Vitamin C is a water-soluble nutrient, chemically known as L-ascorbic acid, that your body needs for immune defense, tissue repair, and antioxidant protection. Unlike most animals, humans can’t produce it internally, so you have to get it from food or supplements every day. The recommended daily amount is 90 mg for adult men and 75 mg for adult women, amounts easily reached through a few servings of fruits and vegetables.
What Vitamin C Does in Your Body
Vitamin C plays several distinct roles, but its most important job is building collagen, the protein that forms the structural framework of your skin, tendons, ligaments, and blood vessels. It activates the enzymes that stabilize and cross-link collagen fibers, which is why a severe deficiency causes wounds to stop healing and gums to break down. Without enough vitamin C, your body literally cannot hold itself together at the tissue level.
It also functions as a powerful antioxidant, neutralizing unstable molecules that damage cells. This protective effect is especially important for immune cells. During an infection, your white blood cells (neutrophils) generate bursts of toxic compounds to kill pathogens, and vitamin C shields those same cells from being destroyed by their own chemical weapons. It also helps direct neutrophils toward infection sites and promotes the development of T cells, the immune cells responsible for targeting specific threats.
Another practical benefit: vitamin C significantly improves iron absorption from plant-based foods like spinach, beans, and fortified cereals. It works by converting the form of iron found in plants into a form your gut can actually take up. This matters most for vegetarians, vegans, and anyone prone to iron deficiency.
Best Food Sources
Oranges get all the credit, but they’re not even the richest source. Half a cup of raw red bell pepper delivers 95 mg of vitamin C, more than a full day’s requirement. Here are some of the top sources, based on NIH data:
- Red bell pepper, raw (½ cup): 95 mg
- Orange juice (¾ cup): 93 mg
- Orange, 1 medium: 70 mg
- Kiwifruit, 1 medium: 64 mg
- Green bell pepper, raw (½ cup): 60 mg
- Broccoli, cooked (½ cup): 51 mg
- Strawberries, fresh (½ cup): 49 mg
- Brussels sprouts, cooked (½ cup): 48 mg
Even foods you might not associate with vitamin C contribute meaningful amounts. A baked potato has 17 mg, and half a cup of cooked cabbage has 28 mg. If you eat a varied diet with several servings of fruits and vegetables daily, you’re almost certainly getting enough.
How Cooking Affects Vitamin C Content
Vitamin C is one of the most fragile nutrients in food. It breaks down with heat, exposure to air, and contact with water. Boiling vegetables is the worst method because the vitamin leaches into the cooking water and degrades from the high temperature simultaneously. Steaming, microwaving, or eating produce raw preserves far more. The length of cooking matters too: the longer food is exposed to heat, the greater the loss. Cutting vegetables right before cooking rather than hours ahead also helps, since the cut surfaces expose more of the vitamin to oxygen.
How Much You Need
The recommended daily intake varies by age, sex, and lifestyle:
- Adult men: 90 mg
- Adult women: 75 mg
- Pregnant women: 85 mg
- Smokers: Add 35 mg to the standard recommendation (so 125 mg for men, 110 mg for women)
Smokers need more because tobacco smoke increases oxidative stress, which depletes vitamin C faster. The FDA’s daily value listed on nutrition labels is set at 90 mg for adults and children age 4 and older.
Absorption Has a Ceiling
Your body absorbs vitamin C through the intestines, but the process has a saturation point. At a dose of 200 mg, absorption is essentially 100%. Once you go above 500 mg in a single dose, absorption drops noticeably, and at 1,250 mg, your body absorbs only about 33% of what you took. The rest passes through unabsorbed. This means megadosing with high-dose supplements is largely wasteful. Plasma levels in the blood max out at around 1,000 mg daily, so anything beyond that simply gets excreted.
For practical purposes, you get the most efficient absorption by spreading your intake across the day through food rather than taking one large supplement dose. If you do supplement, 200 mg is the sweet spot for complete absorption.
What Happens When You Don’t Get Enough
Mild vitamin C deficiency can cause fatigue, irritability, and slow wound healing, symptoms vague enough that they’re easy to miss. Severe, prolonged deficiency leads to scurvy, a condition historically associated with sailors on long voyages who went months without fresh produce. Scurvy causes bleeding gums, loosened teeth, bleeding under the skin, and joint pain. It takes roughly one to three months of very low intake (under 10 mg per day) for scurvy to develop.
Scurvy is rare in developed countries today, but it still occurs in people with extremely limited diets, those with severe alcohol use disorder, and older adults who eat very little fresh food. The early symptoms, particularly fatigue and poor healing, often resolve quickly once vitamin C intake returns to normal levels.
Can You Take Too Much?
Because vitamin C is water-soluble, your body flushes out what it doesn’t need through urine. This makes true toxicity uncommon, but high doses from supplements (typically above 2,000 mg per day) can cause digestive problems like diarrhea, nausea, and stomach cramps. In people prone to kidney stones, large supplemental doses may increase the risk because vitamin C is metabolized into oxalate, a component of the most common type of kidney stone.
Getting vitamin C from food carries virtually no risk of overconsumption. The concern applies only to high-dose supplements, not to eating a lot of bell peppers or citrus fruit.