Tursday Nov 28, 2013 (foodconsumer.org) -- Many studies have linked obesity to increased risk of breast cancer, but not all studies are consistent.  A new study in Breast Cancer Research suggests it is not obesity but a high fat diet with animal fat used at puberty that increases the risk of breast cancer development.

The study led by Richard C Schwartz and Sandra Z Haslam and their colleagues from Michigan State University shows that of pubertal mice exposed to a carcinogen, those fed on a high fat diet with 60% kcal fat mostly lard developed breast cancer earlier, compared with those with a  low fat diet after both groups were exposed to a carcinogen.

The study found the high fat diet induced a range of inflammatory reactions which promote the development of breast cancer.   The saturated-fat-induced changes were persistent and even a low fat diet introduced in adulthood could not offset the negative impact of the high fat diet used at puberty.

The study concluded "exposure to HFD (high fat diet) in the peri-pubertal period, and the sensitivity of the pubertal gland to HFD, initiate a sequence of inflammatory, angiogenic and growth-promoting effects starting as early as 3 weeks on diet, which can lead to the promotion of mammary cancer development in adulthood."

The researchers found the risk of breast cancer development was independent of significant weight gain.  That means that it is not obesity, but eating high animal fat diet that promotes the breast cancer development.  Obese women likely have high intake of animal fat and have to face a high risk of breast cancer, but lean women who have eaten a high fat diet with lots of animal fat are also at the risk for elevated risk of breast cancer, the study suggests.

The study along with other studies also found that a high fat diet not only shortens the tumor latency or promote a tumor to develop earlier, but also boosts the tumorigenesis.  Specifically, the high fat diet increased the proliferation and production of tumor-related growth factors.   Early developed tumors found in mice on the high fat diet were also found to have elevated vascularization among other things indicating that the high fat diet boosts the growth or tumor cells.

For the study, mice started using either a low fat diet or a high fat diet at the age of 3 weeks and continued using the diet for 45 weeks.   At week 4, mice were exposed to a carcinogen 7,12 dimethylbenz(a)anthracene.

High intake of saturated fat at puberty can boost breast cancer.  Other studies suggest that postdiagnosis use of a high fat diet can also worsen the prognosis or outcome of breast cancer.

In Annual Reviews, Nour Makarem from Food Studies and Public Health, New York University in New York, New York and colleagues reported that "high consumption of saturated fat may exert a detrimental effect on breast cancer–specific and all-cause mortality, whereas omega-3 fat may be beneficial."

Candyce Kroenke, ScD, MPH, Kaiser Permanente, Division of Research in Oakland, CA and colleagues reported in the Journal of the National cancer Institute that women with breast cancer who ate a high fat diet after diagnosis were 50% more likely to die from all causes.

Lard is saturated fat from animals particularly beef.  Some "natural health advocates" promote consumption of saturated fat claiming that humans need saturated fat and it is good for human health.  At least some of these advocates are actually meat-sellers or associated with meat business.

The fact is, humans do not need saturated fat as an essential nutrient  Humans can make saturated fat themselves. In other words, saturated fat is not something that is essential and humans do not need to obtain from diet.

"Overall, our current research indicates that avoiding excessive dietary fat of this type may help lower one's risk of breast cancer down the road," Professor Schwartz said in press release. "And since there isn't any evidence suggesting that avoiding this type of diet is harmful, it just makes sense to do it."

It should not be a surprise that high fat diet is linked to a high risk of breast cancer.   Consumption of meat, which is high in saturated fat, has been associated with many cancers.

Other risk factors for breast cancer

Saturated fat is only one risk for breast cancer.  Below are some environmental risk factors associated with increased risk of the disease.

Statins - A study in Epidemiology, Biomarkers & Prevention finds evidence suggesting that long-term use of statins can increased risk of ductal and lobular breast cancer among women aged 55 to 74 years.

Acrylamide - Consumption of acrylamide-containing foods such as fries and bakery products was associated with 43% elevated risk for the development of ER+ PR+ and ER+PR+ breast cancer.

Western diet characterized by high sugar, high fat, and high salt - a study in Epidemiology, Biomarkers & Prevention shows that eating a Western diet can promote the development of breast cancer by increasing the production of sex hormone estrogen.

Many other risk factors also affect the risk of breast cancer.

Foods and dietary supplements that may reduce the risk of breast cancer include soy foods, vitamin D, vitamin C and Berberine among others.

Soy beans - Soy foods including soy milk and tofu may lower risk of both BRCA mutation breast cancer and non-BRCA breast cancer, according to a study in American Journal of Clinical Nutrition.

Vitamin D - A study in American Journal of Clinical Nutrition suggests that women with  vitamin D deficiency were four times as likely as those with vitamin D sufficiency to  develop breast cancer.

Berberine - A Japanese study in Oncology Letter suggests that berberine can be used as an adjuvant therapy to sensitize breast cancer cells and make chemotherapy more effective.

Vitamin C - A study in British Journal of Cancer suggests that high vitamin C intake prediagnosis was associated with 25% reduced risk of death from breast cancer, compared with those with a low intake.

There are many other things a woman can do to reduce the risk of breast cancer.  (David Liu, PHD)