Fiber - especially vegetable and fruit fiber - protects against breast cancer

What are the foods you think of when you hear the word “fiber”? Although most people probably think of whole grains, all plant foods are rich in fiber. In fact, beans contain more fiber than whole grains, and vegetables and fruits (and some seeds) contain comparable amounts – here are a few examples:

  • 1 cup cooked quinoa – 5 grams fiber
  • 1 cup cooked brown rice – 4 grams fiber
  • 1 cup cooked kidney beans – 11 grams fiber
  • 1 cup cooked broccoli – 6 grams fiber
  • 1 cup blueberries – 4 grams fiber
  • 1 tablespoon chia seeds – 6 grams fiber

Broccoli. Flickr: Muffet

Fiber, by definition, is resistant to digestion in the human small intestine. This means that during the digestive process, fiber arrives at the large intestine still intact. Fiber takes up space in the stomach but does not provide absorbable calories, which makes meals feel more satiating and promotes weight loss. In the colon, fiber adds bulk and accelerates movement, factors that are beneficial for colon health. Soluble fiber (primarily from legumes and oats) is effective at removing cholesterol via the digestive tract, resulting in lower blood cholesterol levels. Some types of fiber are fermented by intestinal bacteria. The fermentation products, such as butyrate, have anti-cancer effects in the colon and also serve as energy sources for colonic cells. Fermentable fiber also acts as a prebiotic in the colon, promoting the growth of beneficial bacteria. Fiber intake is associated with a multitude of health benefits, including healthy blood pressure levels and reduced risk of diabetes, heart disease and some cancers.1, 2

Fiber and breast cancer

A recent analysis of 10 scientific studies found that higher fiber intake is associated with lower risk of breast cancer.3  How does fiber impact one’s risk of breast cancer?

First and foremost, since animal products, refined grains, sugars and oils contain little or no fiber, fiber intake is a marker for greater intake of natural plant foods, many of which are known to have a variety of anti-cancer phytochemicals. Some breast cancer protective substances that have already been discovered include isothiocyanates from cruciferous vegetables4, organosulfur compounds from onions and garlic, aromatase inhibitors from mushrooms, flavonoids from berries, lignans from flax, chia and sesame seeds, and inositol pentakisphosphate (an angiogenesis inhibitor) from beans.

Does fiber itself have some potentially breast cancer protective actions?

High-fiber foods help to slow emptying of the stomach and absorption of sugars, which decreases the after-meal elevation in glucose. This is meaningful because elevated glucose levels lead to elevated insulin levels, which can send pro-cancer growth signals in the body, for example via insulin-like growth factor 1 (IGF-1). As such, high dietary glycemic index and glycemic load (characteristic of refined grains and processed foods) are associated with an increase in breast cancer risk.5-7  Accordingly, a study on Korean women found that higher white rice intake was associated with higher breast cancer risk.8

Increased exposure to estrogen is known to increase breast cancer risk.9-11 A woman may be exposed to estrogen via her ovaries’ own production, estrogen production by excess fat tissue, or environmental sources such as endocrine-disrupting chemicals (like BPA). Fiber can reduce circulating estrogen levels, thereby reducing breast cancer risk, because it helps to remove excess estrogen from the body via the digestive tract. Fiber binds up estrogen in the digestive tract, accelerates its removal, and prevents it from being reabsorbed into the body.12-14 In addition, soluble fiber (as shown with prunes and flaxseed) seems to alter estrogen metabolism such that a less dangerous form of estrogen is produced, whereas insoluble fiber (wheat bran) did not have the same effect.15,16  For this reason, beans, oats, chia seeds and flaxseeds may provide some extra protection due to their high soluble fiber content.


One notable case-control study looked specifically at different sources of fiber to determine the associations between vegetable fiber, fruit fiber, and grain fiber with breast cancer. Interestingly, when fiber was split up by source, only fruit fiber and vegetable fiber decreased risk; there was a 52% risk reduction for high intake of vegetable fiber, and a 46% risk reduction for fruit fiber. In contrast, there was no association between grain fiber and breast cancer risk.17 A new study, published in February 2013 came to a similar conclusion when analyzing the association between fiber subtypes and breast cancer risk. This study was part of the larger European Prospective Investigation into Cancer and Nutrition (EPIC) study of over 300,000 women; they found that among the fiber subtypes, only vegetable fiber was linked to decreased risk.18

Fiber itself has some breast cancer-protective properties, like limiting glycemic effects of foods and assisting in estrogen removal, but we get optimal protection when we focus on foods that are both rich in fiber and rich in phytochemicals. G-BOMBS contain numerous anti-cancer phytochemicals, and and greens, mushrooms, and flax and chia seeds in particular contain anti-estrogenic substances in addition to fiber, making them more effective breast cancer fighters than whole grains. 

 

Image credit: Flickr - Muffet

References:

1. Higdon J, Drake VJ: Fiber. In An Evidence-based Approach to Phytochemicals and Other Dietary Factors New York: Thieme; 2013: 133-148
2. Carbohydrates. In Nutritional Sciences: From Fundamentals to Food. Edited by McGuire M, Beerman KA; 2013
3. Dong JY, He K, Wang P, et al: Dietary fiber intake and risk of breast cancer: a meta-analysis of prospective cohort studies. Am J Clin Nutr 2011.
4. Liu X, Lv K: Cruciferous vegetables intake is inversely associated with risk of breast cancer: A meta-analysis. Breast 2012.
5. Dong JY, Qin LQ: Dietary glycemic index, glycemic load, and risk of breast cancer: meta-analysis of prospective cohort studies. Breast Cancer Res Treat 2011, 126:287-294.
6. Romieu I, Ferrari P, Rinaldi S, et al: Dietary glycemic index and glycemic load and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC). Am J Clin Nutr 2012, 96:345-355.
7. Sieri S, Pala V, Brighenti F, et al: High glycemic diet and breast cancer occurrence in the Italian EPIC cohort. Nutrition, metabolism, and cardiovascular diseases : NMCD 2012.
8. Yun SH, Kim K, Nam SJ, et al: The association of carbohydrate intake, glycemic load, glycemic index, and selected rice foods with breast cancer risk: a case-control study in South Korea. Asia Pac J Clin Nutr 2010, 19:383-392.
9. Hankinson SE, Eliassen AH: Endogenous estrogen, testosterone and progesterone levels in relation to breast cancer risk. J Steroid Biochem Mol Biol 2007, 106:24-30.
10. Pike MC, Pearce CL, Wu AH: Prevention of cancers of the breast, endometrium and ovary. Oncogene 2004, 23:6379-6391.
11. Bernstein L, Ross RK: Endogenous hormones and breast cancer risk. Epidemiol Rev 1993, 15:48-65.
12. Aubertin-Leheudre M, Gorbach S, Woods M, et al: Fat/fiber intakes and sex hormones in healthy premenopausal women in USA. J Steroid Biochem Mol Biol 2008, 112:32-39.
13. Aubertin-Leheudre M, Hamalainen E, Adlercreutz H: Diets and hormonal levels in postmenopausal women with or without breast cancer. Nutr Cancer 2011, 63:514-524.
14. Goldin BR, Adlercreutz H, Gorbach SL, et al: Estrogen excretion patterns and plasma levels in vegetarian and omnivorous women. N Engl J Med 1982, 307:1542-1547.
15. Haggans CJ, Travelli EJ, Thomas W, et al: The effect of flaxseed and wheat bran consumption on urinary estrogen metabolites in premenopausal women. Cancer Epidemiol Biomarkers Prev 2000, 9:719-725.
16. Kasim-Karakas SE, Almario RU, Gregory L, et al: Effects of prune consumption on the ratio of 2-hydroxyestrone to 16alpha-hydroxyestrone. Am J Clin Nutr 2002, 76:1422-1427.
17. Zhang CX, Ho SC, Cheng SZ, et al: Effect of dietary fiber intake on breast cancer risk according to estrogen and progesterone receptor status. Eur J Clin Nutr 2011, 65:929-936.
18. Ferrari P, Rinaldi S, Jenab M, et al: Dietary fiber intake and risk of hormonal receptor-defined breast cancer in the European Prospective Investigation into Cancer and Nutrition study1,2. Am J Clin Nutr 2013, 97:344-353.

Interview with a Nutritarian: Carrie

I first got to know Carrie and follow her health and weight loss progress through Dr. Fuhrman’s Member Center when she joined the first Holiday Challenge back in 2010. Then this past summer I met her in person at Dr. Fuhrman’s Health Getaway on Amelia Island. Carrie’s skin just glowed, and she was the epitome of vibrant health and fitness! One would never have known that just two years prior she was overweight and suffering from multiple ailments. Welcome to Disease Proof, Carrie.

 

What was your life like before discovering Dr. Fuhrman’s nutritarian eating-style?

I remember being a sick child, always getting colds which forced me to stay home from school a lot, and I wasn’t any healthier as an adolescent or young adult. By the time I turned 35, I was a mess: overweight and suffering from chronic migraines, allergies and anxiety, not to mention that I would get sick anytime I went on an airplane.

The last straw for me was when my migraines got so bad that I was taking prescription medication and over-the-counter painkillers every afternoon and living in fear of the pain. I could not keep up with my husband or friends nor could I make plans for my future because I was so debilitated by headaches. When I asked my doctor about my options, his only suggestion was for me to consider taking an anti-seizure medication that had been shown to help people with migraines; he never said anything about improving my diet. Fortunately, I discovered Dr. Fuhrman before I began taking them.

 

How did you find out about Dr. Fuhrman and Eat to Live?

I had already switched to a vegan diet prior to discovering Dr. Fuhrman because I was concerned about animal welfare. I listened to a podcast by Colleen Patrick-Goudreau who mentioned Dr. Fuhrman and his book. I was intrigued by his nutrition-based approach to health issues so I asked a friend to give me the book for my upcoming birthday. Little did I realize that reading Eat to Live would be the turning point in my life. I felt so inspired by the section on recovering from headaches that I joined the Holiday Challenge 2010 that was about to begin.

Those first 6 weeks were tough. Although I thought I was eating a healthy diet because I was vegan, I still had tons of changes to make. I cut out caffeine, quadrupled my intake of greens and other vegetables, ate more fresh fruits, got rid of salt and cut way back on added sugars. My husband joined me and ended up experiencing his own health transformation, losing 40 pounds and getting off of two blood pressure medications.

 

How do you feel now?

 I feel better now than I have in my entire life. All my unhealthy eating for all those years, and perhaps combined with environmental exposures, resulted in my being diagnosed with thyroid cancer last year; a slow growing cancer that I could’ve had for more than ten years. I don’t know if I would’ve pulled through so easily if it wasn’t for my new eating habits. I came though that experience with flying colors, and the cancer was small and completely removed. My doctors could not believe how quickly I recovered from surgery. My migraines, allergies and anxiety are distant memories, but I will never forget how far I'e come, and I am so grateful to Dr. Fuhrman for giving me my life back.

 

Do you have any success tips to share?

Preparation is an absolute. I know that the time I spend on the front end will benefit me on the back end, so I often wake up early to cook beans, prep vegetables or make a salad dressing. I also make sure to freeze leftovers so I don’t get caught without foods during those inevitable busy times when I don’t have time to cook.

My husband wanted me to share his tip for getting rid of the salt shaker and that is to use balsamic vinegar or fresh lemon juice on meals; it is amazing how the acidity brightens up the flavor of natural foods.

 

In a nutshell, what has nutritarian eating done for you?

My life now revolves around promoting a whole foods, high-nutrient eating style. I am almost finished with a master’s degree in public health nutrition and I write a blog called Carrie on Vegan where I discuss my journey.

While the numbers speak for themselves, they can’t begin to capture the extent of my personal transformation. I feel like I am living my life to the fullest because I have the energy and freedom from pain to do so.

 

 

Before

After

Weight

138

113

Total Cholesterol

224

165

LDL Cholesterol

102

79

Triglycerides

123

47

Migraines

 

gone

Allergies

 

gone

Anxiety

 

gone

 

Thank you for sharing your story with us Carrie, and all the best of continual health to you!