18 Micronutrients and the Circulatory System

Micronutrients: Role in Heart and Circulatory System

Learning Outcomes

• Define micronutrients.
• List micronutrient groups (minerals, vitamins) and examples of their roles in the body.
• Describe the roles of micronutrients in:
  • Blood clotting
  • Cardiac function
  • Blood pressure
• Discuss the roles of iron in the body.
• Recall the micronutrients involved in red blood cell production, their roles, and deficiency disorders.

Micronutrients

• Substances required in very small quantities (mg per day) to maintain life and growth.
• Include:
  • Minerals (e.g., Ca, P) - inorganic
  • Water-soluble vitamins (organic)
  • Fat-soluble vitamins (organic)
• Different from macronutrients (protein, carbohydrates, fats).
• Micro-nutrition: body requires tiny amounts for basic survival.
• Deficiency can lead to severe health complications.

Micronutrient Groups and Roles

Micronutrients Involved in Body Functions

• Focus on cardiovascular system functions.

Micronutrients in the Heart and Circulatory System

• Red blood cells: Iron, Copper, Vitamin A, Vitamin B2, Vitamin B12, Folate
• Clotting factors: Vitamin K
• Cardiac function: Vitamin B1 (Thiamin), Selenium, Potassium, Calcium, Magnesium
• Blood pressure: Sodium, Potassium, Calcium, Magnesium

Cardiac Function

• Vitamin B1 (Thiamin)
  • Release of energy supplied to the heart.
  • Deficiency:
    • Cardiac enlargement, oedema (swelling).
    • Build-up of lactate and pyruvate.
    • Vasodilation (widening of blood vessels).
    • Increased workload on the heart, potentially leading to cardiomyopathy (difficulty pumping blood).
• Selenium
  • Component of glutathione peroxidase, protecting cells against reactive oxygen species.
  • Present in selenocysteine amino acids at the active site of enzymes.
  • Supplementation may provide antioxidant protection in aged individuals and patients susceptible to ischemic heart disease and myocardial hypoxia.
• Potassium (K), Calcium (Ca), Magnesium (Mg)
  • Involved in electrical signaling in the heart.
  • Deficiencies result in arrhythmias (irregular heartbeat) due to uncoordinated electrical signals.
  • Normally induced by pathological conditions or drug actions rather than dietary inadequacies.
• Cardiac muscle needs adequate nutrition; deficiencies can lead to cardiomyopathy.

Blood Pressure

• Sodium (Na)
  • Main cationic electrolyte of blood and extracellular fluid.
  • Plays a major role in regulating body fluids and acid-base balance through Na/K pump systems.
  • Excessive sodium intake can lead to hypertension (sodium tends to hold water).
• Calcium (Ca)
  • Can reduce blood pressure.
  • Involved in smooth muscle function and blood pressure control.
  • May protect cardiac muscle from injury during ischemia.
• Potassium (K)
  • Primary intracellular cation, exchanged with sodium.
  • Higher dietary potassium intake can reduce blood pressure (promotes natriuresis - excretion of sodium in the urine).
• Magnesium (Mg)
• Mineral Sources:
  • Na: Processed foods
  • K: Potatoes, vegetables, and nuts
  • Ca: Dairy
  • Mg: Cereals, nuts, legumes

Clotting

• Vitamin K
  • Small group of fat-soluble vitamins containing the naphthoquinone group (1,4-Naphthoquinone).
  • Vitamin K1, Vitamin K2 are examples
  • Involved in the synthesis of \gamma-carboxyglutamic acid from glutamic acid.
  • Required for the synthesis of clotting factors (prothrombin, factors VII, IX, and X), which contain \gamma-carboxyglutamates.
• Dietary deficiency is rare as it is prevalent in many food sources, especially dark green vegetables.
• Deficiency leads to major problems with blood clotting.
• Warfarin, an anticoagulant, prevents the regeneration of Vitamin K.

Roles of Iron and Intake/Absorption

• Roles:
  • Iron is key in the oxygen-carrying and storage proteins within the body (hemoglobin and myoglobin).
  • Essential to energy-producing reactions such as electron transfer chains and oxidative phosphorylation (cytochromes).
• Intake/Absorption:
  • Dietary sources are heme (fish, liver, meat, eggs) and non-heme (green vegetables, nuts) iron.
  • Absorption is tightly controlled as iron is toxic.
  • Excess ingested iron is stored in enterocytes and shed at the end of their life cycle.
  • Non-haem iron (Fe^{3+}) - Ferric
  • Haem iron (Fe^{2+}) - Ferrous

Factors Affecting Iron Absorption

• Promote non-heme iron absorption:
  • Vitamin C
  • Citric acid
  • Lactic acid
  • Fructose
  • Peptides from meat sources
• Inhibit non-heme iron absorption:
  • Phytate (whole grain cereal)
  • Polyphenols (tea, coffee)
  • Oxalic acid
  • Phosphates (egg yolk)
  • Zinc and calcium

Red Blood Cells

• Iron
  • 60% of body’s iron is found in RBCs as part of hemoglobin.
  • The remainder is concentrated in bone marrow (site of RBC synthesis) and liver (in Ferritin: protein shell containing iron).
  • Iron deficiency anemia (IDA) is the most common nutritional deficiency in the world.
  • IDA can eventually lead to heart failure (due to cardiac stress).

Red Blood Cell Synthesis

• Copper (Cu)
  • Component of caeruloplasmin in RBCs and blood plasma, which converts Fe^{2+} to Fe^{3+}.
  • Cu deficiency leads to hypochromic anemia (less hemoglobin than normal—appears pale).
  • Cu deficiency is rare as Cu is widely available from many dietary sources.
• Vitamin A (retinol, retinal, carotinoids)
  • Involved in utilizing iron from ferritin.
  • Vitamin A deficiency is a common cause of IDA.
  • Menke’s disease is a congenital disorder that results in copper deficiency due to poor Cu absorption.
• Vitamin B2 (riboflavin)
  • Deficiency leads to hypochromic IDA due to impaired Fe absorption.
• Vitamin B6 (pyridoxine)
  • Involved in the incorporation of Fe into heme.
• Vitamin B12 (cobalamins) and Vitamin B9 (folate)
  • Deficiencies result in reduced DNA synthesis in developing RBCs prior to division, resulting in large dilute cells with low oxygen-carrying capacity.
  • Causes macrocytic anemia or folate deficiency anemia.
  • Vitamin B12 deficiency occurs in vegans as it is only found in animal dietary sources.

Summary Table: Micronutrients and Red Blood Cell Synthesis