Trending Topics pieces (Article Analyses, Evidence Clips and Other Topics) are published in timely response to recent media and journal articles, position statements, clinical guidelines, etc. Since they are based on the most recent evidence/publications, they may not be consistent with PEN evidence in other PEN content areas. As soon as possible, when this occurs, the PEN content will be reviewed and updated as needed.
Taxation of Salt and Foods High in Sodium
A new systematic review (1) looking at the effectiveness and feasibility of taxing salt and foods high in sodium was highlighted in Salt in the News
(June 2020) from World Action on Salt & Health.
The systematic review included eighteen studies found between 2000 and 2019 (1). Fifteen of the studies reported on the effects of salt taxes: eight looked at taxing salt itself, foods high in salt and unhealthy foods (modelling studies, based on estimates of what the effects would be); four looked at the impact of salt taxation (real-world evaluation); two looked at price and subsides (experimental design/simulated online grocery stores); and one looked at cost-effectiveness of taxation (a review). Six of the 18 studies provided information relevant to country implementation of salt taxes and two of the 18 studies reported stakeholder perceptions toward salt taxation.
The authors found that the actual practice of salt taxation is limited (1). Three of the four real-world evaluation studies, mostly gray literature, did not report a measure of uncertainty (e.g. 95%CI or SE) and the two simulation studies showed wide confidence intervals, raising questions about the precision of the study results. Relying mostly on the modelling studies and noting that the studies varied in magnitude and range of measures (making them difficult to compare and summarize), the authors provided the following key summary points:
- There is some indication of potential effectiveness and cost-effectiveness of salt taxation.
- Taxation of food can have unintended outcomes, such as the decreased consumption of healthy foods or an increased consumption of other unhealthy, untaxed substitutes.
- When taxes for unhealthy foods were combined with subsidies towards heathy foods, the benefits were increased.
- Taxing all foods based on their salt content (broader application) is likely to have more impact than taxing only specific products high in salt and minimizes opportunity for substitution for other high sodium foods.
High salt diets (more than 5 g/day for adults (2)) are considered a leading dietary risk for death and disability globally (3). Continued research on population sodium reduction strategies (4) and other fiscal strategies, such as taxation, is needed to help reduce salt consumption.
- Dodd R, Santos JA, Tan M, Campbell NR, Mhurchu CN, Cobb L, et al. Effectiveness and feasibility of taxing salt and foods high in sodium: a systematic review of the evidence. Adv Nutr. 2020 Jun 20;nmaa067.doi: 10.1093/advances/nmaa067. Available from: https://pubmed.ncbi.nlm.nih.gov/32561920/
- World Health Organization. WHO guideline: sodium intake for adults and children. Geneva, Switzerland: WHO Press; 2012. Available from: https://apps.who.int/iris/bitstream/handle/10665/77985/9789241504836_eng.pdf;sequence=1
- GBD 2017 Diet Collaborators. Health effects of dietary risks in 195 countries, 1990-2017: a systematic analysis for the global burden of disease study 2017. Lancet. 2019;393(10184):1958-72. Available from: https://pubmed.ncbi.nlm.nih.gov/30954305/
- WHO. Global strategy on diet, physical activity and health. Population sodium reduction strategies. [cited 2020 Jul 23]. Available from: https://www.who.int/dietphysicalactivity/reducingsalt/en/
DRI Updates for Sodium and Potassium
A press release from the National Academies of Sciences, Engineering, and Medicine outlines a new report titled, Dietary Reference Intakes for Sodium and Potassium. A National Academies committee conducted the study to assess current relevant data and update, as appropriate, the DRIs for sodium and potassium that were developed in 2005.
The report “reaffirms the sodium AI for individuals ages 14-50, decreases the sodium AIs for children age 1-13, increases the sodium AIs for adults ages 51 and older, and decreases the potassium AIs for individuals age 1 and older” (1). In addition, the committee applied recommendations from the 2017 Guiding Principles Report and established a new category of DRIs based on chronic disease, the Chronic Disease Risk Reduction Intake (CDRR) for sodium, based on the benefits of reducing sodium intake on blood pressure and cardiovascular disease risk.
The review was sponsored by Health Canada, the U.S. National Institutes of Health, the Public Health Agency of Canada, the U.S. Centers for Disease Control and Prevention, the U.S. Department of Agriculture, and the U.S. Food and Drug Administration.
Also available is a Consensus Study Report providing report highlights.
National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for sodium and potassium. Washington D.C.: The National Academies Press; 2019. Available from: https://www.nap.edu/read/25353/chapter/1#ii
Salt Intake and CVD: The Ongoing Debate
A Canadian and European Government- and NGO-funded study investigating the associations between community-level mean sodium and potassium intake, cardiovascular disease and mortality was recently published in The Lancet (1). The study reports on clinical outcomes based on an analysis of 94,378 participants from 18 countries. Participants were aged 35 to 70 years and did not have cardiovascular disease at baseline. As a surrogate for sodium intake, morning fasting urine was used to estimate 24-hour sodium and potassium excretion. The authors’ main interpretation was that sodium intake was associated with cardiovascular disease and stroke but only in communities where estimated mean sodium intake was greater than 5 g/day.
The validity of the results has been questioned by others (2,3) for two main reasons. First, this is an observational study based on community averages and not on individual data (ecologic study design). Second, 24-hour sodium excretion was estimated from urine collected after overnight fasting, which is not a reliable measurement of daily salt intake as is a repeated 24-hour urine sample. For more on the salt and hypertension debate, see Salt and Heart Disease: A Second Round of "Bad Science" and Expert Reaction to Study Looking at Salt Consumption and Health Risks.
See Additional PEN content: Does diet have a role in preventing hypertension?
- Mente A, O'Donnell M, Rangarajan S, Yeates K, Teo K, Yusuf S, et al. Urinary sodium excretion, blood pressure, cardiovascular disease, and mortality: a community-level prospective epidemiological cohort study. The Lancet. 2018 Aug;392(10146):496-506. Available from: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31376-X/fulltext
- Messerli FH, Hofstetter L, Bangalore S. Salt and heart disease: a second round of “bad science”? The Lancet. 2018 Aug;392:10146:456-8. Available from: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31724-0/fulltext?rss=yes
- Science Media Centre. Expert reaction to study looking at salt consumption and health risks. 2018 August 9. Available from: http://www.sciencemediacentre.org/expert-reaction-to-study-looking-at-salt-consumption-and-health-risks/
Pink Himalayan Sea Salt
Wondering about the hype around pink Himalayan sea salt? See the review by Harriet Hall, MD from Science-Based Medicine.
Article Analysis and Commentary on Low-salt Diets Research