Water, Minerals, and Body Fluids

Water, Minerals, and Body Fluids

Major concept of human physiology = Homeostasis:

A state of "dynamic (changing) equilibrium (balance)" in which the body's internal environment is maintained within narrow limits even when:1) the external environment changes significantly and 2) things are introduced into or removed from the body Food Urine Drinks Feces Drugs Sweat Air Bleeding Carbon dioxide

Two major components of fluid homeostasis:

1. Water balance – Keeping the right amounts of water in the right places

2. Mineral balance – Keeping the right amounts of minerals (also called “ions” and “electrolytes”) in the right places

These fluid compartments are in equilibrium with each other as both water and all of the atoms and molecules dissolved in that water (including minerals) move from one compartment to another.

That exchange of water and minerals among compartments is possible only because the cells and membranes lining each of those compartments are permeable to them.

For example:

Fluid from the lumen of the intestine crosses its epithelium to get into the extracellular space, then crosses the epithelium of the blood vessels and lymphatic vessels.

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That exchange of water and minerals among compartments is possible only because the cells and membranes lining each of those compartments are permeable to them. For example:


Fluid from the plasma of the blood crosses the epithelium of capillaries to enter the extracellular/interstitial compartment, and those fluids can cross the same epithelium to enter the plasma or lymph compartments.

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That exchange of water and minerals among compartments is possible only because the cells and membranes lining each of those compartments are permeable to them.

For example:


Fluid from the plasma of the blood crosses the epithelium of capillaries to enter the extracellular/interstitial compartment, and those fluids can cross the same epithelium to enter the plasma or lymph compartments.

Fluid from the extracellular/interstitial compartment crosses the plasma membranes of all cells to enter the intracellular compartment, and that fluid crosses the same membrane to enter the extracellular/interstitial compartment.

That equilibrium changes every time - water and minerals are added (food, water, etc); or - water and minerals are lost through sweat, urine, feces, respiration, etc.

Terms we will be using: 1

Water: A specific molecule composed of one oxygen atom and two hydrogen atoms.



Mineral: Elements or atoms with certain chemical characteristics (which, fortunately, you do not need to know)




Ion: Any atom that has either a positive or negative electrical charge

Na+

Ca+

2Fe+3Cl-

PO4-

3




Ion: Any atom that has either a positive or negative electrical charge Cations have a postiive charge Anions have a negative charge

Na+

Ca+

2Fe+3Cl-

PO4-

3


Note:Not all minerals are ions - some are electrically neutralNot all ions are minerals – some have more than one atom

In physiology and nutrition, however, the terms Mineral Ion are often used interchangably Electrolyte

Water = more than 60% of total body mass

Water Balance:


3 major compartments: Plasma (in blood) ~8% of body water Interstitial (between cells) ~25% of body water Intracellular (inside cells) ~65% of body water

Water Balance:


3 major compartments: Plasma (in blood) ~8% of body water Interstitial (between cells) ~25% of body water Intracellular (inside cells) ~65% of body water

Many smaller compartments: ~ 2% Urine, Lymphatic fluid, Cerebrospinal fluid, Saliva, Synovial fluid, Digestive system contents, Semen, Respiratory system fluids, Peritoneal fluid, Tears, Occular fluids, Pericardial fluid, Pleural fluid, etc.

Water Balance:

Movement of water from one compartment to another is due to the concentration of minerals and other atoms or molecules dissolved in it:

Water Balance:

Movement among

Forms urine

Forms tears, saliva, CSF, synovial fluid, semen, lymph, etc.

Water intake is primarily through foodand drink. Some water is gained from metabolic processes like the synthesis of proteins, lipids, and carbohydrates.

Water Balance:

Water intake is primarily through foodand drink. Some water is gained from metabolic processes like the synthesis of proteins, lipids, and carbohydrates.

Water output is primarily through urine,sweat, transcutanous loss, respiration, and feces. These are obviously affected by such things as temperature, exercise, humidity, etc.

Water Balance:

The FDA has set adequate intakes of 2.7 liters of water per day for women 3.7 liters of water per day for men,

but obviously

To remain healthy, water intake must be balanced by water ouput. These can vary from ~2 liters per day to over 5 liters per day.

Water Balance:

To regulate water intake, the body has a complex system of creating a sense of thirst.

Water Balance:

Loss through the skin, lungs, and feces can not easily be controlled, so the kidneys are the primary organs of water balance by controlling how much water is lost in the urine.

To regulate water intake, the body has a complex system of creating a sense of thirst.

Water Balance:

Some things in our diet can act as diuretics – that is, they interfere with the ability of the kidneys to keep water in the body, thus increasing its loss in the urine.

- Alcohol - Caffeine - Theobromines - Theophylline - Drugs used to control blood pressure, heart disease, diabetes insipidus, edema, & other conditions

Found in tea, chocolate

Water Balance:

Some conditions cause rapid water loss & dehydration:

- Excessive diuretics - Extreme heat - Exercise without replenishing water - Vomiting - Diarrhea - Burns

This is almost always accompanied by loss of minerals

Nausea, diorientation, headaches, weaknessMuscle spasms, heart failure, kidney failure, death

Water Balance:

Although not currently common in the US, dehydration from many diseases still kills millions of people each year worldwide, mostly through diarrhea:

- Water contaminated with viruses and/or bacteria - Infant malnutrition - Cholera - Shigellosis - Giardiasis - Celiac disease

Water Balance:

Although less common, the opposite extreme does exist:water intoxication or overhydration is the intake of excess amounts of water, diluting the minerals and other molecules dissolved in body fluids

Water Balance:

Let’s move on to discuss minerals:Inorganic micronutrientsNot destroyed by heat, light, acidity, or alkalinity

Minerals:Inorganic micronutrientsNot destroyed by heat, light, acidity, or alkalinityInvolved many ways in body structure and regulation:For example: Many = cofactors for enzymes Sodium and potassium ions carry electrical signals Sodium and potassium ions regulate blood pressure Calcium ions regulates muscle contraction Calcium provides bone rigidity Iron binds oxygen in hemoglobin Iodine is part of thyroid hormones Sulfer is part of some amino acids Phosphorus is part of DNA, RNA, ATP, phospholipids etc.

Inorganic micronutrientsNot destroyed by heat, light, acidity, or alkalinityInvolved many ways in body structure and regulation:

Found in all plant and animal foodsNot all minerals are easily absorbed in the intestine Major minerals and trace minerals

Minerals:

Minerals in the diet are often classified as

7 Major minerals and 10+ Trace minerals

Minerals:

Each mineral has its own distributrions (where it is found) and functions (what it does) in the body.

Minerals: Sodium (Na+)

By far: The most common mineral in the American diet is sodium.

Adequate Intake for both men and women = 1,500mg/dayTolerable Upper Intake Level = 2,300 mg/day

On average: American men consume between 3,000 and 6,000 mg of sodium per day, while women consume between 2,500 and 4,000 mg (due to their lower calorie intake, not because of restricting sodium).


Sodium is found naturally in many foods, including meat, fish, milk & cheese,eggs, tomatoes, potatoes, nuts, cereals, fruits

Sodium is found naturally in many foods, including meat, fish, milk & cheese,eggs, tomatoes, potatoes, nuts, cereals, fruits

but our major source of sodium is salt.


Salt is sodium chloride, NaCl.

In body fluids the sodium ion (Na+) and the chloride ion (Cl - ) separate, leaving the sodium to function alone.


Salt is sodium chloride, NaCl.

In body fluids the sodium ion (Na+) and the chloride ion (Cl - ) separate, leaving the sodium to function alone.

By weight, salt is 40% sodium and 60% chloride

One teaspoon of salt (5 grams = 5,000 mg) contains about 2,000 mg of Na+ andIt is the most common additivein American food


Sodium is important in maintaining the composition of all of the fluid compartments – primarily the interstitial compartment and the blood plasma.

Like all ions, it attracts water, so cellsand organs can move water from oneplace to another by transporting sodium from place to another.


Sodium is important in maintaining the composition of all of the fluid compartments – primarily the interstitial compartment and the blood plasma.

Like all ions, it attracts water, so cellsand organs can move water from oneplace to another by transporting sodium from place to another.

Sodium is also one of the two major ions (potassium is the other) which carries electrical signals on the membranes of nerve cells and muscle cells.


While excess sodium can be removed by the kidneys and eliminated in the urine, this is not a particularly efficient process since the adrenal glands secrete the hormone aldosterone which causes the kidneys to reabsorb Na+ back into the blood, thus preventing its elimination through the urine.


Another hormone, atrial natriuretic hormone produced by the heart, has the opposite effect, stimulating Na+ loss into the urine.

The resulting high concentrations of sodium can cause a number of problems because - the excess sodium retains water, - which raises blood pressure, - which increases the risks of heart failure, kidney failure, stroke, and vascular damage

- Accumulation of sodium in the interstitial fluid also makes it more difficult for nerve and muscle cells to produce electrical signals.


The resulting high concentrations of sodium can cause a number of problems because - the excess sodium retains water, - which raises blood pressure, - which increases the risks of heart failure, kidney failure, stroke, and vascular damage

- Accumulation of sodium in the interstitial fluid also makes it more difficult for nerve and muscle cells to produce electrical signals.

Sodium deficiency is essentially unknown in developed countries.


Minerals: Chloride (Cl-)

The other part of salt, 60% by weight, is chloride, (Cl-).It also attracts water, so cells can move water from one place to another by transporting chloride ions from one place to another

Cl- is also necessary for the formation of hydrochloric acid (HCl) in the stomach and for maintaining the acid-base balance of the different fluid compartments.

It is necessary for nerve cells and muscle cells to carry electrical signals.

Adequate intake = 2,300 mg (2.3 g) per dayTolerable Upper Intake Level = 3,600 mg (3.6 g) per day

Like sodium, the modern American diet contains much more chloride than it needs.

The average American man consumes 4,500 to 9,000 mg (4.5 to 9 g) of chloride per day, and the average American woman consumes 3,800 to 6,000 mg (3.8 to 6 g) of chloride per day.


Fortunately, the kidneys easily remove excess chloride, so it plays little if any role in disease.

Except in people with excessivevomiting or sweating, chloridedeficiency is almost unheard of in the American population. In populations without excessive salt consumption, it can cause nervous and circulatory problems and can even be fatal.


Minerals: Potassium (K+)

Potassium is one of the two ions (sodium is the other) which move across the membranes of nerve cells and muscle cells to carry an electrical signal.

Because of the much larger mass of of muscles, most of the potassium in the body is in the intracellular fluid.

Like all other ions, it attracts water and thus plays a role in maintaining the volume of that fluid compartment

Dietary sources: dairy products meat, fish, poultry bananas lima beans spinach melons fruits

Adequate intake = 4,700 mg (4.7 g) per dayNo Tolerable Upper Intake Level has been set


Most Americans consume only 2,500 to 3,000 mg/day of potassium, below the Adequate Intake of 4,700 mg/day.

It can also be lost in the urine, sweat, and feces; and vomiting and diarrhea can cause critical deficiencies. - muscle weakness or cramps - nervous disorders - cardiac arrhythmias

- Also linked with bone loss, kidney stones, and acid-base imbalance


Because the kidneys easily remove excess potassium, the risk of toxicity is low.

- cardiac arrhythmias - muscle weakness


The concentration of K+ in the body is primarily regulated by the hormone aldosterone: - it helps retain Na+, but - it stimulates loss of K+ by the kidneys

Because it is part of bones and teeth, calcium is the most abundant mineral in our body. Forms a large molecule called calcium hydroxyapatite.

It also regulates the contraction of muscle (including the heart and smooth muscle in the walls of hollow organs).

It is necessary for clotting of the blood, and plays a role in conducting electrical signals in nerves.

Minerals: Calcium (Ca2+)

Even though calcium is the most abundant mineral in the body, 99% of it is in bones so its turnover is similar to that of other minerals.


Even though calcium is the most abundant mineral in the body, 99% of it is in bones so its turnover is similar to that of other minerals.

Its concentrations in the blood and in bone tissue are regulated by three hormones: - Calcitriol (made in the kidneys from vitamin D) increases absorption of Ca++ from the intestine into the blood - Calcitonin (from the thyroid gland) moves Ca++ from blood into bone tissue - Parathyroid hormone (from the parathyroid glands) moves Ca++ from bone tissue into the blood


Adequate intake = 1,000 to 1,300 mg (1 to 1.3 g) per dayTolerable Upper Intake Level = 2,500 mg (2.5 g) per day

Most people do not get adequate amounts in the diet, even though it is a common supplement in dairy products.

Dietary sources: dairy products califlower, cabbage soybeans some seeds anything with bones


Inadequate intake/absorption or increased loss of Ca++ leads to - loss of bone density (osteoporosis) - muscle weakness - nerve damage - increased risk of hypertension

In fetuses and children, inadequate Ca++ can cause permanent bone and muscle damage.



Inadequate intake/absorption or increased loss of Ca++ leads to - loss of bone density (osteoporosis) - muscle weakness - nerve damage - increased risk of hypertension

In fetuses and children, inadequate Ca++ can cause permanent bone and muscle damage.

Excess: interferes with iron absorption = anemia muscle weakness kidney stones

Almost all phosphorus in the body is combined with oxygento form phosphate which is: - A major component of bone in the form of the calcium phosphate salt called hydroxyapatite (85%) - The hydrophilic component of phospholipids - Part of energy storage molecules adenosine triphosphate, creatine phosphate - Part of nucleic acids (DNA and RNA) - Parts of many hormones, enzymes - One of the major buffers that control pH of body fluids

Minerals: Phosphorus (P3-)

Recommended Dietary Allowance = 700 mg per dayTolerable Upper Intake Level = 4,000 mg (4 g) per day

Dietary sources: dairy products meat, fish, poultry eggs legumes nuts Often used as a supplement High in carbonated drinks


Recommended Dietary Allowance = 700 mg per dayTolerable Upper Intake Level = 4,000 mg (4 g) per day

Dietary sources: dairy products meat, fish, poultry eggs legumes nuts Often used as a supplement High in carbonated drinksBecause 85% of phosphorus is bonded to calcium in bone, they are regulated together by calcitonin, calcitriol, and parathyroid hormone


Deficiency: very rare in healthy individuals may occur in hormone deficiencies or calcium deficiency


Minerals: Phosphorus (P3-)Deficiency: very rare in healthy individuals may occur in hormone deficiencies or calcium deficiency

Excess: very rare in healthy individuals with normal diet may occur with supplement megadoses or kidney failure - muscle spasms - neurological dysfunctions

Helps regulate nerve impulses and muscle contractions

Cofactor for hundreds of enzyme reactions, particularly those of carbohydrate, protein, and fat metabolism

Helps regulate the movement of potassium calcium into and out of cells

Helps regulate blood clotting

60% is in bone tissue25% is in muscle cells

Minerals: Magnesium (Mg2+)

Recommended Dietary Allowances: 400-420 mg per day for men 310-320 mg per day for women Tolerable Upper Intake Level = 350 mg per day

Dietary sources: nuts seafood leafy vegetables legumes Often used as a supplement


Deficiency: rare in healthy individuals with normal diets may occur from diarrhea, vomiting - nausea - bone loss - muscle weakness or cramps - cognitive problems - cardiac arrhythmias


Minerals: Magnesium (Mg2+)Deficiency: rare in healthy individuals with normal diets may occur from diarrhea, vomiting - nausea - bone loss - muscle weakness or cramps - cognitive problems - cardiac arrhythmias

Excess: very rare in healthy individuals with normal diet may occur in kidney failure - diarrhea - muscle weakness or cramps - cognitive problems - cardiac arrhythmias

Minerals: Sulfer (S2-)

Does not have a function alone.

Part of two amino acids (and therefore proteins) Cysteine, MethioninePart of two vitamins Thiamin, Biotin


adequate intake tolerable upper intake level

Dietary sources: foods rich in protein eggs (yolk is very high) meat poultry seafood also found in onions peppers radishes

No have been established


Excess intake: very rare – no common symptoms

Deficiency: very rare except in people who are protein deficient: weak nails joint problems skin problems muscle weakess

Needed only in very small amountsCofactors for enzymesComponents of hormonesRegulate many reactions

Trace Minerals

Trace Minerals: Iron (Fe2+, Fe 3+)

Oxygen transport as part of hemoglobin and myoglobinCofactor for enzymesRequired for normal immune function Required for normal brain function

Trace Minerals: Iron (Fe2+, Fe 3+)Recommended Dietary Allowance 18 mg per day for women before menopause 8 mg per day for men & women after menopause

Tolerable Upper Intake Level = 45 mg per day


Dietary sources: Meat, liver, poultry, fish – both “heme” and “non-heme” iron Eggs Legumes Leafy vegetables

Often used as a supplement

non-heme iron


Not all iron in the diet is absorbed - up to 50% or 60%

- Higher when iron status is low - Lower when iron status is high

- Stomach acid required - Fiber decreases absorption

- Heme iron absorbed more easily

- Other minerals (calcium, zinc) decrease absorption - Vitamin C increases absorption


Body conserves iron, distributing it where needed

Stored in liver

Small amounts lost in sweat and fecesLarger amounts lost in bleeding and menstruation


Excess intake: - Can cause acute poisoning, especially in children vomiting, diarrhea, cardiac arrhythmias, death - Chronic excess: liver damage deposition in tissues around body


Excess intake: - Can cause acute poisoning, especially in children vomiting, diarrhea, cardiac arrhythmias, death - Chronic excess: liver damage deposition in tissues around body Deficiency: - Most common in children growth deficits, nerve damage & cognitive deficits - Adults: anemia

Trace Minerals: Zinc (Zn2+)

Cofactor for numerous enzymesHelps proteins fold and retain shape Helps regulate gene expressionHelps regulate immunityMinor roles in nerve impulse transmission and muscle contraction


Recommended Dietary Allowance 8 mg per day for women Higher when pregnant or breastfeeding 11 mg per day for men

Tolerable Upper Intake Level = 34-40 mg per day

Dietary sources: Meat, liver, poultry, seafood

May be used to supplement cereals



Not all zinc in the diet is absorbed - 10%-35%

- Higher when zinc status is low - Lower when zinc status is high

- Fiber decreases absorption - Other minerals (calcium, iron) decrease absorption - Other chemicals in food can decrease absorbtion

Excess intake: rare in healthy individuals with normal diets - vomiting, - abnormal immune function Deficiency: rare in healthy individuals with normal diets - abnormal immune function - muscle and nerve dysfunction - skin problems and hair loss - growth problems in children


Iodine Copper Manganese Floride Nickel Selenium Chromium Silicon Molybdenum

Other Trace Minerals:

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Water, Minerals, and Body Fluids