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Interview: Teenage Girls, Hormone Balance, and Birth Control Pills

David Zava, Ph.D. is a biochemist and an experienced breast cancer researcher who has spent decades in the laboratory. He is the laboratory director of ZRT Laboratory in Portland, OR, which does state-of-the-art saliva hormone assay testing.

Q. Dr. Zava, you’re concerned about the future health of teenage girls because they’re reaching puberty earlier and thus tend to use birth control pills at an earlier age. How does early puberty increase breast cancer risk?

A. When a young woman reaches puberty her breast cells undergo a rapid growth and development. Puberty is a time when there are more undeveloped breast cells (stem cells) that are vulnerable to cancer-causing agents such as chemicals, viruses, radiation, and estrogens. The hormones of pregnancy, particularly estriol and progesterone, cause many of these undeveloped cells to mature to cell types that no longer can be as easily damaged and transformed into cancer cells. So when girls reach puberty earlier it opens the window of vulnerability to cancer that much wider.

Research clinician Henry Lemon, M.D., many years ago published an interesting experiment in rats that demonstrated the protective effects of pregnancy hormones like estriol. He exposed young female rats to either radiation or potent chemicals known to cause mammary cancers.

As expected, nearly all of the rats developed mammary cancer, which is the equivalent of breast cancer in humans. However, if he pre-exposed these animals to estriol before exposing them to the carcinogens, the mammary cancer rate dropped an amazing 80%.

Q. And we know that girls are reaching puberty earlier today than ever before.

A. Yes, it’s no longer considered abnormal for a girl to begin puberty at age nine or 10, where just a few decades ago it was normal to reach puberty at age 13 or 14. At the turn of the century, puberty was reached at age 16 to 18.

If you consider that the average age of marriage, followed by pregnancy, hasn’t changed much — say age 20-25 — then what this means is that the earlier a girl reaches puberty, the longer her breast cells must wait before they are protected by the hormones of pregnancy. This just increases the number of years that a young woman’s breast cells are exposed to environmental insults that cause cancer later in life.

I think that nature intended a woman to become pregnant within a few years of puberty. With earlier puberty and later marriages and pregnancy, that just isn’t happening in today’s world.


Q. So we have girls exposed to the effects of estrogens at a much earlier age, getting pregnant much later if at all, and thus it sounds like you foresee a much higher rate of breast cancer in the future.

A. Unless we wise up and do something, yes, I think this generation of girls is more susceptible. On top of early puberty you have teenage girls using hormonal contraception very early on. And yet multiple studies have shown that the use of hormonal contraceptives in young girls increases their risk of developing breast cancer by as much as six times. And the younger a girls begins using them, the greater her risk of breast cancer.

A friend of mine brought to my attention an advertisement in a magazine targeting young teenage girls. I was shocked to see a full-page ad for birth control pills that suggested they could also be used to treat acne. I find it hard to believe that drug companies are allowed to market birth control pills directly to young girls when that is a known cancer risk. They will help her acne — but at what price?


Q. What is it about hormonal contraceptives that makes them so dangerous?

A. No one knows for sure, but I suspect it has something to do with the fact that both the synthetic estrogens and synthetic progestins in birth control pills somehow damage the DNA of the undeveloped breast cells in young girls.

Another problem with synthetic hormones is that they can create a state of anovulation — no ovulation. Suppressing ovulation deprives the body of the natural hormones produced by the ovary that are needed for proper growth and development, including pregnenolone, testosterone, androstenedione, DHEA and the estrogens. When ovulation is suppressed for years by birth control pills, not only is the body deprived of its natural hormones, the ovary can forget how to ovulate. I have heard from many clinicians that their patients who took birth control pills for more than a few years are often infertile because they are no longer ovulating.


Q. So we have early puberty, use of birth control pills, and poor diet. How does junk food factor into this equation?

A. I think a poor diet is at the heart of the whole problem. Put simply, sugar-laden junk foods and refined carbohydrates (cookies, french fries, chips), which teenagers have more access to today, cause more body fat, which increases estrogens, which triggers an early puberty.

When too much sugar and refined carbohydrates are consumed in the diet, this raises insulin levels for a longer period of time, which signals the body to deposit fat. For a young girl at puberty, the elevated insulin caused by the poor diet also interferes with the hormonal communication between the brain and the ovaries.

Ultimately, more estrogens and androgens (male hormones that cause acne) and less progesterone is produced by the ovaries. So the acne that the birth control pill is meant to remedy in a young girl is caused by a bad diet high in sugar.

The solution for the acne is not birth control pills, but a better diet.
Birth control pills will just exacerbate the problems with insulin regulation of sugar in the bloodstream,
cause more sugar craving (insulin resistance), more bingeing on sugary foods, and further deposition of body fat.

Smoking cigarettes and lack of exercise, which often go hand-in-hand with a poor diet, just exacerbate insulin resistance even more.

My daughter is nine years old, and I see this beginning to happen to many of her classmates and friends who have poor diets.


Q. What do you recommend to parents who want to postpone their da

ughters’ puberty as long as possible?

A. You can minimize the effects of early puberty by encouraging vigorous aerobic exercise. Soccer, volleyball, basketball, and swimming are great aerobic sports. We know from clinical studies that young women who are involved in regular and vigorous aerobic exercise programs begin puberty later and have nearly a two-fold decreased risk of developing breast cancer later in life. This protection also holds for women who exercise moderately later in life.


Q. What do you recommend parents do about their children’s diets?

A. Having a nine and 11-year-old myself, I am well aware of how difficult it can be to get your kids to eat nutritious foods. But if you are consistent and eat that way yourself, kids will usually follow suit. Kids who eat poorly are doing so because their parents buy the junk food. I fix my kids’ breakfast in the morning, and make sure they get plenty of protein (particularly eggs) and some fruit. And as much as possible, we buy food that is organic, meaning hormone and pesticide-free.

[Reprinted with permission from The John R. Lee, M.D. Medical Letter, January 1999; CCL Family Foundations, May-June 1999]