March
2008
The Salt/Blood Pressure Debate
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Rain, rain, go away…
In response to last week’s canned soup post, reader Dave offered this comment: “I’d just like to point out that just as many Apple readers believe in literature that debunks the lipid hypothesis, there’s a camp that says there is minimal effect on blood pressure from salt. There are two sides to many stories!”
We couldn’t agree more that nutritional (or general health) debates are rarely so simple as they’re made out to be. As long-time readers have probably noticed, we’ll mention salt recommendations now and then and generally try to keep our recipe suggestions fairly low in salt. We do tend to follow general salt recommendations. Blood pressure issue aside, high salt intake (as we mentioned last week) has been associated with osteoporosis, asthma, kidney disease and stomach cancer.
But what about the salt and blood pressure issue? Does it really hold water (pun intended)? We’d say it has enough bearing to figure into our choices, and for some people, research suggests, it’s crucially significant.
For years, scientists have researched the possibility of a “salt sensitive hypertension” that was the general result of a person’s genetic profile. In other words, salt sensitive peoples’ blood pressure is impacted more than the average person’s. To be precise, their blood pressure rises 10% or more in response to a salty meal.
In 2006, researchers at the University of Virginia Health Center announced that they had traced the “sensitive” salt response to particular gene variations and that they were in the process of completing a genetic test for the salt sensitive profile. Salt sensitivity, researchers say, whether it accompanies chronic high blood pressure, negatively impacts the vascular system in the same way high blood pressure itself does. African-Americans are more likely to be salt-sensitive than people of other races in the U.S. The test, once it becomes readily available, will hopefully be a useful tool for people who want to learn more about steps essential for their individual health.
But as for the rest of us, does salt matter for blood pressure? It’s true that many studies in this area, as in all areas, have their failings. And, it’s true that salt is just one piece (albeit an important one) involved in the process of fluid retention and its link to higher blood pressure.
Yet, there seems to be enough suggestion that salt can have a significant or at least measurable impact on blood pressure. A unique look into the connection was found in a recent study that compared blood pressure in groupings of salt mine workers in India, dividing those who worked directly with the processing of salt and those that worked away from the milling plant and its processing steps. The group that worked directly with the salt and had opportunity for inhalation of salt on a daily basis showed higher blood pressure (average of 4 points higher for the systolic measurement) than the group that didn’t work in the mill. After a group of mill workers used face masks and goggles for just four days, their blood pressure dropped an average of ten points in the systolic measurement.
While the above study examines a mode of salt intake other than ingestion, there is no shortage of studies that measure the effects of reducing dietary salt intake. Follow up research on two study groups from the 1990s help strengthen the argument for lower salt intake as helpful in preventing heart disease. Former subjects that had been part of the intake “intervention” group and were given the low salt diet, 10-15 years later had a “25% reduction in the risk of cardiovascular disease.”
Another study out in 2006 showed significant and positive impact of salt substitute use in Northern rural China, which is known to have especially high rates of hypertension as well as high salt intake. The salt substitute, researchers said, “demonstrated that it could reduce blood pressure to about the same extent as single drug therapy.”
And, ultimately, what does a low salt diet look like? First off, it should mean pretty much no processed food. We definitely support that! Up to ¾ of American’s salt intake comes from processed foods – those curious boxed creations you find in the middle of the grocery store, cured meats, etc. Cut those out, and you’re already in good shape. We certainly don’t begrudge anyone reaching for the salt shaker. We do, but we also don’t rely on it for taste. The more people moderate (yes, moderation is the key here, not elimination) their salt intake, the more likely they are to turn to other sources of flavorings, hopefully healthful ones like herbs and more varied, flavorful ingredients like peppers, onions and other vegetables and fruits. At least, that’s what we’d suggest.
This is one of those fascinating discussions that we love to continue. We’re always on the lookout for research from both sides of the issue. Keep your comments coming!
Further Reading:
Sugar Shock - Salt: The “Forgotten Killer”
The Migraineur: Salt No Longer Generally Recognized As Safe?
Ooh, pingback! Thanks!
I loves me some salt. One of the most memorable foods I ate in France was a plate of radishes with soft butter for dipping. The butter was liberally sprinkled with coarse salt.
This dish is absolutely not the same without the salt. I tried making at home and had to keep adding salt until I got it right.
I’ve moderated my opinion on salt somewhat since I wrote the post you’ve referenced above. There probably are people out there whose pressure rises a bit in response to sodium. But I still do think the most effective thing you can do to lower BP is to manage insulin, which means lowering carbs. And if you emphasize whole unprocessed foods, you will reduce your sodium intake so much that you just shouldn’t have to worry about reducing the salt in recipes or limiting your use of salt at table. At least, I think that should be the case for most of us, who are not sodium responders.
And let us not forget that salt is a preservative, one of the oldest known and surely one of the safest. Most of the time I make my own sauerkraut (easy, though rather messy, and very yummy and fun), but now and again I buy a bottle of artisanal sauerkraut that contains nothing but cabbage, maybe a few seasonings, and salt - lots of salt. We’re talking amounts of salt that would send Dean Ornish, the AHA, and the founders of the DASH diet into a gasping, purple-faced, eye-popping apoplexy. (So maybe salt does cause hypertension, >wink<.) How much salt, you ask? I made 5 pints of kraut last night, the yield from a rather large cabbage, and I used at least 4 tablespoons of salt. That’s a quarter cup of salt. To put it in perspective, it was coarse salt, which has more airspaces and therefore less actual salt, than table salt. But still, if Dean Ornish were the chief of police, there’d be a warrant out for my arrest.
But there’s a limit to how low you can go on salt when making lacto-fermented products like sauerkraut. The salt limits the growth of bad microbes so the good microbes (which don’t mind the salty environment) can take hold. If you don’t put in enough, your cabbage spoils before it ferments.
I think it would be a crying shame if the handful of commercial makers of this kind of pickle felt pressure to include some other, much less safe, preservative so they could limit the amount of salt in their product. That would just be bass-ackwards, as my mother used to say.
People’s BP is more related to other factors like a Magnesium and Calcium deficiency, not excessive Sodium. Also isn’t the balance of K/Na a factor? Doesn’t the body just get rid (pee) of excessive Na anyways?
from http://www.second-opinions.co.uk/salt-and-hypertension.html
“Michael Alderman, President of the American Society of Hypertension, Department of Epidemiology and Social Medicine, Albert Einstein College of Medicine, who wrote in 1997:[35]
‘Public health recommendations must be based on proof of safety and benefit. Even if a low sodium diet could lower the blood pressure of most people (probably not true) and both the diet and the change in blood pressure could be sustained (not established), this alone would not justify a recommendation to reduce sodium intake.
‘For such advice to be responsibly given there must be evidence that the change will improve and not impair health. While the advantage of a lower blood pressure, at any level, is well established, it is not true that every method to lower blood pressure would necessarily improve health. Some techniques to lower blood pressure, like giving short acting calcium antagonists, may not be safe.
‘All interventions aimed at enhancing or extending life by manipulating a single mechanism inevitably produce a variety of effects, some of which may not be advantageous. Extrapolation from mechanistic thinking demands evidence that the sum total of all the effects of the intervention — and not just one, such as lowering blood pressure — will help and not harm; and particularly here since the target is the whole population.
‘A low sodium intake produces many effects, not all of which are salutary. The integrated impact of these effects remains to be established. The scanty evidence directly linking sodium intake to morbidity and mortality is not encouraging.
‘Unfortunately, we simply do not know whether a universal change in sodium consumption will cause benefit or harm. Insufficient evidence — for good or ill — is not a sturdy basis for making health policy. Gratuitous exhortation, reflecting the hopes of even the most well meaning authorities, is no substitute for data. Toward this end, a good start would be to collect and analyse further observational data linking sodium intake to subsequent morbid and fatal outcomes.’
‘The important question that emerges from these papers is why the combined intellects of so many distinguished epidemiologists should maintain that the evidence incriminating salt in hypertension is so convincing when clearly it adds up to very little.’[36]
[35]. Alderman M. Data linking sodium intake to subsequent morbid and fatal outcomes must be studied. Br Med J 1997; 315: 484-5
[36]. Le Fanu J. Cross cultural studies such as Intersalt study cannot be used to infer causality. Br Med J 1997; 315: 484″
Is there any information on salt and food intake? I was just wondering since there seems to be some connection between altering the flavours of processed food by adding extra sugar, sugar substitutes, or MSG and decreased satiety signals. Could the same be true for salt?
There are different camps because there should be! We have all heard that sodium is bad for us. This has caused more harm than good, in my opinion. The key is figuring out which camp you belong in.
As mentioned above, the ratio of sodium to potassium is what is important concerning blood pressure. There is all kinds of possibilities. A person can have high sodium/high potassium or low sodium/high potassium. This results in higher bp and fluid retention but also dehydration.
A person can have low sodium and low potassium leading to too low blood pressure, increased heart rate and dehydration.
I don’t see the argument. Some people simply need more sodium while others need less.
Cutting back on sodium may be a good thing for some. But those who actually need more sodium continue to suffer because of the belief that salt is “bad”. Diet plays a part but other factors such as aldosterone(an adrenal hormone that regulates sodium and potassium) plays a big part as well, along with calcium/magnesium.
Um…what I’m trying to say is that the notion that everyone needs to decrease sodium is absolutely wrong. If you’re eating right and feel good, I wouldn’t worry about it. If not, testing sodium/potassium/calcium/magnesium,aldosterone, renin, and keeping track of BP/heartheart can give you some clues. I do think that unprocessed sea salt is the only way to go.
I checked my favorite cereal - Cheerios and it has 280 mg sodium! I’m switching back to Shredded Wheat which has none.
I read we humans should keep our sodium intake under 3000mg (3gm)a day.
I’ve talked with Dr. Robin Felder (the UVA researcher who studies the genetics of salt sensitivity), and “salt sensitive” people are actually pretty common, even among those of European descent. I don’t remember numbers. He has a protocol he uses to determine who’s sensitive by cutting out salt for a couple of weeks and looking at blood pressure.
He claims (and I believe him) that many lives could be saved by cutting out salt alone. Although I will say that I think excess carbohydrate is the real elephant in the room, and without it the effect of salt would be negligible. So I actually don’t watch my salt intake, but I also don’t have a high BP.
On a side note, Dr. Felder is a pretty remarkable person. He runs both a biology lab and a robotics lab, and he’s a pewter smith on the side.
I’ve personally never “felt” my BP go up with additional salt…I have felt it go up with excess carbs.
I’m not a chemist but I would be willing to bet natural sodium found in fruits. veg and sea salt are completely different in how the body absorbs and use than processed food salts/sodium. Of course most fruits/veg have a higher ratio of K than Na.
Kara - I would bet the same people who tell me salt is bad…are also going to tell me to eat low fat and avoid sat fat. I would agree processed foods should be avoided anyways.
gary taubes hit the nail on the head a few years ago about the soft science of salt
like the lipid idea, the obsession with salt masks a desparate desire to squeeze a lot of significance from a little stone of evidence
his points still generally stand, despite more recent “evidence”
the issue is really a red herring
hypertension is part of the constellation of associative symptoms of civilisation diseases
if salt - of itself - has an effect it is too minor to bother about
one “real” issue is salt retention - leading to water retention - resulting from high blood sugar (which is why you loose water and lower blood pressure at first on low carb)
go low carb and you won’t need to worry about salt - you won’t be eating processed junk food anyway
in the context of a balanced traditional low carb diet, SEA salt should be vaunted not taunted
salt is vital to health
markus
FWIW,
I do not cook with salt for most of my cooking. When other people cook or when I eat out, the food is usually to “salty” for my tatste.
However, when I make certain recipes were salt is part of the “flavoring of the recipe” (like roasted kale with generous sprinklng of sea salt)
I never feel like it’s too salty, on the contrary, I could put on more. I never feel my bp spike when I eat it. Nor any other effects. I don’t use “commercial” salt. I agree with the majority of comments to stay away from the processed foods and don’t worry to much about the salt.
Marc
Using the evolutionary template as a guide, we can see that the soium/potassium ratio (more important than the absolute amount of sodium) was much lower than it is today, mainly because of processed foods and table salt and a low intake of fruits and vegetables.
But sodium and salt aren’t necessarly the same thing, as more than 50% of salt is chloride, and this has a big impact in the Acid-Base balance, as a recent study has shown(Frassetto LA, Morris RC Jr, Sebastian A. Dietary sodium chloride intake independently predicts the degree of hyperchloremic metabolic acidosis in healthy humans consuming a net acid-producing diet.Am J Physiol Renal Physiol. 2007 Aug;293(2):F521-5.).
Why this is important? Because many studies done with kidney patients have shown that a chronic metabolic acidosis leads to:
- Bone Loss:
1. Barzel US (1995) The skeleton as an ion exchange system: implications for the role of acid-base imbalance in the genesis of osteoporosis. J Bone Miner Res 10:1431–1436
2. Kraut JA,Mishler DR, Singer FR,Goodman WG. The effects of metabolic acidosis on bone formation and bone resorption in the rat. Kidney Int 1986; 30:694–700)
- Muscle loss:
1. May RC, Kelly RA, Mitch WE . Metabolic acidosis stimulates protein degradation in rat muscle by a glucocorticoid-dependent mechanism. J Clin Invest 1986; 77:614–621
2. Williams B, Layward E, Walls J. Skeletal muscle degradation and nitrogen wasting in rats with chronic metabolic acidosis. Clin Sci 1991; 80:457–462
3. Garibotto G, Russo R, Sofia A, Sala MR, Sabatino C, Moscatelli P, Deferrari G, Tizianello A. Muscle protein turnover in chronic renal failure patients with metabolic acidosis or normal acid-base balance. Miner Electrolyte Metab 1996; 22:58–61
4. Bell JD, Margen S, Calloway DH. Ketosis, weight loss, uric acid, and nitrogen balance in obese women fed single nutrients at low caloric levels. Metabolism 1969; 18:193–208
5. May RC, Kelly RA, Mitch WE. Mechanisms for defects in muscle protein metabolism in rats with chronic uremia. Influence of metabolic acidosis. J Clin Invest 1987; 79:1099–1103
6. Papadoyannakis NJ, Stefanidis CJ, Mc-Geown M. The effect of the correction of metabolic acidosis on nitrogen and potassium balance of patients with chronic renal failure. Am J Clin Nutr 1984¸40:423–627
7. Hannaford MC, Leiter LA, Josse RG, Goldstein MB,Marliss EB,Halperin ML. Protein wasting due to acidosis of prolonged fasting. Am J Physiol 1982; 243:E251–E256
8. Gougeon-Reyburn R, Lariviere F, Marliss EB. Effects of bicarbonate supplementation on urinary mineral excretion during very low energy diets. Am J Med Sci 1991; 302:67–74
9. Mitch WE, Medina R, Grieber S, et al. Metabolic acidosis stimulates muscle protein degradation by activating the adenosine triphosphate-dependent pathway involving ubiquitin and proteasomes. J Clin Invest. 1994; 93:2127–2133.
10. May RC, Masud T, Logue B, Bailey J, England BK. Metabolic acidosis accelerates whole body protein degradation and leucine oxidation by a glucocorticoid-dependent mechanism. Miner Electrolyte Metab. 1992; 18:245–249.
11. May RC, Masud T, Logue B, Bailey J, England B. Chronic metabolic acidosis accelerates whole body proteolysis and oxidation in awake rats. Kidney Int. 1992; 41:1535–1542.
12. May RC, Hara Y, Kelly RA, Block KP, Buse MG, Mitch WE. Branched chain amino acid metabolism in rat muscle: abnormal regulation in acidosis. Am J Physiol. 1987; 252:E712–E718.
- Decreases Growth Hormone Release:
1. Caldas A, Fontoura M. Effects of chronic metabolic acidosis (CMA) in 24-hour growth hormone secretion. J Am Soc Nephrol 1993; 4:828–828
2. McSherry E, Morris RC, Jr. Attainment and maintenance of normal stature with alkali therapy in infants and children with classic renal tubular acidosis. J Clin Invest 1978; 61:509–527
And studies also done by Sebastian’s team have shown that by giving healthy people (who had a low grade, chronic, metabolic acidosis, as everybody who eats the typical american crap food has) potassium bicabonate it improved biomarkers of:
- bone health (Frassetto L, Morris RC Jr, Sebastian A. Long-Term Persistence of the Urine Calcium-Lowering Effect of Potassium Bicarbonate in Postmenopausal Women. J Clin Endocrinol Metab 90: 831–834, 2005)
- and reduced muscle loss (Frassetto L, Morris RC Jr, Sebastian A. Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women. J Clin Endocrinol Metab. 1997 Jan;82(1):254-9)
Finally, in 2006 and 2008, two intervention studies have shown that fruits and vegetables (as opposed to grains) improved bone health (Jajoo R, Song L, Rasmussen H, Harris SS, Dawson-Hughes B.
Dietary acid-base balance, bone resorption, and calcium excretion. J Am Coll Nutr. 2006 Jun;25(3):224-30.) and reduced muscle loss (Bess Dawson-Hughes, Susan S Harris, and Lisa Ceglia. Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr 2008 87: 662-665.)
It’s also important to mention that previous studies had shown that Hypertension could also result from a disturbance in the acid-base balance.
And there are old studies showing that chloride raised blood pressure to a significantly higher level than sodium:
1. Kurtz TW,Morris RC, Jr. (1983) Dietary chloride as a determinant of sodiumdependent
hypertension. Science 22:1139–1141
2. Luft FC, Steinberg H, Ganten U, Meyer D, Gless KH, Lang RE, Fineberg NS, Rascher W, Unger T, Ganten D (1988) Effect of sodium chloride and sodium bicarbonate on blood pressure in stroke-prone spontaneously hypertensive rats. Clin Sci 74:577–585
3. Luft FC,Zemel MB, Sowers JA,Fineberg NS,Weinberger MH (1990) Sodium bicarbonate and sodium chloride: effects on blood pressure and electroyte homeostasis in normal and hypertensive man. J Hypertens 8:663–670
4. Tanaka M, Schmidlin O, Olson JL,Yi SL, Morris RC (2001) Chloride-sensitive renal microangiopathy in the strokeprone spontaneously hypertensive rat. Kidney Int 59:1066–1076
The bottom line is: we never evolved to eat a high salt diet, but if one consumes high amounts of salt, I suggest that the intake of fruits and vegetables also increases (to balance both the POtassium/Sodium Ratio, and the Bicarbonate/Chloride ratio).
This is one reason I do not advocate a diet based exclusivly on animal products, like the Eskimo do. For me a healthy paleo type diet includes a high amount of low glycemic load fruits and vegetables, along with the meat, fish, eggs, nuts and olive oil (our ancestors ate the animal’s fat; yet most of it was monoinsaturated, and since It is hard to find grass fed animal fat, I use olive oil to emulate that).
Congratulations on your work.
Miguel
This is a great article, informative and unbiased with information regarding both sides of the salt and high blood pressure story. I was thinking of doing an article just like this on my site.
The Natural Health Guy
At age 65 I have taken my BP twice a day for 5 years and record the pertinent information(calories of aerobic exercise, low sodium DASH diet, alcohol consumption and weight.)in a diary.
I know I am a bit of a nut case but I like to keep the records so I know how I am doing and how often I can break the rules. There is ABSOLUTELY no question that sodium is important (for me). But sodium is just part of it. Hi potassium (vegetables and fruit), regular aerobic exercise and moderation in the consumption of alcohol are also very, very important. It would be a mistake to try and do it with just low sodium.
It is very easy to eat a low sodium diet if you are willing to bake your own bread and prepare your own meals. I eat 0 processed food. And I mean 0. If I follow my own rules I maintain a steady BP of about 127/77 with a resting heart rate of 45 (I do a lot of aerobics.) I can eat a high sodium diet for 1 day and I go up to about 134. Sometimes I do that on a Saturday night if I go to a party. I don’t worry about breaking the rules for 1 day. That’s life and one of the advantages of keeping records is you can figure this out so your routine is not a BALL AND CHAIN. Breaking the routine for more than1-2 days quickly casues BP to rise. After 3 days (typically on a trip) of eating restaurant food I end up at a BP of about 142/85. Last year I took 2 trips in a month. 1 to Brazil and 1 to Africa. I got no exercise, ate everything they put in front of me, enjoyed life and my BP ended up at about 150/95 with a resting pulse of 55. It took 3 weeks of exercise and proper food to get it back down to my target 127/77 and resting pulse of 45.
If you want to control BP with the mimimum amount of drugs, get a Blood Pressure cuff, keep a diary and figure it out. You should east the DASH low sodium diet and have at least 35 minutes of aerobic exercise every second day 7 days a week. That should do it. You may still need drugs but you will need less drugs.
I have read most of the scientific literature as well as Gary Taubes comments on the subject. There is some controvery about sodium and whether or not some people are more sodium sensitive than others. This point is always used to defeat attempts to force the food processing industry to reduce the amount of sodium in processed food. This is a complete red herring. The point is that unless people are willing to prepare low sodium high potassium meals from scratch, they must eat processed food and restaurant food. These people are simply unable to obtain the food that might help them control BP. Cook your own food.