YOUR URINE COLOUR AND YOUR HEALTH

PALE YELLOW

Once your body has absorbed the water it needs, it flushes out excess fluid, and other waste products such as salts, hormones and minerals, through the kidneys.

In a normal, healthy sample of urine, 96 per cent is water and the remainder is made up of waste products.

Urine is usually pale yellow - the colour comes from urochrome, a yellow pigment that's a by-product when bile, a greenish-coloured liquid, is broken down.

Bile is produced by the liver and helps us digest fats. It also removes what is left over when red blood cells are broken down. Most of the bile is excreted from the body in faeces. However, about 10 per cent is filtered out by the kidneys, where it's converted into urochrome.

'Urochrome doesn't serve any function, but it's useful to show how diluted your urine is,' says Marc Laniado, a urologist at Windsor Urology, Berkshire.

'Ideally, if the urine were in a clear bottle, you should be able to read a newspaper or an iPad through it. If your urine is a darker colour, it's a sign you might need to drink more.'

CLEAR

If you have drunk a lot of liquids, this will dilute the yellow-coloured pigments, making urine more transparent. Diuretic drugs - often used to treat blood pressure - can also have this effect, as they encourage the body to flush out more water.

When urine is clear, if it's a short-term thing this is usually not a concern. However, around one in 25,000 people suffers from diabetes insipidus, which makes urine look more clear.

A rare form of diabetes, it is linked to a gene defect or damage to the pituitary gland (for instance, following brain surgery, a head injury or a tumour). As a result the brain does not release enough anti-diuretic hormone, which controls the concentration of urine.

The hormone stops the body excreting too much water - a lack of it means excessive amounts are passed, making those affected very thirsty and unable to sleep because of needing the loo throughout the night.

Sportsmen and women who drink more water than they need during physical activity may find their urine looks clear, says Mr Laniado. 'Rarely, this causes the urine and blood to become very diluted, the sodium levels in the blood drop and the brain swells, sometimes leading to seizures and death.'

BRIGHT YELLOW

If your urine has suddenly turned bright yellow, the most likely cause is vitamin supplements. In fruit and veg in their natural state, vitamins such as B and C are found in relatively small amounts compared with vitamin tablets, which can contain more than the body can digest in one dose.

Nutrients such as vitamin C, and vitamin B complex - also known as riboflavin - are water-soluble and are quickly absorbed in large amounts before they reach the intestines; they then pass quickly into the bloodstream, where they are rapidly filtered out by the kidneys in as little as half an hour.

Other vitamins, such as A, D and E, which are not water soluble, are absorbed more slowly as they move through the gut.

'While the body can absorb the B and C vitamins quickly, it can't store them,' explains Neal Patel, of the Royal Pharmaceutical Society. 'So it has to get rid of them in the urine.' The urine appears bright yellow because the nutrients absorb blue light from the natural light spectrum.

ORANGE

Orange or dark yellow urine suggests you are dehydrated. It is often this hue in the morning, as the kidneys have been working overnight, continuing to pass fluid to your bladder although you haven't taken in any water.

Eating too much salty food can also make wee look orange because the sodium imbalance in the kidneys makes them retain more water, making the pigments more concentrated and visible.

In large amounts, beta carotene - the yellow-orange pigment that gives carrots and sweet potatoes their colour - can also turn urine the same colour. This is more typical in infants and toddlers who have been given too much of these types of vegetables during weaning, and suggests parents should give them more of a variety of foods.

Orange urine can be a sign of jaundice, which is typically caused when the bile duct (which carries bile from the liver to the gallbladder, where it is stored) becomes blocked by a cyst, gallstone or possibly a tumour. Instead of draining from the gallbladder into the intestines, bile passes out through the kidneys in the urine in higher amounts than usual.

BLUE

The most likely explanation for blue urine is that you've eaten large amounts of a food dyed blue, such as cake icing or sweets.

Many dyes are made from complex molecules that are difficult for the gut to absorb, and will pass out through the urine instead.

Urine can also be turned this hue by methylene blue, an antibacterial medicine used to treat conditions including urinary infections and some genetic forms of anaemia.

Urine coloured by a drug is rarely cause for concern, says Professor Munir Pirmohamed, vice-president of the British Pharmacological Society. 'The liver is a fantastic detox organ. Because it has so many enzymes to break down chemicals, it can often convert drugs into different chemical structures.'

GREEN

Bacteria can produce coloured pigments as a by-product, ranging from blue-green to yellow-green and red-brown.

For example, a bacteria called Pseudomonas aeruginosa, which causes cystitis, can tinge the urine green if it has got into the urinary tract from the bowel via the faeces, causing an infection. A large family of chemicals called phenols, used in drugs to treat Parkinson's disease and some antidepressants, can also sometimes turn urine greenish - although normally there is no obvious sign.

The commonly used general anaesthetic propofol also contains phenols and can turn urine green in large doses, but this is rare.

PINK/RED

Fruits and vegetables such as beetroot, rhubarb, and blackberries contain complex pigments called betalains which are not easy for the body to break down and so end up in large doses in the urine.

The same harmless pigments are also used in food colouring.

After taking part in endurance sports such as running, or high- energy sports such as tennis or boxing, you may also see a pink or reddish tinge in the loo afterwards. This is because the impact of the sport can irritate the lining of the bladder so much that it starts to bleed slightly - it takes as little as one millilitre of blood to make urine look pinkish.

Mr Laniado says: 'It is probably harmless, but red urine should still be investigated by a urologist.'

Kidney stones - where crystals of calcium build up and form large stones and blockages - can cause bleeding in the kidney, which can colour the urine red. A blow to the kidneys, caused by a kick in the back for instance, can also lead to blood in the urine.

Red urine may be a possible sign of cancer along the urinary tract - the growth of fragile blood vessels around the tumour can cause blood to seep into the urine. 'Seeing blood in the urine is associated with cancer in about one in five cases - most commonly bladder cancer,' explains Mr Laniado.

PURPLE

Urine can turn purple in the rare genetic disorder called porphyria, which affects around one in 25,000 people in the UK. Here the body makes too much porphyrin - a purplish pigment which helps blood cells carry oxygen. Excess porphyrin is excreted in the urine, turning it purple.

Other symptoms include nervous system problems, joint pain and muscle weakness, and mental health problems, famously seen in the 'madness' of George III (who's said to have had purple urine).

Today, there are drugs given as jabs which stop the body making too many porphyrins.

BROWN/BLACK

lack or brown wee can be a startling sight. In many cases, it is caused by senna, which is used in most laxative drugs.

Made from the leaves of the senna plant, it stimulates the nerves of the intestines to contract more, helping stools move faster through the gut.

However, senna can be hard for the body to break down and if you take too much of it, it can cause urine to look dark.

Eating too many broad beans in one sitting may also given your urine a darker tint, due to the fact that they contain a complex amino acid called L-dopa in high concentrations, which reacts with the liver's enzyme to make a black pigment.

WHITE OR CLOUDY

If your urine looks cloudy, the most likely reason is a bacterial infection. If germs such as E.coli from faeces get into the bladder, the body sends white blood cells to fend off the attack; these can stick together in tiny clumps.

Cloudy or hazy urine may also be caused by crystals of minerals such as calcium or phosphorus. This could be the result of a diet very high in phosphate-rich foods, such as milk, cheese and animal organs such as liver and kidney, but Mr Laniado says it's not usually a sign of something serious.

A man's urine may also look cloudy after sex. During ejaculation, the semen is pushed out of the testicles and goes into the urethra - the tube that both urine and sperm pass through. Trace amounts of semen can get left in the urethra.