Expert Opinions
Flavonoids, Insulin-like Growth Factor, and Colon Cancer
Flavonoids are a class of antioxidant molecules found ubiquitously in plant foods, with certain classes of flavonoids concentrated in certain foods. For example anthocyanins in berries, isoflavones in soybeans, flavonones in citrus fruits, and catechins in tea, grapes and berries; flavanols are the most common flavonoids found many plant foods. Fruits and vegetables are known to be protective against colon cancer, and these effects are thought to be due in part to flavonoids; in addition to their antioxidant activities, flavonoids have additional protective effects on signaling and gene expression within the cell. Because of insufficient fruit and vegetable intake in Western societies, dietary flavonoid intake is low and most people are unfortunately not reaping the valuable health benefits of flavonoids.1,2
Luteolin is a flavonoid that is abundant in celery, peppers, kohlrabi, and culinary herbs like oregano and parsley. Luteolin has documented anti-inflammatory and antioxidant properties. Luteolin has also been shown to interfere with various stages of carcinogenesis in a number of different cancer cells.3 A recent study has found that luteolin blocks the growth of human colon cancer cells by interfering with growth stimulation by a hormone called iinsulin-like growth factor 1 (IGF-1). Insulin-like growth factor 1 (IGF-1) is one of the body’s important growth promoters early in life, but excess IGF-1 promotes cancer and aging later in life.4 When human colon cancer cells were treated with luteolin, the amount of the receptor protein for IGF-1 was decreased, and the cancer cells no longer responded to IGF-1’s growth signals.5
IGF-1 is increased in several cancers, circulating in the blood and in affected tissues. In fact, cancer drugs targeting IGF-1 have been developed.6 Elevated IGF-1 is associated with elevated risk of colorectal cancers; IGF-1 stimulates the rampant growth that is characteristic of cancer and promotes the progression from colon adenoma to colon cancer.7,8,9
The major determinant of IGF-1 levels is dietary protein, especially animal protein; a diet heavy in meat and dairy products strongly elevates IGF-1, and refined carbohydrates also contribute. Essentially, the standard American diet is an IGF-1-raising diet. One important message here is that eating whole plant foods instead of animal products and processed foods tips the balance toward less IGF-1, and therefore protection against cancers. Additionally, eating a variety of plant foods provides us with a variety of phytochemicals, for which more and more health benefits are revealed as time goes on. Celery, parsley, and peppers are rich sources of luteolin plus hundreds of other phytochemicals. For example, celery contains aromatase inhibitors that are protective against breast cancer.10 Other plant foods are rich in additional flavonoids and other phytochemicals; these thousands of phytochemicals work synergistically in our bodies to protect our health.
This simple salad recipe combines the three richest sources of luteolin plus cruciferous leafy green kale and red onion (rich in organosulfur compounds and another flavonoid called quercetin) for a big boost of anti-cancer compounds.
Chopped Vegetable Salad with Orange Sesame Dressing
Salad:
3 organic celery stalks, chopped
1 15-ounce can no-salt garbanzo beans, drained
Dressing:
1/4 cup unhulled sesame seeds, divided
1/4 cup raw cashew nuts or 1/8 cup raw cashew butter
2 oranges, peeled and diced
Instructions:
Combine the salad ingredients in a large bowl and toss. Toast the sesame seeds in a dry skillet over medium-high heat for 3 minutes, shaking the pan frequently. In a high-powered blender, combine 2 tablespoons of the sesame seeds, cashews, orange juice, and vinegar. Toss salad with dressing and diced oranges. Sprinkle the remaining sesame seeds on top.
Dr. Fuhrman is a New York Times best-selling author and board certified family physician specializing in lifestyle and nutritional medicine. His new book Super Immunitydiscusses how to naturally strengthen the immune system against everything from the common cold to cancer. Visit his informative website at DrFuhrman.com and blog at DiseaseProof.com. You can also follow Dr. Fuhrman at Facebook.com/DrFuhrman and on Twitter @DrFuhrman.
References:
- Pierini R, Gee JM, Belshaw NJ, et al:Flavonoids and intestinal cancers.Br J Nutr 2008;99 E Suppl 1:ES53-59.
- Williams RJ, Spencer JP, Rice-Evans C: Flavonoids: antioxidants or signalling molecules?Free Radic Biol Med 2004;36:838-849.
- Lin Y, Shi R, Wang X, et al:Luteolin, a flavonoid with potential for cancer prevention and therapy. Curr Cancer Drug Targets 2008;8:634-646.
- Bartke A: Minireview: role of the growth hormone/insulin-like growth factor system in mammalian aging.Endocrinology 2005;146:3718-3723.
- Lim DY, Cho HJ, Kim J, et al: Luteolin decreases IGF-II production and downregulates insulin-like growth factor-I receptor signaling in HT-29 human colon cancer cells. BMC Gastroenterol 2012;12:9.
- Gualberto A, Pollak M:Emerging role of insulin-like growth factor receptor inhibitors in oncology: early clinical trial results and future directions.Oncogene 2009;28:3009-3021.
- Davies M, Gupta S, Goldspink G, et al: The insulin-like growth factor system and colorectal cancer: clinical and experimental evidence. Int J Colorectal Dis 2006;21:201-208.
- Sandhu MS, Dunger DB, Giovannucci EL: Insulin, insulin-like growth factor-I (IGF-I), IGF binding proteins, their biologic interactions, and colorectal cancer. J Natl Cancer Inst 2002;94:972-980.
- Werner H, Bruchim I:The insulin-like growth factor-I receptor as an oncogene.Arch Physiol Biochem 2009;115:58-71.
- Grube BJ, Eng ET, Kao YC, et al:White button mushroom phytochemicals inhibit aromatase activity and breast cancer cell proliferation.The Journal of nutrition 2001;131:3288-3293.
