If you are worried about your cardiovascular health, one of the things you want to avoid is salt. This was based on ancient research that seems to show even moderate salt intake could do all kinds of bad things for your cardiovascular system.
I was always skeptical of these claims because if you’ve got a healthy set of kidneys, the body has an amazing ability to regulate salt levels in the body. Of course, maybe there is some level of salt consumption that increases the blood pressure, cause retention of water, and other issues that lead to cardiovascular issues.
Recently, a very large prospective epidemiological study examined levels of salt consumption versus cardiovascular events. What did they find? Only high levels of salt consumption are linked to cardiovascular health.
Salt – the new study
The study, by Andrew Mente, Ph.D. and published in Lancet, examined what levels of salt intake had an effect on stroke and hypertension, two important cardiovascular events. This is an update to an earlier study also by Mente et al. and also published in Lancet.
The study design was as follows:
- The prospective cohort study included patients from 21 countries.
- Sodium and potassium levels were assessed using morning urine.
- Blood pressure analysis involved 95,767 participants.
- Analysis of cardiovascular events included 82,544 individuals.
- The median follow-up time was 8.1 years.
- Outcomes were for death, cardiovascular events (myocardial infarction, stroke, heart failure, and cardiovascular death), or composite outcomes.
- The study was fully funded by various governments across the world.
- As with many epidemiological studies, every possible confounding variable may not have been eliminated. This study accounted for known confounders, like smoking and diet.
- Sodium intake >5 g per day was associated with increased systolic blood pressure – 2.87 mm Hg per gram increase in mane intake.
- Sodium intake >5 g per day was also associated with increased stroke risk.
- Sodium intake of >5.08 g per day showed a positive, but statistically nonsignificant, association with myocardial infarction and mortality.
- Potassium intake was associated with reduced cardiovascular outcomes in every country.
So what does salt in the diet mean?
The results of this study indicate that sodium intake above 5 grams a day can lead to increased risks for stroke and hypertension. Five grams of sodium is roughly equivalent to 12.5 grams of salt. For those of you more familiar with the uncivilized (read, non-metric) measuring systems, ask Siri, Alexa, or Google, because I tried, and I got a headache. That’s a lot of lost shakers of salt.
So what do 5 grams of sodium mean in practical terms?
- It is approximately 40-50 slices of wheat bread (of course, it could be a lot more or a lot less depending on brand and country).
- Approximately 50 grams of butter.
- About 20 olives (preserved in brine).
- About 4-6 McDonalds’ Big Macs.
- About 8-10 slices of pizza (and if you put pineapple on your pizza, you’re a heathen who doesn’t care about salt).
Salt is an ingredient in many foods, usually listed as sodium. It actually takes a lot of certain foods to get to 5 g of sodium, although it occurs in almost every food, some of which are surprising like chocolates, so one can get to 5 grams quite quickly.
The first study from Mente et al in 2016 caused a lot of controversies, because the paradigm for cardiovascular health was to significantly limit sodium intake. However, the researchers repeated the study and got essentially the same results.
This is a powerful study, and it probably indicates that there are other factors that are more impactful to cardiovascular health like obesity, diabetes, lifestyle, and other choices.
This doesn’t mean you can start pouring salt on all your foods. It does mean that you should still be careful how much you consume.
- This is a part of my new series of articles that review clinical or epidemiological studies that aren’t usually covered by me. Please like and share it, so that I know that I should continue looking for good research in interesting areas of biomedical sciences.
- This research shouldn’t be used as part of a “science is always wrong” trope pushed by science deniers and pseudoscience lovers. Science-based medicine is based on the accumulation of evidence, and sometimes early research is contradicted by better and more powerful evidence. Moreover, the early ideas about sodium intake were based on limited evidence. On the other hand, the evidence on the safety and effectiveness of vaccines is based on mountains of evidence. To contradict that would require an equivalent mountain of evidence.
- Mente A, O’Donnell M, Rangarajan S, McQueen M, Dagenais G, Wielgosz A, Lear S, Ah STL, Wei L, Diaz R, Avezum A, Lopez-Jaramillo P, Lanas F, Mony P, Szuba A, Iqbal R, Yusuf R, Mohammadifard N, Khatib R, Yusoff K, Ismail N, Gulec S, Rosengren A, Yusufali A, Kruger L, Tsolekile LP, Chifamba J, Dans A, Alhabib KF, Yeates K, Teo K, Yusuf S. Urinary sodium excretion, blood pressure, cardiovascular disease, and mortality: a community-level prospective epidemiological cohort study. Lancet. 2018 Aug 11;392(10146):496-506. doi: 10.1016/S0140-6736(18)31376-X. Epub 2018 Aug 9. PubMed PMID: 30129465.
- Mente A, O’Donnell M, Rangarajan S, Dagenais G, Lear S, McQueen M, Diaz R, Avezum A, Lopez-Jaramillo P, Lanas F, Li W, Lu Y, Yi S, Rensheng L, Iqbal R, Mony P, Yusuf R, Yusoff K, Szuba A, Oguz A, Rosengren A, Bahonar A, Yusufali A, Schutte AE, Chifamba J, Mann JF, Anand SS, Teo K, Yusuf S; PURE, EPIDREAM and ONTARGET/TRANSCEND Investigators.. Associations of urinary sodium excretion with cardiovascular events in individuals with and without hypertension: a pooled analysis of data from four studies. Lancet. 2016 Jul 30;388(10043):465-75. doi: 10.1016/S0140-6736(16)30467-6. Epub 2016 May 20. Review. PubMed PMID: 27216139.
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