Scallions, garlic, and Chinese chives were felt to be the most protective. Several population studies have shown an association between onion intake and reduced risk of stomach cancer. An area of Georgia known for its onion production has about half the stomach cancer incidence of the remainder of the state. Rates were three times lower in Japanese people living in Hawaii who consumed onions about 21 times a month, when compared to those using them less than eight times per month. In Greece those who used lots of onions had less stomach cancer.
Risk appears to decrease as intake increases.
It is felt that both tumor initiation and growth is inhibited by the substances in these foods. A study from the People's Republic of China revealed that tea consumption causes premenstrual syndrome, and that symptoms are more severe as tea intake increases. Other suspected causes of premenstrual syndrome include hormonal imbalance, progesterone deficiency, dietary deficiencies, refined sugar use, high fat foods, tobacco or alcohol use, insufficient exercise, use of oral contraceptives and caffeine use. Caffeine has been known to interfere with insect reproduction, but its effects on human reproduction have not been studied until recently. An infant born to a woman who consumed caffeine during labor contained caffeine and the heart had an irregular heart rhythm.