This article is an excerpt from the Shortform summary of "The China Study" by Colin Campbell. Shortform has the world's best summaries of books you should be reading.
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What is the link between hormone replacement therapy (HRT) and breast cancer? Is there a link between menopause and breast cancer?
One out of eight American women will get breast cancer in her lifetime. Although menopause itself isn’t a risk factor for breast cancer, how you treat symptoms of menopause could increase your risk. We’ll cover the link between HRT and breast cancer and alternative options for easing your transition into menopause.
Hormone Replacement Therapy (HRT) and Menopause
Many women take HRT during menopause to protect their bones, prevent heart disease, and decrease menopause symptoms.
However, HRT has been shown to increase your breast cancer risk by 26-30%. Further, while HRT does seem to help protect against bone fractures and colorectal cancer in later life, some studies suggest it increases your risk for cardiovascular disease.
Why is HRT linked to breast cancer? One reason is that it increases hormones like estrogen in the body. The higher your female hormone levels and the longer you’ve been exposed to high levels, the greater your breast cancer risk.
There may be a healthier alternative to HRT, one that can protect you against breast cancer—eating plants.
Eating a plant-based diet can help smooth the transition into menopause. When women go through menopause, their reproductive hormones decline to a base level. The steepness of this decline may dictate how severe your menopause symptoms are.
Because plant-eaters have lower levels of these hormones throughout their reproductive years, the drop to base level is less dramatic than for meat-eaters. Therefore, plant-eaters experience fewer menopause symptoms.
The Problem With Prolonged Exposure to Female Hormones
Female hormones include estrogen and progesterone. HRT isn’t the only factor that can increase these hormones in the body. Because these hormones are typically at their height during reproductive years, the earlier a female starts menstruating, and the later she starts the process of menopause, the greater her exposure to estrogen over her lifetime.
Animal foods seem to play a part in increasing cancer risk at every stage of a woman’s life:
- Adolescence: In girls, there’s an association between eating high-fat diets and starting menstruation earlier. Because animal foods are often high in fat, they may contribute to early menstruation.
- Adulthood: High-fat diets have also been shown to increase estrogen levels during reproductive years.
- Menopause: Diets rich in animal foods are associated with delays in menopause of three to four years. These additional years of estrogen exposure increase breast cancer risk.
Again, the levels of estrogen and progesterone in your body during your reproductive years affect the severity of your symptoms in menopause. Keeping your female hormones lower now may help you avoid HRT, and the breast cancer risk that comes with it, in the future.
Researchers compared the estrogen levels of Chinese women to the levels of British women, whose breast cancer risk is similar to that of American women.
Chinese women in the study didn’t start menstruating until an average age of 17. Due to their low-fat diets, they also started menopause earlier than British women. Also due to their low-fat diets, Chinese women had half the estrogen levels of British women during their reproductive years.
Because the reproductive lives of Chinese women were 75% shorter than those of British women, and because their estrogen levels were lower throughout life, they had 35-40% less exposure to estrogen over their lifetimes. This dovetails with the fact that Chinese women get breast cancer at one-fifth the rate of Western women.
Other Breast Cancer Risk Factors
1. High Blood Cholesterol
Both dietary fat (found in greater quantities in animal foods than in plant foods) and animal proteins have been shown to increase cholesterol.
2. Genes
Your genes also increase your risk of getting breast cancer, but probably not as much as the media tells us. Although the “breast cancer genes,” BRCA-1 and BRCA-2, have received a lot of attention, studies find that less than 3% of breast cancer cases are genetic. Additionally, only 0.2% of the population carries these genes, so only a small percentage of breast cancer cases can be attributed to them.
The fact that half of the women who carry BRCA-1 or BRCA-2 never get breast cancer also demonstrates that your genes are not your destiny.
It’s not that the discovery of these genes wasn’t important. But we need to pay attention to not only who carries these genes but also what causes them to be expressed. As we know, a diet high in animal fats and proteins has been shown to act as a trigger for both carcinogens and cancer-causing genes.
3. Environmental Chemicals
Environmental chemicals pose another risk. There are different types of carcinogenic chemicals:
Carcinogen Type #1: We can’t metabolize these carcinogens, so they stay in our bodies, accumulating in body fat and the breast milk of lactating mothers. These carcinogens include dioxins and PCBs. 90-95% of exposure to these chemicals comes from eating animal foods.
Carcinogen Type #2: We can metabolize these carcinogens, but the process of metabolism creates dangerous byproducts that alter our DNA. These carcinogens, PAHs, come from car exhaust, tobacco smoke, smokestacks, and some petroleum products.
Animal foods can accelerate the rate at which PAHs bind to DNA and cause cancer. Nutrition can also alter the toxicity of certain carcinogens.
While these carcinogens are dangerous, their role in causing cancer is less important than what we choose to eat and how these foods activate or suppress the carcinogens.
In summary, eating a whole foods, plant-based (WFPB) diet means you naturally consume less fat. This diet raises the age of a girl’s first period, lowers the age of menopause, decreases female hormone levels, and decreases blood cholesterol. In these ways, the WFPB reduces at least four breast cancer risk factors.
The link between menopause and breast cancer is tenuous–menopause doesn’t lead to breast cancer unless you treat its symptoms with hormone replacement therapy. The link between HRT and breast cancer is established. Lower your female hormones now so you don’t need HRT in the future.
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Here's what you'll find in our full The China Study summary :
- Why animal proteins (meat, milk) might cause cancer, diabetes, and other diseases
- Why the medical institution is structured to hide the truth about disease and food
- The precise diet you'll need to eat to live longer and feel happier
