There have been a host of articles over the past few days, the gist of which is that processed meat – Ham, Bacon, etc drastically increase a persons risk of having a heart attack or getting type 2 diabetes. Here’s a classic example from an NHS website titled “Processed meat ‘raises’ heart risk”.
All these articles are based on this press release from the Harvard School of Public Health.
The press release is typical sensationalism, but the actual report is very good. Here are a few excerpts from the report that hasn’t made it into the press release, or the many articles now spreading like a rash across the internet.
All studies were observational, and residual confounding by imprecisely or unmeasured factors cannot be excluded. In particular, studies did not adjust for other dietary habits or socioeconomic status. Thus, associations of processed meat consumption with diabetes mellitus or CHD could relate to generally less healthy diet or lifestyle rather than causal effects of processed meats.
Potential limitations should also be considered. As with all meta-analyses, analyses were restricted to available published and unpublished data. Most of these studies did not separately assess extensive details about specific subcategories of deli meats consumed.
US dietary-guidelines recommend “eating less” red and processed meat. For cardiovascular disease, these recommendations are based largely on expected effects on blood cholesterol of saturated fat and dietary cholesterol in meats. However, relationships of meat intake with cardiometabolic disease outcomes, including coronary heart disease, stroke, and diabetes mellitus, are not well established.
The over ridding problem with these sorts of studies is that as the above passages make clear, the processed meats were more likely to be hot dogs and burgers, than Parma ham. And quite possibly people who eat a lot of burgers and hot dogs do a whole lot of other stuff that’s bad for them as well compared with people who eat more expensive cuts of meat.
Also I think it is important to get the risk into context. CHD is the number one killer in the USA claiming 34.3% of all deaths and 66% of people that die from CHD are smokers. Therefore if you are a smoker your chances of dying from CHD is 16.5 out of 25.2 people (i.e. 66%), but if you are a non smoker then your chances are only 11.6 out of 74.8 (15.5%). If you then take out all the sedentary, overweight people, the risk from dying from CHD for non smokers falls through the floor.
The study doesn’t say what the risk is from processed meat, it just says that it will increase your existing risk by 46%. So smokers go from 66% to 96% and non smokers (including all the fat, coke swilling couch potato non smokers) goes from 15.5% to 22.6%. Of course the study didn’t differentiate between these two groups (because they didn’t have enough data) so we don’t know, but as the study is just a number crunching exercise and no actual tests were done, you can do the maths different ways and get different results. If the results look bonkers (96%) then this should be a reason to be sceptical about the results.
The study also says that the only difference between processed and non processed meat is the level of salt and nitrates and that therefore their conclusion is that it is one of these that is the problem. But it doesn’t compare the results against the total level of salt in a diet. To give you an idea a slice of bread (40 grams) has typically 0.6 grams of salt as does 40 grams of Heinz Baked Beans, and a 40 gram bowl of cornflakes has a missive 1 gram of salt. In contrast a slice of smoked bacon the same size has less than half the salt at 0.48 grams!
Here’s an article from the BBC on salt in the western diet. http://news.bbc.co.uk/1/hi/health/3651380.stm Nothing new here. If you want to keep salt low, cut out bread, cereal, biscuits, crisps and tined food and any microwave meals. Here’s another article about the amount of salt in bread. http://news.bbc.co.uk/1/hi/health/6407343.stm
My take is that if you don’t eat too many of the above salty baddies then a slice of bacon (salt-wise equivalent to two thirds of a slice of bread) isn’t going to do you any harm. But yes a nice piece of steak or chicken breast would be better