Nutrition Diet: What produces folate in the body?

October 12, 2025 •

4 min read

An estimated 10% of the U.S. population has a folate deficiency, and for a very simple reason: the human body cannot produce its own folate. This vital B vitamin is instead acquired through diet and, in a surprising twist, is also produced by beneficial bacteria within our gut microbiome.

Quick Summary

The human body cannot produce its own folate and must rely on external sources. Primary sources include foods naturally rich in folate, fortified foods containing synthetic folic acid, and the beneficial bacteria of the gut microbiome that synthesize the nutrient for absorption.

Key Points

Humans cannot produce folate: The human body cannot create its own supply of this essential B vitamin and must obtain it from external sources.
Diet is the main source: A primary source of folate is a balanced diet rich in leafy greens, legumes, and fortified grain products.
Gut bacteria contribute to folate: Certain beneficial gut bacteria, particularly Bifidobacterium, can produce folate that is absorbed through the colon, supplementing dietary intake.
Natural vs. synthetic folate: The two forms differ in stability and how they are metabolized by the body, with folic acid being a more stable synthetic version often added to fortified foods.
Adequate intake is critical: Sufficient folate is vital for DNA synthesis, red blood cell production, and preventing neural tube defects in infants.
Cooking methods affect folate levels: Because it is water-soluble, natural folate can be lost when vegetables are boiled; steaming or microwaving helps retain it.
Genetics can affect metabolism: Individuals with a variation in the MTHFR gene may have a reduced ability to convert folic acid and natural folate into their active form.

Humans cannot produce folate: The reliance on external sources

Unlike plants, fungi, and many bacteria, humans and other animals lack the complete biosynthetic pathway to produce folate de novo. This means that we are entirely dependent on external sources to acquire this crucial vitamin, also known as vitamin B9. Folate is essential for numerous biological processes, including DNA synthesis and repair, the production of red blood cells, and a process called one-carbon metabolism, which is vital for cell growth and methylation. Because our cells cannot synthesize it, the question of what produces folate in the body is more complex than it first appears, involving a symbiotic relationship with our diet and our gut flora.

The two main external sources of folate

There are two primary ways humans obtain folate:

Dietary Sources: This includes food that naturally contains folate and products fortified with the synthetic version, folic acid.
Gut Microbiota: Certain bacteria residing in our intestines have the ability to synthesize folate, which can then be absorbed by the body.

The crucial role of the gut microbiota

Research has increasingly highlighted the significance of the human gut microbiota in contributing to the body's folate supply. While the full extent of this contribution is still under investigation, studies have demonstrated that certain bacteria can produce and excrete folate, which the host can absorb.

Specific bacterial strains: Key folate-producing species belong to the genus Bifidobacterium, including strains like B. adolescentis and B. pseudocatenulatum. Some species of Lactobacillus, notably L. plantarum (given the right precursors), can also produce folate.
Mechanism of absorption: The folate synthesized by these colonic bacteria can be absorbed through the colon, although the absorption rate is lower than in the small intestine. However, the gut microbiota provides a continuous and steady supply of the vitamin, complementing dietary intake.

Natural folate versus synthetic folic acid

Folate is a generic term that encompasses both naturally occurring forms of vitamin B9 in food and the synthetic form, folic acid. Although they are often used interchangeably, they have important differences in their chemical structure, stability, and how the body metabolizes them.

Table: Natural Folate vs. Synthetic Folic Acid


Feature	Natural Food Folate	Folic Acid (Synthetic)
Source	Found naturally in foods like leafy greens, eggs, liver, and legumes.	Man-made form, added to fortified foods (breads, cereals) and supplements.
Chemical Structure	Exists in various reduced forms (e.g., 5-methyl-THF), often as polyglutamates.	Oxidized monoglutamate form; requires reduction to be used by the body.
Stability	Highly sensitive to heat and light, meaning a significant amount can be lost during cooking and storage.	Highly stable, making it ideal for food fortification.
Absorption	Primarily absorbed in the small intestine after being broken down into monoglutamates.	Absorbed very efficiently and readily by the body.
Metabolism	Metabolized to its active form (5-methyl-THF) via enzymes like MTHFR, primarily in the intestine.	Requires reduction by dihydrofolate reductase (DHFR); high intake can lead to unmetabolized folic acid in the bloodstream.

Key food sources of folate

Since humans depend on dietary intake, incorporating folate-rich foods is crucial for maintaining adequate levels. Here is a list of excellent sources:

Dark Leafy Greens: Spinach, kale, romaine lettuce, and turnip greens are among the richest sources.
Legumes: Lentils, black-eyed peas, chickpeas, and kidney beans contain high amounts of folate.
Animal Products: Beef liver and eggs are significant sources of naturally occurring folate.
Fruits: Citrus fruits, particularly oranges, and avocado are good sources.
Nuts and Seeds: Peanuts, sunflower seeds, and wheat germ also contribute to your intake.
Fortified Grains: Many breakfast cereals, breads, pastas, and rice are fortified with folic acid, especially in countries where fortification is mandated.

Conclusion

In summary, the human body does not possess the capacity for de novo folate synthesis and relies on external sources. This includes a varied diet rich in naturally occurring folate from vegetables, legumes, and animal products, as well as foods fortified with the more stable synthetic folic acid. Furthermore, the beneficial bacteria within our gut microbiome, such as certain Bifidobacterium species, provide an additional, continuous source by synthesizing folate that the body can absorb. Understanding these multiple pathways for acquiring folate is essential for ensuring proper nutrition and supporting critical functions like cell growth, DNA repair, and red blood cell production. Consuming a balanced diet and nurturing a healthy gut microbiome are therefore the cornerstones of maintaining healthy folate levels.

The importance of diet and gut health for folate status

To ensure sufficient folate intake, focus on integrating a wide variety of folate-rich foods into your diet. This strategy provides the body with the natural forms of folate and supports the beneficial gut bacteria that can supplement the supply. For some, especially pregnant women, a folic acid supplement is recommended to ensure adequate levels for fetal development. Consulting a healthcare provider or a dietitian is recommended if there are concerns about meeting daily folate requirements or managing specific health conditions. For more information on dietary recommendations, the National Institutes of Health (NIH) Office of Dietary Supplements offers detailed guidance.

Frequently Asked Questions

No, humans do not naturally produce folate. It is an essential nutrient that our bodies cannot synthesize on their own, making external sources like diet and gut bacteria crucial.

Certain beneficial bacteria in the gut, such as some strains of Bifidobacterium, can synthesize and release folate into the intestines, where it can then be absorbed by the body. This provides a supplementary source of the vitamin.

Excellent food sources include dark leafy greens (spinach, kale), legumes (lentils, black-eyed peas), eggs, beef liver, and citrus fruits like oranges.

Folate is the naturally occurring form of vitamin B9 found in food, while folic acid is the synthetic, man-made version used in supplements and to fortify foods. Folic acid is more stable but must be converted by the body to be used.

Yes, natural folate is sensitive to heat and light. Boiling vegetables can lead to significant folate loss, so steaming, microwaving, or eating them raw is recommended to preserve content.

Folate is crucial for making healthy red blood cells, producing and repairing DNA, and supporting cell growth. It is particularly important during periods of rapid growth, such as pregnancy and infancy.

The MTHFR gene produces an enzyme that helps convert folate into its active form. Some people have a genetic variation in this gene, which can affect their ability to process folate and may require different supplementation strategies.