B Complex

B Vitamin Complex Supplements

May 2021

Which is the Best B Vitamins Supplement?

Check out our unbiased recommendation of the best products on the market using our rigorous methodology. We screen products for the right formulation, bioavailability, safety, and efficacy to bring you only the best supplements available in 2019.

B Vitamins – What You Need to Know

Poor nutrition and stress are the leading causes of B vitamin deficiency, which can lead to a variety of ailments such as chronic fatigue, heart palpitations, skin blemishes, and other health conditions.[1]

B vitamins support the body’s conversion of food into energy and help maintain a healthy nervous system and optimal brain function. If you are not getting sufficient amounts of these critical nutrients in your diet, you may want to consider taking a vitamin B complex, which is a dietary supplement that contains all eight B vitamins.

A vitamin B complex consists of these eight B vitamins: thiamine (Vitamin B1), riboflavin (Vitamin B2), niacin (Vitamin B3), pantothenic acid (Vitamin B5), pyridoxine (Vitamin B6), biotin (Vitamin B7), folate (Vitamin B9), and cobalamin (Vitamin B12). B vitamins help the body metabolize food, promote healthy DNA formation, repair and protect DNA, and promote healthy functioning of the central nervous system and muscles.

B vitamins are water-soluble, which means that the body gets rid of any excess through urination. Furthermore, most B vitamins are not stored in the body, so typically, a vitamin B complex can be taken along with a healthy diet without fear of taking too much. Since the body is constantly excreting these vitamins, it is important to continue to replenish them. As the B vitamins often work together to help the body perform various functions, it makes sense to take a vitamin B complex supplement that includes the recommended intakes of all eight nutrients.

Vitamin B deficiencies can lead to a wide array of health issues. For example, a lack of niacin (Vitamin B3) and thiamine (Vitamin B1) can cause neurological diseases, infertility, and impaired immune function. Many women of childbearing age don’t get enough folate (Vitamin B9), which reduces neural tube defects in babies.

A Closer Look at B Vitamins

Vitamin B complexes consist of eight B vitamins.[1] These water-soluble vitamins can be found in plants, animal proteins, and whole grains, as well as in dietary supplements. B vitamins are needed to metabolize food, to help maintain normal brain function and memory, and for normal blood cell production and nervous system function. They also play major roles in helping the body generate energy and construct and transform bioactive molecules.[2]

Unfortunately, many people do not get adequate amounts of B vitamins from their diet. Those who want to maintain optimal health must ensure that they are getting their B vitamins from daily nutrition or through a supplement.

A vitamin B complex is a dietary supplement that contains these eight B vitamins:

  • Thiamine (Vitamin B1)
  • Riboflavin (Vitamin B2)
  • Niacin (Vitamin B3)
  • Pantothenic acid (Vitamin B5)
  • Pyridoxine (Vitamin B6)
  • Biotin (Vitamin B7)
  • Folate (Vitamin B9)
  • Cobalamin (Vitamin B12)

Why B Vitamins are Crucial for Health

To maintain good health, it is essential that the body gets sufficient amounts of all eight B vitamins.[1, 2, 3] B vitamins do not contain energy, but they do help the body metabolize proteins, fats, and carbohydrates that are converted into fuel during digestion and absorption. At least one of the B vitamins is involved in each aspect of the essential catabolic process of generating energy within cells.[4] A deficiency of any of the B vitamins can negatively impact this process.

Thiamine, riboflavin, niacin, and pantothenic acid (Vitamin B1, Vitamin B2, Vitamin B3, and Vitamin B5) are essential coenzymes in mitochondrial aerobic respiration and cellular energy production. Each nutrient plays a direct role in the citric acid cycle and the electron transport chain, resulting in the formation of adenosine triphosphate (ATP), which is the energy currency of our cells.[5] Thiamine, biotin, and cobalamin (Vitamin B1, Vitamin B7, and Vitamin B12) also play key roles in the mitochondrial metabolism of glucose, fatty acids, and amino acids, thus contributing substrates to the citric acid cycle.[5]

Vitamin B9, also known as folate, is important for red blood cell formation and for healthy cell growth and function. Folate also plays a key role in building DNA, the complex molecules that form our genetic blueprint.[3, 7] Research has shown that Vitamin B9 is critical for fetal development during pregnancy. Folate (commonly known as folic acid in its synthetic form) can help prevent anemia during pregnancy and can reduce the risk of neural tube defects, such as spina bifida. Some research suggests that folate may reduce the risk of breast, cervical, pancreatic, and colon cancer, especially for people who consume alcohol.[6]

Niacin (Vitamin B3) helps the body convert food into energy, improves blood circulation, and promotes healthy cholesterol levels.[8] Pyridoxine (Vitamin B6) helps the body use protein, form red blood cells, and maintain brain function, while cobalamin (Vitamin B12) plays essential roles in red blood cell formation and nerve function.[3]

Internal Processing of B Vitamins

B vitamins are absorbed in the small intestines and then circulate through the bloodstream as food is broken down during digestion.[2] However, since most B vitamins are not stored in the body, people need to replenish their vitamin levels on a regular basis. The kidneys continuously regulate B vitamins, flushing out any excess vitamins during urination.

Cobalamin (Vitamin B12) and folate (Vitamin B9) are the only vitamins in this group that are stored in the liver. During digestion, stomach acid releases Vitamin B12 from protein. It then combines with gastric intrinsic factor before it is absorbed into the bloodstream. The human body stores several years’ worth of Vitamin B12 in the liver.[1, 10] Folate is absorbed in the small intestine, and more than 20 mg of this vitamin can be stored in the liver.[3, 7]

A maximum of 5 mg of thiamine (Vitamin B1) is absorbed through the small intestine. Only 30 mg of thiamine can be stored in skeletal muscles at a time and the body does not produce it. Smaller amounts of this vitamin are found in the brain, heart, liver, and kidneys. Additionally, thiamine has a short half-life, which is the amount of time it takes for 50% of the nutrient to be depleted from the bloodstream.[9]

Before pyridoxine (Vitamin B6) can be absorbed in the small intestine, a phosphate group is removed, allowing it to become a free molecule. Riboflavin (Vitamin B2) is also absorbed in the small intestine. The body can absorb about 27 mg of the nutrient and stores only small amounts in the liver, heart, and kidneys.[11]

Research has shown that biotin (Vitamin B7) and pantothenic acid (Vitamin B5) share the uptake process during absorption; only very small amounts of these vitamins are stored in the body.[12]

B Vitamins Deficiency

Stress and poor diet are the leading causes of deficiencies in B vitamins. For some B vitamins, such as pantothenic acid (Vitamin B5), deficiencies are rare. A lack of cobalamin (Vitamin B12), niacin (Vitamin B3), or thiamine (Vitamin B1), however, can cause serious health problems, including neurological illnesses.

Although most Americans get enough cobalamin (Vitamin B12), there are certain individuals who are more susceptible to deficiencies. People are more likely to have a Vitamin B12 deficiency if they have had an operation to remove a portion of the stomach, if they drink heavily, or if they have taken acid-reducing medication for long periods of time. Individuals who have atrophic gastritis (a condition that causes the stomach lining to thin), pernicious anemia (which makes it difficult for the body to absorb Vitamin B12), and those with immune system disorders such as Graves’ disease or lupus, are more vulnerable to a deficiency.[10]

A Vitamin B12 deficiency can cause permanent nerve damage, resulting in numbness and tingling in the hands and feet, as well as balance problems. Vitamin B12 deficiency has also been linked to anemia, depression, confusion, poor memory, and dementia. Furthermore, concerns have been raised about the apparent link between low levels of Vitamin B12 and an increase in homocysteine, an amino acid that can cause problems within the coronary arteries. Early symptoms of Vitamin B12 deficiency include fatigue, digestive problems, nausea, and loss of menstruation. Advanced symptoms include nerve pain, mental health disorders, infertility, impaired immune function, and anemia.

A lack of niacin (Vitamin B3) can cause pellagra, which can also occur if the body fails to absorb sufficient amounts of the amino acid tryptophan. Symptoms of this disease include digestive problems, mental impairment, and inflamed skin. The condition has been known to develop in people with HIV/AIDS, anorexia, or gastrointestinal diseases. Pellagra is also more likely to occur in connection with alcohol dependence.[13]

Serious isolated deficiencies of pyridoxine (Vitamin B6) are rare, but they can increase your level of homocysteine, and can potentially boost your risk of heart disease and stroke. Though rare, an insufficient level of Vitamin B6 is usually associated with low levels of other B vitamins such as folate (Vitamin B9) or cobalamin (Vitamin B12). Over time, a Vitamin B6 deficiency can cause biochemical changes.[14] People with Crohn’s disease, colitis, or celiac disease can develop a Vitamin B6 deficiency, as those illnesses may prevent the proper absorption of the vitamin. Long-term use of certain drugs, such as anti-epileptic medication, can also lead to Vitamin B6 deficiency.[14]

Wernicke-Korsakoff Syndrome is a brain disorder caused by a lack of thiamine (Vitamin B1). It causes problems with vision, coordination, and balance, and eventually leads to serious brain damage. The syndrome is often found in chronic alcoholics or those with health conditions that impact thiamine absorption.[15]

A pantothenic acid (Vitamin B5) deficiency is rare for those who eat a typical American diet, since the vitamin is found in a variety of animal proteins and plants. According to research, it has only been observed in severe cases of malnutrition. A deficiency of pantothenic acid can cause paresthesia, which is a tingling feeling in the skin.

Biotin (Vitamin B7) deficiency is rare among healthy people, as the daily intake requirement for this vitamin is small and it can be found in many types of food.[16] However, biotin deficiency can occur in people who consume raw egg whites over long periods of time. Raw egg whites contain high levels of avidin, a protein that tightly binds with biotin, preventing the body from absorbing it. In the rare cases when this occurs, biotin deficiency may lead to muscle pain, tongue swelling, or dermatitis.

Genetic Variation and Vitamin B Absorption

Small genetic differences among individuals can have a significant impact on their health and nutritional needs. A single nucleotide polymorphism (SNP) is a type of genetic variation that can impact how a person absorbs B vitamins.[17] Therefore, some people may need to intake more than the average recommended amounts of certain nutrients. SNPs are the most common type of genetic variation in a population. Researchers estimate that at least half of the U.S. population has an SNP that affects the absorption of at least one B vitamin.[18]

Individuals with a single nucleotide polymorphism on the vitamin-dependent enzyme methylenetetrahydrofolate reductase (MTHFR) are not able to properly process certain B vitamins, namely folate (Vitamin B9), cobalamin (Vitamin B12), and pyridoxine (Vitamin B6). These B vitamins are needed for proper neurological function. Severe deficiencies have been linked to an increased risk of neurodevelopmental disorders, psychiatric illnesses, and dementia. Polymorphisms of genes involved in B vitamin absorption, metabolism, and function, such as methylenetetrahydrofolate reductase (MTHFR), cystathionine β synthase (CβS), transcobalamin 2 receptor (TCN2) and methionine synthase reductase (MTRR), have also been linked to an increased incidence of psychiatric and cognitive disorders.[19]

People with these types of gene polymorphisms are advised to monitor their folate (Vitamin B9), cobalamin (Vitamin B12), and pyridoxine (Vitamin B6) levels. They are also encouraged to increase their intake of foods that are rich in B vitamins.

Food Sources

B vitamins can be found in many types of food, including whole grains and animal proteins.[7, 12] What a person needs to eat depends on which specific nutrient is needed. Notably, cobalamin (Vitamin B12) is the only B vitamin that is not found in any fruits or vegetables.

Foods that are particularly rich in riboflavin (Vitamin B2) include eggs, organ meats such as kidneys and liver, lean meats, and milk.[11] Riboflavin can also be found in green vegetables. To ensure that people get enough riboflavin and thiamine (Vitamin B1), the United States and many other countries fortify cereals and grains with these nutrients. Other sources of thiamine include whole grains, meat, and fish.

Individuals who want to increase their niacin (Vitamin B3) levels should consume lean meats, poultry, fish, organ meats, brewer’s yeast, peanuts, and peanut butter. Increases in pyridoxine (Vitamin B6) can be achieved by eating fortified and enriched grains, whole-grain products, poultry, fish, soybeans, nuts, peas, and bananas.[3, 14]

Folate (Vitamin B9) deficiency is fairly rare in the United States because this vitamin can be found in many food sources, including citrus fruits and juices, beans, nuts, seeds, liver, dark green leafy vegetables, and fortified breads and cereals.[7] However, girls and women between the ages of 14 and 30 often don’t get as much folate as they need, particularly during pregnancy. People who drink heavily and individuals with celiac disease or inflammatory bowel disease often have difficulty absorbing nutrients, and frequently do not absorb enough folate from dietary sources.

To get the recommended amount of biotin (Vitamin B7), cereal, legumes, nuts, egg yolks, milk, yeast, chocolate, pork, and organ meats (specifically liver and kidneys) should be eaten.

Pantothenic acid (Vitamin B5) is found in numerous foods, including animal proteins, eggs, milk, legumes and lentils, avocados, mushrooms, broccoli, kale, white and sweet potatoes, whole-grain cereals, and yeast.[12]

Cobalamin (Vitamin B12) is the only B vitamin that cannot be found in any plant sources.[10] Vitamin B12 is found in fish, shellfish, poultry, eggs, dairy products, fortified cereals, and yeast.


Since many people are not getting the recommended amounts of B vitamins, it is wise to consider taking a supplement. Age, gender, medical conditions, and specific vitamin needs should be considered when choosing a supplement.[1] For instance, women who are pregnant should take a prenatal vitamin that contains folate (Vitamin B9), cobalamin (Vitamin B12), and iron, as they need more of these nutrients during pregnancy.

Some research has suggested that since 40% to 60% of people have a genetic variation that prevents them from converting supplemental folic acid (Vitamin B9) into its active form of methylfolate, it is best to take a methylfolate supplement. Methylfolate is the bioavailable form of folate. The bioavailable form of any nutrient ensures higher levels of absorption and makes it more likely that sufficient amounts are being provided to the body.[20]

High levels of stress or exercise increase the body’s need for B vitamins, as does extra water intake.

Proper Dosage

The recommended daily intakes of B vitamins from food and supplements vary from person to person. Gender, age, lifestyle habits such as drinking alcohol, and other factors such as pregnancy, can all impact the amounts of B vitamins that a person needs.[7, 12, 13] The Food and Nutrition Board of the Institute of Medicine at the National Academy of Sciences developed the Dietary Reference Intake system, which recommends doses for average, healthy individuals.

When used in high doses, B vitamins may be viewed as prescription medicines. For example, studies show that niacin (Vitamin B3) may slow the development of atherosclerosis – the narrowing and hardening of the arteries – when used in conjunction with cholesterol-lowering drugs, a healthy diet, and regular exercise.[8] To achieve these effects, however, a person would need to take more than 1,000 mg of niacin per day. For women, the recommended dietary allowance is 14 mg per day, and for men, the recommended dose is 16 mg per day. Since 1,000 mg per day would clearly be considered a high dose, and since too much niacin can cause liver damage, high-dose niacin intakes should be considered a prescribed medication, not a vitamin, and should only be consumed while under the care of a physician.

Several B vitamins, such as folate (Vitamin B9), are important during pregnancy and lactation.[3, 7] Therefore, it is recommended that women increase their daily intakes of these nutrients. It is recommended that pregnant women get 600 mcg per day and those nursing should intake 500 mcg per day through food or a supplement, according to the National Institutes of Health. Adult women who are not pregnant or lactating, as well as adult men, should consume about 400 mcg of folate from dietary and/or supplemental sources.

To maintain healthy levels of pyridoxine (Vitamin B6), it is recommended that women and men under age 50 intake 1.3 mg per day. Women aged 51 and older should intake 1.5 mg per day, while men aged 51 and older should intake 1.7 mg per day. It is recommended that pregnant women intake 1.9 mg of Vitamin B6 daily, while lactating women should intake 2 mg per day.[14]

Pantothenic acid (Vitamin B5) is equally important for women. Women aged 14 and older need 5 mg of pantothenic acid per day. Pregnant women need 6 mg per day and lactating women need 7 mg per day.[12]

According to the NIH, adult males must get 1.2 mg daily of thiamine (Vitamin B1) and females must get 1.1 mg daily. It is recommended that pregnant and breastfeeding women get 1.4 mg daily.[9]

It is recommended that adults get 2.4 mcg per day of cobalamin (Vitamin B12), while pregnant women must get 2.6 mcg per day and lactating women must get 2.8 mcg.

Men should get 1.3 mg per day of riboflavin ((Vitamin B2) and women should intake 1.1 mg. Total riboflavin consumption should increase to 1.4 mg per day for those who are pregnant and to 1.6 mg per day for those who are nursing.[3, 10]

To maintain biotin (Vitamin B7) levels, it is recommended that adults over the age of 19 intake 30 mcg per day of biotin through nutrition and/or a supplement.


Since B vitamins are water-soluble, any excess is eliminated by the kidneys through the urine. However, individuals taking certain medications can sometimes experience negative side effects when taking a vitamin B complex supplement.[1, 2, 7]

All B vitamins prevent the antibiotic tetracycline from being absorbed properly. To ensure that the antibiotic is absorbed, it should not be taken at the same time as a supplement.[20]

Several medications used to treat high blood pressure, tuberculosis, asthma, and rheumatoid arthritis can negatively impact the absorption of pyridoxine (Vitamin B6). Individuals who take the medications Cycloserine, Hydralazine, Isoniazid, Penicillamine, and Theophylline should ensure that they are getting enough pyridoxine (Vitamin B6) from their diets or from supplements, as these medications prevent the absorption of Vitamin B6.[20]

Niacin (Vitamin B3) should not be taken by people who have stomach ulcers, kidney disease, liver disease, low blood pressure, gout, gallbladder disease, or diabetes.[8]

Recommended Products and Methodology

When choosing a vitamin B complex, choose a high-quality brand. It is important to note that we look at the large inventory of supplements on the market to make recommendations. To identify the best products, we look at scientific research, follow the latest industry news, and are advised by experts in the field. Our process also includes looking at certifications and approvals from consumer protection agencies, as well as laboratory testing reports and FDA warning letters that indicate when companies have failed to meet manufacturing standards.

When it is time to choose a supplement, ensure that it is “USP Verified,” which means that the strength, quality, and purity of the product was established by the testing organization U.S. Pharmacopeia.[1] However, USP verification is only a small part of our methodology for choosing recommended products. It can be difficult to find a quality supplement since they are not comprehensively regulated. Many companies cut corners or add unnecessary fillers to keep their costs down, which leads to less effective supplements. When we evaluate supplements, we use a scientific approach, analyze research and data, and apply our methodology.

During our evaluations, we ensure that supplements contain the correct doses and concentrations as advertised on the label, and that those doses meet with industry standards. We also check to ensure that the dosage and formulations can effectively correct a vitamin insufficiency.

A vitamin B complex supplement is better than a supplement containing a single type of B vitamin. Research has shown that B vitamins are absorbed better when they are taken together, rather than separately. B vitamins are highly dependent on one another for various functions in the body. For example, studies have shown that folic acid, the synthetic form of folate, works together with pyridoxine (Vitamin B6) and cobalamin (Vitamin B12) to control elevated blood levels of homocysteine, which is associated with an increased risk of heart disease. When healthy levels of all B vitamins are maintained, the body works more efficiently.[2]

Individuals should select a vitamin B complex supplement that provides approximately 100% of the daily recommended allowances.[1] High-dose supplements can cause dangerous side effects and toxicities. For example, too much pyridoxine (Vitamin B6) can cause nerve damage and too much niacin (Vitamin B3) can cause liver damage.

Finally, when it comes to supplements, less is sometimes best. Avoid supplements with extra herbs or special ingredients because they can have adverse interactions with certain medical conditions or prescriptions.[1]

Some of the most important factors to consider when choosing a vitamin B complex include the source of the supplement, the processing it went through, the manufacturer’s reputation, and its molecular form.

Which is the Best B Vitamins Supplement?

Check out our unbiased recommendation of the best products on the market using our rigorous methodology. We screen products for the right formulation, bioavailability, safety, and efficacy to bring you only the best supplements available in 2019.

1 “Vitamins and Minerals: What You Should Know About Essential Nutrients.” Mayo Clinic Women’s HEALTHSOURCE. July 2009. Accessed through: http://www.mayoclinic.org/documents/mc5129-0709-sp-rpt-pdf/doc-20079085
2 Kennedy DO. “B Vitamins and the Brain: Mechanism, Dose, and Efficacy – A Review.” Nutrients. 2016 Feb;8(2):68. doi: 10.3390/nu8020068. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4772032/
3 “Three of the B Vitamins: Folate, Vitamin B6, and Vitamin B12.” The Nutrition Source. Harvard School of Public Health. 2017 Accessed through: https://www.hsph.harvard.edu/nutritionsource/vitamin-b/
4 Mock DM. “Biotin.” In: Zempleni J, Rucker RB, McCormick DB, Suttie JW, editors. “Handbook of Vitamins.” 4th ed. CRC Press; Boca Raton, FL, USA: 2007.
5 Rivlin RS. “Riboflavin (vitamin B2).” In: Zempleni J, Rucker RB, McCormick DB, Suttie JW, editors. “Handbook of Vitamins.” 4th ed. CRC Press; Boca Raton, FL, USA: 2007.
6 Giovannucci E, Stampfer MJ, Colditz GA, Hunter DJ, Fuchs C, Rosner BA, Speizer FE, Willett WC. “Multivitamin use, folate, and colon cancer in women in the Nurses’ Health Study.” Ann Intern Med. 1998 Oct 1;129(7):517-24. PubMed PMID: 9758570. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/9758570
7 “Folate–Dietary Supplement Fact Sheet.” National Institutes of Health Office of Dietary Supplements. April 2016. Accessed through: https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/
8 “Niacin.” U.S. National Library of Medicine. January 2017. Accessed through: https://medlineplus.gov/ency/article/002409.htm
9 “Thiamine – Fact Sheet for Health Professionals.” National Institutes of Health Office of Dietary Supplements. February 2016. Accessed through: https://ods.od.nih.gov/factsheets/Thiamin-HealthProfessional/#h2
10 “Vitamin B12–Fact Sheet for Health Professionals.” National Institutes of Health Office of Dietary Supplements. February 2016. Accessed through: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/#h2
11 “Riboflavin–Fact Sheet for Health Professionals.” National Institutes of Health Office of Dietary Supplements. February 2016. Accessed through: https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/#h2
12 “Pantothenic Acid and Biotin.” U.S. National Library of Medicine. January 2017. Accessed through: https://medlineplus.gov/ency/article/002410.htm
13 Kinsella LJ, Riley DE. “Nutritional deficiencies and syndromes associated with alcoholism.” In: Goetz CG, Pappert EJ, editors. “Textbook of Clinical Neurology.” Philadelphia: W.B. Saunders Company; 1999.
14 “Vitamin B-6–Fact Sheet for Health Professionals.” National Institutes of Health Office of Dietary Supplements. February 2016. Accessed through: https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/#h2
15 Singleton CK, Martin PR. “Molecular mechanisms of thiamine utilization.” Curr Mol Med. 2001 May;1(2):197-207. Review. PubMed PMID: 11899071. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/11899071
16 Durance TD. “Residual Avid in Activity in Cooked Egg White Assayed with Improved Sensitivity.” Journal of Food Science. 1991;56(3):707-709. DOI: 10.1111/j.1365-2621.1991.tb05361.x. Accessed through: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1991.tb05361.x/abstract
17 “What are single nucleotide polymorphisms (SNPs)?” Genetics Home Reference. January 2018. Accessed through: https://ghr.nlm.nih.gov/primer/genomicresearch/snp
18 Ames BN, Elson-Schwab I, Silver EA. “High-dose vitamin therapy stimulates variant enzymes with decreased coenzyme binding affinity (increased K(m)): relevance to genetic disease and polymorphisms.” Am J Clin Nutr. 2002 Apr;75(4):616-58. Review. PubMed PMID: 11916749. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/11916749
19 Mitchell ES, Conus N, Kaput J. “B vitamin polymorphisms and behavior: Evidence of associations with neurodevelopment, depression, schizophrenia, bipolar disorder and cognitive decline.” Neuroscience & Biobehavioral Reviews. 2014 Nov;7:307-320. DOI: https://doi.org/10.1016/j.neubiorev.2014.08.006. Accessed through: http://www.sciencedirect.com/science/article/pii/S0149763414002048?via%3Dihub
20 Greenberg J, Bell S. “Multivitamin Supplementation During Pregnancy: Emphasis on Folic Acid and Methylfolate.” Rev Obstet Gynecol. 2011;4(3-4):126–127. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250974/