B vitamins form an essential family of micronutrients. Despite their fundamental role in numerous physiological mechanisms (energy metabolism, nervous system function, cell renewal), they are often misunderstood or confused. In this article, we offer a comprehensive overview: definition, role, food sources, potential deficiencies, and how to ensure adequate daily intake. This will help you better understand how these nutrients contribute to your overall health.
A vitamin is an organic substance that the body cannot synthesize (or in insufficient quantity) and must therefore obtain through food.
The so-called "B group" vitamins include several distinct molecules but with common characteristics: they are water-soluble vitamins, which means that they are not stored in large quantities in the body and that a regular intake is necessary.
They often function as enzymatic cofactors, that is, small molecules necessary for enzymes (the body's biochemical "machines") to function properly. For example, an active form of vitamin B1, thiamine pyrophosphate, serves as a cofactor for certain enzymes involved in carbohydrate metabolism.
The fact that it is water-soluble and not highly stored means that, in the event of insufficient intake or disturbed absorption, there is a risk of deficiency.
The term "B group" simply refers to the fact that initially, several vitamins discovered simultaneously shared certain characteristics (solubility, localization in grains, etc.). However, it is important to understand that it is not a single vitamin, but a group of at least eight distinct molecules, each with its own specific functions (even if there is some overlap).
This family approach also serves as a reminder that, in food, these vitamins are often present together, but their needs, deficiencies or effects can vary.
Main role : it is involved in carbohydrate metabolism (transformation of sugars), in energy production and in the proper functioning of the nervous system.
Technical term : "thiamine pyrophosphate" is the active form which serves as a cofactor for enzymes in the Krebs cycle (energy production cycle).
Food sources : whole grains, legumes, lean pork, seeds.
Signs of deficiency : fatigue, irritability, nervous disorders
Note : It is particularly important in cases of high carbohydrate intake (lots of sugars) or excessive alcohol consumption.
Main role : plays a key role in energy metabolism by participating in electron transfer, a crucial step in the production of ATP (cellular energy). It is also involved in maintaining tissues, particularly skin and mucous membranes (intestine, mouth, etc.), and in protecting against oxidative stress by helping to reduce free radicals, unstable molecules that can damage cells.
Technical term : flavin-adenine-dinucleotide (FAD) and flavin-mononucleotide (FMN) are active forms of riboflavin.
Food sources : dairy products, eggs, offal, green vegetables.
Signs of deficiency : chapped lips, cracks at the corners of the mouth, inflamed tongue.
Notes : often sufficient in a balanced diet, but may be deficient in very restrictive diets.
Primary role : In the body, it is converted into two major coenzymes: NAD⁺ (nicotinamide adenine dinucleotide) and NADP⁺ (its phosphorylated version). These coenzymes act as electron carriers, essential for redox reactions, that is, for energy exchange within cells. Specifically, they enable energy production, DNA repair, and support normal cellular function.
Food sources : meat, fish, poultry, brewer's yeast, fortified cereals.
Signs of deficiency : pellagra (which manifests itself through the triad "diarrhea, dermatitis, dementia") is the extreme form.
Note : The body can synthesize a small amount of niacin from tryptophan , an essential amino acid, but this is insufficient to meet daily requirements. A balanced diet is therefore essential.
Primary role : It is a precursor of coenzyme A (CoA), an essential molecule that acts as a "biochemical adaptor" to convert nutrients into energy. CoA is involved in the metabolism of lipids, carbohydrates, and proteins, enabling their transformation into compounds usable by cells. It is also essential for the synthesis of fatty acids, components of cell membranes and hormones.
Food sources : very widespread: meat, eggs, cereals, vegetables.
Signs of deficiency : Vitamin B5 deficiency is rare and manifests as a burning sensation in the feet. Insufficient intake can cause fatigue, headaches, insomnia, and tingling.
Note : As part of a varied diet, vitamin B5 intake is generally sufficient, making deficiencies very rare.
Main role : involved in amino acid metabolism, neurotransmitter synthesis (e.g., serotonin, GABA), immune function.
Technical term : pyridoxal-5-phosphate (PLP) is the active form.
Food sources : meat, fish, banana, legumes, whole grains.
Signs of deficiency : mild anemia, neurological disorders (tingling), irritability; more common in alcoholics or people taking certain medications.
Note : B6 is often cited for its role in mood and stress, but this should not be considered a treatment.
Main role : participates in fatty acid metabolism (transformation and use of fats), and in gluconeogenesis, a process by which the body produces glucose from non-carbohydrate sources (e.g., amino acids, fatty acids). It also plays an important role in tissue renewal, which explains its involvement in the health of skin, hair, and nails.
Food sources : egg yolk, liver, dried fruit, whole grains.
Signs of deficiency : deficiencies are exceptional, but when they occur, they can manifest as hair loss , dry or irritated skin , or mild neurological disorders (fatigue, drowsiness).
Note : Biotin supplements are often recommended for hair/nails, but effectiveness varies from person to person.
Primary role : essential in DNA synthesis (our genetic material), cell division (the process by which cells multiply), and cell renewal, particularly in rapidly renewing tissues such as skin and mucous membranes. It is crucial during pregnancy, as it participates in the closure of the neural tube in the fetus, a key stage in the development of the nervous system. A deficiency during this period increases the risk of birth defects, hence the importance of vitamin B9 supplementation, which is recommended as soon as a pregnancy is planned.
Technical term : 5-methyltetrahydrofolate (5-MTHF) is the active circulating form.
Food sources : green vegetables (spinach, broccoli), legumes, fortified cereals.
Signs of deficiency : macrocytic anemia (large red blood cells), increased risk of neural tube defects in the fetus.
Note : In France, ANSES recommends special attention during pregnancy.
Primary role : essential for the formation of red blood cells, the cells responsible for transporting oxygen in the blood. It also plays a major role in the functioning of the nervous system, notably by participating in the synthesis of myelin, an insulating sheath that surrounds nerve fibers and allows for the rapid transmission of nerve impulses. Without myelin, nerve signals are slowed down or even blocked.
Food sources : exclusively animal: meat, eggs, dairy products.
Signs of deficiency : A deficiency can lead to megaloblastic anemia, a form of anemia where red blood cells become too large and less effective. It can also cause peripheral neuropathy: tingling, numbness, burning sensations, and loss of sensation, particularly in the extremities (hands, feet). In more advanced stages, this can progress to cognitive impairment (memory problems, difficulty concentrating), especially in older adults.
Note : Strict vegans/vegetarians and the elderly are particularly at risk.
Several factors can lead to insufficient intake or misuse of B vitamins:
It is therefore important to consider not only food intake but also digestive status and absorption.
The basic rule: consume foods rich in B vitamins regularly. Here are some key points:
| Vitamin | Main sources | Things to watch out for at… |
|---|---|---|
| B1 | Whole grains, legumes, pork | High-sugar diet + alcohol |
| B2 | Dairy products, eggs, offal | strict vegan diet |
| B3 | Meat, fish, yeast | Low intake of animal protein |
| B5 | Varied foods | Rarely deficient |
| B6 | Meat, bananas, legumes | Alcoholism, certain medications |
| B7 | Egg yolk, dried fruit | prolonged parenteral nutrition |
| B9 | Green vegetables, legumes | Pregnant woman, low-vegetarian diet |
| B12 | Meat, animal products | Vegan, senior citizen |
Although nutrition remains the priority, in certain situations supplementation may be considered under medical supervision.
B vitamins are often offered as a "B complex" (containing several B vitamins) or individually (e.g., B12 alone). It's important to check the dosage, the form (e.g., B12: methylcobalamin, adenosylcobalamin), and the duration of treatment.
Conclusion
B vitamins are a cornerstone of nutritional health that is often underestimated. They play a central role in the body by being involved in fundamental mechanisms such as energy metabolism, cell division, proper functioning of the nervous system, and immune regulation.
To ensure you get enough nutrients: prioritize a varied diet rich in minimally processed foods, and, for those at risk, pay close attention to absorption and monitoring (especially with a healthcare professional). If you have any doubts or experience symptoms (persistent fatigue, neurological problems, anemia), a nutritional assessment is necessary.
By better understanding B vitamins, you are better equipped to support your long-term well-being.