|
|
|
|
|
|
|
Caffeine
One study
finds a strong link between drinking very high concentrations of black tea
and healthy arteries in individuals who have heart disease, according to a
report in today's Circulation: Journal of
the American Heart Association. Black tea can
offer some of the same benefits as other foods rich in the antioxidants known
as flavonoids, such as purple grape juice, onions
and red wine. Flavonoids, the major antioxidants
found in tea, have been shown to prevent the oxidation of low-density
lipoproteins or "bad" cholesterol that leads to the formation of
plaque in artery walls. The new study shows that flavonoids
improve the function of the vascular endothelium, which forms the inner
lining of cells in all blood vessels. It responds to minute to minute changes
in the body's oxygen and blood flow needs, by causing blood vessels to expand
(dilate) or contract. The vessels expand when the need for blood flow is
higher, as occurs during exercise, and the vessels return to original size
when the individual is at rest. Black tea also inhibits the formation of
blood clots and the development of inflammation in the vessel wall, which can
help prevent heart attacks and stroke. Researchers
measured the immediate and longer-term effects of black tea vs. water
consumption on the arteries of 50 individuals who had coronary artery
disease. They found that tea improved endothelial-dependent dilation in their
arteries, while water had no effect. Some people
think that caffeine can help them lose weight. Caffeine is a diuretic so it
increases water loss from the body via urine. Water loss decreases body
weight, but the weight lost is not body fat .Caffeine can suppress appetite,
but these effects don't last long enough to cause significant weight loss. A
few studies have indicated that for people who exercise and maintain a
low-fat diet, consuming large amounts of caffeine and other stimulants may
slightly enhance weight loss. However , large
amounts of caffeine can also cause jitters, irritability, insomnia and
elevated blood pressure. It stimulates the central nervous system by
increasing heart rate and releasing free fatty acids from fatty tissue,
although it doesn't seem to boost the metabolic rate or promote loss of body
fat. On the contrary, many caffeinated beverages contain sugar, which can add
calories. Moderate
coffee drinking (1-2 cups per day) doesn't seem to be harmful. However,
caffeine-habituated individuals can experience "caffeine
withdrawal" 12 to 24 hours after the last dose of caffeine. It resolves
within 24-48 hours. The most prominent symptom is headache. They can also
feel anxiety, fatigue, drowsiness and depression. |
|
