BBC News reported that reducing salt “would cut cancer.” They said that cutting back on foods that are often overlooked as having high levels of salt, such as bacon, bread and breakfast cereals, may reduce people’s risk of developing stomach cancer.
The news stories were based on a report by the World Cancer Research Fund (WCRF), which has said that one in seven cases of stomach cancer in the UK could be prevented if everyone reduced their salt intake to the recommended daily maximum of 6g, which is equivalent to about one teaspoon. Currently we are said to be consuming about 8.6g a day, which is just under half (43%) higher than the recommended maximum.
The WCRF reported that 14% of cases of stomach cancer could be avoided through reducing our salt intake. Kate Mendoza, head of health information at WCRF, said, “Stomach cancer is difficult to treat successfully because most cases are not caught until the disease is well established. This places even greater emphasis on making lifestyle choices to prevent the disease occurring in the first place – such as cutting down on salt intake and eating more fruit and vegetables.”
Eating too much salt is also linked to high blood pressure, which can increase the risk of having a stroke or heart attack.
The WCRF reported that one of the ways in which we consume a lot of extra salt is in processed food. It is calling for a standardised ‘traffic light’ system on the front of food and drink packaging that clearly displays the level of salt, fat and sugar in food products.
What is the news based on?
The World Cancer Research Fund (WCRF) is part of an international network of charities whose aim is cancer prevention. In 2007, it produced a report ‘Food Nutrition, Physical Activity and the Prevention of Cancer – a Global Perspective’, which gave recommendations for cancer prevention, based on an expert review of the evidence from thousands of studies.
Due to the constantly growing body of available research, the WCRF established the Continuous Update Project (CUP) to maintain a database that continuously accumulated evidence related to food, nutrition, physical activity and cancer. The most recent information on salt comes from a Second Expert Report produced by the CUP in 2011.
What did the WCRF say about salt and cancer?
The WCRF said that in the UK we are consuming an average of 8.6g of salt a day, which is 2.6g or 43% higher than the recommended maximum daily intake for adults of 6g daily. Figures from the 2011 National Diet and Nutrition Survey for England showed that men were consuming an average of 9.3g a day, and women 6.8g. It was estimated that 75% of this salt comes from processed foods, 15% from salt naturally found in food, and 10% from table salt that we add to our food.
In 2009, there were 7,500 new cases of stomach cancer diagnosed in the UK. The WCRF estimated that if we cut our salt intake to the recommended 6g a day, 1,050 or 14% of these cases could have been prevented. Stomach cancer is the seventh most common cause of cancer death in the UK. In 2010, there were 4,966 deaths from the disease. The WCRF report concluded that salt is a ‘probable’ cause of stomach cancer. The reason why salt may increase the risk of stomach cancer is not known for definite, although the report describes how previous observational studies have noted that certain dietary factors, in particular salty and salted foods, are associated with what is called atrophic gastritis. This is a condition where there is inflammation and cellular changes in the lining of the stomach, and there is the potential for cancerous change.
Additionally the WCRF estimated that 21% of stomach cancer cases could be prevented by increased consumption of non-starchy vegetables, and 18% of cases could be prevented by increased consumption of fruit. Aside from diet, smoking is a well-established risk factor for stomach cancer.
What is the evidence behind these claims?
The WCRF reported that the CUP captures and reviews the evidence related to food, nutrition, physical activity and cancer in a systematic and thorough way. The CUP then produces a report, which is reviewed by an expert panel that provides an impartial analysis and interpretation in order to ensure that the recommendations for cancer prevention are based on the latest available evidence.
For their statistics on salt, information on average salt intake in the UK is based on reports by the Food Standards Agency and the Department of Health. Stomach cancer incidence figures come from the Office for National Statistics, and other relevant registries for Wales, Scotland and Northern Ireland.
Regarding preventability estimates – estimating how much stomach cancer could be prevented by reducing salt intake – the WCRF looked at the evidence on how much different patterns of diet and physical activity affect cancer risk and cross-referenced this against dietary surveys for the UK, US, Brazil and China. They emphasised though, that making estimates on the proportion of cancers that could be prevented by altering dietary patterns is complex, and therefore figures should be treated as estimates rather than exact figures.
What are the current recommendations on salt consumption?
Not only could high salt consumption increase risk of stomach cancer, it is also linked to high blood pressure, which can increase the risk of cardiovascular diseases such as stroke and heart attack. Our bodies do need some daily salt, though. Current recommendations are that the daily intake of salt for an adult should be less than 6g; which is around a teaspoon’s worth.
The WCRF estimated that 75% of the salt we eat comes from processed foods such as ready meals, cheese, crisps, bread, biscuits and processed meats. Ten percent is added during cooking or at the table.
Some food labels list the sodium content instead salt content. Sodium is a component of salt, and to work out how much salt a food contains, multiply the sodium content by 2.5. Therefore the recommended maximum intake for an adult of 6g of salt a day, equates to a maximum of 2.4g sodium.
NHS Choices report that a food with more than 1.5g of salt per 100g is considered to be high in salt. A food that contains less than 0.3g of salt per 100g is considered to be low in salt.
To cut down salt intake the WCRF suggest:
- checking food labels and selecting products with less salt or sodium, bearing in mind that foods labelled as reduced salt or sodium can still be quite salty
- choosing tinned or packaged foods with no added salt (or sugar)
- gradually reducing, and then cutting out, the amount of salt you add to food during cooking and at the table
- using spices, herbs, garlic and lemon instead of salt
- making your own meals from scratch from fresh ingredients, to give you more opportunity to control the amount of salt in your diet
- eating fresh meat rather than processed meats, such as bacon, cured meats and some sausages, which contain high levels of salt
- limiting the amount of salty snacks you eat
replacing salty snacks, such as crisps and salted nuts, with small portions of dried fruit or unsalted nuts
What other ways can an unhealthy diet contribute towards an increased risk of cancer?
Overall, in the UK in 2009 there were 321,210 new cases of cancer diagnosed. The WCRF reported that scientists estimate about one-third of cases of the most common cancers – around 83,500 a year – could be prevented through changes to diet, physical activity and weight.
Based on their review of the evidence, the top 10 recommendations of the WCRF for cancer prevention are:
- to be as lean as possible without being underweight
- be physically active for at least 30 minutes every day
- limit consumption of energy dense foods high in fat or sugars and low in fibre, and avoid sugary drinks
- eat a variety of vegetables, fruits, wholegrains and pulses
- limit consumption of red meat and avoid processed meat
- limit alcoholic drinks to two a day for me and one for women
- do not use nutritional supplements to prevent cancer
- limit salt consumption
For specific population groups:
- breastfeeding exclusively for up to six months
- after treatment, cancer survivors should follow the recommendations for cancer prevention
Analysis by NHS Choices. Follow Behind the Headlines on twitter.