Skip to main content
Medicine LibreTexts

10.2: Vitamins Important for Metabolism and Blood Function

  • Page ID
    21165
  • Learning Objectives

    • Summarize the role of the B vitamins in metabolism.
    • Describe the role of the B vitamins in blood function.
    • Explain how Vitamin K supports blood function.

    While the macronutrients (carbohydrates, lipids, and proteins) and alcohol can be broken down (catabolized) to release energy, vitamins and minerals play a different kind of role in energy metabolism; they are required as functional parts of enzymes involved in energy release and storage. In other words, they're necessary for obtaining energy from the macronutrients (vitamins and minerals don't directly provide energy/calories). Vitamins and minerals that make up part of enzymes are referred to as coenzymes and cofactors, respectively. Coenzymes and cofactors are required by enzymes to catalyze a specific reaction. They assist in converting a substrate to an end-product (Figure \(\PageIndex{1}\)). Coenzymes and cofactors play many roles in catabolic and anabolic pathways.

    Coenzymes combine with enzymes to activate them, ensuring that the chemical reactions that depend upon these enzymes can occur.
    Figure \(\PageIndex{1}\): Coenzymes and cofactors are the particular vitamin or mineral required for enzymes to catalyze a specific reaction. (CC BY 4.0; by OpenStax)

    In addition to being essential for metabolism, many vitamins and minerals are required for blood to function properly. At insufficient levels in the diet these vitamins and minerals impair the health of blood and consequently the delivery of nutrients and removal of wastes. In this section we will focus on the vitamins that take part in metabolism and blood function.

    Thiamin (Vitamin B1)

    The water-soluble vitamin, thiamin, is especially important in glucose metabolism. It acts as a coenzyme for enzymes that break down glucose and branched chain amino acids for energy production. Additionally, thiamin plays a role in the synthesis of ribose from glucose and is therefore required for RNA, DNA, and ATP synthesis. The brain and heart are most affected by a deficiency in thiamin. Thiamin deficiency, also known as beriberi, can cause symptoms of fatigue, confusion, muscle wasting, nerve damage, movement impairment, pain in the lower extremities, swelling, and heart failure. The DRIs for thiamin are listed in Table \(\PageIndex{1}\)1. A Tolerable Upper Intake Level (UL) for thiamin has not been set. Food sources of thiamin include whole grains, meat, fish, and enriched or fortified grains. Other good food sources of thiamin are included in Table \(\PageIndex{2}\)2.

    Table \(\PageIndex{1}\): Dietary Reference Intakes for Thiamin
    Age Group RDA (mg/day)
    Infants (0–6 months) 0.2*
    Infants (7–12 months) 0.3*
    Children (1–3 years) 0.5
    Children (4–8 years) 0.6
    Children (9–13 years) 0.9
    Adolescents (14–18 years) 1.2 (males), 1.0 (females)
    Adults (> 19 years) 1.2 (males), 1.1 (females)
    * denotes Adequate Intake

     

    Table \(\PageIndex{2}\): Dietary Sources of Thiamin
    Food Thiamin (mg) % Daily Value
    Rice, white, enriched, cooked (1/2 cup) 1.4 117
    Breakfast cereals, fortified (1 serving) 1.2 100
    Pork chop (3 ounces) 0.4 33
    Black beans, boiled (1/2 cup) 0.4 33

    Learn even more about this nutrient by reading the Thiamin Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Riboflavin (Vitamin B2)

    Riboflavin is a water-soluble vitamin that is an essential component of flavoproteins, which are coenzymes involved in many metabolic pathways of carbohydrate, lipid, and protein metabolism. Furthermore, the functions of other B-vitamin coenzymes, such as vitamin B6 and folate, are dependent on the actions of flavoproteins. In addition, ribovlavin is part of the antioxidant enzyme glutathione peroxidase. The “flavin” portion of riboflavin gives a bright yellow color to riboflavin, an attribute that led to its discovery as a vitamin. Riboflavin is destroyed when exposed to light. Riboflavin deficiency, sometimes referred to as ariboflavinosis, is often accompanied by other dietary deficiencies (most notably protein) and can be common in people that suffer from alcoholism. Signs and symptoms of riboflavin deficiency include dry, scaly skin, mouth inflammation and sores, sore throat, itchy eyes, fatigue, muscle weakness, and light sensitivity. The DRIs for riboflavin are listed in Table \(\PageIndex{3}\)1. A Tolerable Upper Intake Level (UL) for riboflavin has not been set. Food sources of riboflavin include eggs, meat, and milk. Other good food sources of riboflavin are included in Table \(\PageIndex{4}\)3.

    Table \(\PageIndex{3}\): Dietary Reference Intakes for Riboflavin
    Age Group RDA (mg/day)
    Infants (0–6 months) 0.3*
    Infants (7–12 months) 0.4*
    Children (1–3 years) 0.5
    Children (4–8 years) 0.6
    Children (9–13 years) 0.9
    Adolescents (14–18 years) 1.3 (males), 1.0 (females)
    Adults (> 19 years) 1.3 (males), 1.1 (females)
    * denotes Adequate Intake

     

    Table \(\PageIndex{4}\): Dietary Sources of Riboflavin
    Food Riboflavin (mg) % Daily Value
    Beef liver (3 ounces) 2.9 223
    Breakfast cereals, fortified (1 serving) 1.3 100
    Yogurt, plain, fat free (1 cup) 0.6 46
    Portabella mushrooms (1/2 cup) 0.3 23
    Almonds (1 ounce) 0.3 23

    Learn even more about this nutrient by reading the Riboflavin Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Niacin (Vitamin B3)

    Niacin is a water-soluble vitamin that is a component of coenzymes involved in the catabolism and/or anabolism of carbohydrates, lipids, and proteins. Niacin deficiency is commonly known as pellagra and is characterized by diarrhea, dermatitis, dementia, and sometimes death. Niacin toxicity may result from taking niacin supplements; symptoms include flushing (burning, tingling, itching, and red skin). The DRIs for niacin are listed in Table \(\PageIndex{5}\)1. Niacin is present in a wide variety of foods including those listed in Table \(\PageIndex{6}\)4.

    Table \(\PageIndex{5}\): Dietary Reference Intakes for Niacin
    Age Group RDA (mg/day) UL (mg/day)
    Infants (0–6 months) 2* ND
    Infants (7–12 months) 4* ND
    Children (1–3 years) 6 10
    Children (4–8 years) 8 15
    Children (9–13 years) 12 20
    Adolescents (14–18 years) 16 (males), 14 (females) 30
    Adults (> 19 years) 16 (males), 14 (females) 35
    * denotes Adequate Intake; ND=not determined  

     

    Table \(\PageIndex{6}\): Dietary Sources of Niacin
    Food Niacin (mg) % Daily Value
    Beef liver (3 ounces) 14.9 93
    Chicken breast (3 ounces) 10.3 64
    Salmon (3 ounces) 8.6 54
    Peanuts (1 ounce) 4.2 26
    Potato, baked (1 medium) 2.3 14

    Learn even more about this nutrient by reading the Niacin Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Vitamin B6

    Vitamin B6 is a water-soluble vitamin and coenzyme involved in nitrogen transfer between amino acids (transamination) and therefore plays a role in non-essential amino acid synthesis and catabolism. Also, it functions to release glucose from glycogen in the catabolic pathway of glycogenolysis and is required by enzymes for the synthesis of multiple neurotransmitters and hemoglobin. A deficiency in vitamin B6 can cause signs and symptoms of muscle weakness, dermatitis, mouth sores, fatigue, and confusion. Vitamin B6 is a required coenzyme for the synthesis of hemoglobin. A deficiency in vitamin B6 can cause a type of anemia where the red blood cell size is normal or somewhat smaller but the hemoglobin content is lower. This means each red blood cell has less capacity for carrying oxygen, resulting in muscle weakness, fatigue, and shortness of breath. A deficiency of vitamin B6 is also associated with an increased risk of cardiovascular disease due to elevated homocysteine levels. Vitamin B6 toxicity may result from supplements and lead to nerve damage. The DRIs for vitamin B6 are listed in Table \(\PageIndex{7}\)1. Vitamin B6 is present in a wide variety of foods including those listed in Table \(\PageIndex{8}\)5.

    Table \(\PageIndex{7}\): Dietary Reference Intakes for Vitamin B6
    Age Group RDA (mg/day) UL (mg/day)
    Infants (0–6 months) 0.1* ND
    Infants (7–12 months) 0.3* ND
    Children (1–3 years) 0.5 30
    Children (4–8 years) 0.6 40
    Children (9–13 years) 1.0 60
    Adolescents (14–18 years) 1.3 (males), 1.2 (females) 80
    Adults (19-50 years) 1.3 100
    Adults (> 50 years) 1.7 (males), 1.5 (females) 100
    * denotes Adequate Intake; ND=not determined  

     

    Table \(\PageIndex{8}\): Dietary Sources of Vitamin B6
    Food Vitamin B6 (mg) % Daily Value
    Chickpeas (1 cup) 1.1 65
    Yellowfin tuna (3 ounces) 0.9 53
    Chicken breast (3 ounces) 0.5 29
    Potatoes, boiled (1 cup) 0.4 25
    Banana (1 medium) 0.4 25

    Learn even more about this nutrient by reading the Vitamin B6 Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Biotin

    Biotin, a water-soluble vitamin, is required as a coenzyme in lipid metabolism. It is also required as an enzyme in the synthesis of glucose and some nonessential amino acids. Biotin is important for gluconeogenesis (the generation of new glucose from amino acids when carbohydrate intake is low). Biotin deficiency is rare, but can be caused by eating large amounts of raw egg whites over an extended period of time. This is because a protein in raw egg whites tightly binds to biotin making it unavailable for absorption. The Adequate Intakes (AIs) for biotin are listed in Table \(\PageIndex{9}\)1. A Tolerable Upper Intake Level (UL) for biotin has not been set. Food sources of biotin include eggs, meat, and fish (Table \(\PageIndex{10}\))6.

    Table \(\PageIndex{9}\): Dietary Reference Intakes for Biotin
    Age Group AI (mcg/day)
    Infants (0–6 months) 5
    Infants (7–12 months) 6
    Children (1–3 years) 8
    Children (4–8 years) 12
    Children (9–13 years) 20
    Adolescents (14–18 years) 25
    Adults (> 19 years) 30

     

    Table \(\PageIndex{10}\): Dietary Sources of Biotin
    Food Biotin (mcg) % Daily Value
    Beef liver (3 ounces) 30.8 103
    Egg, whole, cooked (1 large) 10.0 33
    Salmon, canned (3 ounces) 5.0 17
    Pork chop (3 ounces) 3.8 13
    Sunflower seeds (1/4 cup) 2.6 9

    Learn even more about this nutrient by reading the Biotin Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Folate

    Folate, a water-soluble vitamin, is a required coenzyme for the synthesis of the amino acid methionine as well as RNA and DNA synthesis. Therefore, rapidly dividing cells are most affected by folate deficiency. Folate is especially essential for the growth and specialization of cells of the central nervous system. Children whose mothers were folate-deficient during pregnancy have a higher risk of neural-tube birth defects such as spina bifida, a neural-tube defect that occurs when the spine does not completely enclose the spinal cord (Figure \(\PageIndex{2}\)). Observational studies show that the prevalence of neural-tube defects was decreased after the fortification of enriched cereal grain products with folate in 1996 in the United States compared to before grain products were fortified with folate.

    Drawing of an infant's spinal cord showing an open section of the spinal cord. This is known as spina bifida, a neural-tube defect that occurs when the spine does not completely enclose the spinal cord.
    Figure \(\PageIndex{2}\): Spina bifida is a neural-tube defect that can have severe health consequences. (CC0; by Centers for Disease Control and Prevention via Wikimedia Commons)

    Folate deficiency can lead to macrocytic (also called megaloblastic) anemia. Macrocytic and megaloblastic mean “big cell,” and anemia refers to fewer red blood cells or red blood cells containing less hemoglobin. Macrocytic anemia is characterized by larger and fewer red blood cells. It is caused by red blood cells being unable to produce DNA and RNA fast enough—cells grow but do not divide, making them large in size. Folate toxicity can occur when taking supplements. Excess folate can mask a vitamin B12 deficiency which can lead to nerve damage. The DRIs for folate are listed in Table \(\PageIndex{11}\)1. Folate is present in a wide variety of foods including those listed in Table \(\PageIndex{12}\)7. Folate is sensitive to heat and can lost when foods are cooked.

    Table \(\PageIndex{11}\): Dietary Reference Intakes for Folate
    Age Group RDA (mcg/day) UL (mcg/day)
    Infants (0–6 months) 65* ND
    Infants (7–12 months) 80* ND
    Children (1–3 years) 150 300
    Children (4–8 years) 200 400
    Children (9–13 years) 300 600
    Adolescents (14–18 years) 400 800
    Adults (> 18 years) 400 1,000
    * denotes Adequate Intake; ND=not determined  

     

    Table \(\PageIndex{12}\): Dietary Sources of Folate
    Food Folate (mcg) % Daily Value
    Spinach, boiled (1/2 cup) 131 33
    Black-eyed pea, boiled (1/2 cup) 105 26
    Rice, white, cooked (1/2 cup) 90 22
    Asparagus (4 spears) 89 22
    Lettuce, romaine (1 cup) 64 16

    Learn even more about this nutrient by reading the Folate Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Vitamin B12

    Vitamin B12 is a water-soluble vitamin and an essential part of coenzymes necessary for fat and protein catabolism, for folate coenzyme function, and for hemoglobin synthesis. In addition, vitamin B12 is required for proper nerve functioning. Vitamin B12 works with folate to convert homocysteine into methionine; by preventing a build-up of homocysteine these nutrients help reduce cardiovascular disease risk. An enzyme requiring vitamin B12 is needed by a folate-dependent enzyme to synthesize DNA. Thus, a deficiency in vitamin B12 has similar consequences to health as folate deficiency. In children and adults, vitamin B12 deficiency causes macrocytic anemia; in babies born to vitamin B12-deficient mothers there is an increased risk for neural-tube defects.

    In order for the human body to absorb vitamin B12, the stomach, pancreas, and small intestine must be functioning properly. Cells in the stomach secrete a protein called intrinsic factor that is necessary for vitamin B12 absorption, which occurs in the small intestine. Impairment of secretion of this protein either can lead to the disease pernicious anemia, a type of macrocytic anemia. Atrophic gastritis, a condition where there is chronic inflammation of the stomach (often due to an H. pylori  infection or an autoimmune disorder), can lead to reduced stomach acid production and then in turn less vitamin B12 absorption. Atrophic gastritis becomes more common in people over the age of 50. Pernicious anemia is treated by large oral doses of vitamin B12 or by putting the vitamin under the tongue (sublingual), where it is absorbed into the blood stream without passing through the intestine. In patients that do not respond to oral or sublingual treatment, vitamin B12 is given by injection. Individuals consuming a vegan diet or older than 50 years of age are advised to eat foods fortified with vitamin B12, take vitamin B12 supplements, or receive vitamin B12 injections. There are no known adverse effects related to vitamin B12 toxicity.

    The DRIs for vitamin B12 are listed in Table \(\PageIndex{13}\)1. A Tolerable Upper Intake Level (UL) for vitamin B12 has not been set. Vitamin B12 is naturally found in animal products (Table \(\PageIndex{14}\))8.

    Table \(\PageIndex{13}\): Dietary Reference Intakes for Vitamin B12
    Age Group RDA (mcg/day)
    Infants (0–6 months) 0.4*
    Infants (7–12 months) 0.5*
    Children (1–3 years) 0.9
    Children (4–8 years) 1.2
    Children (9–13 years) 1.8
    Adolescents (14–18 years) 2.4
    Adults (> 19 years) 2.4
    * denotes Adequate Intake

     

    Table \(\PageIndex{14}\): Dietary Sources of Vitamin B12
    Food Vitamin B12 (mcg) % Daily Value
    Rainbow trout, wild (3 ounces) 5.4 225
    Salmon (3 ounces) 4.8 200
    Tuna, light, canned in water (3 ounces) 2.5 104
    Milk, low-fat (1 cup) 1.2 50
    Egg (1 large) 0.6 25

    Learn even more about this nutrient by reading the Vitamin B12 Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    B Vitamin Summary

    B vitamins are water-soluble and are not stored in significant amounts in the body. Therefore, they must be continuously obtained from the diet. B vitamins are naturally present in numerous foods, and many other foods are enriched with them. In the United States, B-vitamin deficiencies are rare. A summary of the prominent functions of the B vitamins in metabolism and blood function, and their deficiency syndromes is given in Table \(\PageIndex{15}\).

    Table \(\PageIndex{15}\): B-Vitamin Functions in Metabolism and Blood, and Deficiency Syndromes
    B Vitamin Function Deficiency: Signs and Symptoms
    B1 (thiamin) Coenzyme: assists in glucose metabolism, RNA, DNA, and ATP synthesis Beriberi: fatigue, confusion, movement impairment, swelling, heart failure
    B2 (riboflavin) Coenzyme: assists in glucose, fat and carbohydrate metabolism, electron carrier, other B vitamins are dependent on Ariboflavinosis: dry scaly skin, mouth inflammation and sores, sore throat, itchy eyes, light sensitivity
    B3 (niacin) Coenzyme: assists in glucose, fat, and protein metabolism, electron carrier Pellagra: diarrhea, dermatitis, dementia, death
    Vitamin B6 Coenzyme; assists in amino-acid synthesis, glycongenolysis, neurotransmitter and hemoglobin synthesis Muscle weakness, dermatitis, mouth sores, fatigue, confusion
    Biotin Coenzyme; assists in glucose, fat, and protein metabolism, amino-acid synthesis Muscle weakness, dermatitis, fatigue, hair loss
    Folate Coenzyme; amino acid synthesis, RNA, DNA, and red blood cell synthesis Diarrhea, mouth sores, confusion, anemia, neural-tube defects
    B12 (cobalamin) Coenzyme; fat and protein catabolism, folate function, red-blood-cell synthesis Muscle weakness, sore tongue, anemia, nerve damage, neural-tube defects

    Vitamin K

    Vitamin K is a fat-soluble vitamin. As discussed in Chapter 9, Vitamin K is required for optimal bone metabolism. Vitamin K is also critical for blood function, as it is a coenzyme for enzymes involved in blood clotting. Blood-clotting proteins are continuously circulating in the blood. Upon injury to a blood vessel, platelets stick to the wound forming a plug. The clotting factors circulating close by respond in a series of protein-protein interactions resulting in the formation of the fibrous protein, fibrin, which reinforces the platelet plug. A deficiency in vitamin K causes bleeding disorders. Signs and symptoms include nosebleeds, easy bruising, broken blood vessels, bleeding gums, and heavy menstrual bleeding in women. The function of the anticoagulant drug warfarin is impaired by excess vitamin K intake from supplements. The Adequate Intakes (AIs) for vitamin K are listed in Table \(\PageIndex{16}\)1. A Tolerable Upper Intake Level (UL) for vitamin K has not been set. Vitamin K is present in many foods and most highly concentrated in green leafy vegetables. Desirable intestinal bacteria also produce vitamin K in the large intestine. See Table \(\PageIndex{17}\)9 for a list of dietary sources of vitamin K.

    Table \(\PageIndex{16}\): Dietary Reference Intakes for Vitamin K
    Age Group AI (mcg/day)
    Infants (0–6 months) 2.0
    Infants (7–12 months) 2.5
    Children (1–3 years) 30
    Children (4–8 years) 55
    Children (9–13 years) 60
    Adolescents (14–18 years) 75
    Adults (> 19 years) 120 (males), 90 (females)

     

    Table \(\PageIndex{17}\): Dietary Sources of Vitamin K
    Food Vitamin K (mcg) % Daily Value
    Natto (3 ounces) 850 708
    Collards, frozen, boiled (1/2 cup) 530 442
    Spinach, raw (1 cup) 145 121
    Broccoli, boiled (1/2 cup) 110 92
    Soybeans, roasted (1/2 cup) 43 36
    Edamame (1/2 cup) 21 18

    Learn even more about this nutrient by reading the Vitamin K Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Key Takeaways

    • Vitamins play a different kind of role in energy metabolism; they are required as functional parts of enzymes involved in energy release and storage.
    • The water-soluble B vitamins are involved as coenzymes in the breakdown of nutrients and in the building of macromolecules, such as protein, RNA, and DNA.
    • B-vitamin deficiencies are relatively rare especially in developed countries; although the health consequences can be severe as with folate deficiency during pregnancy and the increased risk of neural-tube defects in offspring.
    • The B vitamins, pyroxidine (B6), folate, and cobalamin (B12) are needed for blood-cell renewal and/or function.
    • Vitamin K is necessary for blood clotting.

    References

    1. Summary Report of the Dietary Reference Intakes. nationalacademies.org. www.nationalacademies.org/our-work/summary-report-of-the-dietary-reference-intakes. Accessed July 4, 2020.
    2. Thiamin - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Thiamin-HealthProfessional/. Accessed July 4, 2020.
    3. Riboflavin - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/. Accessed July 4, 2020.
    4. Niacin - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Niacin-HealthProfessional/. Accessed July 4, 2020.
    5. Vitamin B6 - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/. Accessed July 4, 2020.
    6. Biotin - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Biotin-HealthProfessional/. Accessed July 4, 2020.
    7. Folate - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/. Accessed July 4, 2020.
    8. Vitamin B12 - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/. Accessed July 4, 2020.
    9. Vitamin K - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/. Accessed July 4, 2020.