Fiber and breast cancer prevention

fiber and breast cancer prevention

Research shows fiber is the most important nutrient for breast cancer prevention.

Researchers have long linked certain diets to lower rates of breast cancer, but why? For estrogen/progesterone-positive breast cancers, which account for between 70-80% of breast cancers, one of the most powerful tools for prevention is diet. It's true that there are genetic and environmental factors at play, but many of those risks are out of your hands. However, a few simple modifications to your diet can go a long way in preventing hormone-related cancer risk.

What the research says

The research is steeped in conflict due to the inherently challenging nature of nutrition science, but one dietary factor shines through time and time again—soluble fiber.

A 2016 meta-analysis clearly states "Dose-response analysis showed that every 10g/d increment in dietary fibre intake was associated with a 4% reduction in breast cancer risk, and little evidence of publication bias was found. Thus, dietary fibre consumption is significantly associated with a reduced risk of breast cancer, particularly in postmenopausal women."

What they didn't factor in is the difference between intake of soluble vs. insoluble fiber. Our perspective at Florasophy is that both forms are important, but when it comes to binding and excreting excess hormones, soluble fiber reigns supreme. We recommend 20g insoluble fiber and 20g soluble fiber each and every day.

Why soluble fiber is so critical for estrogen excretion

Estrogen is produced primarily in the ovaries prior to menopause and then mainly by adipose tissue (fat cells) after menopause (one reason our bodies are programed to gain weight after menopause). Estrogens (estradiol, estrone, and estriol) circulate throughout the body, attaching to cells and affecting functions such as reproduction, heart and blood vessel health, balance of mucosal membranes, histamine release, bone growth, cognition, breast development, fat placement and more. Some forms of estrogen are very bioactive (they affect change), while others are fairly lazy. Some variations of estrogen are known to trigger tumor growth while others are known to protect against it.

Most women don't know that their bodies are constantly working to remove excess estrogen from the body. After hormones "do their job," they are converted to a different molecule that signals to the liver that the hormone needs to go. The liver does some fancy biochemical magic (requiring very specific micronutrients) and attaches the hormone waste to bile, which is then shuttled into the gallbladder.

From there, the bile-hormone compound is secreted into the small intestine where bile has two potential routes:

  1. The bile will help you emulsify and absorb dietary fat, in which case the toxic hormone that your liver was trying to get rid of is reabsorbed into your bloodstream where it increases your hormone levels and increases risk of hormone imbalance.
  2. or
  3. The bile/hormone molecule is trapped by soluble fiber in your diet, preventing reabsorption and the new bile-hormone-fiber compound is shuttled into the colon and into your toilet as waste.

If route #2 happens consistently, the risk of hormone imbalance and excess circulating estrogen is significantly reduced. It is this process that helps to prevent breast cancer. If this is not happening regularly, research indicates increased risk.

The Nurses’ Health Study II reported significantly elevated estradiol levels in women with breast cancer compared to controls with a higher magnitude effect for women with ER+/PR+ breast cancer.

The study reported "circulating levels of estrogens and androgens were significantly positively associated with risk of breast cancer before age 50 years."

How do we boost estrogen clearance?

By increasing soluble fiber intake! Consider your body's amazing detox system. Once estrogen is ready to clock out, your liver must first change the shape of estrogen and make it water soluble. Then, it attaches estrogen metabolites to bile and shuttles that compound to the gallbladder and ultimately to the small intestine to get rid of it.

There, the bile-estrogen must attach to dietary soluble fiber found in beans, lentils, flax, chia, avocado, Brussels sprouts and the like, to prevent the bile/estrogen from being reabsorbed back into the bloodstream. If your diet provides enough soluble fiber, this fiber will carry the excess estrogen/bile waste into your colon and into the toilet by way of poop.  

Voila – you’ve cleared estrogen!

But if your diet is low in soluble fiber, you'll reabsorb the estrogen, keeping the vicious estrogen-recycling process going while your estrogens increase over time.

How to boost soluble and insoluble fiber

Most plants contain a combination, but as a rule increasing vegetable and fruit intake will largely boost insoluble fiber, while consuming plenty of beans, lentils, oat bran, avocado, chia, and flax is an effective way to increase soluble fiber. (Learn more here about how to eat more soluble fiber).

Many people find it hard to reach the target of 20g soluble fiber with diet alone, and, in fact, we've analyzed the real-life diets of Florasophy users. Our findings were that even very healthy diets were still far short of 20 grams per day of soluble fiber. This is why Florasophy is such a valuable addition to your fiber routine and an insurance policy for your health. Every tablespoon of Florasophy contains 4g soluble fiber, so you can match your dose to your fiber needs.

About Megan Barnett, MS, CNS

Megan Barnett, MSMegan Barnett is a functional medicine practitioner in Portland, Oregon. In her clinical practice, she helps patients identify the root cause of their health problems, then designs individualized and evidence-based approaches to alleviate symptoms and help their bodies heal. She has a Bachelor of Science in Dietetics from Kansas State University and a Master of Science in Nutrition and Functional Medicine from University of Western States.