IGF insulin-like growth factors is a natural substance that mediates the effects of growth hormones in cows and humans. The molecular structure of bovine IGF-1 and human IGF are identical, and since the chemical is not species specific the impact of increased levels due to rBST is important.
IGF-1 content in milk varies over the lactation cycle and between cows in their first or subsequent cycle. The study maintains that the amounts of IGF-1 in cows administered rBST are within the normal of that found in untreated cows. Opponents of rBST use maintain that elevated levels of IGF-1 can lead to a disease called acromegaly which results in enlargement of hands, feet, nose and chin; glucose intolerance, and hypertension. The Consumer Policy Institute maintains that recent evidence suggests a potential link between IGF-1 and cancer and tumor growth.
Epstein, letter to FDA commissioner D. Another study, not referred to in the Science article, that took place near the end of the lactation cycle when IGF-1 levels are normally at a minimum , revealed IGF-1 levels at least 3.
Hansen notes that a problem with virtually all studies is that a number of investigators have recently shown that the most common IGF-1 test is unreliable. It cites a study that suggests IGF-1 in milk can survive the human digestive tract and be taken up by the body. According to the institute, the study found that IGF-1 stimulates growth in cultures of epithelial cells lining the intestine.
The institute also disagrees with the conclusions and finds fault with the reasoning of a Monsanto sponsored study to determine whether IGF-1 is orally active in normal rats.
The study was relied on by the FDA. The institute concludes:. In sum, we believe that the lone oral feeding study involving normal rats described in Science , is a poor study that appears to have been designed to minimize the chance of finding IGF-1 to be orally active. In spite of this, the study contains suggestive data that IGF-1 may be orally active. This, combined with the facts that IGF-1 stimulates growth and division of epidermal cells in the intestine and has also been associated with colon tumor growth and, potentially, with human epidermal carcinoma, suggests that until we know more about the role of IGF-1, extreme caution should be exercised.
Among these foods are supplements that come from rendering animals. The institute argues that since use of rBST will increase the amount of rendered protein fed to cows, it may accelerate spread of bovine spongiform encephalopathy BSE , a disease affecting the central nervous system, particularly the brain. A group of related diseases known as transmissible spongiform encephalopathies occur in both humans and animals.
They have a long incubation period, are typically fatal, have as yet unknown infective agents that are resistant to most types of sterilization, and produce no host immune response. Although a sheep form of the disease known as scrapie has been around for hundreds of years, the bovine form was found in England in Cows likely develop the disease by eating scrapie-infested animal protein feed supplements of meat and bone meal. The disease is believed to have emerged due to use of meat and bone meal in dairy cow feed, and a change in rendering processes in the early s that abandoned use of high heat and solvents which likely killed the infectious agent.
Although the institute notes that scientists and government officials say there is no evidence that BSE can affect humans, it cites some anecdotal reports which cast doubt on such assertions.
The institute recognizes that there are no cases of BSE in the U. General Perspective. The U. Office of Technology Assessment notes that use of rBST in dairy cows has been claimed to cause a variety of adverse health effects including ketosis a nutritional disease , fatty liver, chronic wasting, lameness, milk fever, mastitis, infertility and heat intolerance.
OTA maintains that if metabolic disorders occurred they would most likely appear during the first few days of rBST use, and that none of the catastrophic health effects described above have been observed in long-or short-term studies since the first studies in , including in acute or chronic toxicity studies.
The digested proteolytic fragments have no biological activity. Furthermore, even if it was injected, bST does not promote biological activity in the human body because somatotropins from lower mammalian species have no activity in humans.
Numerous international health and food safety organizations and many national regulatory agencies have confirmed the safety of milk and meat from bST-treated cows for human consumption. Additional information on the safety of milk and meat from treated cows is provided in the references below. Many of the studies were conducted under typical farm conditions in multiple regions of the U. A post-approval monitoring study in 28 herds around the U.
On the other hand, products in which milk is only one ingredient among many ice cream, for example are classified as Canadian products, no matter where their raw materials may have originated. I f rbST is approved for use in Canada, the issue of a notice of compliance would imply that the product had been found not to pose any particular threat to human health.
When a product does not pose a threat, Health Canada does not require any mandatory labelling, but voluntary labelling is permitted if the information is verifiable. I n October , Health Canada issued the first Experimental Studies Certificate for an rbST-based product, concluding that the milk of animals given the product did not present risks to human health.
P rovel, a division of Eli Lilly Canada Inc. I n , Monsanto Canada made an application for approval of its rbST-based product sometribove, marketed under the name "Nutrilac".
The Committee made seven recommendations including the imposition of a one-year moratorium for conducting a detailed review of the impact of rbST and creation of a task force to carry out that review. A one-year moratorium on the sale of rbST was put in place in July This moratorium is still in effect.
I n May , an article in the Globe and Mail reported that some Health Canada scientists had questioned the process for assessing the impact of rbST on human health. I n July , the Dairy Farmers of Canada asked that the Auditor General to review the rbST approval process, that the Codex alimentarius Commission 1 express an opinion on whether the hormone is harmless, and that Health Canada inform the public of the process for assessing the approach used in deciding whether to grant approval.
I n July , the Netherlands proposed a motion to the Codex alimentarius requesting that establishment of a maximum limit for residues be delayed while data relating to human health were reassessed by the Joint FAO-WHO Expert Committee on Food Additives and the application of "legitimate factors other than the scientific analysis" was reviewed.
Canada voted against the motion. I n January , Health Canada set up an internal review team made up of four evaluators, including two scientists who had worked at the office responsible for evaluating an rbST-based product and had challenged the evaluation process in the press.
The team produced two reports: the first, dated 21 April , on the analysis of shortcomings in the evaluation process, is unanimous; the second, dated June 10, , is signed by the two Health Canada evaluators who did not work for the office responsible for evaluating the rbST-based product.
Both reports state that the rbST evaluation process had methodological and scientific shortcomings. These hearings indicated that the rbST evaluation process had not always been correctly followed. Witnesses told the Committee of management problems at Health Canada, claiming that there had been pressure, coercion, theft of documents on rbST, and a rule of silence with respect to rbST.
M eanwhile, two expert panels, one working under the auspices of the Royal College of Physicians and Surgeons of Canada and a second working under the auspices of the Canadian Veterinary Medical Association, evaluated whether rbST was harmful to human and animal health respectively.
Both panels submitted their reports in January A s long as rbST has not received a notice of compliance, it cannot be sold legally in Canada. Since it was established in , one of its goals has been to define food standards and codes governing hygiene and technology in light of the safety of food additives and contaminants it has evaluated more than additives and determined more than 3, maximum levels of pesticide residues.
S ales of recombinant bovine somatotropin rbST have been permitted in the United States since February American law does not require the milk from rbST-treated cows to be labelled as such, although it is possible to label milk as being rbST-free. Where this is done, however, it must also be indicated that the Food and Drug Administration has determined that there is no significant difference between the milk from cows treated with rbST and milk from cows that have not been so treated.
A merican consumer reaction has been studied by Georges Brinkman, an economist at the University of Guelph. I n the year following the introduction of rbST, milk consumption remained steady.
It would appear that this trend can be explained primarily by the fact that the product available did not make distinctions: in the United States, milk is not identified as coming or not coming from cows treated with rbST. Milk may be labelled as rbST-free, provided that it is also specified that there is no significant difference in the milk of cows that have been treated with rbST and cows that have not.
During the period from January to August , milk consumption even increased by 0. In Wisconsin and Vermont, however, buying habits are different. In Wisconsin, milk identified as being rbST-free was the choice of most consumers in ; however, in , most milk sold for consumption in that state was unlabelled and could have come from cows treated with the hormone. In Vermont, consumer milk from companies known to produce rbST-free milk represented most of the sales in In these two States, a double system offering both and undifferentiated milk seems to have been necessary to maintain sales.
However, opposition to rbST apparently resulted in part from concerns about a threat to the rural way of life and came as much from producers as consumers. A cross the country, studies conducted in showed that rbST was no longer of concern to American consumers.
Milk consumption in the United States seems to vary more according to price increases, advertising and fat content than to the use of this hormone. However, in light of the information published by the Senate of Canada concerning scientific shortcomings in the rbST evaluation process, two United States Senators and a number of public interest groups have urged the Food and Drug Administration to review its conclusions on rbST. E ven though it claims that rbST has no impact on human health, the European Union has imposed a moratorium on the use of this hormone until 31 December This decision was based essentially on social and economic considerations such as a fear of penalizing small farmers, the existence of milk surpluses and the fear of consumer reaction.
However, there is no ban on the importation of dairy products from countries that have approved the use of rbST. In June , the Institute of Food Science and Technology in Great British announced that there was no scientific or moral reason to require labelling identifying between milk or meat from rbST-treated cows.
In July , the Netherlands, speaking for the European Union, proposed a motion to the Codex alimentarius 1 requesting a postponement of the establishment of a maximum limit for residues in order to allow for a reassessment by the Joint FAO-WHO Expert Committee on Food Additives of the data concerning human health and a review of the "application of factors other than the scientific analysis.
The Scientific Committee on Animal Health and Animal Welfare recommended that rbST not be used because it causes mastitis, lameness, and reactions at injection sites in dairy cows. T he Scientific Committee on Veterinary Measures Relating to Public Health identified various risks: risks of cancer caused by lifelong exposure to IGF-1; allergic reactions caused by possible changes in the composition of milk proteins; and resistant bacteria caused by possible antibiotic residues in milk.
Unlike the Canadian experts, the European committee did not evaluate the level of risk but instead recommended that an evaluation be carried out in greater depth. A fter a month-long study, Australia decided in September not to approve rbST for purely commercial reasons. In fact, most Australian exports of dairy products are to countries that have not approved rbST. The issue has not been reopened since that time.
R ecent international and Canadian developments relating to rbST raise a number of questions. T he World Trade Organization WTO is making increasing use of the decisions of the Codex alimentarius as a technical and scientific reference when it has to resolve trade disputes between countries see the decision of the Canada-Europe panel on bans of imports of beef from Canada to Europe.
Nevertheless, participating countries are not obliged to abide by decisions of the Codex alimentarius. I n making its January decision on rbST, Health Canada noted that consumption of products from animals that have been given rbST does not present significant risks to human health; it banned the sale and use of rbST in Canada for reasons of animal health. Thus Canada does not ban dairy products imported from countries where rbST is used, and is thus unlikely to be the subject of a complaint to the WTO in this matter.
The lack of international agreement on the effects of rbST on human health and the resulting lack of an international standard make the likelihood of a complaint to the WTO even more remote. Although Monsanto seemed to want to do so, in August it had not yet taken steps to submit a further NDS. In this regard, the April and May hearings of the Standing Senate Committee on Agriculture and Forestry indicated that there is still disagreement in Canada on whether rbST is harmful to human health.
Animal Health T he most important negative effect on the health of rbST-treated animals is the possibility of increased incidence of mastitis.
0コメント