Nutrition
Nutrition
The building blocks of every single one of your cells, as well as the energy that fuels your heart, the thoughts you have, and the movements you make, come from the food you eat. Your immune system's antibodies, your muscles' proteins, and your brain's membranes, which are rich in lipids, are all created from nutritional building blocks.
Nutrition is the process by which all living organisms sustain life. Growth and energy needed by all living organisms are derived from food and the chemical substances in the food. This process is integral for all living organisms. This system creates a link between biology and the practical aspects of life.
Types of Nutrition
There are two primary types of nutrition that all organisms obtain.
Autotrophic Nutrition
Autotrophs use external sources of energy as a means of synthesizing organic food molecules from simple inorganic raw materials.
Photoautotrophic:
Certain species can adapt to an autotrophic mode of nutrition. Photoautotrophic species rely on light energy to form organic compounds from carbon dioxide and water. Plants, algae, and cyanobacteria perform photosynthesis and form glucose, which, along with photosynthesis, represents the most advanced and significant form of autotrophic nutrition. It also serves as an entry point for energy into the majority of Earth's ecosystems.
Chemoautotrophic:
Chemoautotrophic species rely on chemical energy to synthesize organic compounds, but do not utilize light energy. Some bacteria, for example, can adapt to life without sunlight, as is the case with the deep-sea hydrothermal vents, where they oxidize the inorganic gas hydrogen sulfide and utilize the energy derived from the process to produce organic compounds.
Heterotrophic Nutrition
Heterotrophs are unable to synthesize their own food, and consequently, must rely on the intake of organic compounds produced by other organisms.
Holozoic nutrition involves the ingestion of solid food, digestion of the food, and the absorption of the products. Lastly, the individual expels any undigested portion of the food. This form of nutrition is exhibited by most animals, including humans.
Saprotrophic nutrition entails the placement of digestive enzymes on a mass of dead organic matter, which facilitates the breakdown of the matter and the absorption of the resultant soluble products. This method is exhibited by fungi and many bacteria.
Parasitic nutrition involves extracting nutrients from a living host organism, thereby inflicting harm to the host.
Essential Nutrients
Nutrients are chemical compounds acquired from food and provide energy, structural components, and regulatory substances. Nutrients can be classified into macronutrients and micronutrients.
Carbohydrates
Carbohydrates serve as the main energy source for the body.
Structure: Carbohydrates contain carbon, hydrogen, and oxygen and can be as simple as monosaccharides, e.g., glucose, or as complex as polysaccharides, e.g., starch and glycogen.
Functions:
- Primary substrate for cellular respiration and ATP production
- Structural component (cellulose in plants, chitin in fungi and arthropods)
- Energy storage (starch in plants, glycogen in animals)
- Component of nucleic acids (ribose in RNA, deoxyribose in DNA)
Deficiency: Deficiency of carbohydrates causes fatigue, muscle weakness, and leads the body to break down proteins and fat for energy.
Sources: grains, bread, pasta, rice, fruits, vegetables, and legumes.
Proteins
Proteins are critical for almost every structural and functional role in the body.
Structure: Proteins are structurally formed by polymers of amino acids. There are twenty different amino acids, of which eight are essential and can only be taken from foods.
The functions of proteins include:
- Enzymes, which are catalysts for almost all metabolic reactions
- Structural proteins, which form muscle and connective tissue, as a component of cells
- Transport proteins that carry substances in the blood and across cell membranes
- Hormones that play a major role in regulating physiological functions
- Antibodies that function as the first line of defense against pathogens
- Proteins that are involved in cell signaling and the regulation of genes
Sources: meat, fish, eggs, dairy, legumes, nuts, and tofu.
Deficiency: Deficiency of protein leads to stunted growth, muscle wasting, and a compromised immune function. Severe protein deficiency in children causes kwashiorkor.
Fats
Fats are highly energy-dense macronutrients as they provide over twice the energy per gram compared to carbohydrates and proteins.
Structure: Triglycerides consist of a glycerol backbone esterified to three fatty acid chains. Saturated fatty acids contain no double bonds. Unsaturated fatty acids contain one or more double bonds.
Functions: Fats perform the following functions:
- Store concentrated, long-term energy.
- Form the phospholipid bilayer of all cell membranes.
- Insulate the body and protect its organs.
- Aids the absorption of fat-soluble vitamins (A, D, E, and K).
- Serve as precursors to steroid hormones and prostaglandins.
Essential fatty acids, namely, Omega-3 and Omega-6 fatty acids, cannot be synthesized by the body. They must be obtained through the diet. Omega-3 and omega-6 fatty acids are important for brain function, the regulation of inflammation, and cardiovascular health.
Sources: oils, nuts, seeds, fish, dairy, and meat.
Excess: Obesity, increased risk of cardiovascular disease, and elevated blood cholesterol.
Water
Water is essential for the processes of all forms of life. It is required to be taken from food and drink.
Functions:
- It serves as a solvent for all biochemical reactions.
- It serves as a means of transport (in blood and within cells).
- It helps to regulate body temperature via evaporative cooling.
- It acts as a lubricant for joints and as a cushion for organs.
- Water is a participant (reactant) in hydrolysis reactions.
In total, adults need to consume approximately 2 to 3 liters of water daily from all sources. Even 2 percent dehydration measurably impairs physical and cognitive performance.
Micronutrients
Although required in small quantities, micronutrients are essential for normal physiological function.
Vitamins
Vitamins are considered to be organic compounds that work as coenzymes or as antioxidants.
| Vitamin | Type | Key Function | Deficiency |
|---|---|---|---|
| A | Fat-soluble | Vision, immune function, epithelial maintenance | Night blindness |
| C | Water-soluble | Collagen synthesis, antioxidant | Scurvy |
| D | Fat-soluble | Calcium absorption, bone mineralization | Rickets, osteoporosis |
| E | Fat-soluble | Antioxidant protects cell membranes | Nerve and muscle damage |
| K | Fat-soluble | Blood clotting, bone metabolism | Impaired clotting |
| B1 (Thiamine) | Water-soluble | Coenzyme in carbohydrate metabolism | Beriberi |
| B12 | Water-soluble | Red blood cell formation, nerve function | Anemia, nerve damage |
| Folate (B9) | Water-soluble | DNA synthesis, cell division | Anemia, neural tube defects |
Minerals
Minerals are defined as the inorganic elements that are needed in many of the structural and functional roles.
| Mineral | Key Function | Deficiency |
|---|---|---|
| Calcium | Bone and teeth structure, muscle contraction, nerve signaling | Osteoporosis, rickets |
| Iron | Component of hemoglobin and myoglobin | Anemia, fatigue |
| Iodine | Thyroid hormone synthesis | Goiter, hypothyroidism |
| Sodium | Fluid balance, nerve impulse transmission | Muscle cramps, neurological problems |
| Potassium | Nerve function, muscle contraction, fluid balance | Muscle weakness, heart arrhythmia |
| Phosphorus | Bone structure, ATP, and DNA | Bone weakness, metabolic problems |
| Magnesium | Enzyme cofactor, muscle, and nerve function | Muscle spasms, weakness |
| Zinc | Enzyme cofactor, immune function, wound healing | Impaired immunity, poor growth |
A Balanced Diet
A balanced diet provides all essential nutrients in the correct proportions. It ensures that the body's needs for energy, growth, repair, and regulation are all simultaneously addressed.
The particular needs of each individual differ based on:
- Age: Children and adolescents need more protein and calcium for growth
- Sex: Adult females require more iron due to menstrual blood loss
- Physical activity level: More active individuals require more energy
- Health status: Illness or injury increases nutrient requirements
- Pregnancy and lactation: Dramatically increase requirements for most nutrients
- Climate: Cold environments increase energy requirements for heat production
A balanced diet generally emphasizes:
- Carbohydrates as the primary energy source, with an emphasis on complex carbohydrates and fiber
- Adequate protein from varied sources, including plant-based proteins
- Healthy unsaturated fats in moderation
- A wide variety of vegetables and fruits provides vitamins, minerals, and phytochemicals
- Limited saturated fats, refined sugars, and excess salt
Malnutrition
Malnutrition refers to a lack, excess, or imbalance in the intake of nutrients.
Undernutrition
Undernutrition happens when the intake of energy or certain nutrients is inadequate. The repercussions of this include delayed development of both physical and cognitive aspects of a person. There is also a reduction of the body's immune defenses and an elevated susceptibility to infections; the ultimate result could be the failure of the organs and the death of the organism. Chronic undernutrition afflicts an estimated 800 million individuals.
Overnutrition
Overnutrition is defined as when energy intake is more than energy expenditure. The energy is stored as fat causing overweight and obesity. Obesity is linked to a higher risk of type 2 diabetes, cardiovascular diseases, hypertension, and some cancers, as well as joint issues.
Specific Deficiencies
Deficiencies can be specific, meaning some nutrients can be missing while total caloric intake is adequate. Deficiencies of vitamin A results in hundreds of thousands of children going blind each year. Deficiency of iron causes anemia and is the most common form of nutritional deficiency. A lack of iodine is the most common cause of preventable intellectual disabilities.