One cup of coffee a day is the healthiest.

Benefit: Greek studies have found that drinking a cup of coffee a day can help lower blood pressure. The volunteers who drank one or two cups of coffee a day had the healthiest cardiovascular system. Scientists believe this is because antioxidants in coffee help increase the production of nitrogen oxides, which relax the walls of blood vessels, thereby lowering blood pressure. In addition, a British study found that people who drank a cup of regular coffee a day were smarter than those who drank decaf or did not drink coffee.

Cons: members of the British Dietary Association say that even if you drink only one cup of coffee a day, you may suffer from insomnia. Because it takes about eight hours for the body to fully metabolize caffeine, it's best not to drink coffee after three or four o'clock in the afternoon, or you'll have to count sheep at night.

Two cups of coffee to prevent dementia

It can also lead to miscarriage.

Benefit: drinking two cups of coffee a day can help reduce the risk of Alzheimer's, according to scientists at the University of Florida. In addition, the International Journal of Sports Medicine suggests that drinking two cups of coffee 30 minutes before exercise can improve exercise ability. Because coffee stimulates the production of fatty acids, the body can use these fatty acids as fuel to provide energy for the exercising body.

Cons: if you are pregnant, your daily caffeine intake should be limited to less than 200 milligrams, or less than two cups of coffee. Because coffee can increase the risk of miscarriage by raising levels of the stress hormones cortisol and epinephrine in the body.

Three cups of coffee to remove stones

It also shrinks the chest.

Pros: according to a 2008 report in the American Medical Journal-Cancer, women who drank three cups of coffee a day reduced their risk of ovarian cancer by 1 / 5, and for those who took contraceptive and hormone replacement therapy, they benefited more, reducing their risk of ovarian cancer by 35% to 43%.

Men who drink three cups of coffee a day can reduce their risk of gallstones by 40 percent, according to a study in the Journal of the American Medical Association. Scientists believe that caffeine can stimulate the contraction of the gallbladder, helping to expel some tiny rubble and prevent them from forming larger, hard-to-remove stones.

Cons: in 2006, a US study found that people who drank three cups of coffee a day had an increased risk of heart disease. The scientists explained that after three cups of coffee, the heart beats faster, which can cause a significant increase in blood pressure.

Another study from Lund University in Stockholm, Sweden, found that drinking three cups of coffee a day may shrink women's breasts. This may be related to the effect of caffeine on estrogen levels.

Four cups of coffee to protect the mouth

Can also cause arthritis.

Pros: four cups of coffee contains about 400 milligrams of caffeine, which is the most effective amount of coffee to play an antioxidant role. Both tea and coffee are rich in antioxidants, polyphenols, which can effectively reduce the risk of cancer. Scientists at the University of Utah found that people who drank four cups of coffee a day had a 39% lower risk of developing oral and throat cancer.

Cons: people who drank four cups of coffee doubled their risk of developing rheumatoid arthritis. The researchers believe that coffee increases levels of certain chemicals in the body that can cause inflammation and joint pain.

Five cups of coffee to protect the liver

It can also cause calcium deficiency.

Benefit: researchers at the National Cancer Center in Tokyo found that drinking five cups of coffee a day reduced people's risk of severe liver damage by 3/4, which may be related to antioxidants in coffee.

Cons: several studies have found that coffee is an important factor in osteoporosis because it interferes with calcium absorption. However, many experts are controversial. The National Osteoporosis Association says there is no absolute evidence that coffee causes bone loss, but advises people to drink no more than five cups of coffee a day.

Six cups of coffee to nourish the skin

It can also destroy nutrients.

Pros: drinking six or more cups of coffee a day reduces the risk of skin cancer by 31%, according to research from Wayne State University in Detroit. The researchers believe this may be because the antioxidants in coffee protect skin cells.