This lunchtime staple, the humble ham sandwich, has been heavily criticized in the press recently, with many reports suggesting that eating two slices of ham a day may increase the risk of developing type 2 diabetes.
But what is behind these headlines?
Research offers a more complex picture. A new study from Cambridge University has shown a link between developing type 2 diabetes and eating processed meats such as ham and bacon, and red meats such as beef and lamb. This led to headlines suggesting that the risk was mainly linked to ham sandwiches. This seems to stem from the press release, which used ham as an example to quantify the amount of processed meat associated with a 15% increased risk of developing type 2 diabetes within ten years.
The study found that this risk was linked to eating an extra 50g of processed meat per day, which happens to be the equivalent of two slices of ham. So a useful example seems to have been seized upon by the media as the main cause, perhaps ignoring some of the key messages of the study. So can processed and red meat really increase your risk of developing type 2 diabetes?
The biggest risk factors for developing type 2 diabetes are being over 40, having family members with type 2 diabetes, being of South Asian or African descent, being overweight – and, above all, having a larger waist circumference. The Cambridge study used data from almost 2 million people from 31 studies. The participants were followed for an average of ten years. During this time, about one in 20 people developed type 2 diabetes.
The research found that for every additional 100g of red meat consumed per day, the risk of developing type 2 diabetes increased by 10%. Eating just half that amount of processed meat per day was associated with an even greater increase in the risk of the disease.
This is not the first time that both processed and red meat have been linked to an increased risk of type 2 diabetes, but the key strength of the Cambridge study was that it attempted to control for many of the other factors associated with the disease, including smoking, excess weight, diet and exercise.
However, the magnitude of the increased risk is small considering that few of the people involved in the study ate 50g or more of processed meat per day, meaning that moderate ham consumption is unlikely to have a significant impact on your risk.
What is the link?
Processed meats are linked to an increased risk of type 2 diabetes because they contain nitrates and salt – additives used to preserve many processed meats. Nitrates and salt in processed meats are also linked to an increased risk of developing colon cancer. In fact, the World Health Organization classifies these additives as Group 1 carcinogens, meaning they can cause a number of cancers.
The mechanism linking processed meat to cancer appears to be similar to that potentially linked to type 2 diabetes. During digestion, processed meat produces N-nitroso chemicals that can damage cells. This can cause inflammation and interfere with the action of insulin, the hormone that controls blood sugar (glucose). This, in turn, can lead to insulin resistance, when the cells in your muscles, fat and liver don’t respond well to insulin and can’t easily absorb glucose from your blood.
Red meat is rich in iron. Research suggests that people with high iron levels are more likely to develop type 2 diabetes. However, low iron levels are more of a health risk for the general population. Another possible link with red meat could be the way it is prepared.
Previous studies have shown that charred meat cooked over an open flame or at high temperatures is also linked to an increased risk of type 2 diabetes. Charred meat leads to the formation of toxic chemicals such as heterocyclic aromatic amines and harmful compounds such as advanced glycation end products, both of which have been linked to insulin resistance and type 2 diabetes.
Goodbye barbecue and bacon butties?
The key message is reduction, not avoidance. The UK government’s dietary recommendations give good advice: limit your combined consumption of red and processed meat to no more than an average of 70g per day. However, these guidelines also suggest that red meat can be a valuable source of iron, so if you decide to stop eating red meat, consider eating alternative sources of iron such as beans, lentils, dark green vegetables and fortified cereals.
This must be done as part of a carefully planned diet. Non-meat sources of iron are harder for our bodies to absorb and should therefore be consumed together with a source of vitamin C, which is found in green vegetables and citrus fruits. The best advice to reduce your risk of type 2 diabetes is to maintain a healthy weight – think about losing weight if you are overweight – and to do as much physical activity as possible.
A healthy diet should be based on plenty of vegetables, fruit, beans, peas, lentils, nuts and seeds, as well as some whole grains, some dairy, fish and white meat (or vegetarian alternatives) – as well as moderate amounts of red meat and as little processed meat as possible. This will help lower your risk of type 2 diabetes, heart disease and many cancers – and is also better for the environment. However, if you have a penchant for ham sandwiches, you can still indulge in them occasionally. It’s your overall lifestyle and diet that really determines your health and your risk of developing type 2 diabetes.
