Don’t panic, but each time you eat a bacon sandwich it is estimated you reduce your life by half an hour. We used to think that was due to the high fat content but the evidence now suggests it is to do with how bacon is made.
Definitions of processed food vary depending on your viewpoint. Everyone agrees that a tub of pot noodles, instant ramen or most ready meals that students ‘nuke’ in the microwave are highly processed. Other foods like frozen lasagne or pizza, chicken nuggets, cakes, biscuits, corn snacks, margarine, processed cheese, spaghetti sauces and ketchup are also now generally recognised as processed.
But what about other common foods? How about white pasta made from highly refined grains? We know that for a food to be healthy it needs to be as unrefined as possible and when it comes to rice and pasta this means brown or wholegrain because these varieties include more fibre and nutrients. (When polished rice was first produced there was an epidemic of a vitamin B deficiency called beriberi — a clear example of the health hazards caused by processing.)
But how do we sort the good from the bad?
Processed food is usually defined as food prepared with chemical additives or that has undergone processes to alter its flavour or shelf life. At its most extreme it can be called any food with something added to it that doesn’t occur in nature. Many products you may not have thought about are processed. Bagged salads in supermarkets usually contain some preservatives and chemicals from the washing process and packaging and so are all to some extent processed.
Natural ‘Greek-style’ yoghurt, as opposed to natural Greek yoghurt, is cleverly processed, using a variety of shortcuts, milk powders and starches to replace real milk and flavour in order to simplify manufacture. These don’t appear on the label.
Most of our bread is also highly processed and contains chemicals and preservatives and colourants to make it look brown and wholesome.
The WHO outraged many European citizens when they labelled many countries’ favourite foods — from bacon to Wurst, salami to jamon — as processed and containing potential carcinogens. Over time, with trickery and marketing, we have forgotten which foods are made artificially for us. A study recently found that about 60 per cent of dietary calories of US adults came from ultra-processed food and a further 10 per cent moderately processed.
Our love of bacon comes at a cost. Most bacon you buy has nasty added chemicals like nitrites and phosphates that are used to bind the meat scraps and retain water. This is the milky liquid that oozes out when you first put them in the pan. When bacon is heated the mix of the natural and artificial chemicals produces a whole range of other chemicals, many of which the WHO label as carcinogenic. It appears that the more added chemicals and extractions used in the process, the greater the risk of producing carcinogens.
It is possible to find cured bacon using simple methods that are hundreds of years old. There are villages in Italy that produce their own salami without having to add the usual myriad colourants, enzymes, extractors, acids, emulsifiers, binders, bulkers and preservatives to convert industrial meat into something edible. What should make us all nervous is that the label is misleading and doesn’t allow the consumer to tell the difference between a fake and an artisan salami.
A general rule of processing food means that the cheapest ingredients are combined from around the world using bland frozen products that lost their nutritional value and flavour long ago. To make them look appetising and taste of something resembling food they add as many chemicals as they can get away with.
This was easy — there are thousands of approved additives to choose from — until E numbers hit the headlines and the public started equating these with ill-health. As Joanna Blythman shows in her excellent behind-the-scenes book Swallow This, the industry has got round this by using names and varieties that sound less deadly. These include replacing colourants with vegetable extracts and using the word malted rather than modified starch (E1422). They also still have large amounts of salt, sugar and fat added in the right proportion to achieve the magical bliss point that make customers return.
Although many of the chemicals and additives approved in processed foods are theoretically harmful there is surprisingly little research performed on humans and no high-quality trials. The closest data we have comes from very large observational studies of the habits of hundreds of thousands of people. They found that regularly eating processed meats carried an increased risk of heart disease, obesity and an increased risk of colon cancer. These risks are considerably higher than just eating red meat.
Is there a unifying factor that explains how processed food is bad? The old scare story of high fat content had some truth in it when we had many foods with artificial trans fats in them — but these are nearly absent in most processed foods in sensible countries. We now know, after being told the opposite for years, that natural saturated fat as part of a balanced diet (as in the Mediterranean diet) is not harmful in moderation for most people. So what is the common factor that is upsetting our bodies?
Many substances used in the processing of food don’t actually appear in the final product or on the label. All substances that get added to manufactured foods need to be approved as safe for consumption in humans. These tests usually involve giving enormous amounts to poor lab rodents and seeing how their livers and organs react.
But we have probably been testing these chemicals in the wrong animals. In the last year several labs have started to test them unofficially in tiny animals — that you need a microscope to see — called microbes. One hundred trillion or so (ten times more than human cells) live happily in our guts feeding off our food and producing vitamins and chemicals that keep our immune systems healthy. When our microbes are disrupted, it makes us sick. It turns out that our microbes dislike these ‘harmless’ substances like emulsifiers, preservatives and artificial sweeteners, making them produce unusual obesity- and diabetes-promoting chemicals and killing off many friendly species. Microbes in our mouth can also convert nitrites to nitrosamines — a classic carcinogen.
Back in human guts, losing your diversity of microbial species (there are usually thousands) is associated with an increased risk of many diseases as well as obesity. Our gut microbes are pretty sensitive. I fed my (initially willing) student son Tom a McDonald’s burger and nuggets diet for 10 days and he lost 40 per cent of his species diversity. (This could have been due to the surge of chemical additives as well as the effects of nutritional and fibre deprivation.) Two weeks later Tom’s poor microbes hadn’t recovered to pre-Big Mac levels.
So should you be worried about all the chemicals in processed food? The answer is yes. We should be very concerned about what food manufacturers are getting away with. When there are often ingredients that don’t have to appear on the label it’s almost impossible to know what we are eating and how it affects us. All of these chemicals could be upsetting our gut communities. Until the regulators and governments start prioritising the health of humans and their gut microbes above cheap food prices it will continue to be virtually impossible to avoid processed foods. I suggest we be wary of food in slick packaging and long shelf lives and stick as much as possible to this maxim: if your great-grandmother wouldn’t recognise it as food, avoid it.
Tim Spector is professor of genetic epidemiology at King’s College London and author of The Diet Myth: The Real Science Behind What We Eat