Vitamin C deficiency develops when your body consistently takes in less vitamin C than it uses, loses more than it absorbs, or both. The recommended daily intake is 90 mg for adult men and 75 mg for adult women, and falling short of that over several weeks is enough to cause problems. Symptoms of scurvy, the clinical endpoint of severe deficiency, appear within 4 to 12 weeks of truly insufficient intake. In high-income countries, somewhere between 0% and 15% of the population is deficient at any given time, meaning this is far from a historical curiosity.
Not Eating Enough Fruits and Vegetables
The most straightforward cause is a diet low in vitamin C-rich foods. Your body cannot make or store large amounts of this vitamin, so you depend on a steady dietary supply. People who eat very few fruits and vegetables, those on highly restrictive diets, older adults with limited appetites, and individuals experiencing food insecurity are all at elevated risk. A diet built primarily around processed or shelf-stable foods with little fresh produce can easily fall short of the 75 to 90 mg daily target.
How Cooking Destroys Vitamin C
Even when you buy vitamin C-rich vegetables, the way you prepare them matters enormously. Vitamin C is water-soluble and heat-sensitive, which means it leaches into cooking water and breaks down at high temperatures. A study measuring vitamin C retention across different cooking methods found that boiling destroyed the most, with retention ranging from 0% to about 74% depending on the vegetable. Boiled spinach retained only 40% of its original vitamin C. Boiled chard retained none at all.
Steaming performed better, generally preserving 45% to 89% of vitamin C content. Microwaving was the gentlest method, with retention above 90% for spinach, carrots, sweet potatoes, and broccoli. The difference comes down to water contact and temperature: boiling submerges food in hot water, pulling the vitamin out, while microwaving uses less water and shorter cook times. If you’re concerned about vitamin C intake, microwaving or steaming vegetables rather than boiling them makes a real difference.
Smoking and Oxidative Stress
Smokers need significantly more vitamin C than nonsmokers. The Institute of Medicine sets their requirement 35 mg per day higher, bringing the target to 125 mg for men and 110 mg for women who smoke. This isn’t arbitrary. Cigarette smoke floods the body with reactive compounds that vitamin C neutralizes. Specifically, compounds in cigarette smoke cause protein damage and cell death in lung tissue, and vitamin C gets consumed in the process of intercepting and deactivating those harmful molecules. The metabolic turnover of vitamin C is roughly 35 mg per day greater in smokers, meaning their bodies burn through it faster even if their diet is identical to a nonsmoker’s.
This makes smoking a double-edged problem: it increases demand while often coinciding with dietary patterns that don’t compensate. Smokers who don’t deliberately eat more vitamin C-rich foods or take supplements are at particular risk for deficiency.
Alcohol Use
Chronic alcohol consumption depletes vitamin C through multiple routes. One direct mechanism is increased urinary loss. Research has shown that alcohol produces a 47% increase in urinary vitamin C excretion. In people who drink heavily over time, this ongoing loss compounds with the poor dietary intake that often accompanies alcohol use disorder. The combination of eating less and excreting more creates a reliable path toward deficiency.
Digestive Conditions That Block Absorption
Vitamin C is primarily absorbed in the jejunum and ileum, two sections of the small intestine. Any condition that damages or inflames these areas can reduce how much vitamin C actually makes it into your bloodstream, regardless of how much you eat.
Crohn’s disease is a particular risk factor because it frequently affects exactly those segments of the small bowel where vitamin C uptake occurs. But ulcerative colitis also poses problems through a different mechanism. In inflammatory bowel disease, the body produces elevated levels of an inflammatory signaling molecule called TNF-alpha, which actively turns down the production of the transporters your intestinal cells use to absorb vitamin C. Some patients with IBD also carry genetic variations in those transporter genes, further reducing their absorption capacity. The result is that even a diet adequate in vitamin C may not prevent deficiency if your gut can’t absorb it properly.
Medications That Increase Losses
Several common medications can tip the balance toward deficiency. Diuretics increase urinary output and can carry vitamin C out with it. Birth control pills and aspirin have also been identified as drugs that can contribute to lower vitamin C levels over time. If you take any of these medications long-term and your diet is only borderline adequate in vitamin C, the additional losses could push you into deficiency territory.
Burns, Surgery, and Physical Trauma
Severe physical stress dramatically increases your body’s demand for vitamin C. Major burns are a striking example. After a serious burn, the body generates large quantities of reactive oxygen species that damage blood vessel walls, making them leak fluid into surrounding tissue. Vitamin C acts as an antioxidant that can reduce this oxidative damage and help tighten those leaky blood vessel barriers. The body’s consumption of vitamin C during this process is so high that stores can be rapidly exhausted. The same principle applies after major surgery or significant physical trauma, where inflammation and tissue repair create a surge in demand that normal dietary intake cannot meet.
Other Groups at Higher Risk
Several other situations raise your likelihood of deficiency. People with eating disorders, particularly those who severely restrict food intake, often fall short of basic vitamin C needs. Individuals with kidney disease undergoing dialysis face altered nutrient metabolism and dietary restrictions that can limit vitamin C intake. People experiencing homelessness or social isolation, especially elderly individuals living alone, frequently have diets that lack fresh produce for extended periods.
Pregnancy and breastfeeding increase vitamin C requirements as well, since the developing baby and breast milk production both draw on the mother’s stores. Infants fed exclusively on boiled or evaporated milk (which destroys vitamin C) without supplementation are another classic at-risk group, though this is uncommon in countries where commercial formula is fortified.
How Deficiency Develops Over Time
Vitamin C deficiency doesn’t happen overnight. Your body maintains a pool of the vitamin, and it takes sustained inadequate intake to deplete it. In the earliest weeks, you might notice fatigue, irritability, or general malaise. These nonspecific symptoms appear within 4 to 12 weeks of insufficient intake. As the deficiency deepens, more recognizable signs emerge: bleeding gums, easy bruising, slow wound healing, dry or splitting hair, and joint pain. Left untreated, full scurvy develops, with loosening teeth, severe skin hemorrhages, and potentially life-threatening complications.
The good news is that vitamin C levels respond quickly to correction. Eating adequate fruits and vegetables or taking a supplement can reverse early deficiency symptoms within days to weeks. The body’s threshold for adequate blood levels is around 50 micromoles per liter, and most people can reach and maintain that with consistent dietary intake at or above the recommended 75 to 90 mg per day.