Where Does Vitamin C Come From?

January 7, 2026 •

3 min read

While many animals can produce their own vitamin C, humans and other primates cannot due to a genetic mutation, making dietary intake essential. Knowing where does vitamin C come from is therefore crucial for maintaining good health and preventing deficiency diseases like scurvy. This vital nutrient, also known as ascorbic acid, is found in a wide variety of plant foods and is also produced through modern industrial methods.

Quick Summary

This guide explores the various origins of vitamin C, from its rich natural presence in fruits and vegetables to its modern production for fortified foods and supplements. It details why humans must get this essential nutrient from external sources and provides an in-depth comparison of its natural versus synthetic forms.

Key Points

Dietary Dependence: Humans cannot produce their own vitamin C and must obtain it from external sources, primarily through diet.
Natural Sources: The richest natural sources of vitamin C are fruits and vegetables, including citrus, berries, peppers, and broccoli.
Industrial Production: Synthetic ascorbic acid is manufactured from glucose and used to create supplements and fortify many foods.
Loss of GULO Gene: The inability of humans to synthesize vitamin C is due to a genetic mutation that deactivated the L-gulonolactone oxidase (GULO) enzyme in our ancestors.
Natural vs. Synthetic: Natural and synthetic vitamin C are chemically identical and have equivalent bioavailability, although natural sources offer additional phytonutrients.
Importance of Raw Foods: Cooking can reduce vitamin C content in food, so consuming raw or lightly cooked produce is ideal for maximum intake.

Natural Food Sources: A Colorful Abundance

The most common and accessible source of vitamin C for humans is a diet rich in fruits and vegetables. Almost all produce contains some amount of ascorbic acid, but some foods are exceptionally high in it, making them excellent staples for meeting your daily needs. Raw or lightly cooked vegetables and fresh fruits are typically the best options, as vitamin C can be destroyed by heat and exposure to light.

Fruits High in Vitamin C

Citrus Fruits: Oranges, lemons, and grapefruits are classic sources of vitamin C.
Berries: Strawberries, kiwifruit, and blackcurrants pack a significant vitamin C punch.
Tropical Fruits: Mangos, papayas, and pineapple are delicious and potent sources.
Other Notables: Cantaloupe and watermelon also contribute to your intake.

Vegetables High in Vitamin C

Peppers: Red and green bell peppers are among the richest vegetable sources.
Cruciferous Vegetables: Broccoli, Brussels sprouts, and cauliflower are excellent additions to a vitamin C-rich diet.
Leafy Greens: Spinach and turnip greens provide a good amount of the nutrient.
Potatoes: Both sweet and white potatoes contain vitamin C.

Industrial Synthesis and Fortified Products

Beyond natural food, a significant portion of the world's vitamin C comes from industrial synthesis. This is used for manufacturing dietary supplements and fortifying many foods and beverages. Synthetic ascorbic acid is chemically identical to the naturally occurring form and is equally bioavailable to the body.

The industrial process for synthesizing ascorbic acid from glucose was pioneered in the 1930s and has been refined over time. Today, a two-step fermentation process is common. The resulting ascorbic acid is a staple in various products, including tablets, capsules, chewable tablets, and fortified breakfast cereals and juices.

The Evolutionary Reason: Why Humans Can't Produce Their Own

Most animals, including the majority of mammals, have the genetic ability to produce their own vitamin C in their livers. However, approximately 40 million years ago, a crucial gene mutation occurred in the lineage of ancestral primates. The gene responsible for the enzyme L-gulonolactone oxidase (GULO), which catalyzes the final step of vitamin C biosynthesis, became non-functional.

This loss of function was likely not a major disadvantage for early primates, whose diets were naturally rich in fresh fruits and vegetables, ensuring a constant supply of vitamin C. As a result, there was no selective pressure to retain the functional gene. Today, this genetic inheritance means humans, along with other primates and a few other animals like guinea pigs, are dependent on external sources for this essential vitamin.

Comparison: Natural vs. Synthetic Vitamin C


Aspect	Natural Vitamin C (from food)	Synthetic Vitamin C (from supplements/fortified foods)
Bioavailability	High, especially when consumed with other phytochemicals in food.	High; the body absorbs and uses synthetic ascorbic acid just as effectively.
Added Nutrients	Comes with a complex mix of other vitamins, minerals, and phytonutrients.	Pure ascorbic acid, though some supplements may add bioflavonoids.
Form	Naturally occurring in plant cell structures.	Produced industrially, available in various forms (pills, powders, etc.).
Preparation Impact	Can be lost through heat, light, and cooking.	Stable, but form matters (e.g., buffered vs. ascorbic acid).
Cost	Varies widely; fresh produce can be expensive, but is a regular part of a balanced diet.	Can be very inexpensive, especially in bulk form.

Conclusion

Vitamin C, an indispensable nutrient for human health, comes primarily from plant-based foods, industrial synthesis, and supplements. Our evolutionary history, marked by a genetic mutation millions of years ago, necessitates a dietary or supplemental intake of this vital compound. Whether from a juicy orange, a cup of fresh broccoli, or a manufactured supplement, obtaining sufficient vitamin C is a cornerstone of a healthy diet. Both natural and synthetic forms are effective and bioavailable, allowing individuals flexibility in meeting their nutritional needs. Ultimately, a balanced diet is the surest path to getting this essential vitamin, providing not only ascorbic acid but a host of other beneficial compounds. For more information on the benefits and functions of vitamin C, visit the Office of Dietary Supplements fact sheet from the National Institutes of Health.

Frequently Asked Questions

Humans cannot produce their own vitamin C because of a genetic mutation that occurred in ancestral primates. This mutation caused the loss of the enzyme L-gulonolactone oxidase (GULO), which is necessary for the final step of vitamin C biosynthesis.

Yes, synthetic ascorbic acid is chemically identical to the ascorbic acid found in food. Studies have shown they have equivalent bioavailability and biological activity in humans, though food provides additional beneficial compounds.

Excellent food sources of vitamin C include a wide variety of fruits and vegetables such as red and green peppers, oranges, kiwifruit, strawberries, broccoli, and Brussels sprouts.

Yes, vitamin C is water-soluble and easily destroyed by heat, light, and exposure to oxygen. To minimize loss, it is best to consume fruits and vegetables raw, steam them, or use microwaving methods.

Dietary supplements typically use industrially synthesized ascorbic acid. This can be in the form of capsules, tablets, or powders. Various forms like sodium ascorbate or calcium ascorbate are also available.

Yes, it is entirely possible to get enough vitamin C from a varied, balanced diet rich in fruits and vegetables. For many, a single orange or serving of bell peppers can provide a large portion of the daily requirement.

No, as a water-soluble vitamin, vitamin C is not stored in the body for long periods. Excess amounts are excreted through urine, which is why a consistent daily intake is important to maintain adequate levels.