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.