The B Vitamins

11 minute read

The B Vitamins are my favourite vitamins! Collectively they are important for a wide variety of processes to do with metabolism, energy production and for the general functioning of our bodies. Yet each individual vitamin has their own specific role to play. The really great thing about the B vitamins, is that for most of the healthy population, reaching the recommended nutrient intakes through diet alone is very easy, with manufacturers of cereals and dairy-free milk products opting to fortify with some B vitamins. As water soluble vitamins it is difficult to consume levels of B vitamins to reach toxicity as any surplus vitamins will typically get excreted in your urine. However, if someone consumes a lot of fortified products daily over a long period of time, on top of an already balanced diet, this increases the risk of toxicity. You may be surprised though to discover that certain components in food and drink can inhibit your absorption of these vitamins, and you may be unwittingly, giving yourself a functional deficiency. Have a look below to see what role each B vitamin has in your body. Could you be losing out on some of these amazing vitamins?

Thiamine (Vitamin B1)

Thiamine is involved in energy production, but especially carbohydrate metabolism.

Due to thiamine’s involvement in carbohydrate metabolism, the amount required daily is dependent on your carbohydrate intake. For people aged 15 -64 years, 1mg/day and 0.8mg/day is recommended for men and women respectively. Recommendations assume that an individual is eating 40% of their energy requirements with carbohydrate. Therefore, if you are following a low-fat diet, your requirements may be higher, and if you consume a lot of alcohol, this can increase your risk of deficiency due to the higher energy intake. Sources rich in thiamine are brewer’s yeast, raw fruit, animal-derived food products, fortified cereals, and the germ of grains (this is lost during milling). By law in the UK, white flour is fortified with thiamine to match the nutritional content of wholemeal flour.

Riboflavin (Vitamin B2)

Riboflavin is a component of two important molecules in the body; flavin adenine dinucleotide and flavin mononucleotide. These have several roles during aerobic respiration (exercise lasting longer than a few minutes), fatty acid oxidation, vitamin B3 and B6 metabolism, folate metabolism, vitamin A metabolism, and glutathione (an important antioxidant) metabolism. For people aged 15 years and above, the recommended intake is 1.3mg/day for men and 1.1mg/day for women. In the UK and other Western countries, the greatest sources for riboflavin are milk and dairy products making up about 25% of riboflavin intake in the average diet. Meat, oily fish, grains and dark leafy green vegetables are also reasonably good sources.

Niacin (Vitamin B3)

Sometimes referred to as the B3 complex, niacin has 3 forms, nicotinic acid, nicotinamide, and nicotinamide riboside. All 3 forms are converted to nicotinamide adenine dinucleotide (NAD). NAD is used for many processes in our bodies, but it is notably important in energy production, DNA repair and altering the structures of proteins. Nicotinic acid is converted to nicotinamide, and nicotinamide is then converted to the active form NAD. Humans can synthesis nicotinic acid from the amino acid tryptophan which is found in many protein-containing foods. Nicotinic acid is found in a wide variety of foods, but liver is a particularly rich source. Deficiency is rare in the UK. Recommended intakes are in niacin equivalents that consider both nicotinic acid and tryptophan intake. 16.5mg/day is recommended for men and 13.2mg/day for females aged 11 years and up.

Pantothenic Acid (Vitamin B5)

Pantothenic acid is found in nearly all foods in small amounts, and as such deficiency is extremely rare and there is no recommended intake. Pantothenic acid is converted to coenzyme-A, which is then further converted to acetyl-coenzyme A - an important compound required in energy production.

Pyridoxine (Vitamin B6)

Pyridoxine refers to a group of 6 interconvertible compounds pyridoxine (PN), pyridoxamine (PM), and pyridoxal (PL), and their phosphorylated derivatives pyridoxine 5-phosphate (PNP), pyridoxamine 5-phosphate (PMP), and pyridoxal 5-phosphate (PLP). PLP is the active B6-compound and it is involved in over 100 reactions. Functions include but are not limited to, carbohydrate, fat and protein metabolism, neurotransmitter metabolism, haemoglobin metabolism, gene expression, and may have some antioxidant activity. The best sources for vitamin B6 are protein rich foods (meat, liver, fish, beans, and lentils) but it is also found in wholegrains, bread, and vegetables. Deficiency is rare, but low vitamin B6 status has been reported in contraceptive users, celiac disease and diabetes patients, smokers and alcoholics. 1.4mg/day and 1.2mg/day is recommended for men and women aged 19 years and up respectively.

Biotin (Vitamin B7)

Biotin acts as carbon dioxide carrier in a small, but important, number of reactions involved in gluconeogenesis, fatty acid synthesis and the breakdown of amino acids. Biotin can be synthesised by bacteria in the large intestine, as well as consumed from the diet, however the nutritional significance of bacterial sources is unknown. Biotin can be found in many foods and deficiency is rare, however if people consume large amounts of uncooked egg, the biotin binds to the protein avidin in egg white, inhibiting biotin absorption. There are too few studies to define a safe upper limit, however no adverse effects were reported when participants were administered 9mg/day over 4 years. You will find biotin is added in many hair and nail supplements. Don’t waste your money, it’s a massive con. You can get more than enough from your diet.

Folate (Vitamin B9)

Folate is well known for its use in the prevention of neural defects, which is down to the vitamin’s role in DNA and RNA synthesis, and amino acid metabolism. Folate also plays a role as a methyl donor in the form of 5-methyltetrahydrofolate. A methyl group is basically an extra piece added to the structure of folate that can be transferred onto other compounds. Methyl groups are used in a variety of biochemical reactions in a cell but are also added to DNA, altering the DNA without changing the code. Methyl groups can effectively act as an on or off switch for genes! Vitamin B9 and B12 metabolism are intertwined, and high levels of vitamin B9 could mask a vitamin B12 deficiency. Megaloblastic anaemia can result from a deficiency in either vitamin and your doctor would need to do tests to determine the best treatment. Vitamin B12 is required for vitamin B9 metabolism, and therefore vitamin B12 deficiency could lead to a functional vitamin B9 deficiency. In the UK 200µg/day folate is recommended for males and females aged 11 years and upwards. For women of childbearing age who are planning on having children are advised to take 400µg/day folate prior to conception until the 12th week of pregnancy to avoid birth defects. Good sources of folate are spinach, kale, brussels sprouts, cabbage, broccoli, beans and legumes, yeast and beef extracts, oranges and orange juice, wheat bran and other whole grain foods, poultry, pork, shellfish and liver, some fortified cereals (check the label).

Cobalamin (Vitamin B12)

Cobalamin is required for the development of red blood cells, DNA synthesis, and fatty acid and amino acid metabolism. B12 is nearly exclusively found in animal products, and this makes strict vegans high risk for deficiency. When speaking with vegans you often hear them say you can get cobalamin from algae and seaweed. In truth the officially recognised method for determining presence of cobalamin can lead to false positive results. Where biologically active B12 is found to be present in plant sources, this is most likely due to bacterial contamination. Vitamin B12 concentrations would be negligible, therefore, vegans need to get vitamin B12 injections or can take ethically acceptable supplements where the B12 has been synthesised by bacteria. In the UK, the recommendations for vitamin B12 are 1.5µg/day for both males and females aged 15 years and above.

If you eat a balanced diet with no extreme calorie restrictions, you should be able to get enough of these amazing vitamins in your diet as they can be found in so many food groups. A good bit of advice is to eat plenty of leafy greens and wholegrains, as these contain all the B vitamins, with the exception of vitamin B12, which you need to get from animal products or supplements.

If you would like your diet looked at by a qualified registered nutritionist, head over to Xeno Nutrition at where they can provide an in-depth analysis and full report including some advice on how to achieve a more balanced diet.