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dimanche 9 juillet 2017

Three questions to James DiNicolantonio about his recent book: The salt fix

1) Dysnutrition: Evolution data are rather in favour of low salt consumption; currently, groups of people who have a Paleo way of life consume less than half the amount of salt consumed by people in Western countries. How can we adapt to high salt intake and how can it be favourable to a longer life?

 I actually cover why the evolutionary perspective that we consumed low-salt was flawed and wrong. I even cite the NEJM paper that this idea is based on.  Basically, the reason why we think we consumed low-salt during evolutionary times is that we haven't thought it through enough.  The idea is that even if we consumed an all meat diet this would only give us 1,400 mg of sodium per day.  However, we also consumed the blood, interstitial fluid, organs, skin, bone marrow, lymphatic fluids etc. which are VERY high in salt.  We also consumed salty insects (like grasshoppers and bees), salty soils, clays, and even piths of certain tree trunks are high in salt.  And yes we would consume salt at salt licks (urine, dried up salt lakes, salt rocks, etc.).  We also consumed aquatic animals and plants (which was not recognised in the main NEJM paper) which would have given us more salt.  If you think about the last 10,000 years we used salt as our main food preservative and now that we have refrigerators our salt intake has dropped by up to 10-fold.  In the 1600s in Sweden, it was estimated that the average salt intake was 100 grams per person per day and now we consume about 8 to 10 grammes of salt per day.  It is very easy for the kidneys to adapt to a high salt intake as if you have healthy kidneys they can excrete any salt they do not need even up to 100 grams of more of salt per day.  The hard part is trying to hold onto salt when little is available and that is the biggest stressor on the kidneys and our body.

2) Dysnutrition: We know that genomic diversity is a rule in human populations. What is relevant to genetics in salt and health if any?

We do know that Asians and African Americans are more "salt-sensitive" when it comes to elevations in blood pressure with a higher salt intake but even still the longest living populations (Japan and South Korea) have some of the highest salt intakes in the world. Also, it appears that much of this "salt sensitivity" when it comes to blood pressure seems to be driven by insulin resistance and a diet high in refined carbohydrates and sugar.

3) Dysnutrition: Pure sodium chloride is added to processed foods. Is it fair to let people consuming salt ad libitum knowing that this advice will probably increase the number of processed foods they will buy and eat?

In fact, in my book, I show how it's the low-salt versions of processed foods that will likely drive people to overconsume them.  This is because the body determines salt intake which is why the intake of salt across numerous populations around the world has remained incredibly stable and in a tight range for over 50 years (most people consuming between 8 to 10 grams of salt per day).  When you lower the salt content of food the body still wants to eat that 8 to 10 grams of salt so people will need to eat 2-3 times as many processed foods to obtain the salt their body demands.  In other words, low-salt diets and low-salt processed foods likely drive increased food consumption and hence diabetes and obesity.  Low-salt versions of processed foods are also more susceptible to microbial overgrowth, which can increase the risk of foodborne illness.  Moreover, when you take the salt out the food tastes like garbage so generally low-salt versions of foods are higher in sugar and other more harmful food preservatives to provide flavour and microbial stability.  Also, low-salt versions of foods have a much lower expiration date.  In other words, low-salt versions of foods will increase food waste.

Thank you, James DiNicolantonio for this opportunity to share views on salt.
Here is the book

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