There are 8 B vitamins:
Thiamin (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Pyridoxine (B6)
Biotin
Cobalamin (B12)
Folic acid
The B vitamins as a group have a lot of important roles. Generally these roles include macronutrient metabolism (meaning carbs, protein and fat), energy production and release from these substrates and carbon metabolism (the transfer of carbon units to make compounds with in the body).
All of the B vitamins are water soluble. What that means is they are uptaken rapidly into the bloodstream, used where needed and then excreted in the urine. It is not easy to overdose on B vitamins since they are excreted this way although it is possible if someone takes a very large dose to cause some toxicity.
Today I will talk about the first four- tomorrow the second four.
Thiamin (B1)
Major metabolic role is the energy release from food. Thiamin is converted into its coenzyme form in the body called thiamin pyrophosphate (TPP) which participates in many metabolic reactions (coenzyme form in the "active form").
Deficiency of thiamin results in a condition called "Beri beri" which means, "I can't I can't". The symptoms of this disease include neurological symptoms, anorexia, paralysis, cardiovascular and respiratory distress. This condition however is rapidly reversed with thiamin supplementation. The symptoms and condition make sense when the metabolic role is considered, if one is unable to metabolize food, soon the body's systems that demand lots of energy will start to respond- followed by weight loss as the body tries to cope with these losses by metabolizing its own stores. Deficiency is rare in Canada due to the fortification of flour with thiamin.
Active, coenzyme form of thiamin, TPP:
Deficiency of thiamin results in a condition called "Beri beri" which means, "I can't I can't". The symptoms of this disease include neurological symptoms, anorexia, paralysis, cardiovascular and respiratory distress. This condition however is rapidly reversed with thiamin supplementation. The symptoms and condition make sense when the metabolic role is considered, if one is unable to metabolize food, soon the body's systems that demand lots of energy will start to respond- followed by weight loss as the body tries to cope with these losses by metabolizing its own stores. Deficiency is rare in Canada due to the fortification of flour with thiamin.
Active, coenzyme form of thiamin, TPP:
Riboflavin (B2)
Riboflavin also participates in energy metabolism within the body. Its coenzyme forms are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These enzymes participate in accepting and donating hydrogen atoms within the body to produce energy. Together these two "active" forms are referred to as "flavoproteins". Riboflavin can be found in meat, liver, milk and milk products and is also fortified in flour. Deficiency is rare due to the widespread availability of the vitamin however it can happen but is never fatal and results in lesions on the body as well as a condition called "magenta tongue".
Riboflavin also participates in energy metabolism within the body. Its coenzyme forms are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These enzymes participate in accepting and donating hydrogen atoms within the body to produce energy. Together these two "active" forms are referred to as "flavoproteins". Riboflavin can be found in meat, liver, milk and milk products and is also fortified in flour. Deficiency is rare due to the widespread availability of the vitamin however it can happen but is never fatal and results in lesions on the body as well as a condition called "magenta tongue".
Besides participating in energy metabolism, riboflavin also facilitates the conversion of vitamin B6 to its coenzyme form (which I'll talk about tomorrow) as well helps with the adsorption of iron. Adequate levels of riboflavin are necessary to ensure proper iron metabolism as well.
Niacin (B3)
Niacin in addition to being found in food sources, is also produced in our bodies. However the ability to make niacin does not completely fulfill our needs for it so we must still consume it. We can make niacin out of tryptophan (an amino acid, famously in high amounts in turkey meat) via the kynurenine pathway. In dogs, pigs and rodents their dietary need for niacin is zero as this pathway makes enough for their needs. This pathway requires other B vitamins in order to work. Both riboflavin and B6 are needed to make niacin out of tryptophan. Niacin has two coenzyme forms, NAD(P) and NAD(P)H, referred to as nicotinic acid and nicotinamide (this is the circulating form in the blood).
Like the other B vitamins, niacin particpates in metabolic roles such as micronutrient metabolism and the transfer of hydrogen atoms. Niacin spends a lot of its time becoming oxidized (NAD(P)H) and then reduced (NAD(P)).
Deficiency of niacin has four famous symptoms, also known as the "four D's of Pellagra":
- diarrhea
- dimentia
- dermatitis
- DEATH
Clearly niacin is an important B vitamin, and essential for life.
Niacin has also been implicated for use as a cholesterol-lowering agent. This vitamin must be taken in large doses of up to 1.5g to have this effect. It is important however to talk to a doctor before starting this regimen as liver toxicity can be a problem. It is best to take it with food or use it to supplement other cholesterol-loweing agents.
Niacin has also been implicated for use as a cholesterol-lowering agent. This vitamin must be taken in large doses of up to 1.5g to have this effect. It is important however to talk to a doctor before starting this regimen as liver toxicity can be a problem. It is best to take it with food or use it to supplement other cholesterol-loweing agents.
The citric acid cycle, also known as the TCA or Kreb's cycle where energy is produced within the body. Notice all of the places where FAD (riboflavin!) and NAD (niacin!) come into the process. We need B vitamins to make energy!
Biotin
Biotin is a vitamin that is implicated with four important enzymes in the body:
- pyruvate carboxylase: glucose metabolism
- acetyl CoA carboxylase: fatty acid synthesis
- proprionyl CoA carboxylase: energy production
- methylcrotonyl CoA carboxylase: amino acid metabolism
These are four enzymes in the body that if not working properly can cause serious problems, as they clearly serve important functions. Biotin can actually be produced in our intestines however it is not clear how much is absorbed so it should also be consumed to ensure adequate amounts. Biotin can be found in large amounts in cooked egg white (raw egg if eaten will not supply you with biotin as the vitamin is essentially stuck to one of the egg's proteins and it will not come loose unless cooked), liver, whole-grains, nuts, legumes and peanut butter. If deficient in biotin, the first symptoms seen will be a thinning of the hair and dermatitis, eventually followed by neurological symptoms. Since this vitamin is also quite widely spread in many foods, deficiency is rare.
Biotin is a complicated vitamin. In food, biotin is bound to protein (such as in raw egg white). In many foods when consumed, we must use an enzyme we have called biotinidase to cleave off the protein so the biotin can be freely absorbed by our bodies. It is possible to measure urinary metabolites to test if we are biotin deficient or if there seems to be a problem with one of our enzymes that is biotin-dependent. Biotinidase because it is such an important enzyme is included as a test for newborns leaving the hospital. The inability to make these enzymes has been implicated in SIDS and is known to play a role in immunodeficiency diseases.
Someone making/consuming plenty of biotin:
Biotin is a complicated vitamin. In food, biotin is bound to protein (such as in raw egg white). In many foods when consumed, we must use an enzyme we have called biotinidase to cleave off the protein so the biotin can be freely absorbed by our bodies. It is possible to measure urinary metabolites to test if we are biotin deficient or if there seems to be a problem with one of our enzymes that is biotin-dependent. Biotinidase because it is such an important enzyme is included as a test for newborns leaving the hospital. The inability to make these enzymes has been implicated in SIDS and is known to play a role in immunodeficiency diseases.
Someone making/consuming plenty of biotin:
"mm! biotin!"More B vitamins tomorrow :)
lol
ReplyDeleteThis post is cool, it's like studying and teaching all at once, with the reward of dreamy hunk at the end hah
Haha. I'm glad you enjoyed it. His photo is what came up when I googled biotin and hair. I had my midterm yesterday... I think it went OK. There were a few really tricky questions though.
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