Vitamin B9: Folic Acid and Folates – Benefits, Sources & Deficiency

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Often overlooked, vitamin B9 plays a key role in our daily health. From the formation of red blood cells to the protection of the nervous system, and even the healthy development of the fetus, its functions are multiple and essential.

In this comprehensive article, discover what distinguishes folates from folic acid, the best dietary sources, and how to preserve this vitamin during cooking.

We also explore the signs of deficiency, at-risk populations, and the often-ignored risks of excess. Are you pregnant? An athlete? Feeling tired for no reason? Vitamin B9 may concern you more closely than you think. A clear, accessible, and well-documented guide to better understand this essential vitamin. Adopt the right habits, avoid the pitfalls, and adjust your intake with full knowledge. A must-read to take care of your health… starting today.

TABLE OF CONTENTS

WHAT IS VITAMIN B9?

Vitamin B9, also known as folates in its natural form and folic acid in its synthetic form, is a water-soluble vitamin that belongs to the B-vitamin group. It is essential for maintaining balance in the body, as it plays a key role in functions such as DNA creation, cell multiplication, red blood cell production, and nervous system development.

Folates are naturally present in many foods, including leafy green vegetables, legumes, citrus fruits, and organ meats. Folic acid, on the other hand, is the synthetic form of vitamin B9, often used in supplements and fortified foods (such as certain cereals), because it is more stable and better absorbed by the body.

This vitamin is particularly important during periods of rapid growth, such as childhood, adolescence, and especially pregnancy. For pregnant women, it contributes to the proper closure of the fetal neural tube and helps prevent abnormalities such as spina bifida. This is why folic acid supplementation is generally recommended as soon as pregnancy is planned.

In addition, vitamin B9 helps regulate the metabolism of homocysteine, an amino acid whose excess is associated with an increased cardiovascular risk. It also plays a role in the production of neurotransmitters, making it an ally for mental well-being.

Since the body cannot store large amounts of vitamin B9, a regular intake through diet (or supplementation if necessary) is essential to avoid deficiency and maintain optimal health.

WHAT IS THE DIFFERENCE BETWEEN FOLATES AND FOLIC ACID?

Vitamin B9 exists in two main forms: folates, naturally present in food, and folic acid, a synthetic form used in supplementation and fortified products. While they share similar functions in the body, these two forms differ significantly in terms of structure, origin, stability, and metabolism.

Folates refer to a group of compounds derived from pteroylmonoglutamic acid, found in many foods such as leafy green vegetables, legumes, fruits (especially citrus), whole grains, and certain organ meats. However, these compounds are naturally unstable: they degrade easily when exposed to heat, light, or air. Their bioavailability—that is, their ability to be absorbed and used by the body—can also vary depending on the type of folate and interactions with other nutrients.

Folic acid, on the other hand, is a stable synthetic form of vitamin B9, used since the 1940s in dietary supplements and fortified products (breakfast cereals, flour, infant formulas, etc.). It is chemically simpler, which makes industrial production easier. Thanks to its greater stability during storage, cooking, and processing, it is often preferred in public health programs aimed at preventing deficiencies, particularly in pregnant women.

However, folic acid cannot act directly in the body. It must first be converted in the liver into 5-methyltetrahydrofolate, its active form (5-MTHF). This process is usually effective, but it depends on proper enzyme function. A portion of the population carries a genetic mutation in the MTHFR gene, which reduces their ability to convert folic acid into active folate. In such cases, supplementation with 5-MTHF directly (instead of folic acid) is sometimes recommended to bypass this metabolic limitation.

Excessive intake of folic acid, when not properly metabolized, can lead to the prolonged presence of inactive forms in the bloodstream. This accumulation may interfere with various biological mechanisms, mask a possible vitamin B12 deficiency, or, in the long term, be linked to certain conditions still under study, including cognitive or cancer-related risks.

In summary:

  • Folates are natural, less stable, but well recognized by the body.
  • Folic acid is synthetic, more stable, and better absorbed, but requires conversion to be active.
  • Their biological effectiveness may vary depending on the individual and context, which justifies special attention, particularly in the case of long-term supplementation.

WHAT ARE THE BENEFITS OF VITAMIN B9?

Vitamin B9, also known as folate in its natural form or folic acid in its synthetic form, is involved in a wide range of essential biological functions. It works deeply, with lasting effects on overall well-being, both at the cellular and mental levels. Here are the main benefits associated with this crucial vitamin.

1. A cornerstone of cell division and DNA synthesis.
Vitamin B9 plays an active role in the production of DNA and RNA, the carriers of genetic information. This role is essential in rapidly renewing cells, such as those in the blood, skin, intestines, or immune system. In case of deficiency, cell division becomes less efficient, which can lead to impaired tissue renewal and certain forms of anemia.

2. An essential nutrient during growth periods.
Vitamin B9 needs are particularly high during periods of rapid development, especially during pregnancy, childhood, and adolescence. In pregnant women, it plays a central role in the closure of the fetal neural tube, which will give rise to the spinal cord and brain. A deficiency at this critical time can cause severe congenital malformations such as spina bifida. This is why early supplementation with folic acid (400 µg/day) is systematically recommended as soon as pregnancy is planned.

3. An ally against anemia.
Vitamin B9 is necessary for the production of red blood cells. It helps prevent so-called megaloblastic anemias, characterized by red blood cells that are too large and inefficient. These blood disorders can cause chronic fatigue, shortness of breath, headaches, or excessive paleness. Adequate intake therefore helps maintain optimal oxygenation of tissues.

4. A key role in cardiovascular prevention.
B9 works by regulating homocysteine levels, an amino acid that, in excess, is a cardiovascular risk factor. Together with vitamins B6 and B12, it converts homocysteine into methionine, a beneficial amino acid. This regulation helps reduce the risk of strokes, heart attacks, and other heart problems.

5. Support for healthy brain function and emotional balance.
Vitamin B9 is also involved in the synthesis of neurotransmitters such as dopamine, serotonin, and norepinephrine, which are essential for emotional balance, memory, and concentration. A deficiency in folates has been linked to increased vulnerability to mood disorders, particularly depression, especially in older populations.

6. Potential protection against certain cancers.

Thanks to its role in DNA repair, vitamin B9 may also have a protective effect against the development of certain cancers, particularly colorectal cancer. However, research on this topic is still ongoing, and effects vary depending on dosage, form (folate or folic acid), and individual profile.

In summary, vitamin B9 contributes to:

  • Cell growth and renewal;
  • Protecting the fetus against birth development defects;
  • Stimulating red blood cell production, reducing the risk of anemia;
  • Regulating homocysteine levels;
  • Supporting the nervous system and mood;
  • And potentially, preventing certain cancers.

A varied diet, supplemented if necessary with the right supplementation, allows you to fully benefit from the advantages of this essential yet often overlooked vitamin.

WHICH FOODS ARE RICH IN VITAMIN B9?

Present in food in the form of folates, vitamin B9 is naturally abundant in many sources, mainly plant-based. However, its sensitivity to heat, oxygen, and light makes its preservation and preparation particularly important to maintain its benefits.

Leafy green vegetables: an essential source.

Among the foods richest in folates, dark green leafy vegetables top the list. Spinach, romaine lettuce, kale, arugula, chard, or turnip greens: the deeper the color, the higher the vitamin B9 content tends to be. Eating them raw or lightly cooked is best, as cooking can cause a significant loss of micronutrients.

Legumes: rich, affordable, and filling.

Chickpeas, lentils, red beans, fava beans, or split peas are excellent sources of both folates and plant-based protein. Well integrated into a balanced diet, they are particularly suitable for vegetarian or vegan diets. To preserve as many nutrients as possible, cook them just enough without overcooking.

Fresh fruits: a valuable complementary source.

Citrus fruits such as oranges, grapefruits, and lemons naturally provide vitamin B9. Strawberries, kiwis, avocados, and even bananas also contain it. For maximum benefit, it is best to consume them whole, unprocessed, and preferably raw.

Whole grains: a stable and accessible source.

Brown rice, whole-grain pasta, multigrain bread, and wheat germ naturally contain folates, particularly when they are minimally refined. In some countries, certain flours are fortified with folic acid to prevent deficiencies in women of childbearing age — this is not systematic in Europe, where such fortification remains debated.

Organ meats: very rich but to be consumed in moderation.

Liver, particularly poultry liver, is one of the foods most dense in vitamin B9. However, due to its high vitamin A content, it is best consumed sparingly, especially during pregnancy.

Other useful sources.

Other foods that provide smaller amounts include eggs, certain aged cheeses, nuts (almonds, walnuts, hazelnuts), seeds (sunflower, flax, sesame), as well as nutritional or brewer’s yeast, often valued for its richness in B vitamins.

And fortified products?

Some plant-based drinks, breakfast cereals, or nutrition bars are enriched with folic acid. This type of fortification is mainly aimed at meeting the increased needs of certain populations, such as pregnant women or seniors. However, within a varied diet, these products are not essential.

Adopting a diet based on whole, fresh, and minimally processed foods is the best way to ensure an optimal intake of vitamin B9. Varying plant sources, favoring gentle cooking methods, and regularly including leafy greens and legumes make it easy to meet daily requirements.

HOW TO PRESERVE VITAMIN B9 DURING COOKING?

Vitamin B9, naturally present in foods in the form of folates, is particularly unstable. It can degrade quickly when exposed to heat, light, or even prolonged contact with air. This fragility makes its preservation tricky, especially when cooking fresh produce. Without precautions, up to 70% of vitamin B9 can be lost during cooking.

A water-soluble vitamin easily washed out.

Unlike fat-soluble vitamins that dissolve in fats, vitamin B9 dissolves in water. This means that when vegetables are cooked in large amounts of water — for example by boiling — a significant portion of the folates leach into the cooking water. If that water is then discarded, as in filtered soups or drained vegetables, the losses are considerable.

Gentle cooking methods to prioritize.

To minimize this loss, it is best to use cooking methods that better preserve vitamins. Steaming, in particular, is an excellent option: it heats food without direct contact with water, and at a more moderate temperature. Braising or lightly sautéing with a small amount of fat can also be beneficial, provided the cooking time is not too long.

Raw = maximum preservation.

When possible, eating foods raw remains the best way to preserve all the folates. Salads made with spinach, lamb’s lettuce, arugula, or lettuce, for example, retain all their vitamins. Fruits rich in B9, such as oranges, kiwis, or avocados, are often consumed raw, which is ideal.

Quick preparation and thoughtful storage.

Beyond cooking, preparation also plays a role. Cutting vegetables too far in advance or leaving them at room temperature exposed to light encourages oxidation of vitamin B9. It is therefore recommended to cut foods just before cooking or serving, store them in the fridge in opaque, sealed containers, and avoid soaking them in water for too long.

Don’t throw away cooking water!

When boiling is unavoidable — for example with lentils or chickpeas — it can be useful to reuse the cooking water, provided it is not too salty. It can serve as a base for sauces, soups, or purées, thereby restoring part of the micronutrients that were transferred.

Watch out for industrial processing.

Processes such as pasteurization, sterilization, or repeated microwaving of prepared meals often lead to a significant reduction in vitamin B9 content. Cooking meals yourself from fresh products is therefore an excellent way to limit these losses and maintain nutritional quality.

Key tips to preserve vitamin B9:

  • Steam cook to limit losses;
  • Eat vegetables raw whenever possible;
  • Avoid long boiling, especially if the broth is discarded;
  • Prepare foods just before cooking or eating;
  • Limit exposure to light and air;
  • Reuse cooking water if it is consumable.

Adopting these simple habits in daily cooking allows you to fully benefit from vitamin B9 intake without relying excessively on supplements. Proper cooking techniques thus become a true tool for preventive health.

WHAT ARE THE SYMPTOMS OF A VITAMIN B9 DEFICIENCY?

A deficiency in vitamin B9 can have many repercussions on health, due to its key role in DNA production, red blood cell formation, and proper functioning of the nervous system. When it is lacking over time, both physical and psychological signs may appear, sometimes subtly.

Persistent fatigue linked to anemia.

One of the most frequent manifestations is a specific form of anemia called megaloblastic anemia. It is characterized by abnormally large red blood cells that are inefficient at carrying oxygen. This imbalance results from slowed cell renewal, due to insufficient vitamin B9 to allow proper DNA replication. The outcome: constant fatigue, shortness of breath, pale complexion, headaches, or palpitations.

Notable digestive disorders.

The digestive system, particularly the rapidly renewing intestinal lining, is also affected. Deficiency can lead to loss of appetite, nausea after meals, slowed digestion, or even bouts of diarrhea. This alteration can impair nutrient absorption and worsen folate deficiency.

Visible signs in the mouth.

Oral symptoms can also occur: a red, painful tongue, frequent canker sores, or a burning sensation in the mouth. These issues reflect slowed regeneration of oral mucosal cells.

An impact on emotional balance and memory.

Vitamin B9 plays an indirect role in the production of neurotransmitters such as serotonin and dopamine, which influence mood. Prolonged deficiency can therefore contribute to depressive mood, irritability, or even mild cognitive disorders, especially in older individuals or those already psychologically fragile.

Increased danger during pregnancy.

In pregnant women, insufficient intake from the very first weeks of gestation can have serious consequences on fetal development, particularly on the formation of the nervous system. A deficiency in B9 significantly increases the risk of neural tube defects, such as spina bifida. This is why early supplementation is systematically recommended.

A sometimes silent deficiency.

Some people may suffer from a lack of vitamin B9 without realizing it. This is particularly the case for seniors, individuals with inflammatory bowel disease, heavy alcohol consumers, smokers, or those taking certain medications (antiepileptics, immunosuppressants). In these individuals, symptoms develop slowly and may be mistaken for other disorders.

The most common signs of vitamin B9 deficiency:

  • Unexplained fatigue, paleness, and shortness of breath;
  • Digestive problems (loss of appetite, nausea, diarrhea);
  • Oral inflammations (red tongue, canker sores, hypersensitivity);
  • Difficulty concentrating or mood disorders;
  • Risk of malformations in cases of pregnancy without supplementation.

A diagnosis is based on a blood test (serum and intra-erythrocyte folates). Appropriate supplementation, combined with dietary improvements, usually helps correct the situation quickly.

WHAT ARE THE CAUSES OF A VITAMIN B9 DEFICIENCY?

A vitamin B9 deficiency can result from multiple factors. It generally occurs when there is an imbalance between intake, the body’s needs, and its ability to absorb or use this vitamin. Understanding the possible causes of this deficiency is essential for effective prevention.

1. An unbalanced or nutrient-depleted diet

The most common cause is a diet low in fresh plant-based foods. Folates are mainly found in green vegetables, legumes, fruits, whole grains, and organ meats. A diet too rich in ultra-processed or refined products can therefore lead to insufficient intake. In addition, certain cooking methods such as prolonged boiling or repeated reheating significantly reduce vitamin B9 content in foods.

2. Chronic digestive disorders

Certain intestinal conditions reduce the body’s ability to properly absorb folates. This is particularly the case with:

  • Crohn’s disease or ulcerative colitis;
  • Untreated celiac disease (gluten intolerance);
  • Other conditions that damage the intestinal lining, especially in the jejunum, the main site of vitamin B9 absorption.

3. Excessive alcohol consumption

Alcohol negatively affects the absorption, use, and retention of vitamin B9. It reduces intestinal absorption, increases urinary elimination, and disrupts liver functions involved in folate metabolism. This factor is particularly concerning for people with already deficient diets.

4. The influence of certain medications

Several medications can reduce the availability or effectiveness of vitamin B9:

  • Antiepileptics such as phenytoin or valproate;
  • Certain antibiotics such as trimethoprim or sulfadiazine;
  • Methotrexate and other anticancer or immunosuppressive treatments;
  • Certain oral contraceptives, when taken for long periods.

5. Increased needs at certain life stages

Some physiological situations increase vitamin B9 requirements to the point where diet alone is not enough:

  • Pregnancy (particularly in early gestation);
  • Breastfeeding;
  • Periods of rapid growth (childhood, adolescence);
  • Aging, which can affect both dietary intake and intestinal absorption efficiency.

6. Genetic factors

Finally, some individuals have a mutation of the MTHFR gene, which codes for an enzyme essential to folate activation. This genetic variation can reduce the efficiency of vitamin B9 metabolism, thereby increasing the need for the active form (5-MTHF).

IN SUMMARY: THE MAIN CAUSES OF A VITAMIN B9 DEFICIENCY

  • Insufficient dietary intake or inadequate cooking methods;
  • Chronic digestive disorders affecting absorption;
  • Chronic alcoholism;
  • Medications disrupting folate metabolism;
  • Periods of increased needs (pregnancy, growth, breastfeeding, aging);
  • Genetic factors linked to reduced activation of vitamin B9.

Adjusting the diet, accounting for individual needs, and considering targeted supplementation when necessary (always under medical supervision) can effectively prevent this type of deficiency.

HOW TO DIAGNOSE A VITAMIN B9 DEFICIENCY?

Detecting a vitamin B9 deficiency requires combining the analysis of clinical symptoms with targeted laboratory tests. Essential for DNA and blood cell production, vitamin B9 deficiency can lead to a series of more or less visible symptoms that should be assessed as a whole.

When a healthcare professional suspects a folate deficiency, a blood test may be prescribed to precisely measure the levels of vitamin B9 in the body. Two types of analyses are commonly used and complement each other:

Serum folate measurement

This test evaluates the concentration of folates in plasma (or serum), i.e., the liquid part of the blood. It reflects recent dietary intake. A level below 4 ng/mL (or 10 nmol/L) is generally considered indicative of a deficiency. These figures may vary slightly depending on the analytical method or testing center.

It should be noted that this measurement is sensitive to daily dietary variations, which limits its reliability if interpreted alone.

Red blood cell folate measurement

This more specific test measures the amount of folates inside red blood cells (erythrocytes). It provides a more stable picture over time, since red blood cells incorporate folates during their formation in the bone marrow.

This measurement reflects vitamin B9 availability in the body over several weeks. A level below 140 ng/mL (or 317 nmol/L) in erythrocytes suggests an established deficiency, even if serum levels are still normal.

Other complementary tests

In addition to these dosages, other biological markers can be tested to refine the diagnosis:

  • A complete blood count (CBC) may reveal macrocytic anemia, characterized by abnormally large red blood cells, typical of folate (or vitamin B12) deficiency.
  • Homocysteine levels, an amino acid dependent on vitamins B9, B6, and B12, may be measured. Elevated levels strengthen the suspicion of deficiency.
  • Vitamin B12 measurement is recommended, as deficiencies in both can coexist or mask each other.

It is also essential to consider the patient’s individual context. For example, a person on medication affecting folate metabolism or suffering from chronic digestive disorders will be at higher risk. Similarly, a pregnant woman, even without apparent symptoms, may have increased needs justifying preventive screening.

In some cases, a single blood test may not be enough. Monitoring changes in folate levels after dietary adjustments or supplementation can help assess treatment effectiveness and confirm the diagnosis.

In summary: how to diagnose a vitamin B9 deficiency?

  • Measure folate levels in both serum and red blood cells;
  • Complement with homocysteine and CBC analysis;
  • Interpret results in light of the patient’s profile, medical history, and current treatments.

A precise diagnosis then allows for an appropriate treatment plan, ranging from dietary adjustments to targeted supplementation, in order to restore optimal levels of this essential vitamin.

VITAMIN B9 AND PREGNANCY.

Pregnancy is one of the life stages where micronutrient requirements increase significantly, especially for vitamin B9, also known as folic acid in its synthetic form. This vitamin plays a crucial role in fetal development, particularly during the very first weeks, often before pregnancy is even known. That’s why sufficient intake should be anticipated, ideally starting at the beginning of a conception project.

What is the fundamental role of vitamin B9 during pregnancy?

During the first month of pregnancy, the fetus undergoes extremely rapid development. One of the most critical processes of this period is the closure of the neural tube, which forms the basis of the central nervous system, including the brain and spinal cord. This closure generally occurs between the 21st and 28th day after conception, often before a pregnancy test is even taken.

A vitamin B9 deficiency during this decisive period may contribute to neural tube defects, such as spina bifida (incomplete closure of the spine) or anencephaly (partial or complete absence of the brain). These serious and irreversible conditions can sometimes lead to medical termination of pregnancy or require significant care after birth.

Beyond its preventive role in neurological development, vitamin B9 also contributes to the healthy growth of the placenta, the formation of the fetus’s blood cells, and the development of DNA in all its cells. It also supports maternal metabolism, which is already highly solicited, and helps regulate homocysteine, a cardiovascular risk factor.

Research also suggests that adequate vitamin B9 intake during pregnancy may reduce the risk of complications such as intrauterine growth restriction, heart defects, or developmental disorders after birth. While these links are still being studied, they highlight the importance of early and sufficient intake.

What folic acid intake is recommended for pregnant women?

Health authorities recommend systematic folic acid supplementation for all women planning a pregnancy. The generally advised dose is 400 micrograms per day. This supplement should ideally be started at least one month before conception and continued until the end of the first trimester, around the 10th to 12th week of pregnancy.

Why start so early? Because the time when vitamin B9 is most critical often precedes the awareness of pregnancy. Starting supplementation early ensures that the body has sufficient reserves from the very first days of embryonic development.

Increased needs in certain cases

There are specific situations where a higher amount of folic acid may be recommended:

  • In cases of a previous pregnancy with a neural tube defect;
  • In the presence of certain medical conditions (diabetes, epilepsy treated with specific medications);
  • For women carrying MTHFR gene mutations, which reduce the conversion of folic acid into its active form.

In such cases, the dose may be increased to 4 to 5 mg per day, under medical supervision. It is always advisable to seek the guidance of a doctor or specialist to assess individual needs.

Finally, it is recommended to maintain a diet rich in folates alongside supplementation, by regularly consuming leafy green vegetables, legumes, fresh fruits, and whole grains. However, diet alone is usually insufficient to meet the requirements during this critical period, hence the importance of supplementation.

EXCESS AND INTERACTIONS.

While vitamin B9 is essential for the balance of many biological processes, it is also important to consider whether an excessive intake, particularly in its synthetic form (folic acid), may pose risks. Unlike natural folates, which the body regulates more easily, folic acid from supplements and fortified foods can, in high doses or over long periods, create issues when it exceeds the body’s metabolic capacity.

Can you consume too much vitamin B9?

In theory, an excess of vitamin B9 from food alone is unlikely. Folates found in vegetables, legumes, or fruits are naturally balanced and their absorption is self-regulated by the body. The main risk comes from folic acid supplementation, which can accumulate in the blood if taken in doses that are too high or for too long.

One major concern is that excess folic acid can mask a vitamin B12 deficiency. Both vitamins work together in the production of red blood cells. If someone is deficient in B12 but takes high doses of folic acid, the anemia may appear improved, creating a false sense of security. Meanwhile, the untreated B12 deficiency can continue silently, potentially leading to irreversible neurological damage if not diagnosed and corrected in time.

What are the risks of excessive folic acid supplementation?

When consumed in very high amounts, unmetabolized folic acid can accumulate in the bloodstream, indicating that the body has not converted all of it into its active form (5-MTHF) due to limited enzymatic capacity. This accumulation has raised concerns in research about possible long-term effects.

Some studies suggest that excessive folic acid may interfere with the immune system, particularly the activity of natural killer (NK) cells, which play a role in tumor defense. This disruption could theoretically increase the risk of certain cancers, especially colorectal cancer, although evidence remains inconclusive.

High levels of unmetabolized folic acid have also been linked to potential cognitive issues in older adults, such as memory impairment or slower reasoning, particularly when combined with a vitamin B12 deficiency.

During pregnancy, excessive and unsupervised supplementation may interfere with neurological or immune development of the fetus. This is why, although folic acid is recommended before and during pregnancy, the dosage must remain within recommended limits unless otherwise prescribed by a doctor.

Important: folic acid may also interact with certain medications, particularly anticancer or immunosuppressive drugs that act by inhibiting DNA synthesis. In such cases, inappropriate supplementation may reduce treatment effectiveness or increase side effects.

Key takeaways: potential risks of vitamin B9 excess

  • Masking vitamin B12 deficiency, which can lead to nervous system damage;
  • Increased presence of unmetabolized folic acid in the blood, with unclear long-term effects;
  • Possible disruption of cognitive or immune functions, especially in sensitive populations;
  • Drug interactions requiring medical supervision.

For these reasons, it is always best to respect the recommended doses and consult a healthcare professional before starting prolonged supplementation.

COACH'S TIPS

At QNT, you’ll find vitamin B9 in Daily Vitamin, in Multivitamin Men’s, and in Multivitamin Women’s.

Yves Bondroit coach for QNT

Posted in: Our tips

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