What is the difference between folic acid and folate levels?

October 8, 2025 •

4 min read

The Centers for Disease Control and Prevention reports that folic acid fortification has significantly reduced neural tube defects. Understanding what is the difference between folic acid and folate levels is key to grasping how this essential B vitamin impacts health, depending on its source and how the body metabolizes it.

Quick Summary

This article explores the key distinctions between natural folate found in food and synthetic folic acid in supplements and fortified foods, examining their different metabolic pathways, bioavailability, and health implications for overall wellness.

Key Points

Source Difference: Folate is naturally occurring in foods, while folic acid is the synthetic, man-made version added to supplements and fortified foods.
Metabolic Pathway: The body processes folate efficiently through the small intestine, but folic acid is primarily metabolized in the liver, a slower process that can lead to unmetabolized folic acid in the bloodstream.
Bioavailability and Stability: Folic acid is more stable and has higher bioavailability than natural folate, which is sensitive to heat and light during cooking.
Pregnancy Importance: For women who are pregnant or planning to conceive, the stability and absorbability of folic acid from supplements are critical for preventing neural tube defects.
Risk of Masking B12 Deficiency: High doses of folic acid can mask the symptoms of a vitamin B12 deficiency, potentially leading to irreversible nerve damage if left untreated.
Genetic Factors: Individuals with an MTHFR gene variant may have reduced ability to convert folic acid and might need alternative forms of supplementation.

What is Vitamin B9?

Vitamin B9 is an essential nutrient critical for many bodily functions, including DNA synthesis and repair, cell growth, and the creation of red blood cells. A deficiency can lead to various health issues, most notably a type of anemia called megaloblastic anemia. Vitamin B9 exists in several forms, with the most common being folate and folic acid, and it is vital to understand the distinctions between them for optimal health.

Folate: The Natural Form of Vitamin B9

Folate is the form of vitamin B9 that occurs naturally in foods. It is not a single compound but rather a family of related compounds. Your body is designed to absorb and utilize this natural form efficiently. Once consumed, dietary folate undergoes a process in the small intestine to convert it into a usable form, 5-MTHF (5-methyltetrahydrofolate), for circulation in the bloodstream.

Dietary Sources: Excellent sources of natural folate include a wide array of foods:
- Leafy Greens: Spinach, kale, and romaine lettuce.
- Legumes: Lentils, black beans, and chickpeas.
- Fruits: Citrus fruits (oranges), papaya, and bananas.
- Other Vegetables: Asparagus, brussels sprouts, and broccoli.
- Animal Products: Beef liver and eggs.
Absorption and Stability: While natural folate is efficiently used by the body, it is sensitive to heat and light. This means that some of the folate in foods can be lost during cooking or processing, and its bioavailability is generally considered to be lower than synthetic folic acid.

Folic Acid: The Synthetic Form

Folic acid is the synthetic, or man-made, version of vitamin B9. It is the form most commonly used in dietary supplements and for fortifying foods like breakfast cereals, bread, pasta, and rice. Its use in fortification was mandated in many countries, including the U.S. in 1998, to reduce the risk of neural tube defects (NTDs) in infants.

The Metabolic Difference: Processing Folate vs. Folic Acid

The most significant difference lies in how the body processes these two forms. Folate is ready for use relatively quickly after digestion. Folic acid, however, must first be converted into the active 5-MTHF form in a process that primarily occurs in the liver. For some people, this conversion process is slower and less efficient, especially when taking high doses.

Unmetabolized Folic Acid: When the body is unable to process all the folic acid it receives, unmetabolized folic acid can build up in the bloodstream. While the long-term health risks associated with unmetabolized folic acid are still under investigation, some concerns have been raised regarding potential impacts on the immune system and cognitive function.
Genetic Factors: A common genetic variation in the MTHFR (methylenetetrahydrofolate reductase) gene can further impair the body's ability to convert folic acid into its active form. Individuals with this mutation may be more susceptible to having unmetabolized folic acid in their system and might benefit from alternative supplements like L-methylfolate.

Why Measuring Levels Can Be Complex

When health professionals measure vitamin B9 status, they often use a blood test that can assess both serum folate and red blood cell folate levels. However, interpreting these results can be tricky due to the metabolic differences. Serum folate reflects recent dietary intake, while red blood cell folate indicates long-term status. In individuals taking high doses of folic acid, blood tests can show high total folate levels, potentially masking a deficiency in the active form of folate or, crucially, a vitamin B12 deficiency.

Comparison: Folate vs. Folic Acid


Feature	Folate (Natural)	Folic Acid (Synthetic)
Source	Found naturally in foods like leafy greens, legumes, and fruits.	Added to fortified foods (breads, cereals) and found in supplements.
Bioavailability	Variable; lower and can be lost during cooking.	High; more stable and absorbed more efficiently.
Metabolism	Converted to active 5-MTHF in the small intestine.	Converted to 5-MTHF primarily in the liver, a slower process.
Potential Risks	Generally safe; body flushes out excess.	High doses can lead to unmetabolized folic acid build-up and can mask vitamin B12 deficiency.
Stability	Less stable; sensitive to heat and light.	Very stable; unaffected by heat and light.

The Critical Role of Context

For many, consuming a balanced diet rich in natural folate is sufficient. However, specific populations, particularly women who are pregnant or planning to become pregnant, require a reliable source of folic acid to prevent NTDs. The stability and high bioavailability of synthetic folic acid make it the recommended form for this crucial period of fetal development. Medical professionals may prescribe higher doses of folic acid in certain high-risk scenarios.

For most healthy adults, prioritizing dietary folate through whole foods and being mindful of intake from fortified products is a balanced approach. Always consult a healthcare provider for personalized advice on supplementation. A registered dietitian or a doctor can help determine if your diet provides adequate folate and whether supplements are necessary, especially if you have an underlying health condition, a genetic variation affecting metabolism, or are at risk for deficiency. For more information on dietary needs, the National Institutes of Health provides comprehensive fact sheets on folate. [https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/]

Conclusion

Understanding what is the difference between folic acid and folate levels is not just a matter of semantics but is crucial for effective nutrition. While both are forms of vitamin B9, their distinct origins, metabolic pathways, and bioavailability have real-world implications for health. Folate from whole foods is processed naturally by the body, whereas synthetic folic acid from supplements and fortified foods requires a more demanding conversion process. This distinction is especially important during pregnancy and when considering long-term supplement use, where consultation with a healthcare provider is essential to ensure adequate intake without potential complications.

Frequently Asked Questions

For most healthy individuals, a balanced diet rich in leafy greens, legumes, fruits, and fortified grains is sufficient to meet their daily folate needs. However, certain individuals, such as pregnant women or those with specific absorption issues, may require supplements.

Folic acid is recommended because it is more stable and has higher bioavailability than natural folate, ensuring a reliable and sufficient intake to prevent neural tube defects early in pregnancy. It is difficult to get the recommended amount from food alone.

Unmetabolized folic acid is the synthetic form of vitamin B9 that remains unprocessed in the bloodstream, a phenomenon that can occur with high supplement intake. While the long-term health effects are still being researched, some studies suggest potential links to changes in immune function and cognitive health.

The MTHFR gene variant can reduce the efficiency of the enzyme that converts folic acid into its active form, 5-MTHF. People with this genetic variation may have more difficulty utilizing synthetic folic acid and might benefit from other supplement types.

Levels are typically measured via a blood test that can assess both serum (blood liquid) and red blood cell folate levels. Fasting for several hours before the test is often required to ensure accurate results.

Yes, excessive intake of synthetic folic acid from supplements or fortified foods can be potentially harmful. It can mask a vitamin B12 deficiency and, in rare cases with very high doses, cause side effects such as nausea, bloating, or irritability.

Yes, in many countries, regulations require manufacturers to add folic acid to enriched grain products like bread, cereal, and pasta. The term 'enriched' on the label indicates this addition.

Yes, while particularly crucial for women of reproductive age, folate is an essential vitamin for everyone. It supports red blood cell production, DNA synthesis, and overall cell health in men as well.