Posted by: Hourglass PJ15 MAY 2013
The influence of a reduced salt intake on blood pressure continues to be much in the news. In its 2012 guidelines, the World Health Organization (WHO) recommended that adults cut their salt intake below 5g daily to reduce blood pressure and risk of stroke and coronary heart disease. A recent Cochrane analysis suggested that the current recommendations to reduce daily salt intake from 9–12g to 5–6g will have a major effect on blood pressure, but a further reduction to 3g would have a greater effect and should be a long-term target.
Some 75 per cent of salt intake comes from processed foods, with bread, processed meat and cheese among the top contributors. According to World Action on Salt and Health, the UK now has the lowest salt intake of any developed country, following a salt reduction programme that includes education, labelling and reformulation of processed food. But current intakes (8.1g/day) remain higher than WHO recommendations. Further reduction is a challenge, because salt adds flavour and texture and any decrease has to be acceptable to the consumer.
A 2012 report by Leatherhead Food Research suggested that the levels of reduction possible using current technologies may be reaching its limit. Potential future methods require more scientific development and many have yet to be tried in foods.
In the context of this challenge, the role of potassium should not be forgotten. Low potassium intake has been associated with high blood pressure and risk of cardiovascular disease while increased intake may reduce blood pressure and mitigate the negative consequences of high sodium consumption. In 2012 the WHO published its first recommendation on potassium, suggesting a daily intake of at least 90mmol (3,510mg, the amount also recommended in the UK) while emphasising that this guideline should be used in conjunction with the sodium guideline. A recent meta-analysis published in the BMJ found an average reduction of 7.1mmHg in systolic blood pressure when potassium intake was in the range of 90–120mmol. In the pre-agricultural era, potassium intake in our human ancestors was high, often exceeding 200mmol/day, while today average consumption in western countries is often below 70–80mmol/day.
Foods containing potassium (approximate quantities in brackets) include beans and peas (1,300mg/100g fresh weight), green leafy vegetables such as spinach and cabbage (550mg/100g), tomatoes and fruits (300mg/100g) and root vegetables (200mg/100g). Bananas are often mentioned as being high in potassium and a large one provides about 500mg. However, the humble potato is also a good source. A small one baked in its skin contains around 700mg; even without the skin a similar amount of potato provides about 450mg.