July 18, 2019

expert reaction to study looking at salt intake, the Public Health Responsibility Deal, and health

Research, published in the Journal of Epidemiology & Community Health, reports that the reduction in dietary salt intake in England has slowed significantly since the introduction of the voluntary pact the UK government made with the food industry in 2011 to curb the salt content of food. It projects that this may be responsible for 26,000 extra cases of heart disease/stroke and 3800 cases of stomach cancer by 2025.

Prof Francesco Cappuccio, Cephalon Professor of Cardiovascular Medicine & Epidemiology, University of Warwick, and President of the British and Irish Hypertension Society, said:

“The present study confirms a general principle that a Public-Private Partnership in public health can work when either the objectives of the partners are shared or when scrutiny is imposed by an independent party or rules are regulated and enforced.  The case of population salt reduction is no exception.

“The present analysis is the first of its kind.  It uses the ‘gold standard’ 24h urinary sodium excretion to estimate salt intake in the NDNS, representing the English population, and it applies a well-validated microsimulation tool (IMPACTNCD) to estimate the health impact of salt reduction.  There are limitations though.  The data cannot imply causality as they are not prospective recordings in the same individuals and not all potential confounders could be considered.  Response rates are low in each survey, thus affecting the overall generalizability and some limitation in data quality is present when assessing associations with socio-economic status.  However, plausibility and consistency with other evidence makes the results not surprising.

“They are a stern reminder of the need for a renewed national salt reduction strategy to reduce cardiovascular disease effectively and equitably.  Food reformulation targets, standard labelling and restrictions on junk food advertising should be set, and pledges monitored independently, with a mandatory regulation as a viable option.”

Tracy Parker, Senior Dietitian, British Heart Foundation, said:

“There is a wealth of evidence that links a high salt consumption to raised blood pressure, a risk factor for coronary heart disease and stroke.

“These findings are interesting, but it is only an observational modelling study that looks at data over time.  It does not give us an accurate reflection of why there has been a recent slower decline in salt intake.  While we’ve seen a positive change in the average salt consumption since the introduction of the voluntary pact, we are still consuming well above the recommended maximum of 6g a day.

“There is still a long way to go, and we were reassured to see the Health Secretary’s pledge to introduce new and ambitious targets to bring salt levels down further.  However, the new programme must be robust in order to truly have an effect and help prevent thousands of cases of heart and circulatory disease.”

Prof Graham MacGregor, Professor of Cardiovascular Medicine, Queen Mary University of London, said:

“We’ve long known that the Public Health Responsibility Deal was a tragedy for public health.  Independent evaluations highlighted its lack of effectiveness and this research markedly brings home the effect the deal had on the UK’s once world-leading salt reduction programme.  The slowing in the reduction of salt intake led to many thousands of entirely preventable occurrences of cardiovascular disease and stomach cancer, particularly in those from more deprived backgrounds.  The Secretary of State for Health promised new salt reduction plans in his delayed prevention green paper and this paper reiterates the overwhelming need for a revived salt reduction strategy in the UK.

“It is a scandal that the UK currently has no active salt reduction strategy, with the last set of salt reduction targets having expired at the end of 2017.  Salt reduction is a shared responsibility and while the food industry do have their part to play in helping consumers eat less salt, this research clearly demonstrates the need for a robustly monitored programme to ensure that progress towards published targets is maintained and where there is a lack of progress, it is addressed in real time.  It’s time to get our salt reduction strategy back on track for the benefit of public health, our overburdened NHS and the economy.”

Prof Alun Hughes, Professor of Cardiovascular Physiology and Pharmacology, UCL, said:

“The press release is an accurate description of the paper.

“The work is good quality and has implications for future national public health strategies.  The study has limitations (as discussed by the authors) – mainly the lack of repeated measures of salt intake in the same individuals, the comparatively small sample sizes, and the assumption that salt intake was set to decline along the same trajectory as it had over the period 2003-10.  This latter assumption is not implausible but, as a counterfactual, is impossible to verify.  Likewise the estimates of mortality, costs, and impact on health inequalities that might result from any slowdown in reductions in salt intake, while based on reasonable (and probably conservative) assumptions, are projections and should be regarded with due caution.

“In summary, despite acknowledged limitations, this study casts doubt on the effectiveness of the Public Health Responsibility Deal (RD) in terms of reducing dietary salt intake.  The findings should contribute to thinking about future public health strategies and underlines the importance of careful evaluation of any public health intervention.”

Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:

“This is a simulation and it makes some assumptions that are questionable, and the benefits seem extraordinarily high in relation to the very modest reduction in salt intake.  Reducing salt intake certainly lowers blood pressure but not in everyone.  The benefit of salt reduction is greater in the over 50 age group and in those of black African ancestry.  The relationship between salt intake and stroke is seen most clearly in populations consuming more than 12 g salt per day, as in China, but is unclear with lower intakes as now the case in the UK.  Although reducing salt levels in processed foods e.g. bread, soup and soya sauce has helped cut salt intakes, individuals also differ markedly in their salt intake and part of this variation is because they add large amounts of salt at table and during food preparation.

“An important limitation is that raised blood pressure develops over decades and is a self-amplifying condition.  Cutting salt intake has a small effect on average blood pressure in the short term but may have a greater impact over decades.  Consequently, the benefits would not be expected to result in big reductions in stroke in the short-term especially as most strokes occur beyond the age of 70 years where hypertension is already well established.  The relationship between salt intake and stomach cancer is also doubtful.  Infection with Helicobacter pylori and other causes of gastritis including excess alcohol intake and oesophageal reflux of acid, which is related to obesity, are probably far more important.

“One reason why salt reduction has hit the buffers is that many consumers find unsalted food unpalatable and salt also has a role in food preservation.  Further reductions in the level of salt in processed food may be better achieved by encouraging the partial replacement with potassium chloride for salt rather than heavy handed legislation.”

‘Quantifying the impact of the Public Health Responsibility Deal on salt intake, cardiovascular disease and gastric cancer burdens: interrupted time series and microsimulation study’ by Anthony A Laverty et al. was published in the Journal of Epidemiology & Community Health at 23:30 UK time on Thursday 18 July 2019. 

DOI: 10.1136.jech-2018-211749

Declared interests

Prof Alun Hughes: “None.”

Prof Tom Sanders: “Honorary Nutritional Director of HEART UK.  Scientific Governor of the British Nutrition Foundation.  He is now emeritus but when he was doing research at King’s College London, the following applied: Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks.  In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011.  This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London.  The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar.  Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.  Tom also used to work for Ajinomoto on aspartame about 8 years ago.  Tom was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain.  Tom has previously acted as a member of the Global Dairy Platform Scientific Advisory Panel and Tom is a member of the Programme Advisory Committee of the Malaysian Palm Oil Board.  In the past Tom has acted as a consultant to Archer Daniel Midland Company and received honoraria for meetings sponsored by Unilever PLC.  Tom’s research on fats was funded by Public Health England/Food Standards Agency.”

None others received.