Natural Sciences

How much salt? How much sugar?

Food is one of the most important driving forces of evolution and is probably one of the most important causes for the modern day diseases. As our understanding of the modern diseases is growing, Dobzhansky’s famous statement, ‘nothing in biology makes sense except in the light of evolution’, is becoming truer. Over the past 10000 years, we have engineered a rapid evolution in our food and lifestyles, ‘producing’ our food in our own backyards. Processing of food, from the simple grinding to the more refined packaging, has weaned us away from natural foods such as vegetables, fish and meat towards mostly cereal based readymade foods. Such food processing has also brought in many additives to enhance taste and to make the food more palatable and likeable. Two such most important additives are the table salt and table sugar. Any consensus on the desired daily doses of these two inseparable additives of our modern diet has been elusive and is likely to remain so, considering the fact that there are many interests pulling in different directions – the health care industry, the Big Pharma, the food industry and the researchers burning their bulbs on their own or with corporate funding.

Salt, sugar and pepper shakers. By wikimedia user Paul Goyette. (Image license: Creative Commons BY-SA-3.0 http://creativecommons.org/licenses/by-sa/3.0/.)

Salt, sugar and pepper shakers. By wikimedia user Paul Goyette. (Image license: Creative Commons BY-SA-3.0 http://creativecommons.org/licenses/by-sa/3.0/.)

How Much Salt?

A little appetite for salt is well known, with even animals, particularly herbivores, going on long treks for salt-licks.[1] Sodium is an essential nutrient, being the principal cation of extracellular fluid and a major determinant of intravascular fluid volume, and maintenance of the volumes of these fluid compartments is very much vital to sustain the tissue perfusion and normal cellular metabolism.[1] Numerous stretch and chemoreceptors along the vascular bed that sense the blood volume and the sodium levels help in controlling the blood flow, cardiac output and renal functions.[1]

A natural diet made of greens and meat has a high potassium (K+)/sodium (Na+) ratio of about 20:1 in the herbivores and 5:1 in the carnivores.[2] Our ancestral diet had at least 4 times more potassium, [3,4] with large amounts of potassium (>200 mmol/day) from vegetables, berries and meat and as little as 2–30 mmol of sodium per day.[4] That food was also rich in HCO3-yielding precursors like citrate, but contained little chloride. Human biological machinery evolved to process this high dietary potassium, our kidneys tending to excrete potassium and conserve sodium.[4] Kidneys respond to large load of sodium by conserving water and lack of sodium is managed by improved conservation.

Although addition of salt in our food has been in practice for more than 2000 years, [5] our consumption of sodium has increased manifold over the last 200 years, with salt (sodium chloride) being added at any stage before, during or after food-processing as well as before, during or after cooking.[2,4] During the same period, consumption of potassium and HCO3 yielding substances has declined, and as a result, with the advent of the modern diet, both the K+/Na+ and HCO3/Cl ratio have become reversed.[4] But our kidneys that evolved to process the ancient diet remain largely unchanged, and the electrolytic mix of the modern diet is therefore mismatched to its genetically determined processing machinery.[4]

At present, the usual intake of sodium in developed societies ranges from about 100 mmol (2400 mg) to 225 mmol (5175 mg) per day.[1] Many isolated physically active population groups living in remote rural areas have been found to be living on less than 50 mmol (1150 mg) sodium per day and in these unacculturated societies, blood pressure is low and does not increase with age, and hypertension is uncommon.[1]

Even after several studies involving thousands of people, the question of our daily requirement of sodium chloride remains unanswered. Data from over 52,000 subjects have revealed that a 100 mmol rise in sodium intake led to only a modest rise in systolic blood pressure in the range of 1–3 mm Hg and diastolic blood pressure of 0–2 mmHg.  On the other, a large series of intervention studies, in which salt was either withheld or supplemented, have shown that a reduction in sodium of approximately 100 mmol/day led to a reduction in systolic blood pressure of 4–5 mm Hg, and a fall in diastolic blood pressure of 1–3 mm Hg.[5] But too much restriction can be counter-productive, leading to marked reduction of the extracellular sodium space and intense activation of the vasoconstricting neuro-hormonal systems including activation of the renin-angiotensin-aldosterone axis, increased resistance to the metabolic actions of insulin etc.[1] Salt restriction at population level has been reported to produce a 1% decrease in blood pressure in normotensives, a 3.5% decrease in hypertensives, a significant increase in plasma renin, plasma aldosterone, plasma adrenaline and plasma noradrenaline, a 2.5% increase in cholesterol, and a 7% increase in triglyceride[6] and to increase the risk for cardiovasuclar disease, heart attacks, stroke, diabetes, and all cause mortality, while providing only a minimal reduction in blood pressure.[6-9] Accordingly, some authors have even termed sodium reduction at population level as “probably the largest delusion in the history of preventive medicine.”[9] Restriction of salt (1800mg/day) in patients with heart failure has also been reported to increase mortality.[10]

What appears to be more important and useful is the reversal of the high sodium-potassium ratio of the present day diet, by reducing sodium chloride and increasing potassium rich vegetables and meat.[4,11-13]

How Much Sugar?

Refined sugar (sucrose, glucose+fructose) was never a part of our ancient diet. Our requirements of carbohydrates are also quite small [14] and we can get all that from our daily vegetables. Several papers have been published in recent years have blamed fructose as the biggest villain for the increasing epidemic of metabolic syndrome disorders such as obesity, type 2 diabetes, hypertension, vascular disease etc.,[15-20] and Lustig et al, in a comment published in Nature, dated Feb 2, 2012, have argued that such dangers to health justify controlling sugar like alcohol, by imposing higher taxes, limiting sales during school hours, and placing age limits on purchasing.[21]

Therefore, the conclusion is simple: Eat a little salt to taste and increase the consumption of vegetables, but avoid sugar completely.

References:

  1. Logan AG. Dietary Sodium Intake and its Relation to Human Health: A Summary of the Evidence. J Am Coll Nutr June 2006;25(3):165-169. Available at http://www.jacn.org/content/25/3/165.full.pdf+html
  2. Dahl LK. Possible role of salt intake in the development of essential hypertension. Int. J. Epidemiol. October 2005;34(5):967-972. doi: 10.1093/ije/dyh317. Available at http://ije.oxfordjournals.org/content/34/5/967.full.pdf+html
  3. Sebastian A, Frassetto LA, Sellmeyer DE, Morris Jr RC. The Evolution-Informed Optimal Dietary Potassium Intake of Human Beings Greatly Exceeds Current and Recommended Intakes. Seminars in Nephrology. November 2006;26(6):447-453. Abstract at http://www.seminarsinnephrology.org/article/S0270-9295(06)00143-4/abstract
  4. Morris RC Jr, Schmidlin O, Frassetto LA, Sebastian A. Relationship and interaction between sodium and potassium. J Am Coll Nutr. 2006 Jun;25(3 Suppl):262S-270S. Available at http://www.jacn.org/cgi/pmidlookup?view=long&pmid=16772638
  5. Hollenberg NK. The Influence of Dietary Sodium on Blood Pressure. J Am Coll Nutr June 2006;25(suppl. 3):240S-246S. Available at http://www.jacn.org/content/25/suppl_3/240S.full.pdf+html
  6. Graudal NA, Hubeck-Graudal T, Jurgens G. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride. Cochrane Database of Systematic Reviews 2011, Issue 11. Art.No.: CD004022. DOI: 10.1002/14651858.CD004022.pub3. Available at http://www.update-software.com/BCP/WileyPDF/EN/CD004022.pdf
  7. Stolarz-Skrzypek K, Kuznwtsova T, Thijs L, et al. Fatal and nonfatal outcomes, incidence of hypertension, and BP changes in relation to urinary sodium excretion. JAMA. 2011;305:1777-1785. Available at http://jama.jamanetwork.com/article.aspx?articleid=899663
  8. Folkow B. On bias in medical research; reflections on present salt-cholesterol controversies. Scandinavian Cardiovascular Journal Aug 2011;45(4):194–197.
  9. Graudal N, Jürgens G. The sodium phantom. BMJ. 2011 Sep 27;343:d6119. doi: 10.1136/bmj.d6119.
  10. DiNicolantonio JJ et al. Low sodium versus normal sodium diets in systolic heart failure: systematic review and meta-analysis. Heart. Aug 2012. doi:10.1136/heartjnl-2012-302337
  11. Cook NR et al. Joint effects of sodium and potassium intake on subsequent cardiovascular disease: the Trials of Hypertension Prevention follow-up study. Arch Intern Med. Jan 2009;169(1):32-40. Available at http://archinte.jamanetwork.com/data/Journals/INTEMED/5731/ioi80146_32_40.pdf
  12. Yang Q et al. Sodium and Potassium Intake and Mortality among US Adults: Prospective Data From the Third National Health and Nutrition Examination Survey.  Arch Intern Med. 2011;171(13):1183-1191. doi:10.1001/archinternmed.2011.257. Available at http://archinte.jamanetwork.com/data/Journals/INTEMED/22518/ioi15023_1183_1191.pdf
  13. Drewnowski A, Maillot M, Rehm C. Reducing the sodium-potassium ratio in the US diet: a challenge for public health. Am J Clin Nutr August 2012;96(2):439-444. Available at http://ajcn.nutrition.org/content/96/2/439.abstract
  14. Manninen AH. Metabolic Effects of the Very-Low-Carbohydrate Diets: Misunderstood “Villains” of Human Metabolism. J Int Soc Sports Nutr. 2004;1(2):7–11. doi:  10.1186/1550-2783-1-2-7. Available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2129159/
  15. Johnson RJ et al. Potential role of sugar (fructose) in the epidemic of hypertension, obesity and the metabolic syndrome, diabetes, kidney disease, and cardiovascular disease. Am J Clin Nutr. 2007;86(4):899-90. http://www.ajcn.org/cgi/content/full/86/4/899
  16. Rizkalla SW. Health implications of fructose consumption: A review of recent data. Nutrition & Metabolism 2010;7:82 doi:10.1186/1743-7075-7-82. Available at http://www.nutritionandmetabolism.com/content/7/1/82
  17. Tappy L, Lê KA. Metabolic Effects of Sweetened Beverages: Pathophysiology and Mechanistic Insights. CMR e Journal December 2010;3(3):13-18. Available at http://www.myhealthywaist.org/cmrejournal/articles/vol3/v3i3a4.php
  18. Tappy L. Q&A: ‘Toxic’ effects of sugar: should we be afraid of fructose? BMC Biology 2012;10:42 doi:10.1186/1741-7007-10-42. Available at http://www.biomedcentral.com/1741-7007/10/42
  19. Lustig RH. Fructose: Metabolic, Hedonic, and Societal Parallels with Ethanol. J Am Diet Assoc. 2010;110:1307-1321. Available at http://podcast.uctv.tv/webdocuments/Fructose-and-Ethanol.pdf
  20. Lindeberg S. Paleolithic diets as a model for prevention and treatment of western disease. Am. J. Hum. Biol. March/April 2012;24(2):110–115. Available at http://onlinelibrary.wiley.com/doi/10.1002/ajhb.22218/full
  21.  Lustig RH, Schmidt LA, Brindis CD. The Toxic Truth about Sugar. Nature. February 2012;482:27–29. doi:10.1038/482027a. Available at http://www.connectwell.biz/pdf/comment_truth_about_sugar.pdf

About the author

Srinivas Kakkilaya

Physician practicing at Mangaluru, South India

19 Comments

      • I tell people I am on a diet. When I have doubts about the quality of the salad, I buy veggies wash then with hot water and cut them in my room. I eat boiled eggs after throwing out the yolk, I eat dal, chicken and nuts. If I am at home fish and dosas made with dals only.It is difficult but not impossible. Beverages are taken without sugar and without milk if possible. A walk around 4 kms each day also helps.

  • A good article. But one doesn’t have to forgo taste to have a healthy diet.

    I find that Indians are averse to using alternative sweeteners like aspartame, sucralose, etc. which are popular in the West. They think they are harmful. There was a study decades ago that showed saccharine causes bladder cancer in mice, and this study spawned an urban legend that all artificial sweeteners are bad for health. (Even this saccharine was later shown to be harmless to humans and the mechanism by which it causes cancer in mice does not apply to humans.)

    Plus the general distrust of anything “not natural” and “Western” among Indians means that most Indians will order regular rather than diet drinks. In fact, since the consumption of diet drinks is very low in India, many places do not even stock/serve them. Indians forget that the real poison is natural sugar which has led to a diabetes epidemic in India. Some Indians will substitute refined sugar with jaggery or palm sugar, but these are also, at the end the same sucralose.

    Some use levulose (fructose), which is a natural sugar from fruits, but from what I have read, this can overload the liver.

    I use sucralose (Natura) packets instead of regular sugar and find it to taste just as good.

    • A good article by Dr. Kakkilaya on salt and sugars must not be commented carelessly, particularly using western vs eastern debate.

      A good science is useful only if it is 1. comprehensive, 2 does not change too quickly and 3. is done honestly.

      The sugar debate is best answered by measuring amount of Insulin in the blood. Lower insulin helps in the flexibility and permeability of cell walls. Higher insulin levels render the cell walls less efficient in absorbing the nutrients and removing the CO2 etc.

      A sweetener like sucralose (natura) is as bad as any sugar in-as-much-as it tends to increase insulin levels.

      The western diet in it self is not bad but HFCS is a cheap sweetener found by food industry and it is loaded in all, packaged foods.

      Only good science can fight bad science. Rest all is publicity.

      Being on the top of food chain human population will go on increasing unless bad science plays its role in limiting it, though. 😉

      • The article is good, no denying that, but did not address artificial sweeteners. Given the fact that Americans and most Europeans consume them in significant amounts, maybe there is some merit to them. I just thought I would bring up the issue, and it is good that the author responded with some links. So I am at a loss to understand how my comment is “careless”. And not all sweeteners can be lumped together, obviously. I hinted that the Indian medical fraternity should conduct its own studies, since in the US, other factors such as HFCS (that you have mentioned) plus junk calories from other sources can confound results.

        Regarding the East vs. West debate, I think many MNCs exploit the craze of Indians for ayurvedic stuff, etc. for their own good. For example, the Henko detergent sold in India advertises that it has neem as an antibacterial. This is basically unethical and misleading advertising(unless Henkel has proved that the miniscule amounts of neem extract in its detergent really has any antibacterial effect to Indian govt. authorities through scientific tests, which I highly doubt). I bet Henkel doesn’t sell this neem detergent in Germany.

        Even when it comes to toothpastes, Colgate mentions ayurvedic terms to increase the appeal to Indians, such as pudina for mint but this is not so bad. The most proven ingredient to reduce tooth decay is fluoride, but in India, this is hardly emphasized, even if the toothpastes contain it. They would rather buy a toothpaste which mentions lavang, for instance.

        I am of the opinion that Indians in general do not make rational decisions when it comes to buying products. The cultural baggage of folklore remedies, etc. seem to cloud their judgement in many cases.

        • You are right. The MNCS try to sell junk in the name of ayruveda. For example- Vicks vaporub which is a useless cold remedy is branded as Ayurvedic with methyl salicylate being called as oil of wintergreen! The same with iodex. That has been done to get out of DPCO and also to take the benefit of the lax laws for such labelled products.
          Ram Kishan Yadav the contortionist with the facial tic is doing the same in the name of promoting ‘swadeshi products’. That is instead of the MNCs making super profits he will do so.Combine some contortions with swadeshi jargon and you have a heady brew of ads with promotion of ‘health for all’! We dont know how far that gets realised- but wealth for him has certainly happened!

        • I mentioned role of insulin in keeping blood sugar optimum, and that artificial sweeteners ALSO increase insulin beyond the limit when it becomes dangerous for body cells.

          A DNA article on research from Univ. of Missouri mentions that laziness increases blood sugar in normally healthy people.

          Second point I mentioned about ‘bad’ science.

          It is only a confirmation that many MNCs indulge in bad science.

          India is not specially chosen for bad science.

          MNCs make money from everybody, all around the globe, using bad science.

          It takes some doing for separating bad science from good science.

          I hope people are not lost in references to scientific journals alone.

          -rkk

  • I am afraid diet drinks are equally or even more unsafe than natural sugars. There are no large, prospective studies on the metabolism and effects of these chemicals on our body. By stimulating sweet buds, they increase hunger and thereby worsen obesity and other metabolic syndrome disorders, contrary to what is claimed by their manufacturers. Here are some of the reports:

    1. Duffey KJ et al. Dietary patterns matter: diet beverages and cardiometabolic risks in the longitudinal Coronary Artery Risk Development in Young Adults (CARDIA) Study. Am J Clin Nutr April 2012 ajcn.026682 Absract here: http://ajcn.nutrition.org/content/early/2012/02/28/ajcn.111.026682.abstract
    2. Gardener H et al. Diet Soft Drink Consumption is Associated with an Increased Risk of Vascular Events in the Northern Manhattan Study. Journal of General Internal Medicine. September 2012;27(9):1120-1126. Abstract here:
    http://link.springer.com/article/10.1007%2Fs11606-011-1968-2
    3. Nettleton JA et al. Diet Soda Intake and Risk of Incident Metabolic Syndrome and Type 2 Diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA). Diabetes Care April 2009;32(4):688-694. Full Text here: http://care.diabetesjournals.org/content/32/4/688.full
    4. Davidson TL, Swithers SE. A Pavlovian approach to the problem of obesity. International Journal of Obesity 2004;28:933–935. doi:10.1038/sj.ijo.0802660 Full Text here: http://www.nature.com/ijo/journal/v28/n7/pdf/0802660a.pdf

    Let’s take care of our big body rather than fall prey to the tiny tongue and the emotions that it stimulates!

    • “Let’s take care of our big body rather than fall prey to the tiny tongue and the emotions that it stimulates!”

      Sure, that’s probably the safest way to go. I am not a big fan of soft drinks myself (regular or diet), but one cannot expect children and teenagers to show this kind of restraint. That said, does it make sense for them to have diet drinks? In the US, from what I have seen, very few order regular drinks in comparison to diet. Here it seems to be the exact opposite. I guess more studies (under Indian conditions) may settle the issue.

  • >>Given the fact that Americans and most Europeans consume them in significant amounts, maybe there is some merit to them.<<
    That does not become evidence by itself. Quite a few of them do the so called yoga as well, but does it prove yoga for health?

    All artificial sweeteners have shown significant adverse effects in animal studies, notably cancers, increasing hunger, increasing obesity etc. Large, prospective human studies have not been done to prove their safety, yet they are approved by agencies such as USFDA for human use.
    See Aspartame, Donald Rumsfeld and USFDA:
    http://dorway.com/doctors-speak-out/aspartame-methanol-the-public-health/
    http://www.fda.gov/ohrms/dockets/dailys/04/july04/071204/02P-0317-emc00346.txt
    http://www.newswithviews.com/NWVexclusive/exclusive15.htm
    http://www.huffingtonpost.com/robbie-gennet/donald-rumsfeld-and-the-s_b_805581.html

    • I am not sure that yoga has no health benefits at all.. I think that, done rightly, it can be beneficial under certain circumstances.. I think there have been studies that do prove this.. again, it may not be for everyone, but so are most other kinds of exercises, and all of these, if done improperly, can lead to injuries. But this is my opinion, don’t want to get into this any further, in this thread, since it takes away focus from the main subject.

      Regarding aspartame, I agree.. but again, there are many types of sweeteners, and you cannot paint all of them with the same brush. Some like stevia, xylitol are natural and are sugar alcohols. Even ADA has established that sugar-free chewing gums are beneficial in preventing tooth decay.

      Regarding cancers, there has not been any study that has conclusively established that the commonly used artificial sweeteners are responsible. I think chances of getting cancer are greater from the yellow coloring used in tikka masalas, for instance.

      We also need to weigh in the relative risks.. for example, if one out of 1000 develop cancer due to artificial sweeteners (which itself has not been established), but prevents obesity and heart aliments in, say, 50 out of 1000, the risk might be worth it.

  • All sweets increase appetite and hunger and decrease satiety, thereby promoting obesity and other problems. We do not need sweets of any kind. Reduction in dental caries is due to avoidance of sugars and not due to xylitol. There have been no large scale studies on the safety of sweeteners and lack of proof of harm is no proof of safety. The fact remains that we need not eat sugars and sweets, can live and remain healthy without them.

    • I agree that avoiding sugar as well as sweeteners is the best strategy. I am not questioning that.

      But can we expect the public to follow this kind of self-restraint? This is like asking people to avoid sex, in order to curb HIV. The fact is, sex and appetite for sweets are powerful instincts, and we cannot expect the majority to heed such advice. So, any health policy has to be formulated with keeping in mind that people are going to yield to their desires, and therefore, what is the second line of strategy. I am not saying that sweeteners are completely benign, but just whether it is the lesser of two evils, given the fact that the vast majority of the population are going to end consuming sweets anyway.

  • * All sweets increase appetite and hunger and decrease satiety*

    How does that work? Can you please give a short mechanistic explanation of how sweets decrease satiety. I thought that people eat deserts after the meal in order to bring about satiety.

  • Sweeteners produce a pleasurable experience that in turn leads to addiction, increased hunger, and overeating that leads to leptin resistance and associated problems. Some sweeteners like fructose and aspartame, apart from sugar, also directly lead to high leptin levels.
    Read ref 4 above:
    Davidson TL, Swithers SE. A Pavlovian approach to the problem of obesity. International Journal of Obesity 2004;28:933–935. doi:10.1038/sj.ijo.0802660 Full Text here: http://www.nature.com/ijo/journal/v28/n7/pdf/0802660a.pdf

    Also see:
    http://care.diabetesjournals.org/content/34/5/e46.full
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892765/
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714382/

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