Breast Cancer Linked to Red Meat Consumption

Research from Harvard University and other institutions over the last decade has increasingly shown that cancer is positively linked to greater consumption of red meat. The link has been profound in colon cancer, prostate cancer and other forms of cancer.

And new studies keep coming in linking cancer to meat consumption. For example, a study published in 2015 found that red meat intake increased the incidence of squamous cell carcinoma of the lung by 81 percent, and beef consumption more than doubled (222 percent) the incidence of this dangerous form of cancer. Squamous cell carcinoma of the lung has only a 15 percent five-year survival rate.

What about breast cancer?

But a firm link between breast cancer and red meat consumption has been less obvious.

This doesn’t mean that there isn’t some clear evidence. A new review of past research published in 2015, provides some clarity. This study analyzed 26 studies through October of 2014, including 14 studies on red meat and 12 studies on processed meat. The researchers calculated relative risks for different intakes of red meat among the various studies.

Their research found that for every increase of 120 grams of red meat per day, breast cancer incidence increased by 11 percent. And for every increase of 50 grams of processed meat per day, breast cancer incidence increased by 9 percent.

That said, some of the studies showed even higher associations. This included up to 16 percent increased breast cancer incidence for every 120 grams of red meat consumption, and 16 percent for every 50 grams of processed meat consumption.

Some have hypothesized that the reason for the difference in studies relates not just to the type of meat, but the amount of iron in the meat. Others have pointed to the levels of potential nitrites in the meat. Processed meat is typically higher in nitrites.

This review has prompted cancer researchers to investigate the link between breast cancer and meat intake more definitively.

NIH focuses on breast cancer and meat

One group of cancer researchers has significant clout and resources at its disposal to investigate this more definitely: Scientists at the National Cancer Institute of the National Institutes of Health, to be specific.

The NIH’s National Cancer Institute has 69 cancer centers throughout the U.S., where doctors conduct research and provide treatment for patients. The combined budget for the National Cancer Institute in 2013 was $4.789 billion.

Yes, in mine and many other people’s opinions, the NIH’s cancer research is not providing enough focus on natural and herbal medicine. But that’s another topic.

But one thing the NIH is good at is population research. In this topic in particular, the research clout and funding provides some significant clarity in the case of breast cancer and meat consumption.

Hundreds of thousands of women followed

The NIH researchers followed 193,742 postmenopausal women for 11 years – between 1995 and 2006. The researchers conducted food frequency questionnaires to determine meat intake, along with nitrite intake and heme iron.

The researchers categorized the different women into groups rated by their intakes. These were divided into quintiles. This means the women were divided into five groups for each of the intakes. This allowed the researchers to compare the number of cancers among the different diets among the women.

During the study, 9,305 breast cancers occurred among the women.

The research found that those in the highest quintile red meat consumption group had 25 percent higher incidence of localized breast cancer compared to the lowest quintile of red meat consumption.

The processed meat consumption was a little higher. Those in the highest group had 27 percent increased incidence of localized breast cancer compared to the lowest quintile of processed meat consumption.

Nitrite consumption also increased the incidence of breast cancer. Those in the highest group of nitrite consumption had 23 percent greater incidence of breast cancer compared to the lowest group. Heme iron consumption also increased the incidence.

The researchers concluded that the heme iron and nitrites may increase the cancer risk notably because meat contains heme iron and nitrites. But they were clear that meat consumption provided significant risk:

“Our findings suggest that high consumption of red meat and processed meat may increase risk of postmenopausal breast cancer.”

It should be noted that this study only compared those who ate the most meat to those who ate the least, in five increments. It did not compare those who ate meat with those who did not eat meat. Logically, this should equate to a significantly higher difference.

Greater breast cancer risk has been found in studies on processed meats. For example, one study of 500 women – including 250 women with breast cancer – found that processed meats eaten once or twice a week increased the risk of breast cancer among the women by 265 percent – that is, nearly 2.7-fold risk.

Why does meat increase cancer?

There are a number of reasons, according to the research. These relate to our gut bacteria, to toxin intake and many others. One proposal has been gaining evidence: The notion that the heterocyclic amines that are formed when meat is cooked increases free radicals within the body.

This theory was tested recently by scientists from Brazil’s University of Sao Paulo. The researchers tested 561 adults. The researchers conducted a 24-hour dietary recall with each of the subjects. They also tested each of the human subjects’ levels of oxidative stress. The researchers used malondialdehyde concentration testing to find that heterocyclic amine consumption linked to greater oxidative stress.

But heterocyclic amines intake is not the only toxin to be concerned about. A 2009 study from Germany’s German Cancer Research Center studied the breast DNA adducts of 44 women who underwent breast reduction.

A DNA adduct is a portion of DNA that has bonded with a chemical linked with cancer.

The researchers found that DNA adducts were linked with higher intakes of fried meat, beef and total heterocyclic amine intake. Because the DNA adducts were not all specific to heterocyclic amines: They concluded that there were other potential cancer-causing agents in the meat, including polycyclic aromatic hydrocarbons.

REFERENCES:

Guo J, Wei W, Zhan L. Red and processed meat intake and risk of breast cancer: a meta-analysis of prospective studies. Breast Cancer Res Treat. 2015 May;151(1):191-8. doi: 10.1007/s10549-015-3380-9.

Inoue-Choi M, Sinha R, Gierach GL, Ward MH. Red and processed meat, nitrite, and heme iron intakes and postmenopausal breast cancer risk in the NIH-AARP Diet and Health Study. Int J Cancer. 2015 Oct 27. doi: 10.1002/ijc.29901.

Mourouti N, Kontogianni MD, Papavagelis C, Plytzanopoulou P, Vassilakou T, Psaltopoulou T, Malamos N, Linos A, Panagiotakos DB. Meat consumption and breast cancer: a case-control study in women. Meat Sci. 2015 Feb;100:195-201.

Carvalho AM, Miranda AM, Santos FA, Loureiro AP, Fisberg RM, Marchioni DM. High intake of heterocyclic amines from meat is associated with oxidative stress. Br J Nutr. 2015 Apr 28;113(8):1301-7. doi: 10.1017/S0007114515000628.

Rohrmann S, Lukas Jung SU, Linseisen J, Pfau W. Dietary intake of meat and meat-derived heterocyclic aromatic amines and breast tissue DNA adducts. Mutagenesis. 2009 Mar;24(2):127-32. doi: 10.1093/mutage/gen058.

Deneo-Pellegrini H, Ronco AL, De Stefani E. Meat consumption and risk of squamous cell carcinoma of the lung: a case-control study in Uruguayan men. Nutr Cancer. 2015;67(1):82-8. doi: 10.1080/01635581.2015.970290.