The B Vitamins
There are probably a couple B vitamins that you’ve heard of, maybe B-6 and B-12, but what about the other six? B-vitamins are a broad category of vitamins, all water-soluble and responsible for many vital functions in the body. They’re given different names based on differing compounds they contain. Being that as vitamins were discovered, they were named after the alphabet, you’ve probably figured out that vitamin B was the second one discovered. There are 8 B-vitamins but only two are commonly referred to with the letter B and a number, the others have lost their older designations and are now most commonly known by their full names: Thiamin, Riboflavin, Niacin, Pantothenic Acid, Biotin & Folate.
All 8 B-vitamins play a major role in energy metabolism. Grains are an important source of many of the B-vitamins, unfortunately when grains are milled, the outer layers that contain many of the vitamins, minerals and fiber are crushed and removed. To counteract the loss of nutrients, the U.S. enriches nearly all bread and cereal products with thiamin, riboflavin, niacin, folic acid and iron. Even with enrichment, these products still contain much fewer nutrients than whole grain products, so it is recommended that half of the grains consumed each day be whole grains.
Thiamin
Thiamin is found in a wide variety of foods but in small quantities. Foods highest in thiamin are pork, sunflower seeds and legumes. Other sources are enriched grain products (breads & cereals), green peas, asparagus, organ meats, peanuts and mushrooms.
There are certain foods that contain compounds which oxidize thiamin and make it inactive, they are: coffee, tea, blueberries, red cabbage, Brussel Sprouts and beets. People with a thiamin deficiency may want to avoid eating these foods.
The recommended daily allowance (RDA) for thiamin is 1.2mg/day for men and 1.1mg/day for women. Average intake of thiamin in the U.S. meets these recommendations. There appear to be no issues with people consuming too much thiamin as excess is excreted in the urine.
Thiamin is needed for normal function of the nervous system. Without enough thiamin, glucose metabolism is disrupted and the nervous system doesn’t have the energy it needs to function. Thiamin deficiency is known as Beriberi, and there are two forms: wet beriberi affects the heart and circulatory system and dry beriberi damages the nerves and can lead to decreased muscle strength and eventually, muscle paralysis. Wernicke-Korsakoff Syndrome is found mainly among people who heavily abuse alcohol. Alcohol decreases thiamin absorption, increases thiamin excretion and alcoholics often have poor diets that contain little thiamin.
Riboflavin
Riboflavin was once called the “yellow enzyme” because it has a distinctive yellow-green color. Nearly one quarter of the riboflavin in our diets comes from milk products. The rest typically comes from enriched foods (cereal & bread), as well as eggs and meat. Foods rich in riboflavin are mushrooms, liver, green leafy vegetables, broccoli, asparagus, milk and cottage cheese. Exposure to light causes riboflavin to break down, that is why clear containers aren’t used for storage, especially for milk products & cereals.
The RDAs are 1.3mg/day for men and 1.1 mg/day for women. In the U.S., we typically get more than enough in our diet to meet this recommendation. There appear to be no issues with people consuming too much riboflavin because of its limited absorption and rapid excretion in the urine.
Riboflavin plays a role in energy metabolism, activation of niacin, B-6 and folate, and the synthesis of the antioxidant compound glutathione. Riboflavin deficiency is called ariboflavinosis, and it primarily affects the mouth, skin and red blood cells. It can cause inflammation of the throat, mouth and tongue, cracks at the corner of the mouth, anemia, fatigue, confusion and headaches can also occur.
Niacin
Pellagra or Niacin deficiency is the only dietary deficiency disease to ever reach epidemic proportions in the United States. Thousands in the southeastern states were affected by this in the early 1900s. Niacin comes in two forms and can be eaten in the vitamin form in some foods and it can also be synthesized in the body from the amino acid tryptophan (this might sound familiar, we hear about it a lot when Thanksgiving rolls around because of turkey consumption).
About 25% of the Niacin in American diets comes from poultry, meat and fish, another 11% comes from enriched bread products. Other sources of Niacin are coffee, tea, mushrooms, wheat bran and peanuts. Unlike Thiamin and Riboflavin, Niacin is very heat stable and isn’t lost during the cooking process.
Men need 16mg/day and women need 14 mg/day. In the U.S., we typically get ample Niacin in our diets. Niacin is absorbed very well, so we generally absorb all the Niacin we consume in our diet. The bioavailability (how well our body uses it) varies, it is low in some grains, especially corn. Toxicity (too much Niacin) shows itself through flushing of the skin and can lead to liver damage with prolonged consumption.
Niacin functions in at least 200 reactions in cellular metabolic pathways, especially those that produce energy. It is needed to breakdown carbohydrates, proteins and fats. Niacin deficiency causes widespread damage in the body because of its link to so many metabolic pathways. Pellagra symptoms include a rough, red rash on areas exposed to sunlight (face, arms, neck), diarrhea and dementia. Areas where diets rely heavily on corn have been linked to Niacin deficiency. More than 10,000 Americans died from Pellagra in 1915, and another 200,000 suffered from it from 1918 until the end of World War II.
Pantothenic Acid
Pantothenic acid gets its name from the Greek word panthonen, which means “from every side”. It was called this because it is present in all body cells and is supplied by a wide variety of foods. It is part of coenzyme A (CoA), which you may have heard of before.
We get a lot of pantothenic acid in our food supply. Some common sources are milk, meat, many vegetables, avocados, egg yolks and soy milk. It is best to eat unprocessed foods as processed foods go through milling, refining, freezing, heating and canning which can reduce the amount of pantothenic acid. Adults need to consume 5mg/day and typically have no problem consuming this amount. There is no know toxicity level, so no upper level has been set.
Pantothenic acid is essential in energy production (breakdown of carbs, protein, alcohol and fat). It is also a building block in the formation of fatty acids, cholesterol, bile acids and steroid hormones. Deficiency is very rare but symptoms would include headache, fatigue, impaired muscle coordination and GI tract issues.
Biotin
Biotin’s discovery came in the 1920s and was linked to experiments conducted with egg-white consumption in rats. It is widely distributed in foods but in low amounts. Sources include eggs, nuts, whole grains and legumes. We actually excrete more biotin than we consume. Research and study is in its early stages but it appears that the bacteria in our large intestine actually synthesizes biotin. It isn’t yet known how bioavailable this biotin is because it is absorbed most efficiently in the small intestine.
Only a very small amount of Biotin is needed each day, significantly less than most of the other water-soluble vitamins, 30 μg/day (1000 μg equals 1 mg), so only a tiny bit is required. There isn’t a toxicity level known for biotin.
Biotin functions as a coenzyme that adds carbon dioxide to various compounds, which is required for the metabolism of carbs, proteins and fats. You’re probably noticing a trend among the B vitamins, the breakdown of foods rely heavily on them. Biotin is also thought to help gene stability by helping DNA fold in the cell nucleus.
Deficiency is rare, with only 1 in 112,000 infants born with a genetic defect. Those affected will be treated with regular doses of biotin supplements throughout their life. Deficiency can occur from the use of anticonvulsant medications, diseases that cause malabsorption and the regular consumption of raw eggs. Raw eggs contain a protein that binds biotin, limiting its absorption. Cooking eggs denatures it and prevents it from binding.
B-6
This vitamin is critical in the metabolism of amino acids (protein building blocks). A large portion of our cells, muscles and tissues are made up of amino acids. Vitamin B-6 is stored in the muscle tissue of animals, therefore, meat, poultry and fish are some of the richest sources of this vitamin. Whole grains are also a good source but B-6 is lost during the refining process and it is not added during enrichment. There are a few fruits and vegetables that are also a good source: carrots, potatoes, spinach, bananas and avocados. Like many water-soluble vitamins, B-6 can be lost when food is exposed to heat or other processing methods.
The RDA is 1.3mg/day for men and women up to age 50. In older adults the RDA increases to 1.7 in men and 1.5 in women. Toxicity can occur, so an Upper Level has been set at 100md/day to avoid nerve problems. Muscle tissue is the main storage site for B-6, with excess being excreted in the urine.
Like the previously covered B vitamins, B-6 also plays a major role in metabolism. It is essential in the synthesis of nonessential amino acids, without it every amino acid would be essential and would have to be supplied by the diet. It also helps maintain blood glucose(sugar) concentration and aids in the synthesis of red blood cells. It also plays a role in synthesizing neurotransmitters (serotonin, dopamine and norepinephrine). Recent research is also connecting B-6 in the prevention of colon cancer and reduction of inflammation.
B-6 deficiency is rare in the U.S., but when it does occur the symptoms are dermatitis, anemia, convulsions, depression and confusion (altered neurotransmitters). The elderly, smokers and alcoholics are at risk for deficiency and may need supplementation.
Folate
The name folate comes from the Greek word folium, which means leaf. Folate was given this name because leafy green vegetables are excellent sources of this vitamin. You may have heard of Folic Acid, this is the man-made version that is found in supplements and fortified foods. The foods with the most bioavailable folate are liver, legumes, and leafy green vegetables. Other sources are avocados and oranges.
The U.S. began mandatory fortification of enriched grain cereals in 1998, which has made these products good sources of folic acid. Food processing and preparation can destroy 50-90% of the folate in food, as it is extremely susceptible to heat, oxidation and light damage. Adults need 400 μg/day, which most Americans exceed. The Upper Level is 1000 μg. Intakes above this level can mask B-12 deficiency. The Upper Level applies to folic acid, not folate found naturally in food.
Folate is required for the synthesis and maintenance of new cells and is critical for DNA synthesis and amino acid metabolism. Another key function is the formation of neurotransmitters (serotonin, dopamine and norepinephrine) in the brain.
Folate deficiency was fairly common in the U.S. before mandatory fortification was established. The need for this vitamin is greatly increased in pregnant women (increased rate of cell division & DNA synthesis), and it is estimated that nearly 20% of women in their childbearing years are deficient. Deficiency can cause anemia, decreased absorption capabilities in the GI tract, diminished immune function and increased neural tube birth defects in early pregnancy.
B-12
B-12 has two unique characteristics among all the vitamins. First, foods of animal origin (meat, poultry, fish and dairy) are the only reliable food sources and secondly, it is the only vitamin that contains the mineral cobalt as part of its structure. The discovery of B-12 and how it prevents pernicious anemia, were so significant that the researchers who made the discovery were awarded six Nobel prizes between 1934-1965.
Plants don’t make B-12 at all, so animals actually get it from soil (bacteria) ingested during grazing. Animals such as cows and sheep also synthesize B-12 from the bacteria in their stomachs. Humans get the necessary B-12 from meat, poultry, seafood, eggs and dairy products. Organ meats are especially rich in B-12. Those who don’t eat animal products can get B-12 from fortified products such as cereal. The RDA is 2.4 μg/day for adults. Americans typically exceed this amount which provides the average person with 2 to 3 years storage of B-12 in the liver. No toxicity has been reported with excess consumption from food or supplement use.
B-12 is needed in methylation reactions for DNA & RNA regulation, myelin regulation and the synthesis of many biochemical compounds. It is also needed for folate to be re-formed and used in the body.
Deficiency can cause pernicious anemia due to inadequate production of intrinsic factor (required for B-12 absorption), megoblastic anemia, nerve degeneration, mental problems, visual disturbances, elevated homocysteine levels (heart attack & stroke). Deficiency occurs in nearly 20% of the elderly population due to impaired absorption as we age. Eating more foods that are fortified with B-12 is recommended. Injections, nasal gel and very high oral doses are also options for those with a deficiency.