Chinese officials continue to deal with the aftermath of over 1250 babies falling ill and two dying after consuming tainted milk powder sold by Sanlu, a Chinese manufacturer part-owned by New Zealand dairy giant Fonterra.
The scandal has led to worldwide scrutiny of Chinese milk products and revived worries about melamine, a chemical used in plastics and glues, being added to food products. Melamine was found in batches of milk powder, mirroring cases last year of melamine finding its way into Chinese-made pet food, leading to illness in cats and dogs in the US.
This European Food Safety report outlines the toxic effect of melamine on the body.
The Science Media Centre asked local experts to comment on the impact of melamine when consumed in food.
John Reeve, Principal Adviser (Toxicology), Science Group, NZ Food Safety Authority:
“Protein powder for use in the manufacture of food products is usually tested for its quality prior to use, and the measure of that quality is the level of protein in the powder. This is usually tested for by digesting the powder in a chemical solution that completely breaks the powder down into its basic components and the nitrogen content measured.
“The higher the nitrogen, the higher the level of protein in the powder, and consequently the higher the price the powder fetches. As the testing procedure breaks the powder down completely, if a substance high in nitrogen had been added, then this would simply give rise to a higher nitrogen reading and hence give the impression that the powder contained more nitrogen than it actually did. The additive would not be able to be detected in this test procedure. Thus, inferior quality protein powder (such as milk powder) could have melamine added to it to disguise its poor quality, and thus fetch a higher price than it was really worth. Hence the likely reason for someone to add melamine to the milk powder.
“Melamine is absorbed from the gut and quickly transported around the body, but is concentrated in the kidney where it is able to be excreted without metabolism. The effects of melamine are a result of its low solubility, and the effectiveness of mammalian kidneys to concentrate the level of it in urine, leading to precipitation of crystals in the kidney. This leads to blockage and subsequent health effects that can be fatal if not treated quickly enough.
“Combination of the melamine with other naturally occurring body substances such as uric acid can lead to formation of kidney stones. Melamine is of relatively low toxicity apart from this physical effect due to its low solubility in water. The melamine that gets to other parts of the body is at levels below that which leads to precipitation. [Incidentally, cats and dogs are at higher risk than humans because their urine is acidic, whereas human urine is neutral and melamine is of lower solubility in acid than when in neutral solution. Hence the devastating effect of the contaminated pet food that was discovered in the USA a year or two ago].”
NZFSA test results for melamine in food products sold in New Zealand – so far negative.
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