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.