Feel the Burn
The disease pellagra has been known since the introduction of corn to Europe in the 1700s. The connection between pellagra and niacin was confirmed in 1937 by an American scientist who was searching for the cause of pellagra.
Vitamin B3 can be found in two different forms, niacin and niacinamide. Niacin is known chemically as nicotinic acid and can cause skin flushing if taken in larger doses. Niacinamide is the form of niacin commonly found in the blood and is known chemically as nicotinamide. Nicotinic acid can easily be converted into nicotinamide in the body. By the way, there is no chemical relationship to the nicotine in tobacco.
Niacin = Nicotinic Acid
Niacinamide = Nicotinamide
Niacin is used in two coenzyme forms, Nicotinamide Adenine Dinucleotide (NAD) and Nicotinamide Adenine Dinucleotide Phosphate (NADP). Hundreds of enzymes require the niacin coenzymes, NAD and NADP. These enzymes are mainly used to accept or donate electrons to make energy or build molecules. NAD often functions in reactions involving the release of energy from carbohydrates, fats, proteins, and alcohol. Please note that NAD is used in many reactions involving energy production, as seen in Figure -9. NADP functions more often in biosynthesis, such as in the synthesis of fatty acids and cholesterol.
Niacin Coenzyme forms are:
Nicotinamide Adenine Dinucleotide (NAD)
Nicotinamide Adenine Dinucleotide Phosphate (NADP)
Niacin can be made in the body from the essential amino acid tryptophan. When tryptophan is consumed in excess of protein needs, one sixtieth of the excess tryptophan can be converted to niacin. The niacin quivalent (NE) of food includes the niacin present plus the amount of niacin that can be made from tryptophan. In some foods, the tryptophan content is more important than the niacin content in providing niacin equivalents.
When a severe deficiency of niacin occurs, the deficiency disease is called pellagra. Pellagra is characterized by the four Ds: diarrhea, dermatitis, dementia, and death. Pellagra killed thousands of people in the South in the early twentieth
Figure -9 Niacin assists energy production from protein, fats, and carbohydrates.
century who were eating a diet consisting of mostly corn. Most of the niacin in corn is unavailable for easy assimilation, and corn is also low in tryptophan. In Mexico, pellagra is rare even in people on low-protein corn diets (tortillas, for example) because the corn is soaked in lime before the tortillas are cooked. This process releases the niacin for absorption.
Niacin is not toxic when obtained from food. The niacinamide (nicotinamide) form of niacin has not been found to be bothersome when taken in amounts less than 2000 mg per day. Decreased insulin sensitivity and liver toxicity can result from daily amounts over 2000 mg. However, niacin in the form of nicotinic acid can cause “niacin flush” in amounts as low as 35 mg. Nicotinic acid can dilate the capillaries, causing a brief tingling and flushing of the skin.
Summary for Niacin—Vitamin B3
Main function: energy metabolism.
RDA: men, 16 mg; women, 14 mg (niacin equivalent).
No toxicity has been reported from food; flushing has been reported above 35 mg in the nicotinic acid form; no effects have been noted below 2000 mg of niacinamide.
Deficiency disease: pellagra.
Healthy food sources: whole grains and nuts.
Degradation: heat resistant.
Coenzyme forms: Nicotinamide Adenine Dinucleotide
Nicotinic acid has been used to lower blood cholesterol in large doses of 3000 mg or more per day. This has resulted in a lowering of the bad LDL (low density lipoprotein) cholesterol and also raises the good HDL (high density lipoprotein) cholesterol. Liver damage and aggravation of diabetes are potential dangers of such high doses. People with a history of liver disease or abnormal liver function, diabetes, peptic ulcers, gout, cardiac arrhythmias, inflammatory bowel disease, migraine headaches, or alcoholism are more susceptible to the adverse effects of excessive nicotinic acid intake. Doses of 3000 mg or more per day are potentially dangerous therapies and must be supervised.
The average diet supplies an adequate amount of niacin. Niacin is not stored in the body. Cooked whole grains, legumes, and seeds are preferred sources of niacin; please refer to Graph 3. Enriched grains, mushrooms, leafy green vegetables, and nutritional yeast are other good sources. Pork, beef, chicken, fish, and dairy products are very high in niacin, but are also high in cholesterol.
Niacin is somewhat heat-resistant and is not depleted with normal cooking. Niacin may, however, be leached into cooking water. Niacin is also subject to losses during processing and storage, as seen in Figure -10.
The RDA for niacin is 16 mg for men and 14 mg for women. For the nicotinic acid form of niacin, the upper limit to avoid flushing is 35 mg per day. Niacin used in supplements and as food fortification is usually in the form of nicotinamide (niacinamide), which has no flushing effect. Nicotinic acid (niacin) is also available as a supplement, but should be kept to small doses to avoid flushing.
.Graph 3 Niacin amounts in some common foods.
The name biotin is taken from the Greek word bios, which means life. Biotin was originally referred to as vitamin H. Biotin was discovered in late 1930s when animals developed skin problems when fed only egg whites. It took forty years of research to confirm biotin as a B vitamin because deficiency is so rare. Biotin is
required by plants and animals. Biotin can only be synthesized by bacteria, algae, yeasts, molds, and a few plant species.
Biotin is used in four important enzymes, known as carboxylases (enzymes that donate carbon dioxide). Acetyl-CoA carboxylase is required for the synthesis of fatty acids. Pyruvate carboxylase is needed for the production of glucose from fats and proteins (called gluconeogenesis). Methylcrotonyl-CoA carboxylase is a catalyst in the metabolism of leucine, an essential amino acid. Propionyl-CoA carboxylase is needed for the metabolism of cholesterol, amino acids, and certain fatty acids.
Biotin Coenzyme forms are:
Acetyl-CoA carboxylase helps make fatty acids Pyruvate carboxylase helps make blood sugar from fats and protein Methylcrotonyl-CoA carboxylase helps metabolize the amino acid leucine Propionyl-CoA carboxylase helps burn fats
Biotin is needed to make energy in the mitochondria of the cell as shown in Figure -11. Biotin may also play a role in the transcription and replication of DNA.
Figure -11 Biotin assists energy production in the cell.
Deficiency of biotin has been noted in prolonged intravenous feeding where biotin was omitted. The only other example of biotin deficiency is from long-term consumption of raw egg whites. Biotin can bind to avadin, a protein found in egg whites. Cooking inactivates this bond, so cooked egg whites do not bind biotin.
Deficiency can result from a genetic lack of biotinidase, an enzyme that releases biotin from small proteins. This lack of biotinidase is a rare hereditary disorder. Pregnant women may be at risk for borderline biotin deficiency. The developing fetus requires more biotin than is sometimes available. Also, large doses of pantothenic acid may compete with biotin for absorption in the intestines; this is because pantothenic acid and biotin have very similar structures.
Biotin is made by the bacteria living in healthy large intestines. The wall of the large intestine has a specialized process for the uptake of biotin. This may be one reason why biotin deficiency is so rare.
Summary for Biotin
Main function: energy metabolism.
Adequate Intake: Men and women, 30 mcg.
No toxicity reported.
Deficiency is very rare.
Healthy food sources: found in a wide variety of foods.
Degradation: uncooked egg whites bind biotin.
Coenzyme forms: Acetyl-CoA carboxylase, Pyruvate carboxylase, Methylcrotonyl-CoA carboxylase, and
Propionyl-CoA carboxylase.
Adequate intake for biotin has been set at 30 mcg per day for healthy adults. Biotin is found in a wide variety of foods. Anticonvulsant medications may lower biotin levels. Additionally, antibiotics may lower the production of biotin because some antibiotics kill bacteria in the colon. Biotin is not known to be toxic.
The disease pellagra has been known since the introduction of corn to Europe in the 1700s. The connection between pellagra and niacin was confirmed in 1937 by an American scientist who was searching for the cause of pellagra.
Vitamin B3 can be found in two different forms, niacin and niacinamide. Niacin is known chemically as nicotinic acid and can cause skin flushing if taken in larger doses. Niacinamide is the form of niacin commonly found in the blood and is known chemically as nicotinamide. Nicotinic acid can easily be converted into nicotinamide in the body. By the way, there is no chemical relationship to the nicotine in tobacco.
Niacin = Nicotinic Acid
Niacinamide = Nicotinamide
Niacin is used in two coenzyme forms, Nicotinamide Adenine Dinucleotide (NAD) and Nicotinamide Adenine Dinucleotide Phosphate (NADP). Hundreds of enzymes require the niacin coenzymes, NAD and NADP. These enzymes are mainly used to accept or donate electrons to make energy or build molecules. NAD often functions in reactions involving the release of energy from carbohydrates, fats, proteins, and alcohol. Please note that NAD is used in many reactions involving energy production, as seen in Figure -9. NADP functions more often in biosynthesis, such as in the synthesis of fatty acids and cholesterol.
Niacin Coenzyme forms are:
Nicotinamide Adenine Dinucleotide (NAD)
Nicotinamide Adenine Dinucleotide Phosphate (NADP)
Niacin can be made in the body from the essential amino acid tryptophan. When tryptophan is consumed in excess of protein needs, one sixtieth of the excess tryptophan can be converted to niacin. The niacin quivalent (NE) of food includes the niacin present plus the amount of niacin that can be made from tryptophan. In some foods, the tryptophan content is more important than the niacin content in providing niacin equivalents.
When a severe deficiency of niacin occurs, the deficiency disease is called pellagra. Pellagra is characterized by the four Ds: diarrhea, dermatitis, dementia, and death. Pellagra killed thousands of people in the South in the early twentieth
century who were eating a diet consisting of mostly corn. Most of the niacin in corn is unavailable for easy assimilation, and corn is also low in tryptophan. In Mexico, pellagra is rare even in people on low-protein corn diets (tortillas, for example) because the corn is soaked in lime before the tortillas are cooked. This process releases the niacin for absorption.
Niacin is not toxic when obtained from food. The niacinamide (nicotinamide) form of niacin has not been found to be bothersome when taken in amounts less than 2000 mg per day. Decreased insulin sensitivity and liver toxicity can result from daily amounts over 2000 mg. However, niacin in the form of nicotinic acid can cause “niacin flush” in amounts as low as 35 mg. Nicotinic acid can dilate the capillaries, causing a brief tingling and flushing of the skin.
Summary for Niacin—Vitamin B3
Main function: energy metabolism.
RDA: men, 16 mg; women, 14 mg (niacin equivalent).
No toxicity has been reported from food; flushing has been reported above 35 mg in the nicotinic acid form; no effects have been noted below 2000 mg of niacinamide.
Deficiency disease: pellagra.
Healthy food sources: whole grains and nuts.
Degradation: heat resistant.
Coenzyme forms: Nicotinamide Adenine Dinucleotide
Nicotinic acid has been used to lower blood cholesterol in large doses of 3000 mg or more per day. This has resulted in a lowering of the bad LDL (low density lipoprotein) cholesterol and also raises the good HDL (high density lipoprotein) cholesterol. Liver damage and aggravation of diabetes are potential dangers of such high doses. People with a history of liver disease or abnormal liver function, diabetes, peptic ulcers, gout, cardiac arrhythmias, inflammatory bowel disease, migraine headaches, or alcoholism are more susceptible to the adverse effects of excessive nicotinic acid intake. Doses of 3000 mg or more per day are potentially dangerous therapies and must be supervised.
The average diet supplies an adequate amount of niacin. Niacin is not stored in the body. Cooked whole grains, legumes, and seeds are preferred sources of niacin; please refer to Graph 3. Enriched grains, mushrooms, leafy green vegetables, and nutritional yeast are other good sources. Pork, beef, chicken, fish, and dairy products are very high in niacin, but are also high in cholesterol.
Niacin is somewhat heat-resistant and is not depleted with normal cooking. Niacin may, however, be leached into cooking water. Niacin is also subject to losses during processing and storage, as seen in Figure -10.
The RDA for niacin is 16 mg for men and 14 mg for women. For the nicotinic acid form of niacin, the upper limit to avoid flushing is 35 mg per day. Niacin used in supplements and as food fortification is usually in the form of nicotinamide (niacinamide), which has no flushing effect. Nicotinic acid (niacin) is also available as a supplement, but should be kept to small doses to avoid flushing.
.Graph 3 Niacin amounts in some common foods.
Figure -10 Niacin can leach into cooking water and can be lost during storage
and processing.
Biotin—the Energy Catalyst
required by plants and animals. Biotin can only be synthesized by bacteria, algae, yeasts, molds, and a few plant species.
Biotin is used in four important enzymes, known as carboxylases (enzymes that donate carbon dioxide). Acetyl-CoA carboxylase is required for the synthesis of fatty acids. Pyruvate carboxylase is needed for the production of glucose from fats and proteins (called gluconeogenesis). Methylcrotonyl-CoA carboxylase is a catalyst in the metabolism of leucine, an essential amino acid. Propionyl-CoA carboxylase is needed for the metabolism of cholesterol, amino acids, and certain fatty acids.
Biotin Coenzyme forms are:
Acetyl-CoA carboxylase helps make fatty acids Pyruvate carboxylase helps make blood sugar from fats and protein Methylcrotonyl-CoA carboxylase helps metabolize the amino acid leucine Propionyl-CoA carboxylase helps burn fats
Biotin is needed to make energy in the mitochondria of the cell as shown in Figure -11. Biotin may also play a role in the transcription and replication of DNA.
Figure -11 Biotin assists energy production in the cell.
Deficiency of biotin has been noted in prolonged intravenous feeding where biotin was omitted. The only other example of biotin deficiency is from long-term consumption of raw egg whites. Biotin can bind to avadin, a protein found in egg whites. Cooking inactivates this bond, so cooked egg whites do not bind biotin.
Deficiency can result from a genetic lack of biotinidase, an enzyme that releases biotin from small proteins. This lack of biotinidase is a rare hereditary disorder. Pregnant women may be at risk for borderline biotin deficiency. The developing fetus requires more biotin than is sometimes available. Also, large doses of pantothenic acid may compete with biotin for absorption in the intestines; this is because pantothenic acid and biotin have very similar structures.
Biotin is made by the bacteria living in healthy large intestines. The wall of the large intestine has a specialized process for the uptake of biotin. This may be one reason why biotin deficiency is so rare.
Summary for Biotin
Main function: energy metabolism.
Adequate Intake: Men and women, 30 mcg.
No toxicity reported.
Deficiency is very rare.
Healthy food sources: found in a wide variety of foods.
Degradation: uncooked egg whites bind biotin.
Coenzyme forms: Acetyl-CoA carboxylase, Pyruvate carboxylase, Methylcrotonyl-CoA carboxylase, and
Propionyl-CoA carboxylase.
Adequate intake for biotin has been set at 30 mcg per day for healthy adults. Biotin is found in a wide variety of foods. Anticonvulsant medications may lower biotin levels. Additionally, antibiotics may lower the production of biotin because some antibiotics kill bacteria in the colon. Biotin is not known to be toxic.
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