No. Studies show no evidence that reducing dietary fat decreases a woman's risk of developing postmenopausal breast cancer within the subsequent 14 years (strength of recommendation [SOR]: B, based on large heterogeneous prospective cohort studies and appropriate meta-analyses of these studies). Overall, evidence is insufficient to recommend for or against reduction in dietary fat to reduce risk of breast cancer for women, although recommendations for prudent fat intake may be justified on other grounds

Hamilton, Andrew

Hayes, Meg

Klubert, David

Steiner, Elizabeth

University of Missouri: MOspace

	 vol	56,	No	7	/	july	2007	 583www.jfponline.comCliniCal INquIrIes From the Family Physicians Inquiries Networkfast track  Elizabeth Steiner, MDOregon Health and Science University, PortlandDavid Klubert, MDApogee Informatics, Portland, OregonMeg Hayes, MD, andrew Hamilton, MS, MlSOregon Health and Science University, PortlandDoes a low-fat diet  help prevent breast cancer?Evidence-based answerNo.	studies	show	no	evidence	that	reducing	dietary	fat	decreases	a	woman’s	risk	of	developing	postmenopausal	breast	cancer	within	the	subsequent	14	years	(strength	of	recommendation	[sor]:	B,	based	on	large	heterogeneous	prospective	cohort	studies	and	appropriate	meta-analyses	of	these	studies).	overall,	evidence	is	insufficient	to	recommend	for	or	against	reduction	in	dietary	fat	to	reduce	risk	of	breast	cancer	for	women,	although	recommendations	for	prudent	fat	intake	may	be	justified	on	other	grounds.Clinical commentaryLosing weight is still a good strategy Women	at	risk	for	breast	cancer—and	cancer	survivors—want	to	know	about	lifestyle	changes	that	can	reduce	their	risks	for	cancer	or	recurrence.	There	is	growing	evidence	that	obesity	plays	a	role	in	cancer	development	and	promotion.			 A	low-fat	diet	has	been	demonstrated	as	a	successful	strategy	for	weight	loss.	However,	for	most	women,	making	these	changes	can	be	difficult	without	extensive	instruction,	support,	and	motivation.	limiting	sweetened	beverages,	increasing	consumption	of	fruits	and	vegetables,	and	limiting	fat	intake	are	3	strategies	women	can	use	to	achieve	a	healthy	weight.	If	this	turns	out	to	reduce	their	risk	of	breast	cancer,	so	much	the	better!Kathryn Kolasa, PhD, RD, lDneast	Carolina	university,	Greenville,	NCz Evidence summaryOur Medline search retrieved 1114 Eng-lish-language studies published from 1960 through October 2006. We limited this set to randomized controlled trials and cohort studies, leaving 212 articles. We then excluded articles that had small sample sizes, did not follow subjects for at least 5 years, did not include original data, included men, did not give preva-lence or incidence rate of breast cancer in the subjects, or did not discuss diet as-sessment tools. Of the remaining articles, we selected the 11 best studies to include in the review.Early studies evaluating national aver-age dietary fat intake and breast cancer in-cidence rates showed an almost linear rela-tionship between increased dietary fat and increased breast cancer incidence.1 How-ever, increased fat intake occurs primarily in industrialized nations, providing mul-tiple possible confounders for increased rates of breast cancer, such as pollutants and increased consumption of preserva-tives, pesticides, and other chemicals. Case-control studies have shown some minimally increased risk related to dietary fat consumption, but there is con-cern about recall bias in these studies.2 Reducing  a woman’s  dietary fat intake does not appear  to reduce her risk of breast cancerCoNT INueDCopyright® Dowden Health Media  For personal use onlyFor mass reproduction, content licensing and permissions contact Dowden Health Media.fast track584 vol	56,	No	7	/	july	2007		ThE JournaL of famiLy PraCTiCECliniCal INquIrIesSince the late 1970s, 7 large, well-designed prospective cohort studies have examined the possible relationship between dietary fat and breast cancer.1 The findings have been somewhat contradictory, with some studies showing statistically significant associations toward increased risk with higher fat intake.3–5Since the late 1990s, several meta-analyses, a systematic review of these cohort studies, and the Women’s Health Initiative Randomized Controlled Diet Initiative have largely concluded that there is no difference in breast cancer in-cidence between women with a low-fat diet (<20% of total calories from fat) and women with average or high-fat diets (>40% total calories from fat).1,3,6,7 The meta-analysis performed by Boyd et al did find a statistically significant dif-ference, with relative risks ranging from 1.11 for overall to 1.19 for high-saturat-ed-fat diets.8 The upper limit of all confi-dence intervals was no higher than 1.35, however, suggesting a lack of clinical sig-nificance. The best-designed studies also evaluated dietary composition with regard to key types of fat (saturated, mono- and poly-unsaturated; animal vs vegetable vs marine) and found no significant differ-ences based on type of fat consumed.1Preliminary evidence indicates that lowering dietary fat consumption may help with secondary prevention of breast cancer, but no large studies have been per-formed to date.9 Recently, a nested study within the Women’s Intervention Nutri-tion Study did show that women with breast cancer who decreased their fat in-take to a median of 33 g/day had a hazard ratio of 0.76 for relapse over 60 months (compared with controls who ate a me-dian of 51 g/day).10Recommendations from othersThere are no evidence-based or specific recommendations for the primary pre-vention of postmenopausal breast cancer for women through dietary fat reduc-tion. In particular, neither the American Academy of Family Physicians, American College fo Surgeons, National Institutes of Health, American College of Obstetri-cians and Gynecologists, American Col-lege of Physicians, US Preventive Services Task Force, or the Centers for Disease Control and Prevention provide any guidelines on dietary fat restriction for primary prevention of postmenopausal breast cancer. The American Heart Association does have guidelines for coronary artery disease prevention for women, which include a low-fat diet.11 The USPSTF has no specific guidelines regarding dietary fat consump-tion for the general population.  nreferences	 1.	 	Willett	WC.	Diet	 and	breast	 cancer.	J Intern Med 2001;	249:395–411.		 2.	 	Bingham	sA,	luben	r,	Welch	A,	Wareham	N,	Khaw	KT,	Day	N.	Are	imprecise	methods	obscuring	a	rela-tion	 between	 fat	 and	 breast	 cancer?	 Lancet	 2003;	362:212–214.		 3.	 	Mattisson	I,	Wirfalt	e,	Wallstrom	P,	Gullberg	B,	olsson	H,	Berglund	G.	High	fat	and	alcohol	 intakes	are	risk	factors	of	postmenopausal	breast	cancer:	a	prospec-tive	study	from	the	Malmo	diet	and	cancer	cohort.	Int J Cancer	2004;	110:589–597.	 4.	 	sieri	s,	Krogh	v,	Muti	P,	et	al.	Fat	and	Protein	Intake	and	 subsequent	 Breast	 Cancer	 risk	 in	 Postmeno-pausal	Women.	Nutr Cancer	2004;	42:10–17.		 5.	 	velie	e,	Kulldorff	M,	schairer	C,	Block	G,	Albanes	D,	schatzkin	A.	Dietary	fat,	fat	subtypes,	and	breast	can-cer	in	postmenopausal	women:	a	prospective	cohort	study.	J Natl Cancer Inst	2000;	92:833–839.		 6.	 	Holmes	MD,	Hunter	Dj,	Colditz	GA,	et	al.	Associa-tion	of	dietary	intake	of	fat	and	fatty	acids	with	risk	of	breast	cancer.	JAMA	1999;	281:914–920.		 7.	 	low-Fat	Dietary	Pattern	 and	risk	of	Breast	Cancer,	Colorectal	Cancer,	 and	Cardiovascular	Disease:	 The	Women’s	 Health	 Initiative	 randomized	 Controlled	Dietary	Modification	Trial.	Available	at:	www.whi.org/findings/dm/dm.php.	Accessed	on	june	14,	2007.	 8.	 	Boyd	NF,	stone	j,	vogt	KN,	Connelly	Bs,	Martin	lj,	Minkin	s.	Dietary	fat	and	breast	cancer	risk	revisited:	a	meta-analysis	of	the	published	literature.	Br J Cancer	2003;	89:1672–1685.		 9.	 	rock	Cl.	Diet	and	breast	cancer:	can	dietary	factors	influence	survival?	J Mammary Gland Biol Neoplasia	2003;	8:119–132.		10.	 	rowan	T,	Chlebowski,	Gl,	Blackburn	CA,	et	al.	Dietary	Fat	reduction	and	Breast	Cancer	outcome:	 Interim	efficacy	results	From	the	Women’s	Intervention	Nutri-tion	study.	J Natl Cancer Inst	2006;	98:1767–1776.11.	 	Mosca	 l,	 Appel	 lj,	 Benjamin	 ej,	 et	 al.	 evidence-based	guidelines	for	cardiovascular	disease	preven-tion	in	women.	Circulation 2004;	109:672–693.The WHI showed that women with breast cancer who reduced fat intake had a lower hazard ratio for relapse

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