Understanding What is the Main Disease from Deficiency of B9 Folate?

October 8, 2025 •

4 min read

According to the National Institutes of Health, folate is critical for making healthy red blood cells and DNA. When the body lacks sufficient amounts of this vital nutrient, the main disease from deficiency of B9 folate is megaloblastic anemia, characterized by abnormally large, immature red blood cells. In addition to this blood disorder, insufficient folate during pregnancy can lead to severe birth defects, particularly neural tube defects.

Quick Summary

A lack of vitamin B9, or folate, primarily causes megaloblastic anemia, a condition where the bone marrow produces oversized, dysfunctional red blood cells. Folate deficiency is also a significant risk factor for serious birth defects like spina bifida and anencephaly, especially during early pregnancy. Common causes range from poor diet to medical conditions affecting nutrient absorption.

Key Points

Megaloblastic Anemia: The primary disease caused by a vitamin B9 (folate) deficiency is megaloblastic anemia, characterized by abnormally large and immature red blood cells.
Neural Tube Defects (NTDs): During pregnancy, a severe folate deficiency is a major risk factor for serious birth defects of the brain and spine, including spina bifida and anencephaly.
Fatigue and Weakness: Common symptoms of folate deficiency anemia include extreme tiredness, lack of energy, pale skin, and shortness of breath.
Not Stored Long-Term: Unlike some other vitamins, the body's folate stores are limited, making consistent dietary intake or supplementation necessary.
Diagnosis is Key: Blood tests are required to confirm a folate deficiency, which must be distinguished from vitamin B12 deficiency to prevent potential neurological complications.
Prevention Through Diet and Supplements: Including folate-rich foods and taking supplements, especially for women of childbearing age and during pregnancy, is the best way to prevent deficiency.

What is Megaloblastic Anemia?

Megaloblastic anemia is the most common hematological disease resulting from a vitamin B9 (folate) deficiency. This condition is defined by the production of unusually large, immature red blood cells called megaloblasts. These cells are fewer in number and have a shortened lifespan compared to healthy red blood cells. Since red blood cells are responsible for carrying oxygen throughout the body, a reduced count of functional red blood cells leads to anemia.

Symptoms often appear gradually and include extreme fatigue, weakness, pale skin, and shortness of breath. Unlike vitamin B12 deficiency, folate-related megaloblastic anemia does not typically present with severe neurological symptoms, although mood changes and cognitive issues can occur. Early diagnosis and treatment with folic acid supplements are crucial to resolve the condition and prevent complications.

Folate's Crucial Role in Health

Folate is essential for numerous bodily functions. It acts as a coenzyme in single-carbon metabolism, a critical process for synthesizing nucleotides (the building blocks of DNA and RNA) and for methylation reactions.

Importance of Folate for:

DNA Synthesis and Repair: Folate is necessary for the creation of new cells and for repairing genetic material. A deficiency impairs this process, leading to the production of abnormal blood cells seen in megaloblastic anemia.
Fetal Development: During early pregnancy, sufficient folate is critical for the proper formation of the baby's brain and spinal cord. A deficiency can lead to severe birth defects known as neural tube defects (NTDs).
Cardiovascular Health: Folate helps regulate homocysteine levels, an amino acid in the blood. Elevated homocysteine is a risk factor for cardiovascular disease and stroke, and folate supplementation can help lower these levels.
Mental and Neurological Function: Some studies suggest a link between low folate status and neuropsychiatric symptoms like depression and cognitive decline, though research is ongoing.

Causes and Risk Factors of Folate Deficiency

A folate deficiency most often stems from insufficient dietary intake, but several other factors can contribute to the problem.

Common Causes of Low Folate:

Poor Diet: The body cannot store folate for long, so a diet lacking in folate-rich foods like leafy greens, citrus fruits, and legumes is a common cause. Overcooking vegetables can also destroy folate.
Malabsorption: Conditions that affect nutrient absorption in the small intestine, such as celiac disease and Crohn's disease, can lead to a deficiency.
Increased Demand: Periods of rapid cell growth, most notably pregnancy and lactation, significantly increase the body's need for folate.
Alcoholism: Chronic alcohol consumption can interfere with folate absorption and metabolism.
Medications: Certain medications, including some anticonvulsants and drugs like methotrexate, can interfere with the body's ability to absorb or use folate effectively.
Genetics: A genetic mutation in the MTHFR gene affects how some individuals convert folate to its active form, increasing their risk of deficiency.

Diagnosis and Treatment

A healthcare provider can diagnose folate deficiency through a blood test that measures serum folate levels and often assesses red blood cell folate for a longer-term status. A complete blood count (CBC) will show abnormally large red blood cells with a high mean corpuscular volume (MCV).

Treatment primarily involves oral folic acid supplements, which are often needed for several months to replenish stores. Dietary changes to include more folate-rich foods are also recommended. Addressing any underlying medical conditions or medication issues is also a key part of the treatment plan.

Comparison: Folate vs. Vitamin B12 Deficiency

Since both folate and vitamin B12 deficiencies can cause megaloblastic anemia, it is crucial to differentiate between them, as treating one can mask the symptoms of the other and worsen complications.


Feature	Folate (B9) Deficiency	Vitamin B12 Deficiency
Primary Blood Disease	Megaloblastic Anemia	Megaloblastic Anemia
Key Neurological Symptoms	Generally absent, though mood/cognitive issues can occur.	Common, including nerve damage, memory loss, and balance issues.
Homocysteine	Elevated.	Elevated.
Methylmalonic Acid (MMA)	Normal.	Elevated.
Dietary Sources	Leafy greens, legumes, fortified grains, citrus.	Animal products (meat, dairy, eggs), fortified foods.
Storage in Body	Limited storage, requiring consistent dietary intake.	Large liver reserves, can take years to develop a deficiency.
Pregnancy Risk	High risk for neural tube defects.	Associated with a range of pregnancy complications.

It is vital to check both B12 and folate levels when diagnosing megaloblastic anemia. Treating folate deficiency alone when B12 is also low can correct the anemia but allow the neurological damage from B12 deficiency to progress unchecked.

Preventing Folate Deficiency

Prevention is the most effective strategy against folate deficiency. For most healthy adults, a balanced diet is sufficient. However, certain populations require extra caution.

For Women of Childbearing Age: All women who could become pregnant are advised to take 400 micrograms (mcg) of folic acid daily, in addition to dietary folate, to prevent NTDs.
For Pregnant Women: The daily requirement increases to 600 mcg, and supplementation is a standard part of prenatal care.
Dietary Sources: Emphasize folate-rich foods in your diet. Good sources include spinach, lentils, asparagus, broccoli, avocado, and fortified breakfast cereals.
Smart Cooking: Since folate is sensitive to heat, opt for steaming or microwaving vegetables over boiling to preserve nutrient content.

Conclusion

At its core, the main disease from deficiency of B9 folate is megaloblastic anemia, a serious blood disorder that impairs the production of healthy red blood cells. The deficiency's effects extend beyond this, particularly impacting fetal development and potentially contributing to heart disease and neuropsychiatric issues. Fortunately, this condition is easily preventable and treatable through dietary adjustments and folic acid supplementation. By understanding the importance of folate and ensuring adequate intake, individuals can safeguard their health and prevent the cascade of problems associated with this deficiency.

A Final Note

For more in-depth medical information on folate and other vitamins, consult resources like the National Institutes of Health. You can find detailed fact sheets on their Office of Dietary Supplements page, which is an authoritative resource on the topic.

Frequently Asked Questions

Folate is the form of vitamin B9 found naturally in foods. Folic acid is the synthetic, man-made form of B9 used in dietary supplements and fortified foods, which is more stable and better absorbed by the body.

Symptoms include fatigue, muscle weakness, pale skin, shortness of breath, irritability, and a sore or red tongue. Some people may also experience headaches or heart palpitations.

Individuals at high risk include pregnant women, people with chronic alcohol use disorder, those with malabsorption disorders like Crohn's or celiac disease, and people taking certain medications that interfere with folate absorption.

Yes, excessive folic acid intake from supplements can mask a vitamin B12 deficiency, potentially allowing nerve damage to progress undetected. It is important to have both B12 and folate levels checked by a doctor.

Excellent sources include leafy green vegetables like spinach and romaine lettuce, legumes (beans, lentils), asparagus, eggs, nuts, and fortified grains and cereals.

Since folate is a water-soluble and heat-sensitive vitamin, prolonged cooking, especially boiling, can significantly reduce its content in food. Steaming or microwaving can help preserve more of the nutrient.

Folate is crucial for early fetal development, especially in the first few weeks of pregnancy when the neural tube is forming. Insufficient folate during this time dramatically increases the risk of neural tube defects like spina bifida.