What Does Your Body Need for Fuel?
When we talk about fuelling the body, most of us immediately think about food: calories, carbohydrates, protein, vitamins, or whichever nutrient happens to be receiving the most attention at that moment. The body also depends on water and on a continuous exchange with the air around us. Food provides energy and the materials needed to build and repair tissue. Water carries substances around the body and provides the environment in which cells function. Oxygen is used to release much of the energy stored in food. We can survive for quite some time without food and several days without water. Without oxygen, we survive only minutes.
Food
Food provides the energy needed to move, think, maintain body temperature and keep the many less visible processes inside us running. Carbohydrates and fats are major sources of energy. Protein can also provide energy, although much of it is used to build and repair muscles, enzymes, hormones and other tissues. Vitamins and minerals contain no calories, but many of the reactions involved in producing and using energy depend on them. Fibre supports the bowels and feeds parts of the gut microbiome. What we eat eventually becomes involved in almost every part of the body.
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This is why calories give such an incomplete picture of a meal. Two meals may contain a similar amount of energy while differing considerably in protein, fibre, vitamins, minerals and how long they keep someone full. The body needs sufficient energy, together with the materials and micronutrients required to maintain its tissues and regulate everything happening within them.
The details vary across cultures and dietary preferences, although some broad foundations return quite consistently: vegetables, fruit, legumes, whole grains, nuts and seeds, combined with other foods that suit a person’s needs and choices. The World Health Organization recommends at least 400 grams of fruit and vegetables and 25 grams of naturally occurring fibre per day for adults. Few people will want to weigh every carrot, but the figures do give some perspective on what “plenty of vegetables” actually means.
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Tiredness is sometimes related to food intake, but it may also come from poor sleep, dehydration, inadequate recovery, illness or a deficiency such as iron deficiency. A drop in energy does not tell us, by itself, what the body is missing.
Water
Water is involved in almost everything happening inside us. It forms much of our blood, carries nutrients and waste products, supports digestion, helps regulate body temperature and provides the environment in which many reactions inside the cells take place. We continually lose it through urine, the skin, breathing and bowel movements, including on days when we do not visibly sweat. Exercise, hot weather, fever, vomiting and diarrhoea increase those losses.
European reference values place an adequate total daily water intake at around two litres for adult women and two and a half litres for adult men under moderate conditions. This includes water from drinks as well as food and is intended as a general reference. Individual requirements vary with body size and composition, physical activity, temperature, diet, health and fluid losses. Someone exercising outside in hot weather may lose far more water than someone spending the day in a cool room. Pregnancy and breastfeeding can also affect requirements.
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There are circumstances in which more water can cause problems. People with certain heart or kidney conditions, for example, may need to limit their fluid intake. Very high water consumption can also dilute the sodium in the blood to dangerous levels, although this is uncommon under ordinary circumstances.
Air
Air tends to receive less attention in discussions about fuel because breathing usually happens without any conscious effort. Oxygen enters through the lungs, passes into the blood and is carried to the tissues, where cells use it in the processes that release energy from food. The carbon dioxide produced along the way returns to the lungs and is exhaled.
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Breathing changes constantly to match what the body is doing. During exercise it becomes faster and deeper as oxygen use and carbon dioxide production rise. It also changes during speech, sleep and emotional arousal. Most of this regulation happens automatically, with carbon dioxide levels and the acidity of the blood playing an important role.
Large or rapid breaths at rest do not create additional energy when the body has no need for the extra ventilation. They may instead remove too much carbon dioxide. As carbon dioxide falls, blood vessels can narrow and oxygen is released less readily from haemoglobin into the tissues. Light-headedness, tingling, chest discomfort and a feeling of breathlessness can follow. The amount of air moving in and out of the lungs works best when it remains reasonably matched to the body’s metabolic needs.
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The composition of the air matters as well. Along with oxygen, we may breathe in fine particles, smoke, traffic pollution, allergens, biological material and chemicals released indoors. The nose filters part of this. Nasal hairs, mucus and mucociliary clearance trap some inhaled material before it reaches deeper parts of the respiratory tract, while very small particles and gases can still pass through.
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Air pollution affects the cardiovascular system as well as the lungs and is associated with both cardiovascular and respiratory disease. Indoor air can be affected by tobacco smoke, cooking fumes, poor ventilation, dampness, mould, dust and substances released by building materials or household products.
Health doesn't happen in separate boxes. Each foundation influences the others. Explore another part of your health:
Fuel · Act · Recover · Think & Feel · Connect · Environment · Grow