What are the B Vitamins?

How B-Vitamins Are Classified

B vitamins for Runners

The B family of vitamins, and vitamins in general, have an interesting history. Why are there 8 B vitamins but only 1 of the other letters? Well, there are actually more than 1 of the others, but B vitamins are considered “different,” while for example, vitamin K, has “different forms.”

Vitamins were originally discovered in the early 1900’s as a “necessary substance for growth.” The word vitamin actually comes from two words, “vital” and “amine” – called vitamines. The word, “amine,” because the vitamins were mistaken for amino acids. At first (~1916), there were only 2 recognized vitamins, A and B. Eventually, we realized that they were not “amines,” so that’s when they came to be known as vitamins. Then came vitamins C, D, and E.

The gap between E and K as well as the numerical associations with the B vitamins is also due to reclassification, such as with the “amine” confusion. For example, vitamin G was reclassified as vitamin B2 because of their structural similarities. On the other hand, we have no official vitamin B4, but at one time the title belonged to adenine (a nucleic acid), carnitine (a dipeptide), and choline (an amino acid metabolite).

What’s the Big Deal with B Vitamins and Energy? They’re in Every Energy Drink…

B Vitamins for Cyclists

Well, simply put, the B complex vitamins have numerous roles as co-factors in the synthesis of ATP (source of cellular energy). Some are more important than others, while those others have other roles in the body that are of enormous importance separate from energy metabolism. This is why you’ll usually find all of the same B vitamins across different energy drinks. Plus, they’re dosed in such teeny tiny amounts that they add only trivial cost to products. Without further ado, here is a little more than everything you want to know about all 8 of the B vitamins.

B1 Thiamine

B Vitamin Supplement

Overview: Thiamine’s role in energy metabolism is in decarboxylation and transketolation reactions. One of the most important decarboxylation reactions is by the enzyme pyruvate dehydrogenase, which converts the endproduct of anaerobic glucose metabolism, pyruvate, into acetyl-CoA, which can then enter the Krebs cycle to create more ATP! Transketolase reactions occur during the metabolism of 5-carb sugars (glucose and fructose have 6 carbons), and this process is very active in the myelin sheath of neurons, which is one reason thiamine is important for nervous system health. The RDA for thiamine is 1.0-1.2 mg per day.

For Athletes: Poor thiamine status can negatively impact athletic performance. Following several months of consuming a low-thiamine diet, athletes experienced reduced exercise capacity and greater blood lactate. Greater blood lactate suggests that pyruvate dehydrogenase was insufficient for producing enough acetyl-CoA for optimal ATP production. When pyruvate cannot enter the Krebs cycle, it is converted to lactate, and athletes do have greater need for thiamine. However, most athletes (~90%) have acceptable thiamine status, and poor thiamine status usually coincides with insufficient calorie intake.

Food Sources: 1) Fortified Breakfast Cereals (100%). 2) Rice (73%). 3) Egg noodles (33%). 4) Pork (27%). 5) Trout (27%).

B2 Riboflavin

B Vitamins Obstacle Course Racing

Overview: Riboflavin has an incredibly important job in forming 2 cofactors in metabolism, Flavin mononucleotide (FMN) and Flavin adenine dinucleotide (FAD). Produced during the metabolism of macronutrients, these cofactors go through the electron transport chain to facilitate ATP synthesis. Riboflavin also helps convert vitamin B6 to its active form, which we will discuss. The RDA for riboflavin is 1.0-1.3 mg per day.

For Athletes: Similar to thiamine, riboflavin deficiency also impairs athletic performance. Brining an athlete from poor riboflavin status to adequate status has been shown to improve performance. Athletes may need ~30% more riboflavin than non-exercising individuals, and this can be consumed via the diet. Based on adjusted needs, ~81% of athletes have adequate riboflavin status, while 19% have poor status. Poor status is predominately due to consuming less food than they need.

Food Sources: 1) Beef Liver (171%). 2) Fortified Breakfast Cereals (~100%). 3) Oats (65%). 4) Dairy (18-35%). 5) Steak (24%)

B3 Niacin

Do Athletes Need More Vitamins

Overview: Like riboflavin, niacin is involved in the formation of essential cofactors. Niacin is responsible for nicotinamide adenine dinucleotide (NAD). NAD performs functions nearly identical to that of FAD. However, NAD is also a signaling molecule for a class of proteins known as sirtuins that are currently being investigated for their effects in reversing the process of aging. Conjunctively, niacin may have a role in reversing aging by activating sirtuins, which may repair damaged DNA. The RDA for niacin is 14-16mg per day.

For Athletes: The data surrounding performance is a mixed bag. However, niacin may improve anaerobic performance at the expense of aerobic performance if consumed in large (1-3 grams) doses every day. Niacin may inhibit lipolysis, which reduces the amount of fat that can be used to produce ATP. Conversely, it can enhance blood flow and growth hormone. As you will come to realize, athletes need more B vitamins than sedentary individuals, and niacin is one of them. Athletes are not observed to have inadequate niacin status unless they are not eating enough.

Food Sources: 1) Liver (200%). 2) Turkey (100%). 3) Tuna (56%). 4) Chicken (44%). 5) Beef (36%).

B5 Pantothenic Acid

Sports Drink for Runners

Overview: Pantothenic acid is the rate limiting step in Coenzyme A (CoA) formation. This means that the amount of CoA produced is directly proportional to pantothenic availability. CoA is an extremely important molecule in terms of metabolism. For example, the Krebs cycle requires CoA, as acetyl-CoA, to start, and the cycle needs CoA again to form succinyl CoA (along with NAD!). Pantothenic acid is also involved in the synthesis of heme (red blood cell oxygen carrier protein) and cholesterol. The adequate intake for pantothenic acid is 5 mg per day.

For Athletes: “Pantos” means “everywhere” in Greek, and this reflects how many foods contain pantothenic acid. As such, athletes are typically not deficient. Research indicates that exercise can result in acute decreases in pantothenic acid. However when just examining levels of available pantothenic acid, athletes have been observed as having greater values than controls. Data on pantothenic acid supplementation have produced mixed results. High dose supplementation of pantothenic acid (2 grams per day for 2 weeks) have resulted in reduced lactate production and oxygen consumption at a fixed exercise intensity. However, 1 gram per day for 2 weeks did not improve running performance in trained runners, and 1.8 grams per day for 1 week did not affect lactate, glucose, free-fatty acids, or sprint performance in trained cyclists.

Food Sources: 1) Beef Liver (96%). 2) Avocado (40%). 3) Sunflower Seeds (40%). 4) Duck (32%). 5) Portabella mushrooms (30%).

B6 Pyridoxine

Sports Drink for Cyclists

Overview: Vitamin B6 is mostly found in the muscle tissue as pyridoxal 5’ phosphate (PLP; the active form), where it is a conenzyme in over 100 reactions related to energy metabolism. Much of the reason for its location in the muscle has to do with its role in the glycogen phosphorylase enzyme. Glycogen phosphorylase is involved in the breakdown of muscle glycogen, so B6 is particularly important for accessing our endogenous carbohydrate storages. B6 is also necessary for amino acid transamination and deamination reactions, which are reactions that convert one amino acid to another and break down amino acids to produce carbon skeletons for energy metabolism, respectively. Like pantothenic acid, B6 is crucial for heme synthesis. The RDA for B6 is 1.3-1.7 mg per day.

For Athletes: Because of its role in heme synthesis, some believe taking high doses (150mg per day) will increase oxygen carrying capacity, kind of like EPO. Of course, vitamins are not nearly as powerful as EPO, but even 5% of the effects of EPO would be pretty substantial. You may already know that athletes require greater amounts of red blood cells and oxygen carrying potential, but exercising, especially high-impact exercises like running, reduces red blood cell count, hematocrit, and hemoglobin. A marathon can deplete a runner of greater than 1mg of B6. However, supplementing in high doses (117 – 5,000 mg per day) can damage nerve endings. Supplementing B6 has failed to directly increase performance in scientific investigations with athletes having adequate status. However, vitamin B6 depletion has been observed to negatively impact endurance. Strikingly, as much as 73% of athletes in the US may be deficient in B6. An examination of Polish athletes between 1987 and 1992 found that 9% of athletes were deficient in B6, and endurance athletes had the greatest prevalence of deficiency at 13%. Unfortunately, our food system has not improved, and may even be worse present day, increasing the likelihood of insufficiency. It is estimated that athletes need 1-2mg of vitamin B6 per day added to their diet to maintain adequate levels.

Food Sources: 1) Chickpeas (55%). 2) Beef Liver (45%). 3) Yellowfin Tuna (45%). 4) Sockeye Salmon (30%). 5) Chicken Breast (25%).

B7 Biotin

Triathlete Nutrition

Overview: Biotin is a coenzyme for several enzymes involved in generating intermediate compounds in the Krebs cycle, in fatty acid synthesis, and glycogen synthesis, so it is considered slightly more anabolic than catabolic. It is popular in “hair, skin, and nail” supplements for perceived promotion of more beautiful attributes. The adequate intake for biotin is 30 micrograms per day.

For Athletes: No studies have been conducted examining biotins effects on performance. It would stand to reason that inadequate biotin status would negatively impact energy metabolism and glycogen synthesis, which would hamper performance. However, biotin insufficiencies are very rare when there are no inborn errors of metabolism involving biotinidase. Investigations on athletes suggest no difference in biotin requirements between athletes and non-athletes, making biotin an exception to the rule that athletes generally require more B vitamins. Prevalence of biotin deficiency is less than 1 tenth of 1 percent in the US.

Food Sources: 1) Beef Liver (100%). 2) Egg (33%). 3) Salmon (17%). 4) Pork (13%). 5) Ground Beef (13%).

B9 Folate

Triathlete Diet

Overview: Folate is closely related to the ever-popular B12, and they are so similar that increasing folate can mask a B12 deficiency. Folate is most known for neural tube defects and its importance as a prenatal vitamin. Folate roles are in DNA and RNA synthesis, cell division, and metabolism of the amino acid methionine. DNA synthesis and cell division are closely related, and folate is essential for cells with a high rate of turnover (red blood cells). The relationship between methionine and homocysteine levels are linked to cardiovascular disease, and folate can reduce homocysteine, so it is thought to have a minor role in reducing risk for cardiovascular disease. The RDA for folate is 400 micrograms of dietary folate equivalents (600 if pregnant). Folate equivalents account for greater efficacy of supplemental folate than dietary folate, so 1 mcg of supplemental folate equals 2 mcg of dietary folate or 2 dietary folate equivalents.

For Athletes: Like some other B vitamins, folate is involved in red blood cell formation, so it is critical for endurance athletes. Between 16 and 33% of athletes have a folate insufficiency. Research is limited on folates relationship with performance. However, supplementing female marathon runners that have poor folate status with 5mg of folate per day improved their status after only one week, which slightly improved their endurance performance (not statistically significant, but notable, and this is the only study available). Other investigations suggest exercise may increase homocysteine and folate supplementation is observed to reduce homocysteine levels even when participants already have adequate folate status.

Food Sources: 1) Beef Liver (54%). 2) Spinach (33%). 3) Black-eyed Peas (26%). 4) Fortified Breakfast Cereals (25%). 5) White Rice (23%).

B12 Cobalamin

Best B12 for Athletes

Overview: Of all the B vitamins, B12 gets the most attention. Its functions are very similar to folate, as previously stated. B12 is involved in DNA synthesis and cell division (particularly related to the red blood cells). B12 is also important in the formation of the myelin sheath that surrounds axons of neurons, and several neurological disorders are tied to B12. B12 deficiencies are usually caused by impaired absorption rather than inadequate intake, which results in anemia. B12 absorption can be significantly impaired by mega-doses of vitamin C (~3g), and vegetarians/vegans are at greater risk for B12 deficiency because it is principally found in meats. The RDA for B12 is 2.4 micrograms per day.

For Athletes: Between 20 and 33% of athletes have insufficient intake of B12, but only 5% display inadequate B12 status based on limited evidence. This makes it appear as though athletes may retain B12 better than nonathletes, but B12 measurements are still elementary and do not paint a clear picture. Athletes have altered B12 metabolism that make it more difficult to detect insufficiency because they maintain greater levels of the markers currently used to determine B12 status. These are markers, not B12. Other evidence, which is congruent with other B vitamins, indicate that athletes require more B12 in the diet, but they also have insufficient intake, which would suggest poor status. Non-athletes have a poor B12 status prevalence of 18%, and athletes likely have a similar prevalence. In individuals with B12 deficiency, supplementing B12 dramatically improves exercise performance – athletes included. Supplementing individuals already of adequate B12 status with extra B12 does not appear to further enhance exercise performance.

Food Sources: 1) Clams (1,402%). 2) Beef Liver (1,178%). 3) Fortified Breakfast Cereals (100%). 4) Trout (90%). 5) Salmon (80%).

Vitamin B for Me?

Runners Diet

Vitamins are important, but the need to supplement vitamins, and the amount needed, varies on a case-by-case basis. Including 1,000% of daily needs in an energy drink is unnecessary most of the time and typically without added benefit. A few B vitamins, however, are critical for athletes based on the demands of exercise, typical dietary intake, and observed nutritional statuses. The three B vitamins that athletes should be paying attention to are B6, B9, and B12 (pyridoxine, folate, and cobalamin).

Vitamins B6, B9, and B12 may each have insufficiency prevalence in more than 1 out of every 4 athletes, and endurance athletes appear to be particularly susceptible to vitamin deficiencies due to the great demands placed upon the body. However, this does not mean the athlete should be going vitamin-crazy. With B9 or B12, this would likely have little consequence, as extra B9 or B12 is simply excreted in the urine, but extra B6 can cause some problems. Due to the greater needs of athletes, B6, B9, and B12 are the B vitamins included in our sports drink, SustainElite, without providing way more than is necessary. I don’t know about you, but I’m not a big fan of spending money just so my pee can be used to fill a glow stick. To be certain you’re of adequate B vitamin status, make sure you’re eating plenty of the foods listed above!


Marriott, B. M. (Ed.). (1993). Nutritional Needs in hot environments: Applications for military personnel in field operations. National Academies Press.

Matter, M., Stittfall, T., Graves, J., Myburgh, K., Adams, B., Jacobs, P., & Noakes, T. D. (1987). The effect of iron and folate therapy on maximal exercise performance in female marathon runners with iron and folate deficiency. Clinical Science, 72(4), 415-422.

Molina-López, J., Molina, J. M., Chirosa, L. J., Florea, D. I., Sáez, L., & Planells, E. (2013). Effect of folic acid supplementation on homocysteine concentration and association with training in handball players. Journal of the International Society of Sports Nutrition, 10(1), 10.

Woolf, K., & Manore, M. M. (2006). B-vitamins and exercise: does exercise alter requirements? International journal of sport nutrition and exercise metabolism, 16(5), 453-484.