Frequently Asked Questions

Macronutrients are the three primary categories of nutrients that provide the body with energy, measured in kilocalories. They are carbohydrates, proteins, and fats. Each gram of carbohydrate and protein provides approximately 4 kilocalories, while each gram of fat provides approximately 9 kilocalories. The term "macro" reflects the fact that they are required in relatively large quantities compared to micronutrients.

Carbohydrates serve as the primary energy substrate for most physiological processes, particularly brain function. Proteins provide structural integrity and facilitate enzymatic activity. Fats support cellular membrane function, hormone production, and the absorption of fat-soluble vitamins.

Micronutrients are vitamins and minerals required by the body in comparatively small quantities but essential for proper physiological function. Unlike macronutrients, they do not directly provide energy (with some exceptions such as certain B vitamins involved in metabolic pathways).

Vitamins are organic compounds, classified as fat-soluble (A, D, E, K) or water-soluble (C and the B vitamins). Minerals are inorganic elements including calcium, iron, magnesium, zinc, potassium, and sodium, among others. Each performs specific regulatory and structural roles in the body.

Dietary fibre refers to plant-derived carbohydrates that cannot be fully digested by human digestive enzymes in the small intestine. It is categorised into soluble fibre (which dissolves in water to form a gel-like substance) and insoluble fibre (which does not dissolve and contributes to digestive transit).

Common food sources include legumes (lentils, beans, chickpeas), whole grains (oats, barley, whole wheat), vegetables (broccoli, carrots, leafy greens), fruits (berries, pears, apples), nuts, and seeds. Refining and processing typically reduces the fibre content of foods.

Preparation methods can alter the physical structure, chemical composition, and bioavailability of nutrients in food. For example, boiling vegetables in water may result in the leaching of water-soluble vitamins (such as vitamin C and B vitamins) into the cooking water, while steaming generally reduces this loss.

Heat can also increase the bioavailability of certain nutrients — for example, the lycopene in tomatoes becomes more bioavailable after cooking. Fermentation transforms the chemical composition of foods through microbial activity, potentially affecting mineral bioavailability and introducing distinct metabolic byproducts. Each preparation method involves trade-offs that are well-documented in food science literature.

Water constitutes approximately 60% of the adult human body by weight, varying with age, sex, and body composition. It serves as the solvent for all biochemical reactions, the medium for nutrient transport in blood and lymph, a lubricant for joints and organs, and the primary mechanism for thermoregulation through perspiration.

Fluid requirements vary among individuals based on activity level, ambient temperature, and other physiological factors. Beyond plain water, fluid intake is contributed by many foods, particularly fruits and vegetables with high water content. Nutritional guidelines in most countries include reference values for fluid intake as part of broader dietary recommendations.

Bioavailability refers to the proportion of a nutrient that is absorbed from the digestive tract and made available for use in the body's physiological processes. Not all the nutrients present in a food are fully absorbed; absorption rates vary depending on the chemical form of the nutrient, the food matrix, other foods consumed concurrently, and individual physiological factors.

For example, iron exists in two forms in food — haem iron (found in animal products) and non-haem iron (found in plants). Haem iron is generally absorbed at a higher rate. The simultaneous consumption of vitamin C is documented in research as a factor that can enhance non-haem iron absorption. Such interactions are an important dimension of nutritional biochemistry.

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