Search the Community
Showing results for tags 'cardiovascular disease'.
A recent Swedish study has been in the news a lot, showing that increased milk consumption is associated not only with increased risk of bone fracture, but with increased death rates, cancer rates, heart disease, and general inflammation in the body. As someone who usually drinks a lot of milk (over 1 litre/day) I was concerned, so looked into it further. The original paper is freely available at http://www.bmj.com/c.../bmj.g6015.long. The common advice for people who have had bone fractures or are at risk of osteoporosis is to increase their milk intake, so a clinic interested in bone fractures in the elderly looked at the data to see if milk indeed helped. They used extant Swedish medical records (possible in Sweden because records are so complete, and also linked to a unique patient identification number), and related them to self-reported food intake. They found in women that those who had the maximum fresh milk intake (1.2 litres/day) had a 150% increase in all-cause death rate in any period (i.e. it went up to 250% of baseline rate), a 50% increase in rate of hip fractures, and a slightly higher (20% increase) in rate of other fractures. Overall cancer mortality went up by 50%, and CVD (cardiovascular disease) mortality by 200 %. The effects increased gradually with intake; i.e. there was no absolutely safe level. Bad news! The effects in men were much smaller, but men should not be complacent, because information was collected less adequately on the men, and they presented evidence that similar effects in men might have been lost in the noise in the data. In addition higher milk intake was associated with increased levels of inflammatory markers in the bloodstream, showing that milk puts the body under inflammatory stress. Long-term low-level inflammation is known to be associated with the development of CVD, oxidative damage, more rapid aging, loss of muscle strength in ageing (sarcopenia) and possibly Alzheimer’s disease. On the other hand, increased intake of fermented milk products (cheese, yoghurt) was associated either with none of these effects, or with increased protection. This points the finger at what is missing in fermented milk products, which generally (though not always- see below) contain lower levels of the milk sugar, lactose. The other components of milk stay in fermented products, so they are unlikely to be a factor. In the gut, lactose is broken down into glucose and galactose (unless people have lactose intolerance, in which case it stays in the gut and causes bloating and diarrhoea). Galactose is known to be toxic – injected into the bloodstream of animals it leads to early death, more rapid ageing, neurodegeneration, and inflammatory responses (similar things happen in human beings with a deficiency in the ability to metabolise galactose). It does this in quantities (in relation to body weight) comparable to what human beings would get from milk. So galactose in anything other than very small quantities (it is an essential ingredient of many of the body’s biochemicals) looks like bad news. I have therefore decided to cut my milk intake to about 0.5 litres or less/day. Could there be anything wrong with the study? Studies like these are notoriously difficult, because you are monitoring people over a long time, the population monitored may not stay consistent, and there may be many confounding factors which have not been compensated for properly. The biggest possible factor is what in medical terms is known as “reverse causation” – the people drinking more milk may have been told to do so because they are already known to be at higher risk of a fracture. But this does not explain (1) the reduced risk from eating fermented milk (which they are also told to do), and (2) the effects on all the other markers – CVD, cancer, inflammation, etc. Secondly, self-reported diet – especially reported for a short period a long time ago – is notoriously poor as a predictor. They gave evidence that it went some way to being correct but this remains as a factor. But it still does not explain why they got the effects (errors would tend to dilute out any effects, not enhance them – and this is what they think happened with the data on men). But the study was very good in many ways. It looked at the old and elderly over a long period. It had a very large number of participants, so was able to compensate for the many possible confounding factors (smoking, socio-economic status, other illnesses, etc). But there is always the possibility that the compensation was incorrect, as by its nature you are dealing with the unknown. It was certainly a good study by modern standard. So why have previous studies not found the same? Probably because they did not separate out liquid milk from fermented milk products, which have opposite effects. As for sugar in fermented milk products, the cheese in my fridge lists near-zero sugars (against about 5% in milk), but the yoghurt I normally get (labelled “no added sugar”) has the same sugar content as milk. It is quite possible that Swedish yoghurts are fermented out to a much greater extent than Australian ones – suggest caution is needed in choosing. My good news for the day! Jim.