Module 10

Minerals:

• Minerals

  • inorganic nutrients that are essential in the diet.

• There are two types of minerals

  • macrominerals and microminerals.

• Macrominerals

  • present in greater amounts in the body

  • The recommended intake is ≥100 mg per day.

  • Examples of macrominerals include

    • calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium.

• Microminerals, also called trace minerals

  • have a recommended intake of <100 mg per day.

  • Examples of microminerals include

    • iron, copper, manganese, and iodine.

Calcium:

• Calcium is the most abundant mineral in the body.

  • 99% of calcium is in the skeleton or bones and teeth.

  • 1% is found in blood, extracellular fluids, muscle, and other tissues.

    • Muscle contraction and nerve trasmission

• Blood levels of calcium are regulated by:

  • Vitamin D

  • Parathyriod hormone

• Calcium is constantly deposited into and released from bone

• Calcium plays an important role in hormone regulation

  • A hormone’s impact on a cell may be mediated by the hormone’s effect on cellular calcium levels.

    • The hormone binds to cell surface receptors.

    • This triggers the release of calcium in the cell.

Calcium in Bone:

• Critical calcium function is building and maintenance of bone

• Bone composition

  • Protein collagen is the structural framework of bone.

    • Vitamin C is needed for collagen synthesis.

Minerals in bone:

• Primarily calcium and phosphorus.

• Calcium makes up the crystal in bone, hydroxyapatite, which provides bone strength.

  • Magnesium, sodium, phosphorus, and fluoride are also part of the crystal.

• Blood vessels and nerves deliver nutrients and information to bone.

Functions of calcium in muscle and nerve cells:

• Muscle contraction

  • Calcium enters muscle cells to initiate contraction.

• Conduction of nerve impulses

• Calcium allows the release of neurotransmitters.

  • Calcium regulates levels of Na⁺ and K⁺ ions across the nerve membrane.

Calcium Other Functions:

• Calcium is central to blood clotting

  • Calcium is needed to convert prothrombin into thrombin.

• Calcium can have a protective effect against hypertension

• Pre-eclampsia is a condition that affects some pregnant women, also called toxemia of pregnancy.

  • Symptoms: headache, fatigue, protein in urine, high blood pressure

  • Can lead to eclampsia (seizures during pregnancy - second trimester)

Women at risk for pre-eclampsia:

• overweight women

• teenagers who are pregnant

• women with low calcium status

Blood levels of calcium are regulated by:

• Hormone that regulates calcium

• Parathyroid hormone (PTH)

• Activating vitamin D

Three organs respond to low blood calcium:

• Intestine

• Bones

• Kidneys

Calcium and Vitamin D in Bone Health

• Bone is in a constant state of remodeling or turnover.

  • This involves the simultaneous break down and rebuilding of bone.

  • This enables adaptation to physical stress, injury, growth, and nutritional changes.

  • Bone density peaks around the mid-30s.

• When bone loss is greater than bone gain or maintenance, there is a loss of structure and density.

  • Osteopenia/malacia - weakening/softening of bone density

  • Osteoporosis – bones become porous (loss of strength and density)

    • Higher risk of fractures and breaks

• If there is adequate calcium intake, blood calcium levels remain normal. However, if there is inadequate intake, blood calcium levels will still remain normal, but the bones will give up calcium to the blood, resulting in weak, osteoporotic bones.

Osteoporosis:

• Common bone disease in Western countries.

  • Most prevalent in people > 50 yrs. of age. However, it may occur as early as your 20s.

  • There is no cure for osteoporosis.

Osteoporosis prevention:

• Balanced diet with adequate calcium and vitamin D

• Regular exercise (includes aerobic and strength)

• Avoid smoking

• Limit alcohol intake

Risk Factors for Osteoporosis:

• Nonmodifiable:

  • female gender, older age (>50 yrs. of age), small frame, Caucasian or Asian, family history of osteoporosis or broken bones, personal history of fractures, and estrogen deficiency in women (amenorrhea or menopause)

• Modifiable:

  • sedentary lifestyle, diet, cigarette smoking, excess alcohol consumption, low body weight, use of certain medications

Calcium Absorption and Blood Levels:

• Blood levels of calcium are tightly regulated within a narrow range.

  • Hormones that regulate calcium:

    • Parathyroid hormone (PTH)

    • Vitamin D

Three organs respond to low blood calcium levels:

• Intestine

• Bones

• Kidneys

Dietary Factors and Absorption:

• Average absorption of calcium ingested = 30%

• Dietary factors that can decrease the absorption of calcium and other minerals in the diet

• Some plant based foods contain a compound called:

  • Phytates - bind certain minerals, making them unavailable to cells:

    • Calcium

    • Zinc

    • Iron

      • Cooking, soaking or other methods can help to lessen the effects of phytates.

• Oxalate - another compound that binds minerals with positive charges:

  • found in tea and chocolate

Factors that can increase calcium absorption:

• The presence of milk sugar, lactose, in the gut promotes calcium absorption.

• Increased physiological need for calcium:

  • periods of growth (infancy absorption is 55 to 60% of ingested calcium)

  • pregnancy and lactation (doubles absorption of calcium)

Calcium Requirements:

• RDA for adults ages 19 – 50 yrs. = 1,000 mg per day

• RDA for females > age 50 yrs. and males > 70 yrs. = 1,200 mg per day

• RDA for adolescents = 1,300 mg per day

Food Sources of Calcium:

• Dairy products are the best calcium sources, but other sources are available:

  • Canned sardines and salmon with bones

  • Turnip greens

  • Broccoli

  • Other green, leafy vegetables

    • except spinach

• Supplements and functional foods are popular calcium sources.

  • Calcium absorption varies with the form of calcium in the product.

Phosphorus:

• Phosphorus is the 2nd most abundant mineral in the body.

  • 85% is in our bones and teeth.

  • The remainder is found in soft tissues, for example, muscle.

• Phosphorus is usually found as a compound with four oxygen atoms.

  • The resulting structure is phosphate.

  • Provides energy - as part of ATP

Role of Phosphorus:

• Part of bones and teeth

• Facilitates enzyme function

  • Can also turn off the function of enzymes

• Component of adenosine triphosphate (ATP)

  • “usable” form of energy

  • Most B vitamins become active when phosphate is attached.

• Component of DNA and RNA

• Component of phospholipids

  • Part of cell membranes

  • Lipoproteins

• Involved in acid-base balance

  • Phosphorus ions act as a buffer in the blood

Food Sources of Phosphorus:

• meat, fish, and poultry

• Eggs

• milk and milk products

• cereals and grains

• Legumes

• Other sources

  • tea, coffee, chocolate, and soft drinks

Phosphorus Requirements:

• RDA for adults = 700 mg per day

Magnesium

• Magnesium is the macromineral found in the smallest amount in the body.

• The average adult human body contains ~35 g of magnesium.

  • ~50% is located in bone.

  • The remainder is in:

  • soft tissue

    • skeletal muscle, heart, and liver

      • cells (majority is in cells)

  • body fluids

    • ~1% of the body’s magnesium is in the blood and other fluids.

Role of Magnesium:

• Component of hydroxyapatite crystals in bone matrix

  • Bone serves as a store of magnesium.

• Maintenance of DNA and RNA integrity

  • Works with phosphorus

• Facilitates muscle contraction:

  • Calcium – contraction

  • Magnesium – relaxation

• In the cell, magnesium is a cofactor for almost 300 different enzymes

Absorption may decrease with a low protein intake.

Magnesium Requirements:

• RDA:

  • 400 mg per day for men

  • 320 mg per day for women

  • Most Americans consume below this amount.

Magnesium Food Sources:

• Green leafy vegetables (spinach, collards, and turnip greens – the best!)

• Unpolished grains

• Nuts

• Legumes

• Whole-grain cereals and breads

• Chocolate

Sulfur

• Sulfur is the 7th most abundant mineral in the body.

• In the past, it was used in potions to remedy various ailments, such as skin conditions and parasitic infections.

• The primary storage site for sulfur in the body is in the amino acids methionine and cysteine.

• Sulfur in cysteine can bond to another cysteine to form a bridge or link.

• Sulfur is also a key element in glutathione, a strong antioxidant in the body.

• There are no deficiency conditions associated with sulfur in humans at present.

Sulfur Requirements and Food Sources:

• Dietary sources of sulfur include protein-containing foods.

• B-vitamins biotin and thiamin contain some sulfur.

  • Levels of sulfur in plant-based foods depend on the sulfur content of the soil.

• Sulfur is added to foods as sulfites for preservation or flavoring:

  • breads and other baked goods

  • dried foods

  • canned or pickled foods

  • Condiments

  • wine and beer

• Sulfites added to foods may cause a reaction in some people. This is known as sulfite sensitivity.

• The FDA has banned the use of sulfites in fresh fruits and vegetables.

  • Use is limited to processed foods.

• How can you tell if foods contain sulfites

  • reading the list of ingredients

  • Forms of sulfites include: sulfur dioxide, potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium metabisulfite, or sodium sulfite.

The Microminerals

Iron

• The body stores a relatively small amount of iron (2–4 g).

• Iron deficiency is the most common, widespread nutrient deficiency worldwide.

• Primary Role of Iron:

  • assist in the delivery of O₂ to tissues and cells

    • Iron is found in the center of the hemoglobin molecule.

Roles of Iron - Oxygen delivery

• Iron is found in hemoglobin of red blood cells (RBCs), which delivers O₂ to tissues and cells in the body.

  • It also picks up CO₂.

• The body’s bone marrow produces 2.5 million RBCs per second.

  • An equivalent number of RBCs are destroyed in the liver, spleen, and lymph nodes.

Anemia:

• is a clinical condition in which the hemoglobin level is too low.

• Iron deficiency anemia is one form

  • It is caused by low iron stores or the inability to use iron for hemoglobin synthesis.

• Laboratory tests to screen for anemia include:

  • Hemoglobin, Hematocrit, Ferritin, Transferrin saturation

• Causes of iron-deficiency anemia:

  • Inadequate iron intake

  • Inadequate iron absorption

  • Copper deficiency

  • Blood loss

• Other causes of anemia include:

  • A deficiency of vitamin B₆, vitamin B₁₂, or folate or chronic disease

Forms of Iron in Our Foods:

• Heme iron is the form found in hemoglobin.

  • It is only found in meats, fish, and poultry.

  • It is more readily absorbed in the body.

• Non-heme iron is the elemental form of iron.

  • It is found in plant-based and enriched foods.

  • It is less readily absorbed in the body.

Iron Absorption:

• Iron absorption increases when body stores are low.

• Factors that enhance non-heme iron absorption:

  • Vitamin C

  • Presence of meat, poultry and fish in the diet

    • This is referred to as meat, fish, and poultry factor (MFP).

• Factors that reduce iron absorption:

  • Tannins/polyphenols (coffee, tea)

  • Phytates (whole grains, seeds, nuts, and legumes)

  • Calcium

Iron Requirements:

• RDA:

  • 8 mg/day – males and females over age 50

  • 18 mg/day - women ages 19 to 50 yrs.

    • Increased needs due to iron loss during menstruation

  • 27 mg/day – pregnant women

Iron Food Sources:

• Heme iron:

  • Meat

  • Fish

  • Poultry

  • Shellfish (especially oysters)

• Non-heme iron:

  • Beans

  • Green, leafy vegetables

  • Dried fruit

    • Raisins, Apricots

  • Enriched cereal

Iron Toxicity:

• UL = 45 mg per day

• Some individuals cannot regulate the amount of iron absorbed, which can lead to dangerous levels of iron build-up.

• Hemochromatosis is a genetic disorder that can cause iron toxicity.

• Symptoms of iron toxicity:

  • abdominal pain, fatigue, depression (in early stages)

  • may advance to liver damage if iron build-up is not treated

Zinc

• There has been a great amount of research on zinc in the last 30 years.

• Zinc deficiency is a worldwide problem.

• Zinc is important for the function of nearly 200 different enzymes.

• Zinc is one of the first nutrients known to exert effects at the genetic level.

Roles of Zinc:

• Primary functions:

  • Development of sexual organs and bone growth

  • Alcohol metabolism

  • Antioxidant enzyme function

  • Blood pressure regulation

  • Insulin release and function

  • DNA replication

  • Protein synthesis, growth and development

  • Immune function

  • Hemoglobin synthesis

Zinc Definciency:

• Signs of zinc deficiency

  • Limited growth in young teens, particularly males

  • Poor sexual development (underdeveloped testes in males)

  • Deformed bones

  • Abnormal hair and nails; loss of hair

  • Poor wound healing

  • Hypogeusia

  • Gastrointestinal disturbances

  • Impaired folate and vitamin A absorption

• 40 % of dietary zinc is absorbed in the small intestine.

  • Absorption depends on the body’s needs.

When sufficient body stores exist, the small intestine makes protein to bind zinc and prevent absorption.

Zinc Requirements:

• RDA:

  • 11 mg per day for men

  • 8 mg per day for women

• UL:

  • 40 mg per day

  • Consuming excess zinc may:

    • Decrease HDL

    • Increase risk of infections

Zinc Dietary Sources:

• Good dietary sources

  • Meats

  • poultry (turkey in particular)

  • Oysters

  • Herring

  • Eggs

• Also found in legumes and whole-grain cereals, but these sources have decreased absorption due to the presence of phytates.

Copper

• Copper exerts physiological effects as a cofactor for enzymes.

• It is needed for the absorption, storage, and metabolism of iron.

• Functions of copper:

  • Iron use and incorporation into hemoglobin and RBCs

  • Antioxidant defense against free radicals

  • Strengthening collagen and, therefore, connective tissue

  • Immune defense

  • Synthesis of neurotransmitters

  • Energy production via ATP synthesis

Copper Absorption:

• 50% of dietary copper is absorbed.

• Location of absorption:

  • most absorption occurs in the small intestine.

• Copper and zinc share a protein that regulates how much of each is absorbed. As a result, excess zinc can interfere with copper absorption.

Copper Requirements:

• RDA: 900 µg per day for adult males and females

• Few cases of copper deficiency have been reported.

• UL = 10 mg per day

  • Vomiting and liver damage can occur when the UL is exceeded.

Copper Food Sources:

• Good sources:

  • Organ meats (i.e. liver)

  • Shellfish

  • Chocolate

  • Nuts

  • Legumes

  • Drinking water (especially if water runs through copper pipes)

Selenium

• The selenium content of foods depends on the selenium content of the soil.

• Selenium was once thought to be only a toxic metal.

• Today, selenium is known to be essential for good health and disease prevention.

Roles of Selenium:

• Most important role

  • supports the body’s antioxidant defense system

  • It is part of the antioxidant enzyme, glutathione peroxidase.

  • The activity of the enzyme depends on the level of selenium present.

• Other roles of selenium:

  • Supports production of active thyroid hormone

  • May mediate HIV and AIDS progression

Selenium

• Requirements:

  • RDA: 55 µg per day for adults

    • Increases during pregnancy and lactation

  • UL: 400 µg per day

Selenium Food Sources:

• Good food sources:

  • Seafood (excellent source)

  • Brazil nuts

  • Meats and organ meats

  • Eggs

• Other food sources:

  • Wheat-based cereals and sunflower seeds

    • if grown in areas with adequate selenium soil content

Iodine

• Primary function of iodine

  • facilitates the production of a hormone in the thyroid gland

    • This hormone is called thyroid hormone or thyroxine.

      • It controls basal metabolic rate.

      • It is made from tyrosine and iodine.

Iodine Deficiency:

• A lack of iodine in the diet results in thyroid gland cells enlarging in an attempt to absorb more iodine from the blood.

  • An enlarged thyroid is referred to as a goiter.

Iodine deficiency in pregnant women may cause:

• stunted physical growth

• developmental delays

Iodine Requirements:

• RDA: 150 µg per day

• UL: 1,100 µg per day

  • Excess intake can lead to an enlarged thyroid gland.

Iodine Food Sources:

• Food sources:

  • Seafood

  • Iodized salt

  • Plants grown in areas with sufficient iodine in the soil are also good sources of iodine.