamin C can increase estrogen levels when taken with these medications, particularly if there is a pre-existing vitamin C deficiency and supplementation begins. Oral estrogens can also reduce the effect of vitamin C in the body.
- Protease Inhibitors: Vitamin C may reduce the levels of indinavir, a drug used to treat HIV and AIDS.
- Tetracycline: Some evidence suggests that taking vitamin C with the antibiotic tetracycline can increase the levels of this medication while also reducing the effect of vitamin C in the body.
- Warfarin (Coumadin): There have been reports of vitamin C interfering with the effectiveness of this blood-thinning medication.
Vitamin C is a familiar component in multivitamin tablets or functional supplements. Unless deficient, it is best to supplement vitamin C through a healthy diet that includes fresh fruits and vegetables. Overdosing or abusing vitamin C can cause dangerous side effects, especially for individuals who should avoid taking vitamin C due to the risk of drug interactions with medications used to treat other conditions.
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