Minerals & Water

Learning Outcomes

• Explain the importance and function of water and minerals in the body

• Describe water balance and how your body maintains it

• Describe your daily water needs and the best sources to get it

• Explain what minerals are, and why you need them

• Name the functions, sources, deficiency/toxicity and symptoms of all the minerals

Water: Importance and Functions

Body Water Distribution

The average adult body is composed of 50% to 60% water. Fluid balance refers to the equal distribution of fluid among several compartments in the body:

• Intracellular fluid compartment: Fluid inside your cells

• Extracellular fluid compartment: Fluid outside your cells, including:

  • Interstitial fluids: Space immediately outside your cells

  • Blood fluids: Fluid in your blood

Functions of Water

• Universal Solvent: Water dissolves many substances, allowing chemical reactions (e.g., protein synthesis) to occur in cells.

• Transport Medium: Water in blood and lymph transports nutrients, gases, and waste products throughout the body.

• Temperature Regulation: Water absorbs excess heat and cools the body through perspiration and evaporation.

• Lubrication and Protection: Water lubricates joints, moistens tissues (tears, saliva), and cushions organs from injury.

Water Balance and Hydration

Maintaining Water Balance

Water balance is achieved when the amount of water consumed equals the amount lost daily. Water is obtained from both food and beverages, and is lost through the kidneys, large intestine, lungs, and skin.

• Insensible water loss: Water lost through exhalation and evaporation from the skin.

• Dehydration: Occurs when water loss exceeds intake, due to inadequate intake, excessive loss, diarrhea, vomiting, fever, or diuretics.

• Thirst mechanism: Signals dehydration, often indicated by a dry mouth due to increased electrolyte concentration.

Osmosis

Osmosis is the movement of water from an area of lower solute concentration to an area of higher solute concentration across a membrane, balancing solute concentrations between compartments.

Assessing Hydration

• Cornerstone Method: Measure body weight before and after intense activity. Weight loss indicates water loss; weight gain suggests overhydration.

• Urine Color: A hydration chart can be used to assess hydration status based on urine color.

Overhydration

Excessive water intake can cause electrolyte imbalance, leading to hyponatremia (dangerously low sodium levels in the blood). This is most common in athletes or military personnel during prolonged activity in hot conditions. Sports beverages may help prevent this.

Daily Fluid Needs

• Typical recommendation: 9–13 cups of fluid per day (women on the lower end, men on the higher end)

• Needs vary by activity level, diet, temperature, and individual factors

Minerals: Types, Functions, and Balance

What are Minerals?

Minerals are inorganic elements essential for human nutrition and day-to-day functioning. They do not provide energy (calories) but are vital for:

• Maintaining fluid balance

• Enzyme function

• Immune system support

• Structural growth (bones, teeth)

• Muscle contraction and heart function

Bioavailability of Minerals

Minerals are found in both animal and plant foods (e.g., vegetables, legumes, milk, meats). Bioavailability refers to how well a mineral is absorbed and used by the body. Some minerals compete for absorption (e.g., excess zinc reduces copper absorption), and some are bound to substances that inhibit absorption (e.g., calcium in spinach).

Classification of Minerals

• Major (Macrominerals): Needed in amounts >100 mg/day (e.g., sodium, chloride, potassium, calcium, phosphorus, magnesium, sulfur)

• Trace (Microminerals): Needed in amounts <15 mg/day (e.g., iron, zinc, selenium, fluoride, chromium, copper, iodine, manganese, molybdenum)

Table: Major vs. Trace Minerals

Mineral Toxicity

Overconsumption of minerals, especially trace minerals, can be toxic. Toxicity usually results from excessive supplementation rather than food intake. Some minerals are still being researched for their nutritional importance.

Key Minerals: Functions, Sources, and Balance

Sodium

• Electrolyte essential for fluid balance and nerve function

• ~90% consumed as sodium chloride (table salt)

• Functions: Regulates fluid balance, transports substances across cell membranes, adds flavor, acts as a preservative

• Body Regulation: Kidneys adjust sodium excretion; loss also occurs via sweat and stool

• Daily Needs: Minimum 180 mg/d; recommended 1,500 mg/d for adults up to 51 years; UL is 2,300 mg/d

• Sources: Processed foods (majority), naturally occurring in foods, added during cooking

• Too Much: Increases risk of hypertension (high blood pressure)

• Too Little: Rare in healthy individuals

Potassium

• Functions: Supports fluid balance, blood pH, muscle and nerve function, helps lower blood pressure, supports bone and kidney health

• Daily Needs: Women: 2,600 mg/d; Men: 3,400 mg/d

• Sources: Fruits, vegetables, dairy, nuts, legumes

• Too Much: From supplements can cause hyperkalemia (irregular heartbeats, heart damage)

• Too Little: Muscle weakness, cramps, irregular heartbeats, paralysis; can result from vomiting, diarrhea, eating disorders

Calcium

• Most abundant mineral in the body (99% in bones and teeth)

• Functions: Builds bones and teeth, assists muscle and nerve function, may lower blood pressure, reduces risk of colorectal cancer and kidney stones

• Daily Needs: Adults 19–50: 1,000 mg/d; 51–70: 1,200 mg/d

• Sources: Milk, yogurt, cheese, canned fish, fortified foods

• Too Much: Kidney stones, constipation, impaired absorption of other minerals, hypercalcemia

• Too Little: Weak bones, osteoporosis, increased fracture risk

Magnesium

• Functions: Supports enzyme function, may lower high blood pressure, may reduce risk of diabetes mellitus

• Sources: Vegetables, whole grains, nuts, fruits, milk, yogurt, meat, eggs

• Too Much: (from supplements) Diarrhea, cramps, nausea

Iron

• Not excreted in urine or stool; 95% is recycled

• Forms: Heme (animal sources, easily absorbed), Non-heme (plant sources, less absorbed; vitamin C enhances absorption)

• Functions: Transports oxygen, supports brain function and neurotransmitter synthesis

• Sources: Meat, fish, poultry, iron-enriched breads, cereals

• Deficiency: Iron deficiency anemia (fatigue, impaired immunity, learning difficulties in children)

• Toxicity: Serious, especially in children (diarrhea, constipation, abdominal pain, respiratory collapse, shock); Hemochromatosis (genetic iron overload)

Zinc

• Functions: DNA synthesis, growth, immunity, wound healing, taste and smell, may reduce cold severity, may help fight age-related macular degeneration (AMD)

• Sources: Red meat, seafood, whole grains

• Too Much: Stomach pain, nausea, diarrhea

• Too Little: Hair loss, appetite loss, impaired taste, diarrhea, delayed sexual maturation, skin rashes, slowed growth