Many people think of adolescence as a time to eat without worry about future health consequences. Most teenage girls, if they think about what they eat at all, are concerned about how their nutrition affects their sports performance or weight control.
But research now suggests that adolescence may offer a unique window of opportunity for substantially lowering the risk of breast cancer later in life.
Unlike other tissues in the body, breast tissue in babies and young girls has only one duct. Hormones secreted during puberty cause this duct to grow rapidly into a tree-like structure with more ducts. Carcinogens bind more readily to DNA in the immature cells that develop while this duct expands.
These cells also appear less efficient at repairing damage to genes that these carcinogens may cause. After a woman's first full-term pregnancy, breast cells reach maturity and are much less sensitive to DNA damage.
Genistein, a phytochemical in soy, may promote the development of immature breast cells into more mature cells less vulnerable to carcinogens, according to studies presented at the most recent American Institute for Cancer Research (AICR) international conference on diet and cancer.
The University of Alabama researcher who presented the new studies at the conference said that genistein offered no protection from breast cancer when it was first given to animals in adulthood. But when the animals ate it before puberty, they had less breast cancer development.
The benefits were even greater when they continued to eat it into adulthood. The evidence suggests that the time around puberty offers a chance to imprint cells with a "blueprint" that creates cellular pathways for long-term protection.
Results from human studies support the findings of these laboratory studies. In a study of Chinese women, those who reported consuming three or four servings of soy foods a week as teenagers were half as likely to develop breast cancer as those who rarely ate soy foods.
Soy consumption as adults had no effect on the women's breast cancer risk in this study. In another study, Asian-American women who ate soy even once a week during adolescence reduced their risk of breast cancer later. In this study, regular consumption of soy foods during adolescence lowered their breast cancer risk even if they did not eat it regularly later in life.
But the women who continued eating soy as adults had the lowest risk.
Omega-3 fat, found in salmon and other high-fat fish, may also offer more protection against breast cancer when consumed before or around puberty rather than in adulthood. Several studies have linked omega-3 fat consumption with a lower risk of breast cancer, especially if teenagers eat low amounts of other polyunsaturated fats.
More dangers of smoking
Research presented at the AICR conference showed that omega-3 fats, when part of an overall lowfat diet before puberty, reduced growth of the breast cells most likely to develop cancer and increased the activity of genes responsible for DNA repair. While a lowfat diet with this kind of fat was linked with less DNA damage, girls who consumed a high-fat diet and the same amount of omega-3 fat experienced greater DNA damage.
Healthy eating during adolescence appears to be a significant way to reduce breast cancer risk later, but two other studies make it unclear whether the benefit comes from an immediate effect upon breast tissue or the long-term effects of good eating that continues into adulthood.
Furthermore, since we now know how vulnerable breast tissue is during adolescence, we need more research on the impact of carcinogens from sources like tobacco and alcohol. Some studies suggest that both "passive" and actual smoking during adolescence may increase breast cancer risk.
If science shows such a link, we have another reason to speak out strongly against teenage tobacco and alcohol use.