18 November 2008

Does Eating Dairy Increase Your Cancer Risk?

Minum susu tuh meningkatkan kanker ga sih???
Kalo lagi cekak sih iya. Beli susu, duit gada, kantong kering, gitu deh.
Serius nehhh...
Aku dapet imel berbagi info dari pengelola blog nutritiondata.com (pengelola mendapat imel pertanyaan dari anggotanya) yang dapat disimpulkan bahwa berdasarkan berbagai penelitian, minum susu ga menyebabkan kanker, terutama kanker payudara. Dijelaskan juga bahwa gak ada hubungan antara susu dengan kanker. Coba baca deh, terutama yang tulisan dari blog Monica.

Ini salinan imel yang kuterima :
Does Eating Dairy Increase Your Cancer Risk?

I got an e-mail from a user last week asking why I hadn't mentioned dairy products in my recent post on breast cancer and diet. Arguments laid out in the popular book The China Study had convinced her that the proteins in milk "turn on" cancer cells.

I have to admit that I had not read The China Study. When I picked up a copy, I learned that the study referenced in the title is about 20 years old. So I checked to see if there was more recent research on this topic, and boy, is there ever!

In response to this reader's question, I've posted a summary of the last five or six years' worth of research on whether eating dairy products increases your risk of breast cancer.

Of course, there are many valid reasons for choosing to avoid dairy products. But if you are only concerned about increasing your risk of breast cancer, you might be reassured by a preponderance of evidence (involving more than 100 studies and hundreds of thousands of subjects, and spanning several decades) showing no link between the two.

Good health and good eating,
sincerely yours

Monica Reinagel, L.D.N., C.N.S.


Ini tulisan yang ditulis Monica di blognya :
Diet and Breast Cancer: Is Dairy a Culprit?

Dear Monica, I enjoyed your post on diet and breast cancer. However, I cannot believe that you did not mention the direct relationship between the intake of casein (milk protein) and the growth of mammary tumors. T. Colin Campbell in his The China Study outlines how this protein turns on tumor growth and the lack of it in the diet turns off cancer growth. "

Before saying anything else, let me first say that I completely support anyone who does not care to consume dairy products, for whatever reason. Dairy is certainly not essential to a healthy diet. There are plenty of other ways to get calcium and vitamin D. (And those who do not consume dairy need to take care to be sure they do.) I recently did a podcast episode on the pros and cons of dairy. You can listen to it here.

Now, to Campbell's book: Lots of people commenting on this blog over the years have referenced this book as a definitive scientific rationale for various dietary practices. Obviously, Campbell's prose is compelling. But I have to be honest with you: The science behind his conclusions is less so.

You're right: There are recent (2007) studies showing that milk increases the incidence of chemically-induced breast tumors in rats. Interestingly, I also found a 2007 study showing that soy milk does the same thing. And another (2006) showing that fermented milk (yogurt) prevented tumors; and another (2001) showing that soy protein was preventive.

It appears that studies on things that cause or prevent tumors in rats injected with carcinogens might not provide a definitive answer to the question: Do dairy products cause breast cancer in humans? For that, it makes sense to turn to studies that compare what people eat to their risk of breast cancer.

Do dairy products increase breast cancer risk in humans?

The so-called "China Study" was a nutritional analysis conducted in rural China in the 1980s. This study purportedly found that dairy intake was linked to increased risk of breast cancer. I'm not sure how Campbell selected this one study upon which to ground his argument. But, unless he specifically limited his search to studies more than twenty years old, he would have had to page through literally dozens of more recent studies (done on populations with diets and lifestyles much more similar to ours) which conclude precisely the opposite in order to get to one that supported his point of view.

Here's a brief sampling:

2007 American Journal of Clinical Nutrition (5000 subjects in England and Scottland): Childhood dairy intake was not associated with breast cancer risk.

2007 Cancer Epidemiology (2000 subjects in U.S.): Reduced breast cancer risks were associated with increasing milk consumption from ages 10-29, probably because of the cancer-preventive effects of vitamin D.

2006 Cancer Causes and Controls (5000 subjects in Italy): Consumption of milk and diary products did not increase breast cancer risk (and, in fact, consumption of skim milk slightly reduced risk).

2005 Journal of the American College of Nutrition (meta-analysis of 52 different studies): Evidence does not support an association between diary product consumption and the risk of breast cancer.

2005 Nutrition and Cancer (study looking back 30 years and across 38 countries): No substantial effect of milk consumption on risk of breast (and other) cancers.

2004 American Journal of Clinical Nutrition (meta-analysis of 46 studies): No strong association between the consumption of milk or other dairy products and breast cancer risk.

2002 Journal of the National Cancer Institute (90,000 women followed for 16 years): "We found no association between intake of dairy products and breast cancer in postmenopausal women. Among premenopausal women, high intake of low-fat diary foods was associated with a reduced risk of breast cancer."

2002 International Journal of Epidemiology (meta-analysis of 8 prospective studies involving 350,000 subjects in N. America and W. Europe): "We found no significant associations between intake of meat or dairy products and risk of breast cancer."

Dairy is not essential to a healthy diet but it does not appear to cause breast cancer

Obviously, I would have had to have continued for quite a bit longer to work my way back to the China study. But there didn't seem to be much reason to continue. (And I wasn't cherry-picking, either...these are the studies that came up in response to my query!)

So, let me end this post the way I began: Dairy products are not essential to a healthy diet. Feel free to eliminate them. But I don't actually see evidence to suggest that doing so will reduce your risk of breast cancer. And, in fact, because dairy products are one of the only sources of vitamin D in the American diet, eliminating them might well increase your risk if you're not careful to get that nutrient from other food sources.


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