The Micronutrients and WaterPart 2

Chapter 2

Content in Body

The Minerals - An Overview

• Inorganic elements– Maintain their structure; hard to destroy– Not changed in body; remain their until excreted

• The body’s handling of minerals– Some need to be complexed with proteins (e.g. iron)– Some can be toxic

• Variable bioavailability– Binders; bind minerals and lower their availability

• Phytates: legumes and grains• Oxalates: spinach

• Nutrient interactions:– High sodium causes excretion of Na+ and Ca2+

– Phosphorous bnds magnesium, limits it’s absorption

• Varied rolesCopyright 2005 Wadsworth Group, a division of Thomson Learning

Copyright 2005 Wadsworth Group, a division of Thomson Learning

Minerals

Consist of 22 mostly metallic elements Minerals essential to life

• 7 major minerals (required in amounts >100 mg daily)

• 14 minor or trace minerals (required in amounts <100 mg daily)

A balanced diet generally provides adequate mineral intake, except in some geographic locations lacking specific minerals.

Roles of Minerals

Provide structure in the formation of bones and teeth

Help to maintain normal heart rhythm, muscle contractility, neural conductivity, and acid-base balance

Regulate metabolism by becoming constituents of enzymes and hormones that modulate cellular activity

Mineral Bioavailability

Factors that affect the bioavailability of minerals in food• Type of food • Mineral–mineral interaction • Vitamin–mineral interaction • Fiber–mineral interaction

Bioavailability

Mineral-mineral competition Similar size Similar electrical charges Ex: magnesium, calcium, iron, copper Competition for absorption

Vitamins-mineral competition Vitamin C improves iron absorption Vitamin D improves calcium absorption

Calcium

Most abundant mineral in body Most is found in the bones (99%) Blood calcium (1%)

Kept in balance with hormones and vitamin D. Blood calcium maintained at the expense of

bone calcium. ECF levels of calcium decrease

Kidneys reabsorb Ca

Calcium

Peak bone mass Bone’s fullest potential in size and density Developed in the first three decades of life.

Osteoporosis

Chronic condition Porous bones

Reduced bone density

Osteopenia Weakened bones

These are progressive diseases Calcium is leeched from bones to meet

body’s needs

Osteoporosis

Risk of Osteoporosis

Advanced age White or Asian female Slight build or tendency to

be underweight Anorexia nervosa or

bulimia nervosa Sedentary lifestyle Postmenopause, including

early or surgically induced menopause

Low testosterone levels in men

High protein intake

Excess sodium intake Cigarette smoking Excessive alcohol use Abnormal absence of

menstrual periods Calcium-deficient diet in

years before and after menopause

Family history of osteoporosis

High caffeine intake (possible)

Vitamin D deficiency

Prevention

Diet Prime defense: adequate calcium in diet

Exercise Weight bearing Wolff’s law

Estrogen supplementation Post-menopause Increases GI absorption, reduces renal excretion, facilitates

absorption into bone

Appropriate age of Menarche

The Female Triad

The Triad usually begins with disordered eating and leads to amenorrhea and then osteoporosis.

Women who train intensely and cut calories below energy requirements may adversely affect menstruation.• Oligomenorrhea – irregular cycles• Amenorrhea – cessation of menstruation

The Female Triad

Calcium

Calcium Roles in the Body Calcium in Bones

Mineralization - minerals crystallize, hardening of the bone. Remodeling constantly taking place.

Bone destroying cells (osteoclasts) – resorption Bone forming cells (osteoblasts) – synthesize

Calcium Balance Works with vitamin D Works with parathyroid hormone and calcitonin

Calcium

Calcium Roles in the Body Calcium Absorption

Absorption rate for adults is 25% of calcium consumed. 50% during pregnancy 50-60% during growth

Calcium

Factors that inhibit absorption Lack of stomach acid Vitamin D deficiency High phosphorus intake

Need to increase Ca intake for balance High-fiber diet

Calcium

Calcium Recommendations AI Adolescents: 1300 mg/day AI Adults: 1000 mg/day if 19-50 years of

age AI Adults: 1200 mg/day if greater than 50

years of age Upper level for adults: 2500 mg/day

Calcium

Toxicity symptoms Constipation, Increased risk of urinary stone formation, Kidney dysfunction, Interference with the absorption of other

minerals.

Calcium

Calcium Sources Calcium in Milk Products

Drink milk. Eat yogurt and cheese. Add dry milk during food preparation.

Phosphorus

Phosphorus Roles in the Body Mineralization of bones and teeth (85%) Part of every cell (buffer)

Buffer systems that maintain acid-base balance

An essential component of AMP, PCr, and ATP Adenosine triphosphate (ATP) Phosphocreatine (PCr)

Phosphorus

Phosphorus Roles in the Body Ph + calcium forms hydroxyapatite and

calcium phosphate During mineralization – crystals become

denser Provide strength and rigidity - Bones and teeth

Combines with lipids to form phospholipids Part of the cell membrane – lipid bilayer

Phosphorus

Phosphate enzymes regulate cellular metabolism Thiamin pyrophosphatase Glucose-6-phosphatase

Phosphorus

Phosphorus Recommendations RDA Adults: 700 mg/day for ages 19-

70 years Upper intake level for those 19-70 years

of age is 4,000 mg/day.

Phosphorus

Sources Animal foods including meat, fish and

poultry Milk Eggs

Toxicity Calcification of nonskeletal tissues,

Kidneys.

Magnesium

Helps to regulate metabolism-400 enzymes (including all involved in ATP, RNA and DNA synthesis)

ATP exists in cells as mg2ATP Acts as cofactor in glucose, protein

and fat metabolism Lipid and protein synthesis

Magnesium

Allows the neurologic system to function properly

Supports bone mineralization Regulates cell growth, reproduction

Magnesium

Magnesium Intakes (1997 RDA) RDA Adult Men: 400 mg/day for 19-30

years of age RDA Adult Women: 310 mg/day for 19-30

years of age Upper level for adults: 350 mg nonfood

magnesium/day Supplements

Magnesium

Sources Nuts and legumes, whole grains, dark

green vegetables, seafood, chocolate and cocoa

Hard water and some mineral waters

Magnesium

Deficiency Deficiencies are rare. Symptoms

Weakness and confusion Convulsions in extreme deficiency Bizarre muscle movements of the eye and face Hallucinations Difficulties in swallowing Growth failure in children

Magnesium

Magnesium Toxicity Rare, potentially fatal Symptoms

Diarrhea, alkalosis, and dehydration.

Iron

Most is combined with hemoglobin in red blood cells.

A structural component: Myoglobin Cytochrome

Iron

Some does not combine in functionally active compounds hemosiderin and ferritin

Storage form of iron in the liver, spleen, and bone marrow.

Transferrin Transports iron

Iron

About 40% of American women of childbearing age suffer from dietary iron insufficiency Could lead to iron-deficiency anemia.

Symptoms Sluggishness, Loss of appetite A decreased ability to sustain even mild

activity

Sources of Iron

Nonheme iron• Primarily found in plant products• 2-10% absorption by the intestines

Heme iron• Primarily found in animal products• 10-35% absorption by the intestines

Vegetarian Diets

Nonheme iron Low bioavailability.

Women on vegetarian-type diets Greater risk for developing iron

insufficiency.

Vegetarian Diets

To increase intestinal absorption of nonheme iron. Vitamin C Moderate physical activity

Iron-Deficiency

Most at risk: Infant, toddler, chronic blood loss,

vegans, runners, and women of childbearing years

Signs: Paleness, brittle nails, fatigue, poor

temperature control, poor growth

Iron Toxicity Serious, especially for children Signs:

Diarrhea, constipation, nausea, abdominal pain Causes death due to respiratory collapse (shock)