Day 27: Does dairy do a body good?
You’ve seen the billboards and magazine ads. Models and athletes sporting those sexy milky mustaches. Got Milk may be the most effective ad campaign of my generation. But what exactly is the science behind this clever and influential public relations coup?
Now things get murkier than chocolate chip cookie debris suspended in a creamy white glass of chilled dairy beverage. I am reading a book entitled The China Study, written by T. Colin Campbell, a retired NIH-sponsored researcher. If Campbell is to be believed, dairy product consumption is related to a variety of health maladies. I am approaching the age where PSA results in my annual blood test mean more to me than a passing interest. According to a Harvard University review, 12 of 14 case-control studies and seven of nine cohort studies observed a positive association between dairy consumption and prostate cancer. Campbell goes on to make a compelling case that milk consumption in babies is also related to the risk of developing Type 1 Diabetes. Campbell completes his dairy coups d’état by suggesting that cows milk consumption is associated with Multiple Sclerosis.
I am not a nutritionist; can someone assist me with this Campbell conundrum? Is he a charlatan or have we been hoodwinked by the dairy industry?
Tomorrow: Four weeks of vegetarianism.
February 7th, 2008 at 3:15 pm
Dr. Campbell did his research through Cornell University. I do not believe he is a chalatan. His research credentials include RO1 NIH research awards for Diet and Cancer 1987-93 and for Dietary Protein and Chemical Carcinogens 1984-89. As for casein and its implications, it would seem that we still don’t have the final answer on this. One of Dr. Campbell’s research publications on casein is this one:
YOUNGMAN LD, CAMPBELL TC
THE SUSTAINED DEVELOPMENT OF PRENEOPLASTIC LESIONS DEPENDS ON HIGH PROTEIN-INTAKE NUTRITION AND CANCER-AN INTERNATIONAL JOURNAL 18 (2): 131-142 1992
This study looks at two different levels of casein intake in rats and concludes the rats on the 5% casein diet vs. the 20% casein diet had fewer neoplastic lesions. To conclude from this study that humans should avoid animal protein is quite a leap. Protein is made up of amino acids which the body breaks down and uses. Protein from animal sources and protein from plant sources come with various other moieties and to single out casein as a culprit does not yet seem to have a scientific basis.
While the insulin-like growth factor levels in humans are affected by protein intake, and may also be particularly attributable to milk intake, it is also true that high fat intake, particularly saturated fat is associated with lower levels of insulin-like growth factor binding protein. (High levels of IGFBP equal decreased risk for common cancers) In sum, while it is true that nutritional manipulations of the diet can affect cancer risk, it may be early to separate out casein as a major culprit. The J Am Coll Nutr. 2005 Dec;24(6 Suppl):556S-68S states that 40 case-control studies and 12 cohort studies do not support an association between dairy product consumption and the risk of breast cancer. And a study done on 18 prostate cancer patients in the Clin Cancer Res. 2003;9:3283-7 states that a potentially undesirable effect associated with the administration of a soy protein supplement was an increase in IGF-I serum levels. With this study, the problem I believe, was the isolation of soy protein rather than the use of whole soy that created the increase in IGF-I serum levels, but it helps illustrate the point that perhaps casein is not the major (or only) culprit in this story.
February 4th, 2008 at 1:09 pm
A cursory search in Pubmed demonstrates that at least some of Campbell’s claims about the harms of dairy are backed by evidence.
My own questions about the health implications of dairy and the influence of the industry relate to my and other pediatricians’ fairly uniform advice to give cows’ milk to 1-year olds who have been weaned (or are no longer on formula) despite the apparent lack of scientific evidence for this practice. Is this evidence of the influence of the dairy industry? I’ve been wondering why calcium-fortified soy, nut, or grain milks are not suggested as valid alternatives for toddlers whose diet includes other adequate sources of protein and fat.
LLUSPH has a great nutrition department. What are their thoughts on the various dimensions of the dairy question?