What do Folic Acid and B-12 do for your body?

December 13, 2025 •

3 min read

According to the CDC, all women of childbearing age should consume 400 micrograms of folic acid daily to prevent major birth defects. While both folic acid and vitamin B-12 are essential B vitamins, they have distinct functions, yet work together in crucial bodily processes like DNA synthesis and red blood cell formation.

Quick Summary

Folic acid (B9) and vitamin B-12 (cobalamin) are essential B vitamins that play interconnected roles in DNA synthesis, red blood cell production, and nervous system health.

Key Points

DNA and Red Blood Cell Production: Both folic acid and vitamin B-12 are essential for synthesizing DNA and producing healthy red blood cells, preventing megaloblastic anemia.
Nervous System Health: Vitamin B-12 is crucial for maintaining the nervous system, with deficiency potentially causing severe and irreversible nerve damage.
Maternal and Fetal Health: Folic acid is vital for preventing neural tube defects in infants during early pregnancy, while B-12 supports overall fetal development.
Interaction Risk: High folic acid intake can mask the anemia associated with B-12 deficiency, concealing progressive and permanent neurological damage.
Dietary Sources Differ: Folic acid comes from leafy greens, legumes, and fortified foods, while B-12 is found primarily in animal products.
Absorption Varies: B-12 absorption can be complex due to factors like age and medical conditions, whereas some people with an MTHFR gene mutation struggle to process synthetic folic acid.

Folic Acid (Vitamin B9): The Cellular Architect

Folic acid, the synthetic form of folate (vitamin B9), is a water-soluble vitamin vital for numerous processes. It's a key component in DNA synthesis and repair, which is essential for cell division and the rapid growth of cells in the bone marrow, pregnancy, and infancy. Adequate intake during pregnancy helps prevent neural tube defects (NTDs) like spina bifida.

Functions of Folic Acid

Red Blood Cell Formation: Collaborates with B-12 to produce healthy red blood cells; deficiency can cause megaloblastic anemia.
Tissue Growth and Cell Function: Supports the growth and repair of all body tissues and helps create new proteins.
Heart Health: Assists in metabolizing homocysteine, potentially lowering cardiovascular risk.

Vitamin B-12 (Cobalamin): The Nerve Protector

Vitamin B-12, or cobalamin, is essential for a healthy nervous system and red blood cell formation. Found naturally in animal products, it requires supplementation for vegans and vegetarians. The body stores B-12, so deficiency symptoms can appear slowly but the neurological effects can be severe and permanent if untreated.

Functions of Vitamin B-12

Nerve Health: Maintains the myelin sheath around nerve fibers; deficiency can cause nerve damage symptoms like tingling and balance issues.
DNA and Red Blood Cell Production: Necessary for DNA synthesis and red blood cell maturation, working with folic acid.
Energy Production and Metabolism: Helps convert fatty acids and amino acids into energy.
Cognitive Function: Supports brain health, memory, and mood, particularly in older adults.

A Crucial Partnership: The Interdependence of Folic Acid and B-12

Folic acid and B-12 are metabolically linked, primarily through one-carbon metabolism. B-12 is necessary for an enzyme that utilizes folate to convert homocysteine to methionine. A deficiency in one impacts the other's function.

Critically, high folic acid intake can correct the anemia of a B-12 deficiency, masking the underlying issue. This allows potential neurological damage from B-12 deficiency to progress undetected, particularly dangerous for older adults. Medical professionals often check B-12 levels before prescribing high-dose folic acid.

Folic Acid vs. Vitamin B-12: A Comparison


Aspect	Folic Acid (Vitamin B9)	Vitamin B-12 (Cobalamin)
Source	Green leafy vegetables, citrus fruits, legumes, fortified foods, supplements.	{Link: consensus.app https://consensus.app/questions/difference-between-vitamin-b12-and-folic-acid/}
Primary Function	DNA synthesis, cell growth, neural tube development.	{Link: consensus.app https://consensus.app/questions/difference-between-vitamin-b12-and-folic-acid/}
Deficiency Risks	Megaloblastic anemia, birth defects, fatigue.	Megaloblastic anemia, nerve damage, cognitive issues.
Masking Effect	Can hide B-12 deficiency anemia, allowing neurological damage.	{Link: consensus.app https://consensus.app/questions/difference-between-vitamin-b12-and-folic-acid/}
Absorption	Generally absorbed well; MTHFR mutation affects synthetic form.	Requires intrinsic factor; absorption declines with age.
Storage	Limited body storage.	Stored in liver for years.

Who Is at Risk for Deficiency?

Groups at higher risk for deficiency include:

Pregnant Women: Increased needs for growth.
Older Adults: Impaired B-12 absorption due to reduced stomach acid.
Vegans and Vegetarians: B-12 is mainly from animal products.
Individuals with Gastrointestinal Disorders: Conditions affecting nutrient absorption.
Individuals with MTHFR Mutation: May struggle to process synthetic folic acid.

Conclusion

Folic acid and vitamin B-12 are vital B vitamins that work together on fundamental processes like DNA synthesis and red blood cell production. B-12 is also critical for nervous system health. Deficiencies in either can cause megaloblastic anemia, but B-12 deficiency uniquely risks severe, permanent neurological damage, which high folate intake can mask. For additional health and vitamin guidelines, you can visit the National Institutes of Health (NIH) Office of Dietary Supplements.

Frequently Asked Questions

The primary function of folic acid is to help the body produce and repair DNA and to aid in the creation of new cells. This makes it particularly important during periods of rapid growth, such as pregnancy and infancy.

Vitamin B-12 is crucial for maintaining the myelin sheath, which is the protective covering around nerve fibers. This is essential for proper nerve function and signal transmission throughout the body.

Yes, high intake of folic acid can be harmful if a person also has an underlying vitamin B-12 deficiency. It can mask the anemia caused by B-12 deficiency, allowing severe and often irreversible neurological damage to continue unchecked.

People most at risk for B-12 deficiency include older adults, vegans and vegetarians, and those with certain digestive disorders that affect absorption.

Folic acid and B-12 are involved in a metabolic pathway where B-12 is required to activate folate, which then helps synthesize DNA. This collaboration is crucial for cell division and the production of healthy red blood cells.

Symptoms of a B-12 deficiency can include fatigue, weakness, numbness or tingling in the hands and feet, memory problems, and a sore tongue.

Folate is the naturally occurring form of vitamin B9 found in foods like leafy greens and legumes. Folic acid is the synthetic, more stable form used in fortified foods and supplements.