B Vitamins
Lets move on to the next in our series of micronutrients, B vitamins - certainly not the B-list celebs of the micronutrient world. There are eight separate micronutrients that make up the band commonly known as 'The B Vitamins' - responsible for such well known hits as 'Wouldn't It Be Niacin', 'Too Little, Too Folate' and 'Smile Like You Thiamine It'.
B Vitamins are grouped together because a) they are all water soluble (meaning they dissolve in water), and b) their primary purpose in the human body is as coenzymes or cofactors for many enzymes. Because they are water soluble B vitamins are not stored in the body easily (unlike fat soluble vitamins), this means that they must be continually replenished from our diet. Being cofactors or coenzymes means that they are required to increase the diversity of chemical reactions enzymes can perform as well as the rate and efficiency with which they can perform them. As cofactors/coenzymes B vitamins therefore play key roles in improving the rate and efficiency of most cellular functions. The many functions B vitamins are involved in can be divided into two categories:
- Catabolic metabolism - the process of breaking down molecules into smaller units - providing energy
- Anabolic metabolism - the process of using smaller units to build molecules - requiring energy to do so
As mentioned, the group is made up of eight separate compounds all of which are essential to humans. Essential meaning - needing to be acquired from diet as they cannot be manufactured by the body itself. The Exciting Exceptional Enzyme-enhancing Eight are as follows:
- B1 - Thiamine
- B2 - Riboflavin
- B3 - Niacin
- B5 - Pantothenic Acid
- B6 - Pyridoxine
- B7 - Biotin
- B9 - Folate
- B12 - Cobalamin
The more mathematically gifted reader may well have noticed that those numbers are not entirely sequential - a good spot. The reason for this being that the numbers given to the B vitamins were given in the order that they were established within the group originally and this contained 12 such substances. Then after the substances had been given their numbers it was later determined that some of them did not actually meet the criteria for being a vitamin after all and these were unceremoniously stripped of their B vitamin title - therefore we now have gaps where those pretenders once were eg at B4 and B8.
As you can see, writing about the B Vitamins is quite the undertaking. Therefore I am now going to split the group up in to its individual members - a la Take That when Robbie Williams left and then they all went on to do their own thing - although here the abilities of each individual are probably not so unequal.
Vitamin B1: Thiamine
Thiamine was endowed with the privilege of being known as B1 purely because it was the first to be given the B vitamin tag. The primary function of thiamine in the human body is as a coenzyme in the catabolysm (break down) of proteins, lipids/fats and particularly carbohydrates. Thiamin is a coenzyme within pathways responsible for the synthesis of fatty and amino acids needed to manufacture important neurotransmitters and other compounds crucial to brain function, it is also important in the structure and function of neural cell membranes. Thiamine can be stored in the liver, heart, brain and kidneys but only in small amounts and for a short time, and therefore a continuous supply from the diet is needed.
Deficiency of thiamine in its mild form can cause irritability, disturbed sleep, weight loss, amnesia, cardiac symptoms, general fatigue and weakness. More severe deficiency can lead to Beriberi - which can be categorised wet or dry. Wet Beriberi affecting the circulatory system, manifesting in high output cardiac failure with the signs of which being - increased heart rate, enlarged heart, warm extremities, respiratory distress and oedema. Dry Beriberi predominantly affects the nervous system, the signs of which can include fatigue, weakness, seizures and peripheral nerve damage (peripheral neuropathy). Advanced stage symptoms of thiamine deficiency are encompassed within a condition known as Wernicke-Korsakoff syndrome (WKS) involving damage to multiple peripheral nerves (polyneuropathy), disorders of co-ordination, balance and speech (ataxia) and paralysis of the occular (eye) muscles. It can eventually manifest in psychosis - involving hallucinations, amnesia and disorientation. Several sources of evidence have found associations between thiamine deficiency and Alzheimer's. Parkinson's, Huntington's Disease and dementia. Chronic alcohol consumption, diabetes and obesity are key risk factors to deficiency (making it more likely to occur).
It has been identified that high carbohydrate diets diminish thiamine concentrations therefore contributing to thiamine deficiency in a dose-response relationship (ie the higher the carbs the greater the decrease). In those with diets high in carbohydrates it is therefore important to consume higher levels of thiamine.
Bacteria, plants and fungi are able to synthesise thiamine, whereas animals are unable to do so. Humans unfortunately fall within the later group and therefore need to get thiamine from our diet (it is essential). The highest non-fortified whole food sources of thiamine are listed as:
- Pork
- Fish (tuna, salmon, trout)
- Nuts and seeds (macademia, pistachios, sunflower, flax)
- Legumes
- Whole grains (rice, wheat)
Sources:
Hiding in Plain Sight: Modern Thiamine Deficiency, C.Marrs & D.Lonsdale
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D.O'Kennedy
Vitamin B1 (Thiamine), J.Martel et al
Vitamin B2: Riboflavin
Riboflavin is the second of the B vitamin supergroup, number 2 due only to being pipped to the post in joining the B band only by thiamine. It is the precursor to flavocoenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which are both important in the human body for their role in most cellular enzymatic processes. To give a few examples they play an important role in producing energy through metabolism of carbs, fats and proteins, in the process of mitochondrial aerobic respiration, in metabolism of drugs and toxins, and in reducing oxidative stress throughout the body (antioxidant effect). FAD and FMN are crucial to the synthesis of heme proteins including haemoglobin (an important oxygen carrying component of blood), to the absorption and use of iron within the body, and to regulating thyroid hormones. Like thiamine and the other B vitamins, because riboflavin is water soluble this means it is not stored in the body readily and is therefore used as it is consumed, as such a continuous supply from the diet is needed.
Deficiency of riboflavin is called ariboflavinosis, sounding rather like a fast paced latin dance style. Symptoms of mild to moderate deficiency include red, dry, ulcerated lips, inflammation and discolouration of the tongue and mouth, sore throat, fatigue, weakness, eye irritation including itchiness, redness and sensitivity to light, cataract development and migraine. Deficiency is also associated with anaemia due to its importance in iron absorption and utilisation. Further deficiency can lead to liver and nervous system damage - including personality change and brain dysfunction. Deficiency during pregnancy can also result in preeclampsia. Groups at greater risk of deficiency include excess alcohol consumers, vegans and vegetarians.
Riboflavin is synthesised by bacteria, fungi and plants just like thiamine, unfortunately animals are unable to synthesise their own and thus riboflavin is an essential nutrient (must be consumed). The highest non-fortified whole food sources of riboflavin are:
- Organ meats - heart, liver, kidney
- Meat - beef, lamb, turkey, chicken, pork
- Milk
- Eggs
- Almonds
Sources:
Riboflavin: The Health Benefits of a Forgotten Natural Vitamin, N.Suwannasom et al.
Riboflavin Fact Sheet for Health Professionals, NIH
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D.O'Kennedy
Vitamin B3: Niacin
Niacin or Vitamin B3 or Nicotinic acid - so many names, is essential for creating nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) the human body - more than 400 enzymes require these coenzymes to catalyse (cause or accelerate) their reactions. NAD is involved carb, fat and protein metabolism and energy production and utilisation within mitochondria, it is also important as a coenzyme for enzymes involved in some critical cellular functions including control of gene expression, cell communication and maintaining genome integrity. NADP as a coenzyme is used in anabolic pathways including the synthesis of cholesterol and fatty acids and in maintaining antioxidant protection within cells. Tryptophan (one of the essential amino acids mentioned in the macronutrients post) can be converted into niacin by both plants and animals.
Deficiency of niacin in its severe form results in a condition called pellagra - the term comes from 'pelle-agra' Italian for rough skin. This condition is characterised by 'the four Ds' - diarrhoea, dermititis, dementia and death - not quite as fun loving a group as the Four Tops. Symptoms include a dark scaly rash on areas of skin exposed to sunlight, inflammation of the mouth and tongue, bright redness of the tongue, vomiting, diarrhoea, depression, fatigue, disorientation, weakness, delirium, psychosis and paranoia - if left untreated it will result in death. The condition was most notably recorded in the United States in the early 1900s where corn was the staple food within the diet, niacin in corn is poorly bioavailable, and amounts of the amino acid tryptophan are also low in corn, therefore NAD/NADP production would be low on a corn predominant diet as a result, leading to widespread pellagra at this time.
Plants and bacteria can manufacture niacin, animals can also convert the amino acid tryptophan into niacin themselves. It is more efficient though to consume this from the diet as the conversion is inefficient. The highest non-fortified whole food sources of niacin are:
- Organ meats - heart, liver, kidney
- Meat - beef, lamb, turkey, chicken, pork
- Fish - tuna, salmon, mackerel
- Peanuts
- Avocados
Sources:
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D. O'Kennedy
Niacin Fact Sheet for Health Professionals, NIH
Niacin Deficiency, S.Redzic et al.
Vitamin B5: Pantothenic Acid
Skipping 4 and straight to 5 we have Pantothenic Acid, perhaps a lesser known member of the group. It's name derives from the Greek pantothen which means "from everywhere", a nod to the fact that B5 is found in a wide distribution of foods. It is important in the human body as a component of coenzyme A, this enzyme is involved in many metabolic processes within cells, including metabolism of carbs and fats. It also contributes to the structure and function of brain cells due to its involvement in synthesising cholesterol, amino acids, phospholipids and fatty acids. It is also importantly needed for synthesis of neurotransmitters and steroid hormones.
Deficiency of pantothenic acid is rare owing to its ubiquitous distribution throughout foods commonly consumed in the human diet, in fact almost all plant and animal based foods contain the vitamin. Deficiency is rare and would generally mean a person being severely malnourished, therefore it is difficult to establish the effects of B5 deficiency in isolation. There are few examples of those with the specific deficiency except from experiments which involved subjects being fed a B5 deficient diet or those given a pantothenic acid antagonist as occurred during World War II - these subjects suffered from symptoms including - irritability and restlessness, fatigue, apathy, sleep disturbance, nausea, numbness and burning sensations in the extremities. Brain specific symptoms have been reported as demyelination (loss of the conductive lipid coating of neurones - reducing conductivity), behaviour change and encephalopathy.
Pantothenic acid is synthesised by bacteria from amino acids aspartate and valine. Human gut bacteria can produce the vitamin, however the contribution this makes to normal absorption is unknown. Mostly the vitamin is consumed within the diet, as previously mentioned it is available "from everywhere". Whole, non-fortified foods high in patothenic acid include:
- Meat - beef, lamb, turkey, chicken, pork, duck
- Organ meats - heart, liver, kidney
- Eggs
- Sunflower seeds
- Shiitake mushrooms
Sources:
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D. O'Kennedy
Vitamin B5 (Pantothenic Acid), T.Sanvictores
Vitamin B6: Pyridoxine, Pridoxal, Pyridoxamine
Moving on to number 6, and here things get interesting, because Vitamin B6 is actually the collective term for six chemically similar compounds, a group within a group so to speak. These compounds include: pyridoxal, pyridoxine, pyridoxamine, PLP, PNP and PMP - that's quite a lot to take on board I know. Luckily it is only PLP - which happens to be one of the phosphorylated forms of the first three compounds - that is the functioning structure in the body and therefore this is the important one. As a coenzyme it is involved in over 100 chemical reactions in the human body, mostly those concerning protein metabolism. B6 also plays an important role in cognitive development as it is involved in the synthesis of neurotransmitters - such as serotonin, dopamine, noradrenaline and GABA. It also has a direct role in immune function and in gene expression and transcription. B6 also plays an important role in regulating brain glucose levels.
Vitamin B6 deficiency is associated with symptoms including: seborrhoeic dermatitis, conjunctivitis, scaling of the lips and crack in the corners of the mouth, swollen tongue, depression, confusion, anaemia, weakened immune function, and neuropathy. B6 deficiency has been linked to an increased risk of cardiovascular disease. Deficiency can also lead to cognitive decline, dementia, autonomic dysfunction and convulsions. In the 1950s due to an error in manufacture of infant formula some infants were B6 deficient and as a result suffered seizures. Those at higher risk of developing B6 deficiency are chronic alcohol consumers, end stage renal patients, those suffering from malabsorption syndromes such as Crohns and celiac disease.
Vitamin B6 must be consumed in the diet as humans are unable to synthesise it themselves. Like all of the other B vitamins so far, bacteria are responsible for synthesis of vitamin B6. Plant foods which contain vitamin B6 contain the unique form called pyridoxine glucoside - this form is only around half as bioavailable (meaning not as much of the consumed amount is absorbed in to the blood via the small intestine) compared to the form from other sources (eg meat), this is important to bare in mind when examining good sources of the vitamin. The highest non-fortified whole food sources of niacin are:
- Meat - beef, lamb, turkey, chicken, pork, duck
- Organ meats - liver, heart
- Fish - tuna, salmon
- Bananas
Sources:
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D. O'Kennedy
Vitamin B7: Biotin
Biotin is the vitamin given the number 7 shirt. It is an essential cofactor to enzymes involved in the metabolism of nucleic and amino acids, as well as fatty acids and glucose. It is also a key regulator of gene expression, histone modifications, and cell signalling.
Deficiency of biotin symptoms include hair loss, lethargy, hallucinations, rashes around the eyes, mouth, nose and genitals, tingling and burning of the extremities, depression, seizures and ataxia. Severe deficiency is rare in normal diets but has been demonstrated in individuals consuming raw egg white over long periods - this being because egg whites contain the protein avidin, this binds to biotin and prevents its absorption.
Biotin is, not so surprisingly at this stage, synthesised by bacteria. It is also synthesised in plants. Mammals need to consume biotin in their diet - a diet free from raw egg whites would evidently be advantageous here! The highest non-fortified whole food sources of biotin are:
- Organ meats - liver
- Eggs
- Meat - pork, turkey
- Fish - salmon, tuna
- Peanuts
Sources:
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D. O'Kennedy
Biotin Fact Sheet for Professionals, NIH
Vitamin B9: Folate
At number 9 we have Folate, otherwise known as folic acid - this being the sythetic form available as a supplement which is actually converted to folate within the body after ingestion. Folate is a critical nutrient as it acts as a coenzyme in the metabolism of nucleic acid precursors and amino acids, it is required for the synthesis of DNA and RNA, and in therefore is crucial to cell division.
Folate deficiency may result in megaloblastic anaemia (sounds rough) - anaemia being low red blood cell count, this more specifically is characterised by the presence of large immature pre-red blood cells (called megaloblasts) in the blood. This leads to a reduced oxygen carrying capacity of the blood therefore causing fatigue, weakness, heart palpitations and breathlessness, symptoms can also include a sore tongue, headaches, irritability and loss of appetite. Deficiency can also lead to cognitive impairment, affective disorders, behaviour change and psychosis.
Animals are unable to synthesise folate - that rules us out. It is synthesised by plants, fungi and bacteria, we therefore need to acquire folate from our diet - it is essential. The highest non-fortified whole food sources of folate are:
- Liver - chicken, beef, lamb
- Peanuts
- Beans
- Lentils
- Cabbage, sprouts
Sources:
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D. O'Kennedy
Folate, Linus Pauling Institute
Vitamin B12: Cobalamin
Last but not list in the B-team we have B12 or Cobalamin - a blend of the words cobalt and vitamin (clever...) - the link being that cobalt is an essential element required for the formation of vitamin B12 by rumen microorganisms. B12 plays a key role as a coezyme in DNA and RNA synthesis, fatty acid and amino acid metabolism. It is a crucial nutrient in the nervous system for its role in synthesising myelin (the conductive lipid coating of neurons) and for synthesising neurotransmitters .
Deficiency of vitamin B12 can cause anaemia (folate and B12 have a metabolic interrelationship, and therefore deficiency of either leads to the same anaemic effect), common symptoms include fatigue, shortness of breath, palpitations, hair loss, fainting and joint pain. Deficiency of B12 also causes neurological complications including sensory disturbances (tingling, numbness) most often in the lower limbs, gait abnormalities, cognitive changes including loss of concentration, memory loss, dementia and mood changes. Deficiency can also lead to insomnia, depression, anxiety, visual disturbances, impotency and impaired bowel and bladder function.Those with malabsorption disorders - particularly atrophic gastritis - are more likely to develop deficiency, as well as those on a vegetarian or vegan diet.
Vitamin B12 is synthesised by bacteria and archea, and therefore humans must consume it within their diet, plants are also unable to synthesise the vitamin and therefore it is only present in animal products. The highest non-fortified whole food sources of vitamin B12 are:
- Organs - liver, kidney
- Molluscs - clams, mussels, oysters
- Meat - beef, lamb, turkey
Sources:
B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review, D. O'Kennedy
Vitamin B12, Linus Pauling Institute
Unfortunately/fortunately, depending on how much time you are wanting to invest in learning about B Vitamins, that is the end of my summary of the Enzyme-enhancing Eight. I hope that you have learned a thing or two about the group and just how important they all are to maintaining our health.
I will continue the series on micronutrients with part 3 soon - something to look forward to!
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