Is excess salt killing your healthy gut bacteria?

 

For many years we’ve been told to reduce our salt intake because of the link between a high salt intake, high blood pressure and an increased risk for cardiovascular heart disease.

Recent research provides further insight into the exact mechanism that salt impacts our health – via altering the composition of our gut bacteria, but not just any type of gut bacteria – the Lactobacillus species, which is considered to be the beneficial “good” kind of bacteria.  Lactobacillus is one of the most abundant species of bacteria living in the gut, and is involved in digestion, absorption of nutrients and controlling inflammation. Lower levels of Lactobacillus have been linked with IBS, Type 1 Diabetes, Multiple Sclerosis, obesity and colon cancer. We are born with high levels of Lactobacillus, which slowly declines with age. So, ideally, we want to retain optimal levels of this particular gut bacteria for optimal health.

 

“Studies on mice and a recent study on healthy humans demonstrated that a high salt intake depletes Lactobacillus, increases blood pressure and increases the inflammatory immune response”

 

The study on healthy humans was a small-scale study on 8 men, who took 6g (about a teaspoon) of salt per day for 14 days in addition to their usual diet. Stool samples were taken to monitor the levels of Lactobacillus at the start and end of the trial. After 14 days, there was a decrease in Lactobacillus compared to levels at the start of the trial. Furthermore, their blood pressure and markers of inflammation increased i.e. they were more inflamed after just 2 weeks of following a high salt diet! (1)

 

“It’s easy for our salt intake to creep up especially if eating processed convenience foods”

 

Natural wholefoods (like vegetables, fruit, whole grains, beans, lentils, nuts, seeds, fish, meat, dairy and eggs) contain smaller amounts of naturally occurring salt which is obviously unavoidable. However, we do need some salt (sodium chloride) in the diet, as sodium is a vital electrolyte involved in fluid balance, pH balance, regulating blood pressure and nerve and cell function. The key point here is that we don’t want TOO MUCH salt.

If we stick to whole, unprocessed foods like the foods mentioned above and avoid pre-packaged convenience foods which tend to have much higher amounts of added salt, such as ready-meals, takeaways, frozen breaded meats, cured meats and certain canned foods such as chilli, ravioli, baked beans etc. then our salt intake should be acceptable and our gut bacteria should go unscathed!

As we’re talking about salt, it’s worth mentioning the importance of different types of salt. Natural sea salt (as opposed to refined salt) contains minerals such as magnesium, calcium and potassium and traces amounts of iron, manganese and zinc, which are beneficial for the body and may actually offset the negative effects of consuming sodium chloride. Natural sea salt also contains less sodium than refined salt (i.e. table salt). A study (albeit on rats) demonstrates that sea salt does not increase blood pressure as much as refined salt (2). 

 

“Sea salt does not increase blood pressure as much as refined salt” (2)

 

Refined salt is linked with hypertension, however, because of the mineral content of sea salt, it can actually have an anti-hypertension effect (lowering blood pressure). In particular, it’s the magnesium and potassium that appear to be the important minerals for lowering blood pressure. If you want to increase your potassium and magnesium intake just eat more vegetables, especially leafy greens! And definitely switch from using table salt to natural sea salt. Celtic sea salt is said to contain the most minerals (I do not have evidence to back this up…yet!).

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References
  1. Lee, B., Yang, A., Young, M., Mccurdy, S. and Boisvert, W.A., 2017. Natural sea salt consumption confers protection against hypertension and kidney damage in Dahl salt-sensitive rats. 61(1), pp.1–10.
  2. Wilck, N., Matus, M.G., Kearney, S.M., Olesen, S.W., Forslund, K., Bartolomaeus, H., Haase, S., Mahler, A., Balogh, A., Marko, L., Vvedenskaya, O., Kleiner, F.H., Tsvetkov, D., Klug, L., Costea, P.I., Sunagawa, S., Maier, L., Rakova, N., Schatz, V., Neubert, P., Fratzer, C., Krannich, A., Gollasch, M., Grohme, D.A., Corte-Real, B.F., Gerlach, R.G., Basic, M., Typas, A., Wu, C., Titze, J.M., Jantsch, J., Boschmann, M., Dechend, R., Kleinewietfeld, M., Kempa, S., Bork, P., Linker, R.A., Alm, E.J. and Muller, D.N., 2017. Salt-responsive gut commensal modulates TH17 axis and disease. Nature, [online] 551(7682), pp.585–589. Available at: <http://dx.doi.org/10.1038/nature24628>.

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