Vitamin B - Deficiency, Tips and Foods Rich in Vitamin B
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Indications of vitamin B complex

There are no specific indications for the combination of B-complex vitamins as such. Each of the B vitamins has its own therapeutic indications and can be used independently of the others (see the individual vitamin sheets). However, there is an exception for vitamins B6, B9, and B12 which contribute to the same effects.

Description of vitamin B complex

Vitamin B complex refers to all 8 B vitamins, which include vitamin B1 (thiamin), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine ), vitamin B8 (biotin), vitamin B9 (folic acid or folate) and vitamin B12 (cobalamin or cyanocobalamin).

With sometimes very different chemical formulas, all these vitamins are water-soluble (soluble in water) and necessary for the proper functioning of the body (see the table below).

VitaminsMain functions of B vitamins
B1Carbohydrate metabolism, energy production, and functioning of the nervous system.
B2Energy production, metabolism of carbohydrates, proteins, and lipids, vision, the health of the skin and mucous membranes, and activation of vitamins B6 and B9.
B3Synthesis of sex hormones, metabolism of carbohydrates, proteins, and lipids, and production of red blood cells.
B5Synthesis of hormones and neurotransmitters, nerve transmission, production of red blood cells, cell division, energy production, metabolism.
B6Synthesis of proteins, hormones, and neurotransmitters, production of red blood cells and transport of oxygen, functioning of the immune system, DNA synthesis, regulation of blood sugar, and synthesis of vitamin B3.
B8Carbohydrate, lipid and protein metabolism, cell division.
B9Cell division, DNA and RNA synthesis, protein metabolism, regulation of blood homocysteine ​​levels (with B6 and B12), functioning of the nervous and immune systems, and wound healing.
B12Functioning of the nervous system, DNA and RNA synthesis, production of red blood cells and oxygen transport, synthesis of S-adenosylmethionine (SAMe) with B6 and B9,

With the exception of vitamin B3 which is produced in small quantities by the body and vitamin B12 which is stored in certain organs, the other vitamins of the B complex must be provided by food on a regular basis, because they are not stored and excess food is eliminated in the urine. The daily needs are different for each of them (see the table below).

Recommended (ANR*) or sufficient (AS**) nutrient intake for adults

Vitamins (units)ManWomenPregnancyFeeding with milk

1.7* after age 50

1.5* after age 50

* The RDA, or recommended nutrient intake, is the average daily nutrient intake sufficient to meet the nutritional requirements of almost all (97% to 98%) healthy subjects belonging to a given age and sex group.

** The AI, or adequate intake, is the recommended average daily intake based on data collected from apparently healthy people who appear to maintain adequate nutritional status. It is used when the scientific data are insufficient to establish the ANR.

 1 NE (niacin equivalent) = 1 mg niacin = 60 mg tryptophan.
1 DFE (dietary folate equivalent) = 1 µg dietary folate = 0.6 µg folate from fortified foods or supplements taken with food = 0.5 µg folate from supplements taken alone.

The RDA and AI values, presented in the table, have been established by medical authorities in Canada and the United States. Although they are based on scientific data, they may vary from country to country and are constantly updated.

Food sources of B vitamins

The main dietary sources of B vitamins are brewer’s or food yeast (torula), seeds, whole grains, and nuts, as well as organ meats, dried or green vegetables, fruits, and dairy products.

Vitamin B1: brewer’s yeast, nutritional yeast (torula), pulses (dried peas, lentils, etc.), nuts, seeds, and whole grains.

Vitamin B2: organ meats (veal liver, kidney, heart), nuts, green vegetables, nutritional yeast, brewer’s yeast, wheat germ, wild rice, and mushrooms.

Vitamin B3: yeast, bran, peanuts with husk, wild rice, whole wheat products, almonds, barley, pulses. The tryptophan used in the synthesis of vitamin B3 by the body can be found in meats, poultry, fish, and milk.

Vitamin B5: brewer’s yeast, nutritional yeast, veal liver, mushrooms, soy, peanuts, pecans, cashews, rolled oats, rye flour, buckwheat, sunflower seeds, lentils, red pepper, avocado.

Vitamin B6: brewer’s and nutritional yeasts (torula), sunflower seeds, wheat germ, nuts, lentils, soy, lima beans, buckwheat flour, bananas, and avocados.

Vitamin B8: nutritional yeast (torula), whole grain products (bread), nuts, egg yolk, sardines, cauliflower, liver, banana, and mushrooms.

Vitamin B9: green vegetables (especially dark ones like spinach, broccoli, and asparagus), fruits (orange), rice, brewer’s yeast, beef liver, beans, and soy.

Vitamin B12: Vitamin B12 is only found in foods of animal origin – meats, organ meats, eggs, cheeses, fish, and seafood.

Vegans must compensate for their dietary vitamin B12 deficiency with supplements.

B vitamin deficiency

In developed countries, B vitamin deficiencies have become rare. A diversified diet is generally sufficient to meet the needs of each of them. Nevertheless, certain health problems (alcoholism, anorexia, Crohn’s disease, for example) may require the use of dietary supplements.

   Main Symptoms of B Vitamin Deficiency

VitaminsDiseases and symptoms
B1Beriberi: cardiac and neurological disorders
B2Ariboflavinosis: burning and lesions in the eyes, inflammation of the skin and mucous membranes (lips, mouth, throat)
B3Pellagra: tingling in the feet and hands, loss of appetite, fatigue, headaches, dizziness, photosensitivity
B5Insomnia, leg cramps, tingling or numbness in the feet and hands, fatigue, depression. digestive disorders, immune deficiency
B6Irritability, depression, confusion, inflammation of the tongue and corners of the lips, seborrheic dermatitis
B8Loss of appetite, dermatitis, tingling fingers, hair loss, depression, confusion
B9Diarrhea, loss of appetite, weight loss, inflammation of the tongue, headache, heart palpitations, mood swings
B12Fatigue, weakness, shortness of breath, nausea, constipation, flatulence, weight loss, tingling and numbness of the limbs, mood disorders, difficulty walking

History of B vitamins

The concept of vitamins, substances essential to the body and provided only by food, dates back to the beginning of the 20th  century with the discovery of vitamin B1. In 1901, the Dutch doctor Gerrit Grinjs associated beriberi, a disease rife in Asia, with a deficiency in an essential element contained in the envelope of rice grains. 

This substance, thiamine (or vitamin B1), will be isolated in 1911 and identified in 1934. The discovery of other B vitamins will continue throughout the 1930s, but the last, vitamin B12 will not be identified until 1945.

Vitamin B Complex Research

There are no studies on the effects of combining B-complex vitamins, per se. Instead, research focuses on the properties of each of the B vitamins. There is, however, an exception for the complex formed by vitamins B6, B9, and B12.

 Prevention of cardiovascular diseases. Towards the end of the 1990s and the beginning of the 2000s, studies, mainly epidemiological, revealed the existence of a new risk factor for cardiovascular disease. 

This is homocysteine, an amino acid circulating in the blood, the elevation of which is proportionally associated with the severity of atherosclerosis 2 and the increased risk of coronary heart disease, heart attack myocardium, or cerebrovascular accident (AVC).

The discovery that vitamins B6, B9, and B12 interfered with the metabolism of homocysteine ​​to reduce its plasma concentration made it possible to consider their use in preventing cardiovascular disease.

Clinical studies on this subject have come to contradictory results. In 2009, 2 meta-analyses summarizing this research concluded that vitamins B6, B9, and B12, taken in isolation, have no influence on the risk of developing cardiovascular disease, despite the decrease in homocysteine ​​they induce. 

However, regarding their combined use, opinions are divided. For some, it has no more preventive effect 7 than isolated vitamins; for others, there is a non-significant effect, but sufficient to encourage further research in this direction.

It is important to specify that the daily doses of vitamins B6, B9, and B12 used in the studies cited above are extremely variable. They range from 0.5 mg to 2.5 mg for vitamin B9, with doses of vitamin B6 varying from 0 mg to 50 mg and doses of vitamin B12 varying from 0 mg to 1 mg.

 Prevention of osteoporosis. Epidemiological studies show that there is a proportional relationship between the level of homocysteine ​​in the blood and the risk of fracture associated with osteoporosis, in people over 55 years of age. However, therapies based on vitamins B6, B9, and B12 used successfully to lower homocysteine ​​levels do not seem to have an effect on bone density or on the risk of fracture.

 Prevention of depression. Epidemiological data suggest a relationship between the deficiency of vitamins B2, B6, B9, and B12 and a greater frequency of depressive symptoms. The importance of these vitamins would be different depending on the sex and age of individuals. 

Thus, in adolescent girls, it would be above all the levels of vitamins B2, B6, and B9 that would have an influence, while only vitamins B6 and B9 would be involved in adolescents. In the adult population, the relationship between vitamin deficiency and depression concerns vitamin B9 in men and vitamin B12 in women. 

Finally, over the age of 65, taking vitamin B6 and B12 supplements would reduce the incidence of periods of depression.

These results come from epidemiological studies. In 2008, researchers compared the effects of a B vitamin complex, a multivitamin, and a placebo on 114 young adults. After 6 weeks, their psychological evaluation showed that the B vitamins had no more effect than a placebo on reducing symptoms of depression.

 Strengthening of cognitive functions. Some neurological and psychiatric disorders are associated with elevated homocysteine ​​levels. On the other hand, epidemiological data indicate that elderly people with a high level of homocysteine ​​or a deficiency in vitamins B6, B9, and B12 present a greater risk of suffering from Parkinson’s disease, Alzheimer’s disease, or other forms of dementia.

However, no causal link has been established between the level of homocysteine ​​or the deficiency in the B6, B9, and B12 complex, on the one hand, and the decline of cognitive functions, on the other hand. 

Homocysteine ​​or B vitamin levels might just be indicators of a poor diet caused by cognitive impairment.

Regardless, the use of vitamin B6, B9, and B12 supplements has been considered in order to prevent cognitive decline associated with aging. In 2010, a meta-analysis based on 9 clinical studies came to the conclusion that taking folic acid (vitamin B9) with or without the other B vitamins (in this case B6 and B12), had no preventive effect on cognitive decline. 

However, the authors indicate that additional studies should be undertaken over treatment periods longer than 3 years.



Some B vitamins can have side effects, sometimes serious if taken in too large amounts. Maximum daily doses have been set for vitamins B3 B6 and B9 (see table below).

Tolerable upper intake level (UL*) for vitamins B3, B6, and B9

AgeB3 (niacin)
B6 (pyridoxine)
B9 (folate)
From 1 to 3 years10 mg30 mg300 µg
From 4 to 8 years old15 mg40 mg400 µg
From 9 to 13 years old20 mg60 mg600 µg
From 14 to 18 years old30 mg80 mg800 µg
Over 1835 mg100 mg1 000 µg

Source : Institute of medecine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. The National Academic Press.

* The UL represents the highest daily amount that one can take continuously in the form of supplements or fortified foods without the likely risk of suffering adverse effects.

Daily intake of high doses of 
vitamin B9 (from 400 µg), without vitamin B12, must be done under 
medical supervision, as it can mask the symptoms of 
vitamin B12 deficiency, which would lead to irreversible neurological damage.


  • Taking vitamin B3 in its sustained-release form (see the sheet on vitamin B3) is contraindicated in cases of liver disease (including a history), heavy alcohol consumption (more than 2 glasses per day), gout, and ulcers of the digestive tract.

Side effects

  • Taking more than 100 mg per day of vitamin B3 in the form of niacin frequently causes flushing (hot flashes) which may be accompanied by stomach upset, itching, and migraines. In sensitive people, these effects may appear at doses of 35 mg per day, sometimes even lower.
  • Niacin may raise blood sugar in people with diabetes.
  • Cases of peripheral neuropathy, generally reversible, have been reported at doses of vitamin B6 (pyridoxine) greater than 200 mg per day.
  • Doses of vitamin B9 greater than or equal to 5 mg per day can cause digestive disorders.
  • High doses of vitamin B12 can make acne worse.


With plants or supplements

  • Green tea and black tea decrease the absorption of vitamin B9 (folate).

With medication

  • Combined with statin cholesterol-lowering treatments, high doses of vitamin B3 (greater than 1000 mg per day) may increase the risk of statin-induced rhabdomyolysis (destruction of muscle cells).
  • Niacin can increase the plasma concentration of anticonvulsants (carbamazepine, primidone).
  • Isoniazid, used to treat tuberculosis, can lower vitamin B3 levels.
  • Some drugs limit the absorption of vitamin B6: isoniazid (tuberculosis), penicillamine (rheumatoid arthritis), theophylline (asthma), oral contraceptives, estrogen, hydralazine (hypertension), tetracycline (antibiotic), monoamine oxidase inhibitors (antidepressants).
  • Vitamin B6 decreases the effects of levodopa (Parkinson’s disease) at doses greater than 50 mg per day.
  • Medicines used to lower stomach acid (ranitidine, omeprazole, etc.), anti-inflammatories (aspirin), oral contraceptives, oral hypoglycemic medicines (metformin, phenformin), certain antibiotics (chloramphenicol, neomycin) decrease the absorption of vitamins B9 and B12.
  • Oral contraceptives and phenytoin (anticonvulsants) can decrease the absorption of vitamin B9. On the other hand, folate decreases the effectiveness of phenytoin.
  • Folate reduces some side effects of methotrexate, an immunosuppressant.
  • Colchicine (against gout) and cholestyramine (against cholesterol) can reduce the absorption of vitamin B12.

On the shelves

  • Products sold under the name B-complex generally come in the form of tablets or capsules containing a combination of the 8 B vitamins in varying proportions.
  • In June 2010,, an independent American Laboratory, published the results of the analysis of 12 B-complex supplements, sold in the United States. Three of these products had a lower amount of folic acid than indicated on the label. Several of them provided an amount of vitamin B3 (niacin) above the tolerable upper intake level.

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