As molecular biology, biochemistry, and genetics advance, nutrition has become more focused on metabolism and metabolic pathways - biochemical steps through which substances inside us are transformed from one form to another.
Nutrition also focuses on how diseases, conditions, and problems can be prevented or reduced with a healthy diet.
Similarly, nutrition involves identifying how certain diseases and conditions may be caused by dietary factors, such as poor diet (malnutrition), food allergies, and food intolerance
NUTRITION
Nutrition is the study of nutrients in food, how the body uses nutrients, and the relationship between diet, health, and disease.
Major food manufacturers employ nutritionists and food scientists.
Nutritionists may also work in journalism, education, and research. Many nutritionists work in the field of food science and technology.
There is a lot of overlap between what nutritionists and dietitians do and study. Some nutritionists work in a healthcare setting, some dietitians work in the food industry, but a higher percentage of nutritionists work in the food industry and in food science and technology, and a higher percentage of dietitians work in healthcare, corporate wellness, research, and education.
The human body requires seven major types of nutrients
A nutrient is a source of nourishment, a component of food, for instance, protein, carbohydrate, fat, vitamin, mineral, fiber, and water.
- Macronutrients are nutrients we need in relatively large quantities.
- Micronutrients are nutrients we need in relatively small quantities.
Macronutrients can be further split into energy macronutrients (that provide energy), and macronutrients that do not provide energy.
Energy macronutrients
Energy macronutrients provide energy, which is measured either in kilocalories (kcal or calories) or Joules. 1 kilocalorie (calorie) = 4185.8 joules. Energy macronutrients include:
Carbohydrates - 4 kcal per gram
Carbohydrate molecules include monosaccharides (glucose, fructose, galactose), disaccharides, and polysaccharides (starch).
Nutritionally, polysaccharides are favored over monosaccharides because they are more complex and therefore take longer to break down and be absorbed into the bloodstream; this means that they do not cause major spikes in blood sugar levels, which are linked to heart and vascular diseases.
Proteins - 4 kcal per gram
There are 20 amino acids - organic compounds found in nature that combine to form proteins. Some amino acids are essential, meaning they need to be consumed. Other amino acids are non-essential because the body can make them.
Fats - 9 kcal per gram
Fats are triglycerides - three molecules of fatty acid combined with a molecule of the alcohol glycerol. Fatty acids are simple compounds (monomers) while triglycerides are complex molecules (polymers).
Fats are required in the diet for health as they serve many functions, including lubricating joints, helping organs produce hormones, assisting in absorption of certain vitamins, reducing inflammation, and preserving brain health.
Macronutrients that do not provide energy
These do not provide energy, but are still important:
Fiber
Fiber consists mostly of carbohydrates. However, because it is not easily absorbed by the body, not much of the sugars and starches get into the blood stream. Fiber is a crucial part of nutrition, health, and fuel for gut bacteria.
Water
About 70 percent of the non-fat mass of the human body is water. It is vital for many processes in the human body.
Nobody is completely sure how much water the human body needs - claims vary from 1-7 liters per day to avoid dehydration. We do know that water requirements are very closely linked to body size, age, environmental temperatures, physical activity, different states of health, and dietary habits; for instance, somebody who consumes a lot of salt will require more water than another similar person.
Claims that 'the more water you drink, the healthier you are' are not backed with scientific evidence. The variables that influence water requirements are so vast that accurate advice on water intake would only be valid after evaluating each person individually.
Micronutrients
Micronutrients are required in smaller quantities:
Minerals
Dietary minerals are the other chemical elements our bodies need, other than carbon, hydrogen, oxygen, and nitrogen.
People with a well-balanced diet will, in most cases, obtain all the minerals they need from what they eat.
Minerals are sometimes added to certain foods to make up for any shortages.
The best example of this is iodized salt - iodine is added to prevent iodine deficiency, which affects about 2 billion people, globally; it causes mental retardation and thyroid gland problems. Iodine deficiency remains a serious public health problem in over half the planet
Potassium
What it does - a systemic (affects entire body) electrolyte, essential in co-regulating ATP (an important carrier of energy in cells in the body, also key in making RNA) with sodium.
Deficiency - hypokalemia - can profoundly affect the nervous system and heart.
Excess - hyperkalemia - can also profoundly affect the nervous system and heart.
Chloride
What it does - key for producing stomach acid, important in the transport of molecules between cells, and vital for the proper functioning of nerves.
Deficiency - hypochloremia - low salt levels, which, if severe, can be very dangerous.
Excess - hyperchloremia - usually no symptoms, linked with excessive fluid loss.
Sodium
What it does - a systemic electrolyte, and essential in regulating ATP with potassium. Important for nerve function and regulating body fluid levels.
Deficiency - hyponatremia - causes cells to malfunction; extremely low sodium can be fatal.
Excess - hypernatremia - can also cause cells to malfunction, extremely high levels can be fatal.
Calcium
What it does - important for muscle, heart, and digestive health. Builds bone, assists in the synthesis and function of blood cells.
Deficiency - hypocalcaemia - muscle cramps, abdominal cramps, spasms, and hyperactive deep tendon reflexes.
Excess - hypercalcemia - muscle weakness, constipation, undermined conduction of electrical impulses in the heart, calcium stones in the urinary tract, impaired kidney function, and impaired absorption of iron, leading to iron deficiency.
Phosphorus
What it does - important for the structure of DNA, transporter of energy (ATP), component of cellular membrane, helps strengthen bones.
Deficiency - hypophosphatemia, an example is rickets.
Excess - hyperphosphatemia, often a result of kidney failure.
Magnesium
What it does - processes ATP; required for good bones and management of proper muscle movement. Hundreds of enzymes rely on magnesium to work properly.
Deficiency - hypomagnesemia - irritability of the nervous system with spasms of the hands and feet, muscular twitching and cramps, constipation, and larynx spasms.
Excess - hypermagnesemia - nausea, vomiting, impaired breathing, low blood pressure. Very rare, but may occur if patient has renal problems.
Zinc
What it does - required by many enzymes. Important for reproductive organ growth. Also important in gene expression and regulating the nervous and immune systems.
Deficiency - short stature, anemia, increased pigmentation of skin, enlarged liver and spleen, impaired reproductive function, impaired wound healing, and immune deficiency.
Excess - suppresses copper and iron absorption.
Iron
What it does - required for proteins and enzymes, especially hemoglobin, the oxygen-carrying compound in blood.
Deficiency - anemia.
Excess - iron overload disorder; iron deposits can form in organs, particularly the heart.
Manganese
What it does - a cofactor in enzyme functions.
Deficiency - wobbliness, fainting, hearing loss, weak tendons and ligaments. Less commonly, can be a cause of diabetes.
Excess - interferes with the absorption of dietary iron.
Copper
What it does - component of many enzymes.
Deficiency - anemia or pancytopenia (reduction in the number of red and white blood cells, as well as platelets) and neurodegeneration.
Excess - can interfere with body's formation of blood cellular components; in severe cases, convulsions, palsy, and eventually death (similar to arsenic poisoning).
