Indications of the vitamin B complex
There are no specific indications for the association of B complex vitamins as is. Each of the B vitamins has its own therapeutic indications and can be used independently of the others (see individual vitamin sheets). There is, however, an exception for vitamins B6, B9 and B12 which contribute to the same effects.
Also read : Vitamins : Functions and resources
Description of the vitamin B complex
The vitamin B complex refers to the set of 8 B vitamins, which includes the vitamin B1 (thiamine), the 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).
Sometimes very different chemical formulas, all these vitamins are water-soluble (soluble in water) and necessary for the proper functioning of the organism (see the table below).
|Vitamins||Main functions of B vitamins|
|B1||Carbohydrate metabolism, energy production, functioning of the nervous system.|
|B2||Energy production, carbohydrate, protein and lipid metabolism, vision, skin and mucous membrane health, activation of vitamins B6 and B9.|
|B3||Synthesis of sex hormones, metabolism of carbohydrates, proteins and lipids, production of red blood cells.|
|B5||Synthesis of hormones and neurotransmitters, nerve transmission, production of red blood cells, cell division, energy production, metabolism.|
|B6||Synthesis of proteins, hormones and neurotransmitters, production of red blood cells and transport of oxygen, functioning of the immune system, synthesis of DNA, regulation of blood sugar, synthesis of vitamin B3.|
|B8||Carbohydrate, lipid and protein metabolism, cell division.|
|B9||Cell division, DNA and RNA synthesis, protein metabolism, regulation of blood homocysteine levels (with B6 and B12), functioning of the nervous and immune systems, wound healing.|
|B12||Functioning of the nervous system, synthesis of DNA and RNA, 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 supplied by the body.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 table below).
|Recommended nutritional intake (ANR *) or sufficient (AS **) for adults|
|Vitamins (units)||Man||Women||Pregnancy||Feeding with milk|
(mg / day)
|1.2 *||1.1 *||1.4 *||1.4 *|
(mg / day)
|1.3 *||1.1 *||1.4 *||1.6 *|
|16 *||14 *||18 *||17 *|
(mg / day)
|5 **||5 **||6 **||7 **|
(mg / day)
1.7 * after 50 years
1.5 * after 50 years
|1.9 *||2 *|
(µg / day)
|400 *||400 *||600 *||500 *|
(µg / day)
|2.4 *||2.4 *||2.6 *||2.8 *|
* The ANR, or recommended nutritional intake, is the average daily nutritional intake allowing to meet the nutritional needs of almost all (97% to 98%) of healthy subjects belonging to a given age and sex group.
** SA, or sufficient intake, is the average daily intake recommended from data collected from apparently healthy people who appear to maintain adequate nutritional status. It is used when there is insufficient scientific data to establish the ANR1.
† 1 NS (niacin equivalent) = 1 mg niacin = 60 mg tryptophan.
‡ 1 FAE (equivalent of dietary folate) = 1 µg of dietary folate = 0.6 µg of folate provided by fortified foods or supplements taken with food = 0.5 µg of folate from supplements consumed alone.
|The ANR and AS values, presented in the table, were established by the medical authorities of Canada and the United States. Although based on scientific data, they may vary by country and are constantly updated.|
Food sources of B vitamins
The main dietary sources of B vitamins are brewer’s or edible yeast (torula), seeds, whole grains, nuts, as well as organ meats, pulses or greens, 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. Tryptophan for the body’s synthesis of vitamin B3 can be found in meats, poultry, fish and milk.
Vitamin B5: brewer’s yeast, nutritional yeast, veal liver, mushrooms, soy, peanuts, pecans, cashews, oatmeal, rye flour, buckwheat, sunflower seeds, lentils, red pepper, avocado.
Vitamin B6: brewer’s and food yeast (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, asparagus), fruit (orange), rice, brewer’s yeast, beef liver, beans, soy.
Vitamin B12: Vitamin B12 is only found in foods of animal origin – meats, organ meats, eggs, cheeses, fish and seafood.
|The vegans must compensate for their nutritional deficiency in vitamin B12 with supplements.|
B vitamin deficiency
In developed countries, B vitamin deficiencies have become rare. A diversified food is generally enough to meet the needs in each of them. However, certain health problems (alcoholism, anorexia, Crohn’s disease, for example) may require the use of food supplements.
|Main symptoms of vitamin B deficiency|
|Vitamins||Diseases and symptoms|
|B1||Beriberi: heart and neurological disorders|
|B2||Ariboflavinosis: burning and eye damage, inflammation of the skin and mucous membranes (lips, mouth, throat)|
|B3||Pellagre: tingling in the feet and hands, loss of appetite, fatigue, headache, dizziness, photosensitivity|
|B5||Insomnia, leg cramps, tingling or numbness in the feet and hands, tiredness, depression. digestive disorders, immune deficiency|
|B6||Irritability, depression, confusion, inflammation of the tongue and the commissure of the lips, seborrheic dermatitis|
|B8||Loss of appetite, dermatitis, tingling in the fingers, hair loss, depression, confusion|
|B9||Diarrhea, loss of appetite, weight loss, tongue inflammation, headache, heart palpitations, mood changes|
|B12||Fatigue, weakness, shortness of breath, nausea, constipation, flatulence, weight loss, tingling and numbness of the limbs, mood disorders, difficulty walking|
History of B vitamins
The notion of vitamins, essential substances to the organization and provided only by food, dates back to the beginning of the XXe century with the discovery of vitamin B1. In 1901, Dutch doctor Gerrit Grinjs associated beriberi, a disease prevalent in Asia, with a deficiency in an essential element contained in the husk of rice grains. This substance, thiamine (or vitamin B1), was isolated in 1911 and identified in 1934. The discovery of the others B vitamins continued through the 1930s, but the last, vitamin B12, was not identified until 1945.
Research on the vitamin B complex
- There are no studies on the effects of the combination of vitamins complex B, strictly speaking. Rather, research focuses on 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 disease. In the late 1990s and early 2000s, studies, mostly 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 and increased risk of coronary artery disease, myocardial infarction, or stroke.
- The discovery that vitamins B6, B9 and B12 interfered with the metabolism of homocysteine to reduce the plasma concentration has made it possible to consider their use to prevent cardiovascular diseases.
Clinical studies on this subject have come to conflicting results. In 2009, 2 meta-analyzes synthesizing this research concluded that vitamins B6, B9 and B12, taken in isolation, have no influence on the risk of developing heart disease, despite the decrease in homocysteine they induce. However, with regard to their combined use, opinions are divided. For some, it has no more preventive effect7 that isolated vitamins; for the others, there is an insignificant effect, but sufficient to encourage further research in this direction.
It is important to note 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 ranging from 0 mg to 50 mg and doses of vitamin B12 ranging 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. However, therapies based on vitamins B6, B9 and B12 used successfully to decrease the level of homocysteine 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 higher frequency of depressive symptoms. The importance of these vitamins would be different depending on the sex and age of the individuals. So, among teenage girls, it would be especially the rate of vitamins B2, B6 and B9 which would have an influence, while only vitamins B6 and B9 would be involved in the teenagers. In the adult population, the relationship between vitamin deficiency and depression relates to vitamin B9 for men and vitamin B12 for women. Finally, over the age of 65, taking supplements of vitamins B6 and B12 would decrease the incidence of periods of depression.
These results come from epidemiological studies. In 2008, research compared the effects of a vitamin B complex, multivitamin and placebo on 114 young adults. After 6 weeks, their psychological evaluation showed that B vitamins had no more effect than a placebo on reducing symptoms of depression.
- Strengthening cognitive functions. Some neurological and psychiatric disorders are associated with high homocysteine levels. On the other hand, epidemiological data indicate that elderly people with a high level of homocysteine or a deficiency of vitamins B6, B9 and B12 are more likely to suffer from Parkinson’s disease, Alzheimer’s disease or other forms of dementia20-24.
- However, no causal link has been established between the rate of homocysteine where the deficiency in the B6, B9, B12 complex, on the one hand, and the decline in cognitive functions, on the other hand. Homocysteine or B vitamins could be just indicators of poor nutrition caused by cognitive impairment.
- In any event, the use of vitamin supplements B6, B9 and B12 has been considered 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 the decline in cognitive abilities. The authors indicate, however, that additional studies should be undertaken over treatment periods longer than 3 years.
Some B vitamins may have side effects, sometimes serious, if taken in large quantities. Of maximum daily doses have been set for vitamins B3 B6 and B9 (see table below).
|Maximum tolerable intake (AMT *) for vitamins B3, B6 and B9|
|Age||B3 (niacin)||B6 (pyridoxine)||B9 (folate)|
|1 to 3 years||10 mg||30 mg||300 µg|
|4 to 8 years old||15 mg||40 mg||400 µg|
|From 9 to 13 years old||20 mg||60 mg||600 µg|
|From 14 to 18 years old||30 mg||80 mg||800 µg|
|Over 18||35 mg||100 mg||1000 µg|
* LMO is the highest daily amount that can be taken continuously as supplements or fortified foods without the likely risk of experiencing side effects.
|Taking large doses of vitamin B9 (from 400 µg), without vitamin B12, must be done under medical supervision because it can mask the symptoms of a deficiency in vitamin B12, which would cause irreversible neurological damage.|
- Taking vitamin B3 in its sustained release form (see the sheet on vitamin B3) is contraindicated in case of liver disease (including history), significant consumption of alcohol (more than 2 glasses per day), gout and ulcers of the digestive tract.
- Taking more than 100 mg per day of vitamin B3 as niacin frequently causes flushing (hot flushes) which can be accompanied by upset stomach, itching and migraines. In sensitive people, these effects can appear at doses of 35 mg per day, sometimes even lower.
- The niacin may increase blood sugar for people with diabetes.
- Peripheral neuropathy, usually reversible, has been reported at doses of vitamin B6 (pyridoxine) greater than 200 mg per day.
- Vitamin B9 doses greater than or equal to 5 mg per day can cause digestive upset.
- Large doses of vitamin B12 can worsen acne.
With plants or supplements
- Green tea and black tea decrease the absorption of vitamin B9 (folate).
- Combined with cholesterol-lowering treatments based on statins, large doses of vitamin B3 (greater than 1000 mg per day) could increase the risk of rhabdomyolysis (destruction of muscle cells) induced by statins.
- The niacin may increase the plasma concentration of anticonvulsants (carbamazepine, primidone).
- Isoniazid, used to treat tuberculosis, may decrease the rate of vitamin B3.
- Some drugs limit the absorption of vitamin B6 : isoniazid (tuberculosis), penicillamine (rheumatoid arthritis), theophylline (asthma), oral contraceptives, estrogens, hydralazine (hypertension), tetracycline (antibiotic), monoamine oxidase inhibitors (antidepressants).
- The vitamin B6 decreases the effects of levodopa (Parkinson’s disease) at doses above 50 mg per day.
- Medicines used to decrease stomach acid (ranitidine, omeprazole, etc.), anti-inflammatory drugs (aspirin), oral contraceptives, oral hypoglycemic drugs (metformin, phenformin), certain antibiotics (chloramphenicol, neomycin) decrease the absorption of vitamins B9 and B12.
- Oral contraceptives and phenytoin (anticonvulsant) may decrease the absorption of vitamin B9. In contrast, folate decreases the effectiveness of phenytoin.
- The folate reduces some side effects of methotrexate, an immunosuppressant.
- Colchicine (for gout) and cholestyramine (for cholesterol) can reduce the uptake of vitamin B12.