B vitamins are a group of nutrients that play several important roles in your body.
Most people get the recommended amounts of these vitamins through diet alone, because they are found in a wide variety of foods.
However, factors such as age, pregnancy, dietary choices, medical conditions, genetics, medications, and alcohol consumption increase the body's demand for vitamins.
In these circumstances, supplementation with B vitamins may be necessary.
Nutritional supplements containing all eight B vitamins are called B complex vitamins.
Here are the health benefits of B complex vitamins, along with dosage recommendations and potential side effects.
Table of contents
What are B complex vitamins?
B complex supplements typically contain all eight B vitamins in a single tablet.
B vitamins are water soluble, which means your body doesn't store them. For this reason, your diet must provide it every day.
B vitamins have many important functions and are essential for maintaining good health.
B complex vitamins typically contain the following:
- B1 (thiamine): Thiamine plays an essential role in metabolism by helping convert nutrients into energy. The richest food sources include pork, sunflower seeds, and wheat germ (1).
- B2 (riboflavin): Riboflavin helps convert food into energy and also acts as an antioxidant. Foods richest in riboflavin include organ meats, beef, and mushrooms (2).
- B3 (niacin): Niacin plays a role in cell signaling, metabolism, and DNA production and repair. Chicken, tuna, and lentils are food sources (3).
- B5 (pantothenic acid): Like other B vitamins, pantothenic acid helps your body get energy from food and is also involved in the production of hormones and cholesterol. Liver, fish, yogurt and avocado are good sources (4).
- B6 (pyridoxine): Pyridoxine is involved in amino acid metabolism, red blood cell production and the creation of neurotransmitters. Foods richest in this vitamin include chickpeas, salmon and potatoes (5).
- B7 (biotin): Biotin is essential for carbohydrate and fat metabolism and regulates gene expression. Yeast, eggs, salmon, cheese, and liver are among the best sources of biotin (6).
- B9 (folate): Folate is necessary for cell growth, amino acid metabolism, formation of red and white blood cells, and proper cell division. It can be found in foods like leafy greens, liver, and beans or in supplements like folic acid (7).
- B12 (cobalamin): Perhaps the best known of all the B vitamins, vitamin B12 is essential for neurological function, DNA production and red blood cell development. B12 is found naturally in animal sources such as meat, eggs, seafood, and dairy (8).
Although these vitamins share certain characteristics, they all have unique functions and are needed in different amounts.
Summary B complex supplements typically contain all eight B vitamins in a single tablet.
Who should take a B-complex vitamin?
Since many foods contain B vitamins, you are unlikely to experience a deficiency as long as you eat a balanced diet.
However, certain circumstances increase the need for B vitamins, making supplements necessary.
Pregnant or breastfeeding women
During pregnancy, the demand for B vitamins, especially vitamin B12 and folic acid, increases to support fetal development (9).
In pregnant or breastfeeding women, especially those following a vegetarian or vegan diet, vitamin B supplementation is essential.
Vitamin B12 or folic acid deficiency in pregnant or lactating women can lead to serious neurological damage or birth defects in the fetus or infant (10).
The elders
As you age, your ability to absorb vitamin B12 decreases and your appetite decreases, making it difficult for some people to get enough B12 through diet alone.
The body's ability to release vitamin B12 from food so that it can be absorbed depends on adequate amounts of stomach acid.
However, it is estimated that 10 to 30% of people over the age of 50 do not produce enough stomach acid to properly absorb vitamin B12 (11).
Vitamin B12 deficiency has been linked to increased rates of depression and mood disorders in older adults (12, 13).
Vitamin B6 and folate deficiencies are also common among older adults (14, 15).
Those with certain medical conditions
People with certain conditions such as celiac disease, cancer, Crohn's disease, alcoholism, hypothyroidism, and anorexia are more likely to develop nutritional deficiencies, including B vitamins (16, 17 , 18, 19, 20).
Additionally, the MTHFR genetic mutation can affect the way your body metabolizes folate and can lead to folate deficiency and other health problems (21).
Additionally, people who have undergone certain weight loss surgeries are also more likely to have a B vitamin deficiency (22).
In these circumstances, patients are often advised to take a vitamin B complex to correct or avoid deficiencies.
Vegetarians and vegans
Vitamin B12 is found naturally in animal products such as meat, dairy, eggs and seafood.
Vegans and severe vegetarians are at risk of developing vitamin B12 deficiency if they do not get enough of this vitamin through fortified foods or supplements (23).
A daily vitamin B-complex can help ensure that people who choose to follow a diet that eliminates animal products get enough of these essential nutrients.
People taking certain medications
Commonly prescribed medications can cause B vitamin deficiency.
For example, proton pump inhibitors, which reduce stomach acid, may reduce the absorption of vitamin B12, while metformin, a popular diabetes medication, may reduce vitamin B12 levels. and folate (24, 25).
Birth control pills can also deplete several B vitamins, including vitamins B6, B12, folate, and riboflavin (26).
Summary Pregnancy, medical conditions, surgeries, genetic mutations, medications, dietary restrictions and age can all affect how your body absorbs and uses B vitamins.
Health Benefits of Taking B Complex Vitamins
Although certain conditions require some people to take B-complex vitamins, research has shown that taking a B-complex supplement can be helpful even for people who don't need more.
May reduce stress and boost mood
B complex vitamins are often used to reduce fatigue and improve mood.
Some studies suggest that B-complex vitamins can lift your mood and improve your cognitive performance.
A 33-day study in 215 healthy men showed that treatment with a high-dose B-complex and mineral supplement improved overall mental health and stress, as well as cognitive test performance. (27).
Another study in young adults showed that supplementing with multivitamins containing high levels of B-complex vitamins for 90 days reduced stress and mental fatigue (28).
May reduce symptoms of anxiety or depression
Although B-complex vitamin supplements do not cure mental health problems, they can help alleviate symptoms of depression or anxiety.
A study of 60 adults with depression showed that treatment with a B-complex vitamin for 60 days resulted in significant improvement in symptoms of depression and anxiety compared to a placebo (29).
B vitamins may also improve treatment response when combined with antidepressants.
One study showed that supplementing patients with vitamin B12, B6, and folic acid resulted in an increased and long-lasting antidepressant response for a year, compared to a placebo (30).
Note that low blood levels of certain B vitamins, including B12, B6, and folate, have been linked to an increased risk of depression. This is why it is important to rule out nutritional deficiencies if you have symptoms of depression (31, 32).
Summary B-complex supplements may relieve stress, improve cognitive performance, and reduce symptoms of depression and anxiety, even in people without vitamin B deficiency.
Recommended dosage
Each B vitamin has a specific recommended daily amount that varies based on gender, age, and other variables such as pregnancy.
For women and men, the recommended daily intake of B vitamins is:
| Women | Men | |
| B1 (thiamin) | 1,1 mg | 1,2 mg |
| B2 (riboflavin) | 1,1 mg | 1,3 mg |
| B3 (niacin) | 14 mg | 16 mg |
| B5 (pantothenic acid) | 5 mg (RDI not established; sufficient intake, or AI, provided) | 5mg (AI) |
| B6 (pyridoxine) | 1,3 mg | 1,3 mg |
| B7 (biotin) | 30mcg (AI) | 30mcg (AI) |
| B9 (folate) | 400 mcg | 400 mcg |
| B12 (cobalamin) | 2,4 mcg | 2,4 mcg |
Potential side effects
Because B vitamins are water soluble, you are unlikely to consume an excessive amount through diet alone or by taking a B complex supplement as directed.
However, taking supplements containing excessively high and unnecessary amounts of B-complex vitamins could cause serious side effects.
High doses of supplemental B3 (niacin) can cause vomiting, high blood sugar, skin flushing, and even liver damage (34).
Additionally, high doses of B6 can cause nerve damage, sensitivity to light, and painful skin lesions (35).
Another side effect of B complex supplements is that it can turn urine yellow.
Although discolored urine can be shocking, it is not dangerous, just causing your body to get rid of excess vitamins that it cannot use.
If you must take a B-complex supplement, always choose reputable brands that want their products to be independently tested by organizations such as the US Pharmacopeial Convention (USP).
Summary Although taking B-complex supplements as prescribed is safe, consuming high doses of B3 or B6 can cause serious side effects.
The final result
Pregnant women, older adults, vegans, and people with certain health conditions may benefit from a B complex supplement.
Taking these supplements may also improve mood, cognitive function, and symptoms of depression.
Side effects are unlikely if you follow the recommended dosage, which varies depending on age, nutrient needs, gender and health.
If you are unsure whether taking a B complex supplement will benefit your health, consult your doctor to determine if it is the right choice for you.
