Monday, November 15, 2010

Do you really understand what's unsafe about your food?

There is a lot of concern about the safety of food.  There is also a lot of misinformation and misunderstanding.  Most of us have some concept of the dangers of the modern world, but our perception of risk, i.e. the probability that the hazard will become manifest, is often wide of the mark, perhaps influenced by publicity. 

For example, most of us know that smoking is hazardous and that the risk of lung cancer and heart disease associated with smoking is high.  Ask someone about the risk of flying in an airliner.  If there has been a crash in the recent past, they may respond that flying is a high risk activity.  The truth is that flying on a scheduled commercial flight is very safe.  It's just that if an airliner crashes, it makes the news headlines all around the world, which influences our thinking.

Quite a long time ago, so long that I can't find the original reference, a few simple questions were put to food consumers.  Food scientists assessed the actual risks.  These people were asked "What is the food safety risk posed by the following?"  What would your responses be?

Risk factor                            Perceived risk                    Actual risk

Microbial contamination              Low                                  High

Packaging failure                         Low                                 High

Pesticide residues                       Medium                            Low

Irradiation                                   High                               Very low

Recent events in the USA may have changed your perception, at least with respect to microbial contamination.

Monday, November 8, 2010

Time for red faces? Perhaps raw milk is not all it's cracked up to be.

The last time I wrote a blog on raw milk, I received "fan mail" accusing me of being sensationalist and closed minded.  At risk of more unflattering comments, here is another post on the subject.

Proponents of raw milk consumption have long claimed health benefits of raw milk and products made from it.  One of those claims is that lactose intolerant individuals, who don't produce sufficient lactase in the small intestine, suffer reduced symptoms if they consume raw milk, rather than pasteurised.   

Stanford School of Medicine recently conducted a study of self-reported lactose intolerant individuals, who were given raw milk, pasteurised milk and soy milk in a randomized, double-blind, three-way crossover trial. This classic experimental design removes bias in experimenters and subjects.  If lactose intolerant individuals consume lactose (the sugar found in milk) they cannot break it down to glucose and galactose.  Anaerobic bacteria in the colon grow on the lactose and produce hydrogen, some of which enters the bloodstream and appears in exhaled breath.

The participants were tested for exhaled hydrogen on the first and last days of each 8-day exposure period.  There was no statistically significant difference between consumption of raw or pasteurised milk, but soy milk resulted in much smaller amounts of breath hydrogen.  Similarly, the symptoms reported - flatulence, abdominal cramping and diarrhoea - were the same for both raw and pasteurised milk.

The researchers reported that the results from their work, collected under standardised, controlled conditions, did not support the claim that, with respect to lactose intolerance, raw milk has benefits over pasteurised milk.

Meanwhile, raw milk and raw milk products continue to be linked with outbreaks of Escherichia coli and Listeria diseases