Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: tkadm30 on 27/04/2017 14:27:31

Title: How does sodium intake affect blood pressure?
Post by: tkadm30 on 27/04/2017 14:27:31
According to a new study, lowering sodium intake does NOT decrease blood pressure. This is controversial since the AHA recommends to lower sodium intake. What do you think?

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.trbimg.com%2Fimg-58ff6506%2Fturbine%2Fsd-1493132547-fn0uvi4xbk-snap-image%2F750%2F750x422&hash=f6eda12991e521022a135ca03f70d212)

http://www.sandiegouniontribune.com/business/biotech/sd-me-salt-diet-20170425-story.html
Title: Re: How does sodium intake affect blood pressure?
Post by: chris on 29/04/2017 05:41:59
Lowering blood pressure by reducing salt intake is not the same as preventing blood pressure rise.

What many studies have shown over decades is that blood pressure elevation with age is proportional to salt intake. What had been believed to be a natural part of ageing - blood pressure rising by about 1 mm Hg for each year - is not seen in groups with low salt intake. Therefore it appears to be pathological rather than physiological.

If you do reduce salt intake - the guidance suggests that 1 gram per day is ideal - then some of the age-related blood pressure increase can be prevented, which equates to a lower blood pressure at a given age compared with the average.
Title: Re: How does sodium intake affect blood pressure?
Post by: evan_au on 29/04/2017 09:38:29
Quote from: Moore, San Diego Tribune
people generally consume the amount of sodium they need. In other words, they are biologically driven to keep their consumption within a certain range.
Salt is a biological imperative - if you don't have enough, you crave it. But I expect that very few people in Western society have ever reached the point of inadequate salt intake.

Instead, I think that the designers of our processed food know that salt suppresses bitter flavors, so they add it to most things.

Adding salt to food becomes a habit - you see people adding salt to their meal even before they have tasted the food, even though a balanced diet will have an ample level of salt intake without any addition.

Quote from: San Diego Tribune headline
Higher sodium intake associated with lower blood pressure. You read that right.
There is a possible confusion here - when we talk about salt, we normally mean sea salt (from modern seas) or rock salt (from ancient seas). A large percentage of this is sodium chloride, with a mixture of other salts (https://en.wikipedia.org/wiki/Seawater#Compositional_differences_from_freshwater).

When people hear "excess salt", this is often interpreted as "excess sodium", leading to a number of products claiming to be "low salt", but they are actually salts containing Potassium instead of Sodium ions. When people respond to surveys, would they include these "no salt" products or not?

My recollection from school is that if you increase any sort of salt in a solution, you increase the osmotic pressure (https://en.wikipedia.org/wiki/Osmotic_pressure), ie you need more pressure to separate the water from the salt.

Quote
People on the lowest-sodium diets actually appeared to have higher cardiovascular risk and risk of dying than those taking more sodium...The J-shaped curve
One other famous J-shaped curve (around alcohol intake) turned out to be a fallacy due to relating short-term intake to long-term health. For long-term health impacts, you need to take lifetime intake into account - and recollection is a poor measure of long-term intake. Recollection is really no guide to salt intake, since most of it appears invisibly in pre-processed food.

I suspect that the people with the lowest current salt intake are those who have been diagnosed with severe hypertension (high blood pressure), and told to reduce their salt intake or they will die - and perhaps that message was delivered after a heart attack. On the other hand, those who are naturally resistant to excess salt intake (different gene variants have been implicated) continue with their normal high-salt diet.

This can produce two populations:
1) Those with a short-term low salt intake who are suffering the effects of a lifetime of high salt intake and a previous heart attack.
2) Those with a short-term high salt intake who are not suffering the effects of a lifetime of high salt intake.
Clearly it is the group with the lowest current salt intake who are at highest risk of heart disease.

The only way to separate these confounding factors is with a randomized controlled study, such as the DASH study. This found the best blood pressure control at the lowest salt intake they tested (1500mg/day).

See: https://en.wikipedia.org/wiki/Salt_and_cardiovascular_disease#DASH-Sodium_study
Title: Re: How does sodium intake affect blood pressure?
Post by: tkadm30 on 13/05/2017 18:18:45
Can you decrease your sodium levels by increasing intracellular potassium availability?

I'm a little bit confused by what is stating the study I linked. I always though sodium was a essential element
for all animals, humans, and plants.

See also: https://en.wikipedia.org/wiki/Hyponatremia
Title: Re: How does sodium intake affect blood pressure?
Post by: Karen W. on 14/05/2017 08:15:39
You do need salt as stated above but you do not need the excess salt..  I was wondering in conjunction with your question about salt causing more water retention and thus making it harder for your heart to pump due to excess fluid around your heart.. wouldn't that also go a ways toward elevating the blood pressure too.... forcing the heart to work harder then intended to pump...?
Title: Re: How does sodium intake affect blood pressure?
Post by: tkadm30 on 14/05/2017 10:11:36
You do need salt as stated above but you do not need the excess salt..  I was wondering in conjunction with your question about salt causing more water retention and thus making it harder for your heart to pump due to excess fluid around your heart.. wouldn't that also go a ways toward elevating the blood pressure too.... forcing the heart to work harder then intended to pump...?

Fair enough.
Remember that most foods are already low in sodium, though. 
Title: Re: How does sodium intake affect blood pressure?
Post by: Karen W. on 21/05/2017 22:31:28
It really depends on what foods you are talking about. You have pure fresh food with no preservatives and no salts added those would qualify as no sodium.. I am not a scientist or Doctor but from experience know that there are certain diseases and or illnesses that cause your body to not be able to proseess the excess salt well because say your kidney function is not working properly.. and the fluid intake you are getting is being retained because of excess saly.. or at least I believe that's a issue with some people and my body tends to retain the  as edema throughout my body. A while back months ago I gained 35 lbs in two days and was not able to illuminate it properly I was immediately put on higher doses of dieretics and watched closely to make sure that illumination took place. Now I was on dieretics already for heart failure but apparently my liquid intake compounded with my sodium over the two day period weigh in was more then my kidneys could process and the fluid was building up very quickly around my heart lungs legs hips hands.. etc.. I looked like a balloon and I was miserable as it made it hard to breath as well as hard for my heart to pump efficiently.. and my heart already struggles. So really It is all, important to consult a physician and definitely watch what kind of food you eat,, Canned foods and processed foods can be full of salts etc.. They were able to get my water weight off about as fast as it had accumulated  so I was lucky and am very much more careful now because I know what can happen..