Proteins, fats and carbohydrates: what they are and what role they play in nutrition

The reader encounters the abbreviation PFC (proteins, fats, carbohydrates) more often than they understand it. Behind the three letters are macronutrients — substances from which the body builds tissues and draws energy; their amount in the diet determines both body weight and the blood lipid profile.

What proteins, fats and carbohydrates (PFC) are

The four organogenic elements — oxygen (65%), carbon (18%), hydrogen (10%) and nitrogen (3%) — are called macronutrients; proteins, fats, carbohydrates and nucleic acids are built from them. In everyday terms, PFC are three classes of food substances that supply calories. Fat is more energy-dense: a gram of fat provides 9 kcal (37 kJ), whereas a gram of carbohydrate or protein provides 4 kcal (17 kJ). Any excess — fat, carbohydrate or protein — that is not used by cells and not converted into energy is stored as adipose tissue.

Proteins: what role they play in the body

Proteins are one of the three main macronutrients, along with fats and carbohydrates. The specific grams of protein are calculated by a specialist.

Fats and fatty acids: saturated and unsaturated

A small amount of fat is an essential part of a balanced diet: it supplies essential fatty acids that the body does not synthesize and ensures the absorption of fat-soluble vitamins A, D and E. The main types are saturated and unsaturated fats, and most oils contain both in varying proportions. Saturated fats predominate in animal products — fatty meat, sausages, butter, ghee and lard, hard cheeses, cream and ice cream — as well as in palm and coconut oil. An excess of saturated fats raises "bad" LDL cholesterol and the risk of heart disease and stroke; UK guidelines recommend no more than 30 g per day for men and 20 g for women, and less for children. Trans fats are found in partially hydrogenated vegetable oil and also raise cholesterol; UK guidelines set a limit for adults of about 5 g per day. Unsaturated fats (mono- and polyunsaturated) are found in vegetable oils and fish: monounsaturated fats support "good" HDL cholesterol levels and lower "bad" LDL levels, while polyunsaturated omega-3 and omega-6 are partly essential.

Carbohydrates

A gram of carbohydrates, like a gram of protein, provides 4 kcal.

Where nutrients come from in food and how much energy they provide

The source of macronutrients is ordinary food, and labeling serves as a guide. Under UK labeling rules, a "reduced fat" label means at least 30% less fat than a comparable product, but the product may remain high in fat, and fat is often replaced with sugar — the energy value then hardly decreases.

• Saturated fats are more often found in products of animal origin.
• Monounsaturated fats support HDL cholesterol levels.
• Trans fats are found in partially hydrogenated vegetable oil.

What to consider in nutrition and when to consult a specialist

A doctor can assess the lipid profile, including LDL and HDL, and review the diet — this is not a recommendation for self-correction. Warning signs requiring an emergency call are listed below.

Nutrition alone is not a reason to call an ambulance; 103 or 112 — if, against the background of dietary changes, life-threatening signs arise, such as symptoms of stroke or heart attack.

This material is for reference: it explains terms but does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer