Water and Minerals

Charles Lohman

Water• Water – water constitutes about 60% of an adult’s body

weight– body composition influences how much of the body’s

weight is water because there is more contained in lean tissue and less in fat

– water is an essential nutrient, more important than any others

– the body needs more water each day than any other nutrient

– you can survive only few days without water, where a deficiency of other nutrients may take weeks, months or even years to develop

Water and Body Fluids

• Water and the body’s life processes– water carries nutrients and waste products

throughout the body– water maintains the structure of large molecules– water participates in metabolic processes– water acts as a lubricant and cushion – water aids in the regulation of body temperature– water maintains blood volume

Water Balance and Recommended Intakes

• Water Intake– thirst and satiety influence water intake in response to

changes in the mouth, the hypothalamus and nerves– when there is inadequate water intake the blood becomes

concentrated, the mouth becomes dry, and the hypothalamus initiates drinking behavior

– when water intake is excessive, the stomach expands and stretch receptors send signals to stop drinking

– when too much water is lost from the body and not replaced, dehydration develops

– water intoxication is rare, but can occur with excessive water ingestion and kidney disorders that reduce urine production

Water Balance and Recommended Intakes

• Water Sources– obvious dietary sources of water are water itself and other

beverages– nearly all foods contain water– fruits and vegetables contain about 90% water– meats and cheeses contain about 50% water– water is also generated during metabolism

• Water Losses– the body must excrete at least 2 cups of water each day as

urine, which is enough to carry away waste products generated by the body’s metabolic processes

– water is also lost from the lungs as vapor and from the skin as sweat

Water Balance and Recommended Intakes

• Water Recommendations– about 8 to 12 cups which is based on a person who expends

2000 kcalories a day– total water includes not only drinking water, but water in other

beverages and foods as well– people who are physically active or live in hot environments

may need more– beverages currently represent over 20% of the total energy

intake in the United States– most people would well to select water as their preferred

beverage– some research suggests that people who drink caffeinated

beverages lose a little more fluid than when drinking water because caffeine acts as a diuretic

Water Balance and Recommended Intakes

• Health Effects of Water– drinking water may protect against urinary stones and

constipation– even mild dehydration seems to interfere with daily tasks

involving concentration, alertness, and short term memory– the kind of water a person drinks may also make a

difference to health; hard water vs soft water– hard water has high concentrations of calcium and

magnesium which may benefit hypertension and heart disease

– soft water contains sodium and potassium which may aggravate hypertension and heart disease

The Minerals – An Overview• Major Minerals– major minerals are named so because they are

present, and needed, in larger amounts in the body– although trace minerals are needed in smaller

amounts, they are still vital to the body• Inorganic Elements– unlike organic vitamins, which are easily destroyed,

minerals are inorganic elements that always retain their chemical identity

– once they enter the body, they remain there until they are excreted, they cannot be changed into anything else

• The Body’s Handling of Minerals– minerals also differ from vitamins in the amounts the body can absorb

and in the extent to which they must be specially handled– some minerals such as potassium are easily absorbed and readily

excreted like the water soluble vitamins– some minerals such as calcium need carriers to be absorbed and

transported • Variable Bioavailability

– some foods contain binders that combine chemically with minerals, preventing their absorption and carrying them out of the body with other wastes

– examples of binders are phytates, which are found primarily in legumes and grains

– another example of a binder is oxalates, which are present in rhubarb and spinach

The Minerals – An Overview

The Minerals – An Overview• Nutrient Interactions

– the presence or absence of one mineral can affect another’s absorption, metabolism, and excretion

– the interaction between sodium and calcium cause both to be excreted when sodium intakes are too high

– phosphorus binds with magnesium in the GI tract, so magnesium absorption is limited when phosphorus intakes are too high

• Varied Roles– all of the major minerals help to maintain the body’s fluid

balance, sodium, chloride, and potassium are most noted for this role

– other minerals have roles in bone growth and health- calcium, phosphorus, and magnesium

Sodium• Sodium Roles in the Body

– the principal cation of the extracellular fluid and the primary regulator of its volume

– helps maintain acid-base balance and essential to nerve impulse transmission and muscle contraction

• Sodium Recommendations– diets rarely lack sodium, and even when intakes are low, the body

adapts by reducing sodium losses in urine and sweat– sodium recommendations are set low enough to protect against high

blood pressure, but high enough to allow an adequate intake of other nutrients with a typical diet

– upper level of sodium intake for adults is 2400 mg– the average intake of sodium in the United States exceeds the Upper

Level and most adults will develop hypertension at some point in their life

Sodium• Sodium and Hypertension

– for many years high sodium intake was considered the primary factor responsible for high blood pressure

– salt (sodium chloride) is actually the cause– salt has a greater effect on blood pressure than either sodium

or chloride alone– for some individuals, blood pressure increases in response to

excesses in salt intake– people most likely to have a salt sensitivity include those whose

parents had high blood pressure, those with chronic kidney disease or diabetes, African Americans, and people over the age of 50

– overweight people also appear to be particularly sensitive to the effect of salt on blood pressure

Sodium• Sodium and Bone Loss– a high salt intake is also associated with increased calcium

excretion, but its influence on bone loss is less clear– potassium may prevent the increase in calcium excretion

caused by a high salt diet• Sodium in Foods– processed foods contain the most sodium, whereas

unprocessed foods such as fresh fruits, vegetables, milk, and meats have the least

– 75% of sodium in people’s diets comes from salt added to foods by the manufacturer

– 15% comes from salt added during cooking– 10% comes from the natural content in foods

Chloride• Chloride Roles in the Body

– chloride maintains fluid and electrolyte balance as sodium and potassium

– inside the stomach chloride is part of hydrochloric acid, which maintains the strong acidity of the gastric juice

• Chloride Recommendations and Intakes– chloride is abundant in foods (especially processed foods) as part of

sodium chloride and other salts– because the proportion of chloride in salt is greater than sodium,

chloride recommendations are slightly higher, but still equivalent to, those of sodium

• Chloride Deficiency and Toxicity– diets rarely lack chloride– chloride losses may occur in conditions such as heavy sweating,

chronic diarrhea, and vomiting

Potassium• Potassium Roles in the Body– potassium plays a major role in maintaining fluid and

electrolyte balance and cell integrity– also critical to the maintenance of nerve impulse

transmissions and muscle contractions• Potassium Recommendations and Intakes– potassium is abundant in all living cells, both plant and

animal– because cells remain intact unless foods are processed,

the richest sources of potassium are fresh foods– to meet Adequate Intake for potassium, increase fruit and

vegetable intake to 5 to 9 servings daily

Calcium

• Calcium Roles in the Body– 99% of the body’s calcium is in the bones and

teeth where it plays two roles– first it is an integral part of bone structure,

providing a rigid frame that holds the body upright and serves as attachment points for muscles, making motion possible

– second it serves as a calcium bank, offering a readily available source of the mineral to the body fluids should a drop in blood calcium occur

Calcium• Calcium and Disease Prevention

– calcium may protect against hypertension– for example with the DASH diet(Dietary Approaches to Stop

Hypertension), which isn’t particularly low in sodium, but is rich in calcium, and as well as magnesium and potassium

– the DASH diet, together with a reduced sodium intake, is more effective in lowering blood pressure than either strategy alone

• Calcium and Obesity– calcium may also play a role in maintaining a healthy body weight– in particular, calcium from dairy foods, but not from supplements,

seems to influence body weight– an adequate dietary calcium intake may help prevent excessive fat

accumulation by stimulating hormonal action that targets the breakdown of stored fat

Calcium• Calcium Recommendations

– for adolescents up to the age of 18, 1300 mg of calcium a day– between the ages of 19 to 50, 1000mg of calcium a day– for older adults, over 50, a higher recommendation of calcium is given

at 1200 mg a day to minimize bone loss that occurs later in life• Calcium in Foods

– some cultures do not use milk in their cuisines – some vegetarians exclude milk as well as meat and some people are

allergic to milk protein or lactose intolerant– others simply do not enjoy the taste of milk– some tofu, corn tortillas, some nuts (such as almonds), and some

seeds (such as sesame seeds) can supply calcium for the person who does not use milk products

– also vegetables, mustard and turnip greens, bok choy, kale, parsley, watercess, and broccoli are also good sources of calcium

Phosphorus• Phosphorus Roles in the Body– phosphorus salts are found in not only in bones and

teeth, but in all body cells as part of a major buffer system

– it is also part of DNA and RNA and is therefore necessary for all growth

• Phosphorus Recommendations and Intakes– phosphorus is found in almost all foods– foods rich in proteins are the best sources– research shows that displacement of milk in the diet

by cola drinks, not the phosphoric acid content of the beverages, has adverse effects on bone

Magnesium

• Magnesium Roles in the Body– in addition to maintaining bone health,

magnesium acts in all the cells of the soft tissues, where it forms part of the protein making machinery and is necessary for energy metabolism

• Magnesium Intakes– average dietary magnesium estimates for U.S.

adults fall below recommendations– magnesium can be found in legumes, seeds, and

nuts and also in leafy green vegetables

Sulfate

• Sulfate– is the oxidized form of the mineral sulfur, as it exists

in food and water– the body’s needs for sulfate are easily met by a

variety of foods and beverages– in addition the body receives sulfate from the amino

acids methionine and cysteine found in dietary proteins

– because sulfate needs are easily met with normal protein intakes, there is no recommended intake for sulfate