Mineral matter refers to the inorganic components present in all biological systems and food sources. These substances are the foundation of many life processes, despite making up a relatively small percentage of the body’s total mass. Unlike organic compounds (carbohydrates, fats, and proteins), mineral matter does not contain carbon atoms bonded to hydrogen. These inorganic elements are obtained exclusively through the diet and are continuously needed to maintain the body’s structural integrity and complex chemical functions.
Defining Mineral Matter and Ash Content
Mineral matter is scientifically defined as the portion of a biological sample that remains after the organic material has been completely combusted or oxidized. This residue consists of inorganic compounds, primarily oxides, sulfates, and phosphates of various elements. The term “ash content” is the analytical measurement used in food science to quantify this total mineral matter.
This measurement is typically performed through dry ashing, where a precisely weighed sample is heated in a muffle furnace at extremely high temperatures (500 to 600°C). The intense heat burns away all water and organic compounds, leaving behind the inorganic residue, or ash. The percentage of this residue relative to the original sample weight provides the ash content, which indicates the total mineral load. Analyzing this residue is the first step toward determining the amounts of specific minerals, such as calcium, sodium, and iron, present in the food source.
Essential Biological Functions
The inorganic elements that constitute mineral matter fulfill numerous roles, ranging from providing physical structure to regulating cellular communication.
Structural Roles
Calcium and phosphorus are primarily known for their structural function, forming the dense mineral matrix of bones and teeth. About 99% of the body’s calcium and 80% of its phosphorus are located within the skeletal system, providing rigidity and support.
Regulatory Roles
Other minerals serve regulatory functions, acting as electrolytes that help maintain fluid balance and nerve transmission. Sodium, potassium, and chloride maintain the electrical charge gradients across cell membranes. This process is necessary for muscle contraction and the sending of nerve signals, with sodium and chloride dominating extracellular fluid and potassium dominating intracellular fluid.
Catalytic and Transport Roles
Many minerals also perform catalytic roles, acting as cofactors to help enzymes function correctly in metabolism. Elements like magnesium and zinc are required for thousands of biochemical reactions, including energy production and the synthesis of genetic material. Iron has a specialized transport function, forming a component of hemoglobin in red blood cells necessary for carrying oxygen throughout the body.
Classifying Dietary Minerals
Dietary minerals are systematically categorized based on the quantity the body requires daily, not their relative biological importance. They are split into two groups: macro-minerals and trace minerals.
Macro-minerals, or major minerals, are those needed in amounts greater than 100 milligrams per day. This group includes:
- Calcium
- Phosphorus
- Magnesium
- Sodium
- Potassium
- Chloride
- Sulfur
Trace minerals, or micro-minerals, are required in much smaller amounts, specifically less than 100 milligrams per day. Trace elements include:
- Iron
- Zinc
- Iodine
- Selenium
- Copper
- Chromium
- Molybdenum
This classification reflects the necessary intake amount, confirming that both macro and trace minerals are necessary for maintaining optimal health.
Dietary Sources and Bioavailability
Mineral matter originates from the earth, and humans acquire these elements indirectly through food and water. Plants absorb minerals from the soil, and animals obtain them by consuming these plants, making plant and animal products the primary dietary source for humans. A varied diet ensures a steady supply of these diverse inorganic elements.
The effectiveness of mineral intake is determined not only by the amount consumed but also by its bioavailability. Bioavailability refers to the proportion of a mineral that is absorbed and becomes available for use or storage in the body. Most minerals are not efficiently absorbed, with absorption rates ranging widely from less than 1% to over 90%.
Absorption is significantly affected by the mineral’s chemical form and the presence of other compounds in the meal. For instance, plant compounds like phytates (in whole grains) and oxalates (in some vegetables) can bind to minerals like iron and zinc, inhibiting their absorption. Conversely, other nutrients can enhance uptake, such as Vitamin C improving the absorption of non-heme iron found in plant-based sources.