Panel 6 - Animal experimentation
People in general believe that animal research has contributed to the treatment of human disease. But in the paper "Where is the evidence that animal research benefits humans?", recently published in the British Medical Journal, the authors argue that little evidence is available to support this view and that "systematic reviews of existing and future research are needed. [...] Ideally, new animal studies should not be conducted until the best use has been made of existing animal studies and until their validity and generalisability to clinical medicine has been assessed." [Pound2004] At present, though, the reality is a lot different from this ideal: when it comes to experimental research related to food and nutrition, animals are heavily involved.
"Nutrition research", about the effects of single or compound nutrients, is often conducted on animals, chemicals used in food (as additives, preservatives, and so on) are always tested on animals, basic research on human illnesses caused by a poor nutrition and lifestyle is done on animal "models", and drugs intended to cure such diseases are themselves tested on animals for safety and effectiveness. Even human psychological disorders related to nutrition, like anorexia, are studied on animals
The American Dietetic Association, in their position paper on nutrition misinformation, warns that, in evaluating scientific studies, consumers should consider "the limited applicability of animal experiments to humans" [ADA1989]
Peter Jones, director of the School of Dietetics and Human Nutrition stated that: "The approach to scientific research is changing. In the past, we relied on animal models; we would feed laboratory rats higher concentrations of fat to see how it would affect their metabolism. Now nutritional research is more sophisticated and allows us to look at the human being itself." [Chester1998]
Despite that, rats and mice are still widely used in nutrition research: They are mammals like us, but, unlike us, they are small, inexpensive, easy to handle and breed quickly. But mice and rats are not miniaturized men. They metabolize nutrients and chemicals differently than people do, and they tolerate toxic agents differently. [Laber1998]
In 1914 the first experiment about the needed intake of proteins was conducted, analyzing the optimal intake for rats. The experimenters applied the results to humans, without considering that, if those result were true, the milk from human mothers would be an unsuitable food for human babies! Nevertheless, those result are still applied nowadays by many nutrition professionals. [Osborn1914]
Heart disease is the leading killer of American adults, even though it can be prevented and cured following a correct diet and lifestyle. This disease is studied in rats, but rats are very different from humans in the ways their bodies process fat and cholesterol. Unlike humans, rats are very resistant to changes in serum cholesterol, and are also resistant to diet-induced plaques in the arteries. [Stehbens1986]
Cancer is the second most common cause of death in the U.S., and it is also widely studied on rats. Yet rats differ from humans in many ways that have major effects on cancer research. For example, beta-carotene and related compounds, called carotenoids, are central to cancer and nutrition research, but rats handle beta-carotene differently from people. Moreover, vitamin C plays vital roles in neutralizing free radicals, preventing cancer and scurvy: unfortunately rats synthesize vitamin C in the liver, while humans do not synthesize vitamin C at all. [Chatterjee1961]. Most animal species can synthesize vitamin C, but humans cannot. [Burns1954]
As stated by dr. Jonathan Balcombe: "There is a concerted effort to understand and address anorexia and other eating disorders. Most studies are human clinical studies - but not all. Many researchers are being funded to perform experiments on animals, usually (male) rats. These studies subject rats to the grinding misery of starvation while frustrating their frenetic efforts to seek and find food. And to what end? Anorexia is a complex syndrome, unique to humans, of primarily psychological origin. Trying to understand it by forcing rats to starve in their cages is rather like trying to understand suicide by giving a gun to a depressed guinea pig." [Balcombe2005]
And when a drug is really needed because the disease cannot be cured by a change of diet, the limits of animal research become apparent: it is well known that differences in metabolic functions account for many differences between animals and humans. When testing the effectiveness and toxicity of a drug, if the levels or activities of animal enzymes which interact with that drug are different from those in humans, the results obtained are not valid for the human scenario. As a result, potentially effective drugs can be discarded before being tested on humans. [Tettamanti2005]
Basic and applied reasearch, as well as regulatory tests on chemicals and drugs, should free themselves from the burden of animal experimentation; this applies particularly to nutrition reasearch, which is crucial in order to prevent and reverse chronic disease, which is the leading cause of mortality in western societies.
ADA, American Dietetic Association position paper on nutrition misinformation - Identifying Food and Nutrition Misinformation paper, Nutrition Research Newsletter, February 1989
Balcombe J, Beyond Animal Research, PCRM webiste (http://www.pcrm.org/resch/anexp/beyond/anorexia_0510.html accessed 23-12-2005)
Burns JJ, Mosbach EH, Schulenberg S. Ascorbic acid synthesis in normal and drug-treated rats, studied with L-ascorbic-1-C14 acid. J Biol Chem 1954;207:679-87.
Chatterjee IB, Kar NC, Ghosh NC, Guha BC. Aspects of ascorbic acid biosynthesis in animals. Ann NY Acad Sci 1961;92:36-56.
Bronwyn Chester, "Sound science that tastes good", Mc Gill reportr on-line, 24 Septembre 1998 (http://www.reporter-archive.mcgill.ca/Rep/r3102/food.html accessed October 2005)
Laber E., Stemming the Flow, The Sciences, July/August 1998
Osborn T., "Amino acids in nutrition and growth". Journal of biological chemistry 17:325 1914
Pound P., Ebrahim S., Sandercock P., Bracken M.B., Roberts I., Where is the evidence that animal research benefits humans?, BMJ February 2004;328:514-7
Stehbens WE. An appraisal of cholesterol feeding in experimental atherogenesis. Prog Cardiovasc Dis 1986;29(2):107-28.
Tettamanti M. et al, Human research tissue banks: the ATRA project for establishing a human research tissue bank in Switzerland, ATLA, Vol. 33, No. 1, February 2005