Effects of a Low-Fat, High-Fiber Diet and Exercise Program on Breast Cancer Risk Factors In Vivo and Tumor Cell Growth and Apoptosis In Vitro

Abstract

Abstruct: The present study irwestigated the effects of a diet and exercise intervention on known breast cancer (BCa) risk factors, including estrogen, obesity, insulin, and insulin-like growth factor-I QGF-I), in overweight/obese, postmenopausal women. In addition, using the subjects'pre-and postintervention serum in vitro, serum-stimulated growth and apoptosis of three estrogen receptor-positive BCa cell lines were studied. The women where placed on a low-fat (10-15% kcal), high-fber (30-40 gper 1,000 kcal/day) diet and attended daily exercise classesfor 2 wk. Serum estradiol was reduced in the women on hormone treatment (HT; n : 28) as well as those not on HT (n : I0). Serum insulin and IGF-I were significantly reduced in all women, whereas IGF b in d in g p rot e in-I w a s in cr e as e d s i gnifi c ant ly. In v itro grow t h of the BCa cell lines was reduced by 6.6% for the MCF-7 cells, 93%for the ZR-75-I cells, and 18.5%for the T-47D cells. Apoptosis was inueased by 20% in the ZR-75-l cells, 23% in the MCF-7 cells, and 30% in the T:47D cells (n = I2). These results show that a very-low-fat, high-fiber diet combined with daily exercise results in major reductions in risk factors for BCa while subjects remained overweight/obese. These in vivo serum changes slowed the growth and induced apoptosis in serum-stimulated BCa cell lines in vitro.

Dietary animal-derived iron and fat intake and breast cancer risk in the Shanghai Breast Cancer Study

“…Finally, the possibility that dietary fat may affect iron bioavailability has been raised, and this issue requires further study [35]. The interaction between animal-derived iron and fats that we found may also partly explain the previously reported lack of significant reduction in breast cancer risk with reduction in dietary fat, despite evidence from in vitro studies that breast cancer risk factors can be impacted by low-fat, high-fiber diets [36,37]. Although the effect of dietary fat on breast cancer risk has been thought to be mediated through elevated estrogen levels, this hypothesis has remained controversial and does not explain why animal fats alone are associated with risk [31,38,39].…”

Exercise-induced muscle-derived cytokines inhibit mammary cancer cell growth

“…A similar approach was undertaken by Barnard et al (2), who conducted studies with obese postmenopausal subjects and collected serum 24 h after the exercise intervention. In these studies, the exercise intervention was combined with a low-fat, high-fiber diet for 2 wk, and thus the effect of the metabolic profile in the serum caused by the diet or exercise intervention could not be differentiated.…”

“…Recently, it was shown that conditioned media from electrostimulated C 2 C 12 muscle cells could inhibit mammary cancer cell proliferation (3), suggesting that the contracting myotubes release humoral factors that can inhibit cancer cell growth. In continuation, Barnard et al (2) have shown that serum obtained from subjects after 2 wk of a low-fat, high-fiber diet and exercise intervention could inhibit mammary cancer cell growth in vitro. Similar interventions in men were shown to inhibit prostate cancer cell proliferation (25).…”

Dietary fiber is associated with serum sex hormones and insulin-related peptides in postmenopausal breast cancer survivors

“…Dietary fiber increases the fecal excretion of estrogen [11] and binds estradiol [12] thereby reducing bio-available levels; and most studies in humans have found that estrogen levels decrease as dietary fiber increases [17,19,[34][35][36][37]. Dietary fiber may also influence estrogen levels through its regulation of body weight.…”

“…Therefore, increasing dietary fiber has been suggested as a strategy for breast cancer prevention. Several intervention trials, in women with and without breast cancer, have shown that increasing dietary fiber results in lower serum estrogen levels [17][18][19], although some have found the association modest or nonexistent [20]. The effect of dietary fiber on androgens, SHBG, insulin-related peptides, and leptin is less clear, particularly among women with a previous breast cancer diagnosis.…”