Black skin 'could fight disease'/Vegetables ward off Alzheimer's

[Guest guest]

Being a black vegetarian could be an asset then...?

 

http://news.bbc.co.uk/1/hi/health/1296018.stm

Wednesday, 25 April, 2001, 18:43 GMT 19:43 UK

Black skin 'could fight disease'

 

 

 

Black skin is 'more effective at disease protection'

 

Black skin could be better than white skin at protecting against disease,

according to an independent biologist.

This could explain why dark skin evolved in humans and animals living in

tropical areas, where the threat of disease is greatest.

 

 

 

Melanin is a sticky molecule - bacteria and fungi get all tangled up

and it stops them from proliferating

 

Dr James Mackintosh

Biologist

It has commonly been thought that the extra melanin in darker skin helps to

protect against the harmful effects of ultraviolet radiation from the sun's

rays.

 

However, darker skin also contains large numbers of melanin cells in areas

that are hardly ever exposed to sun's rays - such as the throat and nasal

passages.

 

Research has also shown that melanin is actually a poor " sunscreen " and does

not protect well against ultraviolet radiation.

 

New theory

 

New Scientist magazine reports that Dr James Mackintosh, an independent

biologist based in Sydney, has come up with a new theory to be published in

the Journal of Theoretical Biology.

 

Evidence for the theory

During the Vietnam war US soldiers from a variety of racial

backgrounds were sent into the Mekong Delta.

White soldiers were three times as likely to contract " jungle sores " ,

a skin disease caused by streptococcus pyogenes, compared with their black

comrades.

 

Melanin plays an important role in protecting insects from disease,

neutralising potential invaders by forming capsules around them.

 

Dr Mackintosh believes that melanin performs a similar function in humans

and other large vertebrates.

 

In mammals, melanin is contained inside bladders called melanosomes. Larger,

more numerous melanosomes make for darker skin.

 

Dr Mackintosh believes that melanosomes might engulf invading

micro-organisms and use enzymes to kill them.

 

Sticky molecule

 

Melanosomes from human skin have been shown to inhibit micro-organisms in

laboratory tests.

 

Dr Mackintosh said: " Melanin is a sticky molecule. The bacteria and fungi

get all tangled up and it stops them from proliferating. "

 

Also, a protein called attractin is known to regulate both melanisation and

immunity in humans, suggesting a link between the two.

 

Dr Anders Møller, an evolutionary ecologist from the CNRS, France's centre

for scientific research in Paris, said the theory was a " very good bet " .

 

Prehistoric days

 

" It solves a lot of problems with these other theories. "

 

Dr Mackintosh believes his theory also explains why we do not all have black

skin. Melanin is made from the amino acid tyrosine which is also needed to

build proteins.

 

He believes that in prehistoric days when food was scarce in cold, dry

areas, tyrosine was probably conserved to make essential proteins.

 

It was only worthwhile converting it into extra melanin in the warm, damp

tropics where food was abundant and diseases rampant.

 

Tuesday, 18 February, 2003, 01:11 GMT

 

http://news.bbc.co.uk/1/hi/health/2772499.stm

Vegetables ward off Alzheimer's

 

 

A healthy diet may help reduce Alzheimer's risk

 

Eating a diet rich in vegetables may be one way to reduce the risk of

developing Alzheimer's disease, research suggests.

US scientists found that a diet high in unsaturated, unhydrogenated fats -

found in vegetables and some oils - may help lower risk.

 

However, a separate study found antioxidant vitamins - widely touted as good

for general health - offer no such protective effect against Alzheimer's.

 

In the first study, scientists from Rush-Presbyterian-St. Luke's Medical

Center in Chicago, examined 815 people aged 65 and older over a four year

period.

 

There are studies to suggest that a diet high in unsaturated fat and

low in saturated fat may raise levels of good cholesterol and lower levels

of bad cholesterol in the blood

 

 

 

Dr Martha Clare Morris

 

At the start of the study none of the volunteers had Alzheimer's, but by its

end 131 had developed symptoms.

 

The researchers found that the risk of developing the disease was highest

among those who consumed the highest levels of saturated fat - found in meat

and dairy products.

 

People who consumed a lot of saturated fat were 2.3 times more likely to

develop symptoms than those whose diet was low in these fats.

 

Conversely, people whose diet contained high levels of unsaturated fat were

up to 80% less likely to develop Alzheimer's disease than those who consumed

low levels of unsaturated fats.

 

Lead researcher Dr Martha Clare Morris told BBC NewsOnline more research was

needed to confirm the findings.

 

But she said: " There are studies to suggest that a diet high in unsaturated

fat and low in saturated fat may raise levels of good cholesterol and lower

levels of bad cholesterol in the blood. "

 

It is thought that low-density lipoprotein, or bad, cholesterol may play a

role in the formation of the amyloid plaques found in the brain of

Alzheimer's patients.

 

Dr Morris said people should consider a switch to such a diet - if only

because of abundant evidence that it helped to reduce the risk of heart

disease.

 

Vitamins

 

In a second study researchers at Columbia University in New York concluded

that carotenes and vitamins C and E obtained from diet or through

supplements are not associated with a decreased risk of Alzheimer's.

 

It was suspected that these antioxidant vitamins may have a protective

effect because they mimimise the damage to the body's tissues caused by

charged particles known as free radicals.

 

Some suspect that Alzheimer's is caused in part by damage to brain cells

caused by free radicals.

 

The Columbia researchers examined 980 people, of which 242 developed

Alzheimer's symptoms during the four year study.

 

There was no evidence that those people who consumed carotenes or vitamins A

and E were any less likely to develop the disease.

 

Both studies were published in the journal Archives of Neurology.