Vitamin C

Vitamin C is a water-soluble vitamin your body needs for many important functions. Also called ascorbic acid, this essential nutrient helps your body grow and repair tissues throughout your life. Your body cannot make vitamin C on its own, so you must get it from food or supplements.

Vitamin C works as a powerful antioxidant that protects your cells from damage. Antioxidants are molecules that fight harmful substances called free radicals in your body. This vitamin also helps your body make collagen, a protein that keeps your skin, bones, and blood vessels strong. Many people take vitamin C supplements to support their immune system and fill dietary gaps.

While vitamin C is available naturally in citrus fruits, berries, and vegetables, supplements offer a convenient way to ensure adequate intake. The supplement comes in many forms including tablets, capsules, chewables, and powders. Most healthy adults can safely take vitamin C supplements when used as directed.

• Supporting immune system function and reducing cold duration
• Acting as an antioxidant to protect cells from damage
• Helping produce collagen for healthy skin and wound healing
• Improving iron absorption from plant-based foods
• Supporting cardiovascular health and blood vessel function
• Reducing risk of chronic disease through antioxidant activity
• Treating and preventing vitamin C deficiency or scurvy

Vitamin C works by donating electrons to neutralize free radicals in your body. Free radicals are unstable molecules that can damage your cells and contribute to aging and disease. By stopping this damage, vitamin C protects your tissues and supports overall health. This antioxidant activity is especially important for your immune cells, which produce free radicals when fighting infections.

Vitamin C also plays a direct role in making collagen, the most abundant protein in your body. Your body uses specific enzymes that require vitamin C to build collagen molecules. Without enough vitamin C, your body cannot produce strong collagen. This affects your skin, bones, cartilage, and blood vessels. Vitamin C also helps your white blood cells work more effectively and strengthens your skin's barrier against pathogens.

The recommended daily amount for adults is 90 mg for men and 75 mg for women. Smokers need an additional 35 mg per day due to increased oxidative stress. Many supplements contain 250 mg to 1000 mg per dose. The upper safe limit for adults is 2000 mg per day. Taking more than this amount may cause digestive upset. Your body absorbs vitamin C best when you take doses of 200 mg or less at a time. Water-soluble vitamins like vitamin C are not stored in your body, so excess amounts leave through urine.

• Stomach upset or cramps, especially with high doses
• Diarrhea or loose stools from excess intake
• Nausea when taking on an empty stomach
• Heartburn or acid reflux in sensitive individuals
• Headaches in some people with very high doses

Serious side effects are rare but may include kidney stones in people who take very high doses long term. People with kidney disease, hemochromatosis, or a history of kidney stones should consult a doctor before taking vitamin C supplements. Stop taking vitamin C and contact a doctor if you develop severe stomach pain, blood in urine, or signs of an allergic reaction.

• May increase aluminum absorption from antacids, which can be harmful in kidney disease
• Can reduce effectiveness of certain chemotherapy drugs like bortezomib
• May interact with blood thinners like warfarin by affecting clotting
• High doses can interfere with blood glucose test results
• May increase estrogen levels when taking birth control pills
• Can enhance iron absorption, which may be problematic for people with iron overload
• Should be used cautiously with statins and niacin as it may reduce their effectiveness

While vitamin C is generally safe, monitoring certain biomarkers can help ensure your supplement routine supports your health goals. If you take high doses of vitamin C regularly, your doctor may recommend checking your kidney function through creatinine and blood urea nitrogen levels. People with diabetes should monitor glucose levels, as high-dose vitamin C can interfere with some blood sugar tests. If you have a history of kidney stones, urine tests for oxalate levels may be helpful. Rite Aid offers blood testing services that measure over 200 biomarkers twice per year for $349 annually. These tests can help you understand how supplements affect your body and identify any potential concerns early.