What Stops You from Absorbing Folic Acid?

December 12, 2025 •

4 min read

According to the CDC, some people with the common MTHFR gene variant can still process folic acid, but many factors can interfere with your body's ability to absorb folic acid, leading to potential health issues. The body needs B9 to produce red blood cells and make DNA, so efficient absorption is vital for overall health, especially during pregnancy. This guide explores the common culprits behind poor folic acid uptake.

Quick Summary

Several factors, from genetic mutations like MTHFR to conditions such as celiac disease and Crohn's, can inhibit your body's ability to absorb folic acid. Certain medications, excessive alcohol consumption, and nutritional deficiencies can also play a significant role in reducing your folate levels, impacting essential bodily functions.

Key Points

MTHFR Gene Mutation: A common genetic variation affecting the MTHFR enzyme can impair the body's ability to convert synthetic folic acid into its active form, 5-MTHF.
Digestive Disorders: Conditions like celiac disease, Crohn's disease, and inflammatory bowel disease can damage the intestinal lining, leading to malabsorption of folic acid.
Medication Interactions: Drugs like methotrexate, some anticonvulsants (e.g., phenytoin), and sulfasalazine can interfere with the body's folate metabolism or reduce its levels.
Excessive Alcohol Consumption: Chronic, heavy alcohol use disrupts folate absorption in the gut, impairs its metabolism in the liver, and increases its excretion through the kidneys.
Vitamin B12 Deficiency: A lack of vitamin B12 can lead to a 'folate trap,' where folic acid becomes unusable, causing a functional folate deficiency.
Cooking Methods: Heat-sensitive folate, found naturally in foods, can be destroyed by overcooking, which reduces the amount available for absorption.
Hereditary Folate Malabsorption: A rare genetic disorder that directly impacts the intestinal transport of folate due to a mutation in the PCFT gene.

Folic acid, the synthetic form of vitamin B9, is crucial for numerous bodily processes, from red blood cell formation to DNA synthesis. While many people efficiently absorb and utilize this vital nutrient, several underlying issues can create a roadblock, leading to deficiency and related health problems. Understanding these inhibitors is the first step toward improving your folate status.

Genetic Mutations and Their Role

Certain genetic variations can significantly impair the body's ability to convert folic acid into its active, usable form, 5-methyltetrahydrofolate (5-MTHF).

The MTHFR Gene Variant

The most commonly discussed genetic factor is the methylenetetrahydrofolate reductase (MTHFR) gene polymorphism. This mutation affects the MTHFR enzyme, which is responsible for activating folate. Individuals with this variant may struggle to effectively process synthetic folic acid, leading to an accumulation of unmetabolized folic acid (UMFA) in the bloodstream. While the Centers for Disease Control and Prevention notes that people with an MTHFR variant can still process folic acid, some health experts suggest opting for a supplement with the active form, 5-MTHF, to bypass this conversion process entirely.

Digestive Disorders and Malabsorption

For folic acid to be absorbed, it must be processed correctly in the gastrointestinal tract, particularly in the jejunum of the small intestine. Conditions that damage the intestinal lining can cause malabsorption, preventing the nutrient from ever entering the bloodstream.

Celiac Disease: An autoimmune disorder triggered by gluten, celiac disease causes an inflammatory response that damages the lining of the small intestine, leading to nutrient malabsorption, including folic acid. Strict adherence to a gluten-free diet is necessary to heal the gut and restore proper absorption.
Crohn's Disease and Inflammatory Bowel Disease (IBD): These chronic inflammatory conditions can cause widespread inflammation and damage throughout the digestive tract, impeding nutrient absorption and increasing the risk of folate deficiency.
Hereditary Folate Malabsorption: A rare genetic disorder caused by mutations in the SLC46A1 gene, which encodes the proton-coupled folate transporter (PCFT) necessary for intestinal absorption. Individuals with this condition require high-dose folate supplements or parenteral administration.

Medications That Interfere with Folic Acid

Several common prescription and over-the-counter medications can inhibit folic acid absorption or interfere with its metabolism in the body.

Methotrexate: A folate antagonist used to treat cancer, autoimmune diseases, and psoriasis. It works by blocking the enzyme that converts folate to its active form, and patients are often prescribed folic or folinic acid to minimize side effects.
Anticonvulsants: Some anti-seizure medications, such as phenytoin, phenobarbital, and primidone, can reduce blood folate levels and interfere with the body's ability to use it.
Sulfasalazine: Used for conditions like ulcerative colitis, this medication is known to interfere with folate absorption.
Proton Pump Inhibitors (PPIs): Some research suggests that prolonged use of PPIs, which reduce stomach acid, may affect folate absorption, although further studies are needed.

Lifestyle and Nutritional Factors

While genetic and medical conditions are significant, everyday habits and other nutritional deficiencies also play a role in poor folic acid absorption.

The Impact of Alcohol

Excessive and chronic alcohol consumption is a major inhibitor of folic acid absorption and utilization. Alcohol can irritate the intestinal lining, damaging the cells responsible for absorbing folate. It also disrupts folate metabolism in the liver and increases the rate of folate excretion through urine, leading to lower body stores.

Nutrient Cooking and Processing

Folate, the naturally occurring form of B9 found in food, is highly susceptible to heat. Overcooking fruits and vegetables can destroy a significant amount of their folate content, reducing the amount available for absorption. Fresh, raw, or lightly steamed produce is the best way to preserve folate.

Other Vitamin and Mineral Deficiencies

Folic acid doesn't work alone. Its function is closely linked with other nutrients, particularly vitamin B12. A deficiency in vitamin B12 can trap folate in an unusable form within the body, a phenomenon known as the "folate trap," leading to a functional folate deficiency even if intake is adequate. Zinc is also essential for folate absorption, with studies suggesting a mutual inhibitory effect in intestinal transport, although results on long-term effects vary.

Comparison of Factors Affecting Folic Acid Absorption


Factor	How it Affects Absorption	How to Mitigate the Impact
MTHFR Gene Mutation	Impairs the conversion of synthetic folic acid to its active form, 5-MTHF.	Take methylated folate (5-MTHF) supplements, which do not require conversion by the MTHFR enzyme.
Celiac Disease & IBD	Causes intestinal inflammation and damage, reducing the surface area for nutrient absorption.	Follow a strict gluten-free diet for celiac disease; manage inflammation for IBD with medical supervision.
Chronic Alcohol Use	Disrupts intestinal absorption, impairs liver metabolism, and increases folate excretion.	Reduce or eliminate alcohol consumption, especially if intake is chronic and excessive.
Certain Medications	Antagonists (methotrexate) block folate enzymes; others (anticonvulsants) reduce blood levels.	Consult a doctor about managing medication side effects, adjusting dosage, or considering alternatives.
Vitamin B12 Deficiency	Can trap folate in an inactive form within the body, making it unusable.	Ensure adequate intake of B12, often through supplements, especially if following a vegan diet.

Conclusion

Folic acid absorption is a complex process that can be hindered by a combination of genetic, pathological, and lifestyle factors. While inadequate dietary intake is a common cause of deficiency, underlying medical conditions like digestive disorders and medication use can significantly impair even the best nutritional habits. Genetic variations, such as the MTHFR polymorphism, can also reduce the body's ability to utilize synthetic folic acid. A comprehensive approach, which may involve dietary adjustments, supplement choices (like opting for 5-MTHF), and medical management of underlying conditions, is often necessary to overcome these hurdles and ensure adequate folate status for overall health and well-being. Consulting a healthcare professional is key to identifying the specific root cause and developing an effective strategy for improving absorption.

Frequently Asked Questions

Folate is the natural form of vitamin B9 found in foods like leafy greens and legumes, while folic acid is the synthetic form used in fortified foods and supplements. The body must convert both to the active form, 5-MTHF, to be utilized, but the conversion process differs slightly.

Yes, it is possible to have a folate deficiency even with sufficient dietary intake due to conditions that affect absorption, such as digestive diseases, certain medications, genetic mutations, or excessive alcohol consumption.

The MTHFR gene mutation can reduce the efficiency of converting synthetic folic acid to its active form, 5-MTHF. However, people with this variant can still process all types of folate. Some health experts recommend methylated folate supplements as an alternative.

Chronic and excessive alcohol consumption interferes with folic acid in several ways: it damages the intestinal lining, impairs the liver's ability to store and metabolize folate, and increases folate excretion by the kidneys.

Folic acid and Vitamin B12 work together in the body. If you have a vitamin B12 deficiency, it can create a 'folate trap,' preventing folate from being used correctly. For this reason, doctors will often test B12 levels before supplementing with folic acid.

Diseases affecting the small intestine, like celiac disease, Crohn's disease, and other malabsorption syndromes, are key culprits. Kidney dialysis can also lead to folate loss.

Improving absorption depends on the underlying issue. It may involve: increasing intake of folate-rich foods (preferably raw or lightly cooked), managing medical conditions, reducing alcohol intake, taking supplements with methylated folate (if you have the MTHFR mutation), and addressing any co-existing vitamin B12 deficiency.