Vitamin B9, or folic acid (folates), is essential for cell renewal and fetal development during pregnancy. Discover the role of this vitamin, its recommended nutritional intake, the risks of deficiency or overdose, and its medical applications.

Definition: What is folic acid?

Vitamin B9, or folic acid, is one of the water-soluble vitamins (soluble in water). It is also called: “folate”; this term recalls that vitamin B9 is abundant in green leafy vegetables (spinach, salads, etc.).

What is folic acid used for?

• Vitamin B9 is involved in the metabolism of amino acids (protein components) and the production of DNA (which holds genetic information). It is, therefore, essential for rapidly renewing cells: red blood cells, white blood cells (involved in immune defenses), intestinal cells, skin cells, etc.
• In combination with vitamin B12, it helps reduce blood levels of homocysteine, a compound whose excess is considered to promote cardiovascular disease.
• It participates in the proper functioning of the nervous system and in producing certain neurotransmitters.
• Folate requirements increase during pregnancy in women due to the expansion of maternal tissues (blood, uterus, etc.). It is essential during the fourth week of fetal life for the closure of the neural tube, that is, for the proper formation of the fetus’s nervous system1.

Where to find folic acid in foods?

Animal lovers, dried nuts (hazelnuts, walnuts, almonds, etc.), green vegetables (spinach, salads, sorrel, etc.), certain cheeses, chestnuts, melon, and eggs are the richest sources of vitamin B9. Other fruits and vegetables provide it in smaller quantities.

Many breakfast cereals are fortified with B vitamins, including B9. Brewer’s yeast can supplement the intake.

Medical indications: what is the role of folic acid?

In anticipation of pregnancy

ANSES recommends supplementing 400 mg of folic acid at least two months before conception to prevent a deficiency that can have serious consequences for the fetus2. Indeed, a deficiency can cause deformations of the embryo’s neural tube (primitive nervous system).

Correction of vitamin B9 deficiency

In cases of proven deficiency, folic acid is prescribed in high doses to correct the symptoms, for example, 5 mg per day in an alcoholic patient4. In people who have undergone bariatric surgery (against obesity), vitamin B9 deficiency is observed in 20% of cases one year after the operation. For prevention, the surgeon or attending physician prescribes a multivitamin complex to take daily.

Maintaining intellectual faculties in the elderly

Some observational studies have found a link between low blood folate levels and lower intellectual performance or even increased risk of Alzheimer’s disease or dementia. However, the analysis of several intervention studies does not allow us to conclude that folic acid supplementation – alone or combined with vitamin  B6 and/or vitamin B12 – improves cognitive performance ( memory, concentration…)7. In a trial conducted in the United States, supplementation with vitamins B6, B9, and B12 for 18 months did not slow cognitive decline in patients with Alzheimer’s disease.

Cardiovascular prevention

Vitamin B9 and B12 deficiency increases the blood level of homocysteine, a compound whose excess is associated with an increased cardiovascular risk. In several intervention studies, researchers have shown that long-term supplementation with vitamins B9 and B12 (sometimes also vitamin B6) reduces homocysteine ​​levels but paradoxically does not reduce the number of cardiovascular events9. An analysis published in 2012, which reviewed 19 intervention studies on a total of 47,921 participants, concluded that supplementation with vitamins B6, B9, and B12 does not reduce cardiovascular risk, nor the occurrence of myocardial infarction, nor coronary artery disease (arteries of the heart), nor cardiovascular mortality, but nevertheless reduces the risk of stroke by 12%. The role of vitamin B9 cannot be fully clarified since it is systematically associated with vitamins B6 and B1210.

Folic acid deficiency

Why are we lacking in vitamin B9?

Certain factors can lead to folate deficiency:

• Pregnancy and breast-feeding: folate requirements increase;
• Alcoholism, malnutrition, and undernutrition: vitamin B9 consumption is insufficient;
• Poor absorption of folic acid caused by intestinal pathologies, persistent diarrhea, continuous stress, malabsorption disorder, etc.;
• Certain medications (e.g., medications for ulcerative colitis, diabetes, and high blood pressure) decrease the absorption of folates.