World Cancer Research Fund

Protein from animal sources contains the full range of essential amino acids needed from an adult's diet. But red meat, in particular, should be eaten in limited amounts due to the high level of saturated fat it contains, which may raise blood levels of 'unhealthy' LDL cholesterol.

A high intake of saturated fat can lead to an increased risk of cardiovascular disease and other related disorders. As an alternative source of animal protein, choose poultry, fish and shellfish.

The 2007 World Cancer Research Fund report recommended meat eaters limit their consumption of red meat to no more than 500g a week, with very little processed meat, as these have both been linked to certain forms of cancer.

Fish is a good source of animal protein. Oil-rich fish such as salmon, mackerel, herring, tuna, trout and sardines are all rich in omega-3 fatty acids, which help to reduce the risk of developing cardiovascular disease.

Shellfish is also a good source of protein and is low in fat.

Aim to eat a couple of portions of fish every week, with at least one portion being an oily fish.

Did you know...?

Eggs contain all eight essential amino acids, making them a perfect source of protein. However, you'd have to eat at least eight eggs a day to get all the protein you need. Be sensible; include them as part of a balanced and varied diet.Advice for vegans and vegetarians

Vegetarians rely on plant sources for their daily protein. Plants don’t contain the full range of essential amino acids and so are not as high in nutritional value as animal protein. But by eating a well-balanced diet that contains a variety of different foods, it's possible to consume the required amino acids, regardless of the time of day they’re eaten or in what combinations within a meal.

Foods such as nuts, seeds, beans, pulses, vegetable protein foods and soya products all contain protein. There are also small amounts in grains and dairy products. Due to this variety of protein-rich foods available in the UK, protein deficiency is rare.How much is enough?

Health professionals suggest men should eat 55.5g protein a day and women 45g. In practical terms, eating a moderate amount of protein - in one or two meals every day – should give you all the protein you need. Most people in the UK eat far more protein than they actually need. It's easy to understand the excitement. Protein is an important component of every cell in the body. Hair and nails are mostly made of protein. Your body uses protein to build and repair tissues. You also use protein to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin, and blood.

Along with fat and carbohydrates, protein is a "macronutrient," meaning that the body needs relatively large amounts of it. Vitamins and minerals, which are needed in only small quantities, are called "micronutrients." But unlike fat and carbohydrates, the body does not store protein, and therefore has no reservoir to draw on when it needs a new supply.

So you may assume the solution is to eat protein all day long. Not so fast, say nutritionists.

The truth is, we need less total protein that you might think. But we could all benefit from getting more protein from better food sources.

Liquid is one of the three classical states of matter. Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena.

The density of a liquid is usually close to that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids.

Introduction

Liquid is one of the three primary states of matter, with the others being solid and gas. A liquid is a fluid. Unlike a solid, the molecules in a liquid have a much greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, allowing a liquid to flow while a solid remains rigid.

A liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, and, if placed in a sealed container, will distribute applied pressure evenly to every surface in the container. Unlike a gas, a liquid may not always mix readily with another liquid, will not always fill every space in the container, forming its own surface, and will not compress significantly, except under extremely high pressures. These properties make a liquid suitable for applications such as hydraulics.

Liquid particles are bound firmly but not rigidly. They are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the increased vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its boiling point, the cohesive forces that bind the molecules closely together break, and the liquid changes to its gaseous state (unless superheating occurs). If the temperature is decreased, the distances between the molecules become smaller. When the liquid reaches its freezing point the molecules will usually lock into a very specific order, called crystallizing, and the bonds between them become more rigid, changing the liquid into its solid state (unless supercooling occurs).

Only two elements are liquid at room temperature and pressure: mercury and bromine. Five more elements have melting points slightly above room temperature: francium, caesium, gallium, rubidium and iodine.[1] Metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams (alloys involving mercury).

Pure substances that are liquid under normal conditions include water, ethanol and many other organic solvents. Liquid water is of vital importance in chemistry and biology; it is believed to be a necessity for the existence of life.

Important everyday liquids include aqueous solutions like household bleach, other mixtures of different substances such as mineral oil and gasoline, emulsions like vinaigrette or mayonnaise, suspensions like blood, and colloids like paint and milk.

Many gases can be liquefied by cooling, producing liquids such as liquid oxygen, liquid nitrogen, liquid hydrogen and liquid helium. Not all gases can be liquified at atmospheric pressure, for example carbon dioxide can only be liquified at pressures above 5.1 atm.

Some materials cannot be classified within the classical three states of matter; they possess solid-like and liquid-like properties. Examples include liquid crystals, used in LCD displays, and biological membranes.

Applications

Liquids have a variety of uses, as lubricants, solvents, and coolants. In hydraulic systems, liquid is used to transmit power.

In tribology, liquids are studied for their properties as lubricants. Lubricants such as oil are chosen for viscosity and flow characteristics that are suitable throughout the operating temperature range of the component. Oils are often used in engines, gear boxes, metalworking, and hydraulic systems for their good lubrication properties.

Many liquids are used as solvents, to dissolve other liquids or solids. Solutions are found in a wide variety of applications, including paints, sealants, and adhesives. Naptha and acetone are used frequently in industry to clean oil, grease, and tar from parts and machinery. Body fluids are water based solutions.

Surfactants are commonly found in soaps and detergents. Solvents like alcohol are often used as antimicrobials. They are found in cosmetics, inks, and liquid dye lasers. They are used in the food industry, in processes such as the extraction of vegetable oil.

Liquids tend to have better thermal conductivity than gases, and the ability to flow makes a liquid suitable for removing excess heat from mechanical components. The heat can be removed by channeling the liquid through a heat exchanger, such as a radiator, or the heat can be removed with the liquid during evaporation.Water or glycol coolants are used to keep engines from overheating.[ The coolants used in nuclear reactors include water or liquid metals, such as sodium or bismuth.[6] Liquid propellant films are used to cool the thrust chambers of rockets.In machining, water and oils are used to remove the excess heat generated, which can quickly ruin both the work piece and the tooling. During perspiration, sweat removes heat from the human body by evaporating. In the heating, ventilation, and air-conditioning industry (HVAC), liquids such as water are used to transfer heat from one area to another.

Liquid is the primary component of hydraulic systems, which take advantage of Pascal's law to provide fluid power. Devices such as pumps and waterwheels have been used to change liquid motion into mechanical work since ancient times. Oils are forced through hydraulic pumps, which transmit this force to hydraulic cylinders. Hydraulics can be found in many applications, such as automotive brakes and transmissions, heavy equipment, and airplane control systems. Various hydraulic presses are used extensively in repair and manufacturing, for lifting, pressing, clamping and forming.

Liquids are sometimes used in measuring devices. A thermometer often uses the thermal expansion of liquids, such as mercury, combined with their ability to flow to indicate temperature. A manometer uses the weight of the liquid to indicate air pressure.