Monday, January 10, 2011

The [boring] truth about rBGH and milk safety

A while back, I posted about some concerns brought to my attention by my sister-in-law, several of which dealt with cows and dairy products.  In particular, she had asked about:
  1. rBGH/bST (recombinant bovine growth hormone, or bovine somatotropin):  They give this to cows to increase their growth and milk production.  What if it's still in the products we consume?
  2. IGF-1 (insulin-like growth factor 1):  There are questions about IGF-1 being responsible for some cancers, and rBGH is supposed to elevate IGF-1.  Can it cause cancer in humans who drink milk from these cows?
  3. Can antibiotics given to cows show up in our food supply, and are they increased or more harmful due to the hormones we give the cows?
I did a lot of searches on PubMed trying to find information about rBGH, and most of what I found dealt with animal trials or the public's perceptions of rBGH.  After all, if you've read some of the pro-organic websites out there, you might have seen something about the dangers of these chemicals, or even that the FDA has never studied the effects of these chemicals in milk consumed by humans.  Well, it turns out there's a very good reason why you don't find these studies anywhere -- it's because they're not necessary.  Medically.  Scientifically.  At all.

Why? Because well... Science.  It works, bitches!

I found this wonderful website from Cornell that talks about many of the above concerns in detail.  Before I talk about the information from that website in particular, let me give you a quick recap on some basic physiology, in case it's been a few years/decades since you've taken biology or physiology (if you've taken it at all).

There are 3 main sources of energy (sometimes called macronutrients) your uses: fats (or lipids), carbohydrates (or sugars), and proteins.
  • Fats are usually consumed as multiple fatty "chains" linked together via a backbone molecule called glycerol, in which case your body separates each of those "chains", perhaps shortens them, and then they get absorbed in the digestive tract.  After they get absorbed, your body links the chains back to the glycerol backbone, forming a triacylglycerol (TAG for short).
  • Carbohydrates are handled in a similar manner, where polysaccharides (composed of many sugar molecules linked together) are broken into smaller and smaller chains until you get single sugar molecules (monosaccharides) that are absorbed by your small intestine.  
  • Proteins are composed of long chains of molecules called amino acids, so proteins are broken down into single amino acids or small amino acid chains (a few amino acids linked together) before they are absorbed.

What's important to note here is that your body can take in a lot of crazy foods, composed of all sorts of fats, carbohydrates, and proteins, but still get its energy from those same 3 macronutrients at the most basic level.  If you eat a steak, there are all kinds of proteins in the meat that were made by the cow, but you don't turn into a cow because your body breaks down those proteins before they're absorbed into your body.  This is important because some proteins -- called protein hormones -- are meant to have a physiological effect on an organism's body (say to increase growth).  But if you ingest another organism's protein hormone, it's not going to have an effect on your body because your digestive system breaks down that protein hormone before it's allowed into your blood -- biologically, it's essentially impossible for it to have any hormonal effect on your body.  Also, hormones from one species aren't always active in other species because of small differences between the species' "versions" of the same hormone.  Millions of years of evolution can result in small differences between these hormones in different species, which can change or nullify the effects of a hormone in another species.  Evolutionary biology turns out to be pretty damned useful sometimes! 

With certain pharmaceutical products, neurotransmitters, and other types of chemicals, the above obviously doesn't hold true (or else all of those drugs would be awfully useless).  So while what I talk about below is true for these protein hormones, not everything you eat can be easily classified into these 3 categories of macronutrients, and thus aren't broken down as such.  I won't get into pharmacology here -- both because I'm only learning about it beginning this semester and because it's not pertinent to what is specifically mentioned below. 

With that in mind, let's see what Cornell has to say about the above concerns (emphasis mine):
  1. "Scientists at FDA's Center for Veterinary Medicine have reviewed the studies submitted by the manufacturers of rbGH. FDA scientists have concluded that eating foods with slightly higher levels of rbGH would not affect human health. This is because the amount of rbGH that is in milk or milk products as a result of treatment of the animals is insignificant compared to the amount of growth hormone that is naturally produced by our bodies. Also, rbGH is a protein hormone and is digested into smaller fragments (peptides and amino acids) when eaten. The rbGH hormone used on dairy cattle is effective in promoting growth in cows, but does not work in humans. Scientists know that rbGH is not recognized as a hormone by human cells."
  2. "FDA scientists have concluded that IGF-1 in milk is unlikely to present any human food safety concern for the following reasons: 1) IGF-1 levels in cow's milk from untreated animals vary in nature, depending on the number of calves and the lactation stage; 2) IGF-1 is also present in human breast milk, at levels higher than in hormone-treated cow's milk; 3) IGF-1 in milk is not expected to act as a growth factor in people who drink it because it gets digested in the stomach; 4) IGF-1 needs to be injected into the blood to have a growth-promoting effect; and 5) increased IGF-1 levels in food are not expected to result in higher blood levels of IGF-1 in humans who eat the food."
  3. "Some increase in incidence of antibiotic residues was observed in cow's milk following the use of rbGH. At the same time as rbGH started being used, some of the major dairy states in US switched over to a new and improved method to test for antibiotic residues. It is difficult to determine whether the increase in incidence of antibiotic residues in milk was due to increased use, or better testing methods. New York State (NYS) was one of the states that had not changed its method to test for antibiotic residues in milk at that time. The incidence of antibiotic residues in milk from NYS was not found to be higher after the approval of rbGH use. This suggests that the increased incidence of antibiotic residues observed in some states may have been due to better testing methods rather than an increase in use of antibiotics for treatment of mastitis. An Expert Committee at FDA's Center for Veterinary Medicine has concluded that while rbGH use may cause a slight increase in mastitis, dairy management practices that are currently in use should prevent any increase in antibiotic residues in milk."
rBGH and IGF-1 are protein hormones, so it's clear why those aren't a concern based on simple biology.  The 3rd point is a little more interesting.  As an example, let's say that we're trying to count the number of candies in each family-size package we buy, to make sure we're getting our money's worth.  But instead of counting each piece of candy individually, we just estimate the weight of each piece of candy and then weigh the entire bag to get a rough idea of how many are in there.  Doing this we get an estimate of 200 +/- 15 candies per package -- what a bargain!  But then we buy a brand new candy counter, which counts each individual piece of candy to get us a VERY accurate result (but still prone to some amount of error due to really small candy fragments or when 2 of them get stuck together).  Now our count is 210 +/- 5 candies per package -- what an even better bargain, right?  Not really.  This is still roughly within the range of what we expected before, but it's at the higher end of that range (maybe because our weight estimate was a little high, resulting in us underestimating the number of candies based on weight alone).  Either way, the average number of candies per package never changed -- our new methods were just more accurate and we found out we'd been slightly underestimating the actual number.  This is essentially what happened with antiobiotic residues in milk.  They're still at biologically safe levels, but they certainly didn't increase due to rBGH use.  It was just an artifact of our improved methods for measuring the residue levels.

I did find one more study about IGF-1 on PubMed: "Bovine growth hormone: human food safety evaluation." I was unable to access the full article, but the abstract said (emphasis mine):

Scientists in the Food and Drug Administration (FDA), after reviewing the scientific literature and evaluating studies conducted by pharmaceutical companies, have concluded that the use of recombinant bovine growth hormone (rbGH) in dairy cattle presents no increased health risk to consumers. Bovine GH is not biologically active in humans, and oral toxicity studies have demonstrated that rbGH is not orally active in rats, a species responsive to parenterally administered bGH. Recombinant bGH treatment produces an increase in the concentration of insulin-like growth factor-I (IGF-I) in cow's milk. However, oral toxicity studies have shown that bovine IGF-I lacks oral activity in rats. Additionally, the concentration of IGF-I in milk of rbGH-treated cows is within the normal physiological range found in human breast milk, and IGF-I is denatured under conditions used to process cow's milkbiologically significant levels of intact IGF-I would not be absorbed. for infant formula. On the basis of estimates of the amount of protein absorbed intact in humans and the concentration of IGF-I in cow's milk during rbGH treatment, biologically significant levels of intact IGF-I would not be absorbed.

In much of the pro-organic materials and websites out there, you'll find cleverly-written statements that can really scare the crap out of you.  If I read "increased IGF-1 may be linked to cancer" and "rBGH increases IGF-1 in cows and their milk" I'd be a little worried too.  But, medically and scientifically, at the most basic level, this is not a concern.  It may have taken 5 years of undergrad and $130,000 in medical school loans (thus far) to say that with so much certainty, but at least this education has come in handy for something!

These people love to talk about how A leads to B in animals, and let you assume that A leads to B in humans as well, even though such a thing may be nearly impossible biologically.  It's a dirty trick, and demonstrates either deliberate deception or profound scientific ignorance.

I'm still trying to find information about the so-called "Dirty Dozen" when it comes to which fruits and vegetables to buy organic, but I've been having trouble finding information about this from a reputable source.  Similar to how the National Vaccine Awareness Center is not a reliable source of truthful, scientifically accurate information about vaccines (see SBM for that), I'm not so confident the Environmental Working Group (EWG) can be counted on to offer science-based evidence regarding organic foods. I've never heard of the EWG, so I'm not accusing them of anything, but I couldn't find their sources for the "dirty dozen", nor how significant the amounts of pesticides measured actually were.  Finding biologically insignificant amounts of anything on our food just because we have excellent methods for detecting small amounts of chemical residues means squat if it doesn't have a single effect on our bodies.  I don't know what levels are biologically significant either, but the EWG didn't provide that information when giving their "recommendations", which I find annoying and even a little suspicious.

With many things in science, we can never say with 100% confidence that something is or is not safe.  Organic food being more "natural" in no way means that it is somehow safer, even though organic proponents like to assume such a connection.  Remember, a lot of "natural" stuff can kill you very easily (i.e. the many kinds of  bacterial and viral infections that have plagued humanity throughout its existence).  Some naturally-derived treatments, like Penicillin, have been enormously successful in treating such infections.  And synthetically-derived antibiotics have allowed us to be even more effective in combating infection in recent decades.  Neither approach is inherently better than the other; instead we must judge each on the merits of their proper usage.  And even then, we must keep in mind that the use of any antibiotic can provide an evolutionary pressure that selects for resistant strains of a microorganism.  Make no mistake; infectious disease and immunology are very complicated subjects and they are not for the faint of heart!  Writing a prescription for an antibiotic is no simple, dismissive treatment in the mind of a physician!

I can't say that milk or meat from "conventionally" raised cows is absolutely safe, but the honest truth that organic proponents rarely actually admit is that they can't make that guarantee either!  No one can.  But I can tell you when someone is distorting the truth and using fear mongering in order to drive up their sales numbers.

2 comments:

Anonymous said...

5 years of undergrad and you're still naive enough to believe the FDA is an organization dedicated to providing factual information.

I've got news for you young man... The FDA is in the pockets of big industry. Publishing scientific studies indicating that the use of these profit increasing hormones is detrimental to the health of consumers would cause financial turmoil for these greedy diary farmers.

I'm not saying there is a direct correlation with the huge increase in hormones/additives/processed food consumption and the wests skyrocketing (and thus far unexplained by any governmental organization) cancer rates... but one must use scrutiny when deciding what to put in ones body.

Either way, you're "blog" is for the most part unbiased; you're still lacking experience.

Verbatio said...

I appreciate your comment, but unfortunately you really undermined any legitimate disagreement you might have had with the information I presented. First off, I'll admit that I'm no expert in the above subject, and when I wrote this, it was still pretty early in my medical education. Nevertheless, your slight in referring to me as a "naive [...] young man" did not go unnoticed, and really makes the rest of your comment difficult to take seriously.

Categorically saying that the "FDA is in the pockets of big industry" (without evidence of any widespread influence as you suggest) and thereby dismissing its dissenting opinion is just silly. The FDA isn't the most effective nor most neutral regulatory agency out there (I'm sure you can Google the FDA and find plenty of screw-ups), but that doesn't mean it's useless or nefarious. Similarly, you give off the vibe of being something of a conspiracy theorist, but I'm not going to outright dismiss everything you say. For example, one definitely should use scrutiny when deciding what to put in one's body. I have little to disagree with on that point specifically. But far too much weight is given to organic food because it's more "natural" and thereby that must make it safer. We have very good scientific evidence based on sound medical and biological principles (discussed above) that can give us a lot of confidence in saying that food from those "greedy diary [sic] farmers" is no less safe nor nutritious than the organic foods that are available.