Diet

A balanced diet is not just about eating food; it's about eating the right types of food in the correct amounts. To be healthy, our body needs seven types of nutrients. A diet that contains all seven of these in the right proportions to meet an individual's needs is called a balanced diet. The specific needs of a person depend on their age, gender, body size, and level of physical activity. The seven essential components are: carbohydrates, proteins, fats, vitamins, minerals, dietary fibre, and water.

Macronutrients are the nutrients the body needs in large amounts. They are the main providers of energy and the building blocks for growth and repair. There are three types: carbohydrates, proteins, and fats.

• Carbohydrates: The body's main and preferred source of energy. They are found in foods like bread, pasta, rice, and potatoes. Sugars are simple carbohydrates for quick energy, while starches are complex carbohydrates for slow-release energy.
• Proteins: Essential for growth of new cells and repair of tissues. They are also used to make vital substances like enzymes, antibodies, and some hormones. Good sources include meat, fish, eggs, and beans. If necessary, protein can be used for energy.
• Fats (Lipids): The most concentrated source of energy, providing more than double the energy per gram compared to carbohydrates or proteins. They are used for energy storage, providing insulation, protecting organs, and forming cell membranes. Sources include butter, oils, and nuts.

Beyond the big three macronutrients, our bodies need other substances in smaller quantities to function correctly.

• Vitamins: Organic compounds needed in small amounts to help with various chemical reactions (metabolism). For example, Vitamin C is vital for healthy skin, gums, and blood vessels, and helps with wound healing. Vitamin D is needed to absorb calcium and build strong bones.
• Minerals: Inorganic elements required for a range of bodily functions. For example, Iron is a key component of haemoglobin in red blood cells, which transports oxygen. Calcium is essential for strong bones and teeth, as well as muscle function.
• Dietary Fibre: A type of carbohydrate that cannot be digested. It adds bulk to food, helping it move through the digestive system. This process, called peristalsis, prevents constipation and helps maintain a healthy gut.
• Water: Makes up about 60-70% of the human body. It is crucial as a solvent for chemical reactions, a transport medium in blood, and for temperature regulation through sweating.

Our bodies are constantly using energy, even when we are asleep. This energy fuels our basal metabolic rate (BMR), which covers basic functions like breathing, circulation, and cell production. On top of this, we need energy for physical activity. The total energy needed varies greatly between individuals. Factors affecting energy requirements:

• Age: Growing children and teenagers have high energy needs for their size to fuel growth.
• Gender: On average, males have more muscle mass and a higher metabolic rate, so they require more energy than females of the same age and size.
• Activity Level: The more active you are, the more energy you burn. An athlete's energy needs are far higher than those of an office worker.
• Body Size: Larger individuals require more energy to maintain their bodies.

Energy Balance: This is the relationship between energy intake (from food) and energy expenditure (from BMR and activity).

• Positive Energy Balance: If energy intake > energy expenditure, the excess energy is stored, primarily as fat. This leads to weight gain and can result in obesity.
• Negative Energy Balance: If energy intake < energy expenditure, the body uses its stored energy (fat and glycogen) to make up the difference. This leads to weight loss.

Malnutrition is a broad term for any condition caused by an unbalanced diet. This can mean too little food (undernutrition), too much food (overnutrition), or a deficiency of a specific nutrient.

• Overnutrition: Consuming too much energy, particularly from fats and sugars, leads to obesity. Obesity increases the risk of serious health problems like type 2 diabetes and coronary heart disease (CHD). CHD occurs when arteries supplying the heart become blocked by fatty deposits called atheromas, which contain cholesterol. This can lead to a heart attack.
• Undernutrition: This includes starvation (a lack of all nutrients) and specific deficiencies. Protein-energy malnutrition (PEM) is a major problem in some parts of the world. It can manifest as:
• Kwashiorkor: Caused by a severe lack of protein, even if energy intake is adequate. A key symptom is oedema (swelling, especially in the abdomen) as the body cannot produce enough plasma proteins to regulate fluid balance.
• Marasmus: Caused by a severe lack of both protein and energy. It leads to extreme tissue and muscle wasting, resulting in a 'skin and bones' appearance.
• Specific Nutrient Deficiencies:
• Scurvy: Caused by a lack of Vitamin C. Symptoms include bleeding gums, fatigue, and poor wound healing.
• Rickets: Caused by a lack of Vitamin D or calcium in children, leading to soft, weak, and deformed bones.

Dietary needs are not static; they change throughout our lives and with our lifestyle choices.

• Growing Children: Children require more protein and energy per kilogram of body weight than adults. Protein is crucial for building new tissues for growth. Calcium and Vitamin D are essential for the development of strong bones and teeth. Iron is also needed for the production of red blood cells to support their increasing blood volume.
• Pregnant and Lactating Women: During pregnancy, a woman's diet must support the growth of the fetus. This requires extra protein for the baby's tissues, iron for its blood, and calcium and Vitamin D for its skeleton. During lactation (breastfeeding), the mother's body produces nutrient-rich milk, which places high demands on her stores of protein, calcium, and energy. Her diet must be adequate to support this without depleting her own body.
• Vegetarians and Vegans: Vegetarians who eat dairy and eggs can easily get enough protein. Vegans, who eat no animal products, must be more careful. Animal proteins contain all the essential amino acids we need, but most single plant proteins do not. Vegans must eat a combination of different plant proteins (e.g., beans and rice, or lentils and bread) to ensure they get all the essential amino acids required for building body proteins.