Category: General

The Pizza Paradox: Home Cooking and Personal Science

Seth Roberts26 Comments

Last week I had pizza at the home of my friends Bridget and Carl. It tasted divine. The crust was puffy, chewy and the right amount. The thin-crust bottom was slightly crunchy. The tomato sauce had depth. The toppings (two kinds of mushrooms, Jerusalem artichokes, zucchini, onions, goat cheese) were tasty, creamy and a little crunchy. It was pretty and three-dimensional. It was easily the best pizza I’d ever had, the best home cooking I’d ever had, and much better than the lamb I’d had at Chez Panisse the night before, although the lamb was excellent. The pizza hadn’t been hard to make nor were the ingredients expensive. Do other people wonder why this is so good? I asked my friends.

At some level I knew why it was so good — why the sauce was so good, for example (see below). The puzzle — let me call it the Pizza Paradox — was that commercial pizza, even at fancy restaurants (such as Chez Panisse), is so much worse. In restaurants, pizza-makers make dozens of pizzas per day. Business success is on the line. That should push them to do better. Professional cooks study cooking, have vast experience. They use a pizza oven. My friends have never studied cooking, never cooked professionally. They might make pizza once/month. Nothing is on the line. My friends don’t have a pizza oven. High-end restaurant pizza should be much better, but the opposite was true.

In my experience, high-end restaurant food usually is much better than home-cooked versions. Why is high-end pizza a big exception — at least, compared to Bridget and Carl’s version?

My explanation has two parts. First, the concept of pizza is brilliant. It taps more sources of pleasure than any other food I can think of. Chewiness from crust. Fat from cheese. Umami, sweet, and sour from tomato sauce. Protein from cheese and meat. Complexity of flavor from sauce and toppings. Variety of texture from toppings and crust. Variety of flavor from toppings. Attractive appearance from toppings and bright red tomato sauce. Most foods fail to tap most of these sources. For example, a soft drink isn’t chewy, doesn’t have protein, doesn’t have fat, doesn’t have variety of texture or variety of flavor, and isn’t attractive.

My friends had one goal: to make the best possible pizza. It couldn’t take too long or cost too much but they weren’t trying to save time or cut costs. Over the years, they tweaked the recipe various ways and their pizza got better and better. Experimentation was safe. If a variation made things worse, it didn’t matter. It would still taste plenty good. (Due to the brilliance of pizza.) Variation was fun. After making pizza in a new way, they’d eat the pizza themselves (with guests) and find out if the new twist made a difference.

Professional pizza makers don’t do this. After a restaurant opens, they make pizza roughly the same way forever. The pizza at Chez Panisse, for example, looks the same now as many years ago. The owner might want to make the best possible pizza but is unlikely to experiment month after month year after year. The actual cooks just want to make satisfactory pizza. Making the best possible pizza is not part of the job. The owner might benefit from better pizza but the cooks would not. They’re cranking it out under time pressure (watch Hell’s Kitchen). They do what they’re told. Owners fear experimentation: It might be worse. It won’t be what’s expected. Don’t mess with success.

This illustrates what I’ve said many times: job and science don’t mix well. To do the best possible science or make the best possible pizza, you need freedom to experiment. People with jobs get stuck. All jobs — including professor at research university, rice grower, and pizza maker — depend on steady output of the same thing again and again. Trying to maximize short-term output interferes with long-term improvement. To do the best possible science or make the best possible pizza, you also need the right motivation: You care about nothing else. People with jobs have many goals. This is why we need personal science: To overcome the (serious) limitations of professional science.

All this should be obvious, but curiously isn’t. Long ago, philosophers such as John Stuart Mill claimed that people “maximized utility”, apparently not realizing that maximizing output (which happens when people work “hard”) slows down or prevents innovation. Later thinkers, such as Frederick Hayek and Milton Friedman, glorified markets. They too failed to grasp, or at least say anywhere, that market demands get in the way of innovation.

The recipe for my friends’s pizza had several non-obvious features:

1. Pizza dough from Trader Joe’s. At Chez Panisse and other high-end restaurants, this would be taboo. It might produce better results — you still couldn’t do it.

2. Pizza stones above and below the pizza. My friends use an ordinary oven. Maybe an ordinary oven with two pizza stones produces better results than a pizza oven.

3. Balsamic vinegar in the tomato sauce. They got the idea from a friend. American cooks, including professional ones, routinely fail to understand how much fermented foods (such as balsamic vinegar) can improve taste. My friends also use more traditional flavorings (marjoram, basil, and garlic) in the tomato sauce.

4. Plenty of goat cheese. They scatter goat cheese slices over the top of the sauce.

There you have the secret of Bridget and Carl’s Pizza.

How Meritocratic is Chinese Higher Education?

Seth Roberts6 Comments

A friend of mine taught at Harvard for a few years. Her husband needed a job, so he taught a writing class. He said his students were so bad it appeared to be an experiment: How stupid can you be and succeed at Harvard? They had not been admitted based on SAT scores or grades, that was clear. In a recent article called “The Myth of American Meritocracy”, Ron Unz described considerable evidence of exactly what my friend’s husband noticed: Harvard admission not based on the usual “meritocratic” measures, such as SAT scores and grades. For example, he found evidence of an Asian quota. If Asians weren’t penalized for being Asian, far more would be admitted.

In a follow-up article, Unz wrote:

Near the beginning of my article [about meritocracy] I had noted that although complaints about official corruption of every sort are a leading topic on the Chinese Internet and also in Western media coverage, I had never once heard such a claim about admissions to elite Chinese universities. This led me to conclude that the process was entirely meritocratic, and a couple of individuals with good knowledge of China confirmed this. However, during one of my recent Yale Law events, a student from China stated that he and his friends were firmly convinced that any of China’s 350 Central Committee members could easily obtain an admissions slot for his friends or relatives, so my claim was incorrect. This conflicting evidence may be reconciled if the number of such corrupt admissions each year is so tiny—perhaps a few hundred out of over eight million—that it is completely invisible to the general public. I should note that the New York Times just ran another major story on colleges in China, emphasizing every possible unfair aspect of the system, but nonetheless indicating that admissions were entirely meritocratic and objective.

Here is one reason that there is zero discussion of corruption in admission to elite Chinese universities (such as Tsinghua, where I teach): Rich Chinese universally want their children to go to college outside China, especially America. The more money you have, the easier this is. I’d guess all children of Central Committee members attend college outside China. None of them attend Tsinghua, as far as I know. At least among my students, this is utterly obvious — that education outside China is superior and anyone who can go outside China will. The brake on this is purely cost. One of my students said she didn’t want to burden her parents with the cost.

The test that Chinese high school students take to get into college is the gaokao. One of my students got the highest gaokao score in Beijing. An astonishing achievement. He didn’t get in to any American university. The Chinese public was shocked. Many newspaper articles were written about it. The rest of my students knew about it. His family is not well-off. This is why he failed where thousands of Chinese students from rich families — who didn’t bother to take the gaokao, but surely would have had a lower score – succeeded. Although he went to Tsinghua as a freshman, he too wanted to escape Chinese higher education. First he transferred to the University of Hong Kong. Then he transferred to MIT.

Why is Chinese higher education so bad that everyone who can avoids it? One of my students (a psychology major) said that as the economy quickly improved, the government quickly expanded the college education system. There weren’t enough good teachers to fill the slots. That’s one reason. Another reason is a certain ethos. I asked a friend of mine, a Tsinghua student not majoring in psychology, “In what fraction of your classes do the professors lecture by reading from the textbook?” 80%, she said. That’s at Tsinghua. Below Tsinghua it’s worse. Of course students go to college outside China for reasons that have nothing to do with quality. The most obvious is prestige: It is prestigious to go elsewhere.

Lack of higher education meritocracy in China has a more subtle aspect. It is much easier to get into elite universities, such as Tsinghua, if you live in Beijing or Shanghai than if you live elsewhere, especially poor provinces. Is this unfair? It isn’t easy to say because the gaokao is different in different places. I don’t know the official reason for this (different textbooks?), but the difference in tests makes it easier to have lower admissions cutoff scores for students from Beijing and Shanghai. A Beijing student at Tsinghua will usually have a lower gaokao score than a student at Tsinghua from a poor province. Of course it is much more expensive to live in Beijing and Shanghai than elsewhere. Moreover, a big chunk of the gaokao is about English proficiency. A student’s English proficiency depends heavily on amount and quality of English education, which depends heavily on family income. The richer you are, the better your children’s English.

All this makes political sense. Richer people — whose children have better English — have more political power than the less rich. Those who live in Beijing and Shanghai have more political power than people in poor provinces. Allowing their children get into Tsinghua with lower gaokao scores (Beijing and Shanghai residents) or writing the gaokao so that their children have an advantage (English proficiency) is one way to keep them happy.

 

 

How to Encourage Personal Science?

Seth Roberts10 Comments

I wonder how to encourage personal science (= science done to help yourself or a loved one, usually for health reasons). Please respond in the comments or by emailing me.

An obvious example of personal science is self-measurement (blood tests, acne, sleep, mood, whatever) done to improve what you’re measuring. Science is more than data collection and the data need not come from you. You might study blogs and forums or the scientific literature to get ideas. Self-measurement and data analysis by non-professionals is much easier than ever before. Other people’s experience and the scientific literature are much more available than ever before. This makes personal science is far more promising than ever before.

Personal science has great promise for reasons that aren’t obvious. It seems to be a balancing act: Personal science has strengths and weakness, professional science has strengths and weaknesses. I can say that personal scientists can do research much faster than professionals and are less burdened with conflicts of interest (personal scientists care only about finding a solution; professionals care about other things, including publication, grants, prizes, respect, and so on). A professional scientist might reply that professional scientists have more training and support. History overwhelming favors professional science — at least until you realize that Galileo, Darwin, Mendel, and Wegener (continental drift) were not professional scientists. (Galileo was a math professor.) There is very little personal science of any importance.

These arguments (balancing act, examination of history) miss something important. In a way, it isn’t a balancing act. Professional science and personal science do different things. In some ways history supports personal science. Let me give an example. I believe my most important discovery will turn out to be the effect of morning faces on mood. The basic idea that my findings support is that we have a mood control system that requires seeing faces in the morning to work properly. When the system is working properly, we have a circadian rhythm in mood (happy, eager, serene during the day, unhappy, reluctant, irritable at night). The strangest thing is that if you see faces in the morning (e.g, 7 am) they have no noticeable effect until 6 pm the same day. There is a kind of uncanny valley at work here. If you know little about mood research, this will seem unlikely but possible. If you are an average professional mood researcher, it will seem much worse: can’t possibly be true, total nonsense. If you know a lot about depression research, however, you will know that there is considerable supporting research (e.g., in many cases, depression gets better in the evening). It will still seem very unlikely, but not impossible. However, if you’re a professional scientist, it doesn’t matter what you think. You cannot study it. It is too strange to too many people, including your colleagues. You risk ridicule by studying it. If you’re a personal scientist, of course you can study it. You can study anything.

This illustrates a structural problem:

2013-02-28 personal & professional science in plausibility space

This graph shows what personal and professional scientists can do. Ideas vary in plausibility from low to high; data gathering (e.g., experiments) varies in cost from low to high. Personal scientists can study ideas of any plausibility, but they have a relatively small budget. Professional scientists can spend much more — in fact, must spend much more. I suppose publishing a cheap experiment would be like wearing cheap clothes. Another limitation of professional scientists is that they can only study ideas of medium plausibility. Ideas of low plausibility (such as my morning faces idea) are “crazy”. To take them seriously risks ridicule. Even if you don’t care what your colleagues think, there is the additional problem that a test of them is unlikely to pay off. You cannot publish results showing that a low-plausibility idea is wrong. Too obvious. In addition, professional scientists cannot study ideas of high plausibility. Again, the only publishable result would be that your test shows the idea is wrong. That is unlikely to happen. You cannot publish results that show that something that everybody already believes is true.

It is a bad idea for anyone — personal or professional scientist — to spend a lot of resources testing an idea of low or high plausibility. If the idea has low plausibility, the outcome is too likely to be “it’s wrong”. There are a vast number of low-plausibility ideas. No one can afford to spend a lot of money on one of them. Likewise, it’s a bad idea to spend a lot of resources testing an idea of high plausibility because the information value (information/dollar) of the test is likely to be low. If you’re going to spend a lot of money, you should do it only when both possible outcomes (true and false) are plausible.

This graph explains why health science has so badly stagnated — every year, the Nobel Prize in Medicine is given for something relatively trivial — and why personal science can make a big difference. Health science has stagnated because it is impossible for professionals to study ideas of low plausibility. Yet every new idea begins with low plausibility. The Shangri-La Diet is an example (Drink sugar water to lose weight? Are you crazy?). We need personal science to find plausible new ideas. We also need personal science at the other extreme (high plausibility) to customize what we know. Everyone has their quirks and differences. No matter how well-established a solution, it needs to be tailored to you in particular — to what you eat, when you work, where you live, and so on. Professional scientists won’t do that. My personal science started off with customization. I tested various acne drugs that my dermatologist prescribed. It turned out that one of them didn’t work. It worked in general, just not for me. As I did more and more personal science, I started to discover that certain low-plausibility ideas were true. I’d guess that 99.99% of professional scientists never discover that a low-plausibility idea is true. Whereas I’ve made several such discoveries.

Professional scientists need personal scientists to come up with new ideas plausible enough to be worth testing. The rest of us need personal scientists for the sake of our health. We need them to find new solutions and customize existing ones.

 

 

 

If You Ever Visit Seoul, You Might Want To Skip Bean Table Restaurant

Seth RobertsLeave a comment

A restaurant near Seoul named Bean Table got a surprisingly bad review:

Then came a massive chicken salad dish, given the number of people we had we over ordered. The patrons we brought were split 50/50 on enjoyment for the chicken. We had so much leftovers and were wasting so much food, I asked the waiter to wrap the leftovers. . . . Asking the waiter to wrap this chicken came with a resounding “no”, so again to the kitchen to talk to a manager. Actually ended up talking to a chef, a young man who speaks good English, who also declined our request. We had a six year old and a three year old with us and that was the only food they were eating minus the pungent sauce.

Our driver then proceeded to get angry and went to talk to the chef, Sungmo Lee, and surprisingly Mr. Lee and our driver had a conversation that the whole restaurant could hear despite repeated requests by our driver to discuss outside. As that incident occurred being concerned for my family who flew on average 7,000 miles and were picked up for a total driving commute of two hours to come eat at this restaurant I went to calm both parties down. Things progressed from worse to horrible. I identified myself as a food critic, and Mr. Lee proceeded to take that as a threat and stated, “You don’t know who I am.” . . . . My father, a man in his 70′s, tried to speak reason to him only to be found that we were asked to leave.

At the end of the day, police were called, we weren’t allowed to pay the bill till police arrived even after we stated we wished to leave and skip the remaining courses. Police came and scolded Mr. Lee, telling him that if a customer pays for food then containers should be allowed for the customers to take food home. Keep in mind we are talking about cooked chicken, not fish, or tartar, etc. (Mr. Lee’s argument was that there were no take out containers in the restaurant and remained adamant about the no take out policy when we asked the driver to buy some containers). After the police came they asked us to leave while they dealt with Mr. Lee only to find an employee chasing out bus to pay the bill. No discounts, full price and another time suck of 20-30 minutes and the rest of the meal was safely kept in their fridge due to their “no takeout” policy. . . .

Before all of this nonsense came down my whole Korean family all thought that the restaurant was over rated and there was no single outstanding dish.

Until the Internet, stuff like this was never reported.

 

Assorted Links

Seth Roberts2 Comments

Thanks to Bryan Castañeda and Dave Lull.

Assorted Links

Seth Roberts8 Comments

 

Bariatric Surgery Linked to Acetaminophen Poisoning

Seth Roberts5 Comments

Acetaminophen is a pain killer found in many over-the-counter drugs, such as Tylenol, NyQuil and Sudafed. It can cause liver failure. A new study at the California Pacific Medical Center in San Francisco reports that people who have had bariatric surgery seem to have a much higher risk of this:

Among 54 patients who had suffered acetaminophen-induced liver failure over a three-year period, 17 percent had had weight-loss surgery. . . . Less than 1 percent of the general population has had the surgery.

The study controlled for the possibility that people who have bariatric surgery are more likely to have liver failure unrelated to acetaminophen:

The researchers looked at 101 cases of acute liver failure seen at California Pacific Medical Center, more than half of which were caused by acetaminophen poisoning. Among the nine patients [of the 101] who had had weight-loss surgery, all of them had liver failure caused by acetaminophen overdose.

The article, by a reporter named Erin Allday, goes on to say:

At this time, there is no reason for bariatric surgery patients to be alarmed, and they should continue using acetaminophen if that’s their preferred pain medication or their doctor has prescribed it.

Allday attributes this bizarre advice to unnamed “researchers and weight-loss surgeons.” Of course bariatric surgery patients should be alarmed and cut down or stop using acetaminophen.

The next time someone says “correlation does not equal causation” or belittles epidemiology tell them about this case.

Thanks to David Archer.

Bayesian Shangri-La Diet

Seth Roberts7 Comments

In July, a Cambridge UK programmer named John Aspden wanted to lose weight. He had already lost weight via a low-carb (no potatoes, rice, bread, pasta, fruit juice) diet. That was no longer an option. He came across the Shangri-La Diet. It seemed crazy but people he respected took it seriously so he tried it. It worked. His waist shrank by four belt notches in four months. With no deprivation at all.

Before he started, he estimated the odds (i.e., his belief) of three different outcomes predicted by three different theories. What would happen if he drank 300 calories (2 tablespoons) per day of unflavored olive oil (Sainsbury’s Mild Olive Oil)? Aspden considered the predictions of three theories.

I called my three ideas of what would happen [= three theories that make different predictions] if I started eating extra oil Willpower, Helplessness and Shangri-La. (1) Willpower (W) is the conventional wisdom. If you eat an extra 300 calories a day you should get fatter. This was the almost unanimous prediction of my friends. Your appetite shouldn’t be affected. (2) Helplessness (H) was my own best guess. If you eat more, it will reduce your appetite and so you’ll eat less at other times to compensate, and so your weight won’t move. Whether this appetite loss would be consciously noticeable I couldn’t guess. This was my own best guess. (3) Shangri-La (S) is your theory. The oil will drop the set point for some reason, and as a result, you should see a very noticeable loss of appetite.

More about these theories. His original estimate of the likelihood of each prediction being true: W 39%, H 60%, S 1%. He added later, “I think I was being generous with the 1%”. After the prediction of the S theory turned out to be true, the S theory became 50 times more plausible, Aspden decided.

I like this a lot. Partly because of the quantification. If you were a high jumper in a world without exact measurement, people could only say stuff like “you jumped very high.” It would be more satisfying to have a more precise metric of accomplishment. It is a scientist’s dream of making an unlikely prediction that turns out to be true. The more unlikely, the more progress you have made. Here is quantification of what I accomplished. Although Aspden could find dozens of online reports that following the diet caused weight loss, he still believed that outcome very unlikely. Given that (a) the obesity epidemic has lasted 30-odd years and (b) people hate being fat, you might think that conventional wisdom about weight control should be assigned a very low probability of being correct.

I also like this because it is the essence of science: choosing between theories (including no theory) based on predictions. The more unlikely the outcome, the more you learn. You’d never know this from 99.99% of scientific papers, which say nothing about how unlikely the actual outcome was a priori — at least, nothing numerical. I can’t say why this happens (why an incomplete inferential logic, centered on p values, remains standard), but it has the effect of making good work less distinguishable from poor work. Maybe within the next ten years, a wise journal editor will begin to require both sorts of logic (Bayesian and p value). You need both. In Aspden’s case, the p value — which would indicate the clarity of the belt-tightening — was surely very large. This helped Aspden focus on the Bayesian aspect — the change in belief. This example shows how much you lose by ignoring the Bayesian aspect, as practically all papers do. In this case, you lose a lot. Anyone paying attention understands that the conventional wisdom about weight control must be wrong. Here is guidance towards a better theory. If not mine, you at least want a theory that predicts this result.

 

 

 

 

 

Measuring Yourself to Improve Your Health? Want to Guest-Blog?

Seth Roberts6 Comments

What surprised me most about my self-experimental discoveries was that they were outside my area of expertise (animal learning). I discovered how to sleep better but I’m not a sleep researcher. I discovered how to improve my mood but I’m not a mood researcher. I discovered that flaxseed oil improved brain function but I’m not a nutrition researcher. And so on. This is not supposed to happen. Chemistry professors are not supposed to advance physics. Long ago, this rule was broken. Mendel was not a biologist, Wegener (continental drift) was not a geologist. It hasn’t been broken in the last 100 years. As knowledge increases, the “gains due to specialization” — the advantage of specialists over everyone else within their area of expertise — is supposed to increase. The advantage, and its growth, seem inevitable. It occurs, say economists, because specialized knowledge (e.g., what physicists know that the rest of us, including chemists, don’t know) increases. My theory of human evolution centers on the idea that humans have evolved to specialize and trade. In my life I use thousands of things made by specialists that I couldn’t begin to make myself.

Here we have two things. 1. A general rule (specialists have a big advantage, within their specialty, over the rest of us) that is overwhelmingly true. 2. An exception (my work). How can this be explained? What can we learn from it? I’ve tried to answer these questions but I can add to what I said in that paper. The power of specialization is clearly enormous. Adam Smith, who called specialization “division of labor”, was right. The existence of an exception to the general rule suggests there are forces pushing in the opposite direction (toward specialists being worse than the rest of us in their area of expertise) that can be more powerful than the power of specialization. Given the power of specialization, the countervailing forces must be remarkably strong. Can we learn more about them? Can we harness them? Can we increase them? The power of specialization has been increasing for thousands of years. How strong the countervailing forces may become is unclear.

The more you’ve read this blog, the more you know what I think the countervailing forces are. Some of them weaken specialists: 1. Professors prefer to be useless rather than useful (Veblen). 2. A large fraction (99%?) of health care workers have no interest in remedies that do not allow them to make money. 3. Medical school professors are terrible scientists. 4. Restrictions on research. Some of them strengthen the rest of us: 1. Data storage and analysis have become very cheap. 2. It is easier for non-scientists to read the scientific literature. 3. No one cares more about your health than you. These are examples. The list could be much longer. What’s interesting is not the critique of health care, which is pretty obvious, but the apparent power of these forces, which isn’t obvious at all.

I want to learn more about this. I want learn how to use these opposing forces and, if possible, increase them. One way to do this is find more exceptions to the general rule, that is, find more people who have improved their health beyond expert advice. I have found some examples. To find more, to learn more about them, and to encourage this sort of thing (DIY Health), I offer the opportunity to guest-blog here.

I think the fundamental reason you can improve on what health experts tell you is that you can gather data. Health experts have weakened their position by ignoring vast amounts of data. Three kinds of data are helpful: (a) other people’s experiences, (b) scientific papers and (c) self-measurement (combined with self-experimentation). No doubt (c) is the hardest to collect and the most powerful. I would like to offer one or more people the opportunity to guest-blog here about what happens when they try to do (c). In plain English, I am looking for people who are measuring a health problem and trying to improve on expert advice. For example, trying to lower blood pressure without taking blood pressure medicine. Or counting pimples to figure out what’s causing your acne. Or measuring your mood to test alternatives to anti-depressants. I don’t care what’s measured, so long as it is health-related. (Exception: no weight-loss stories) and you approach these measurements with an open mind (e.g., not trying to promote some product or theory). I am not trying to collect success stories. I am trying to find out what happens when people take this approach.

Guest-blogging may increase your motivation, push you to think more (“ I blog, therefore I think“) and give you access to the collective wisdom of readers of this blog (in the comments). If guest-blogging about your experiences and progress (or lack of it) might interest you, contact me with details of what you are doing or plan to do.

Journal of Personal Science: How Much Salt Should I Eat?

Seth Roberts11 Comments

by Greg Pomerantz

The Journal of Personal Science, suggested by Tom and encouraged by Bryan Castañeda, will contain articles about using science to help yourself. This is the first one. It previously appeared on Greg’s blog. If you have written something or plan to write something or are thinking about writing something that might be included, please let me know. — Seth

I spent a few weeks this summer conducting a self-experiment on salt sensitivity and blood pressure. The experiment included a three week phase on a low carb whole foods diet with no added salt, followed by a moderately extreme salt loading phase. This post is a summary of my results.

I learned a lot from the experiment and came out of it with at least one bit of useful information. Will I try to restrict salt in my diet? No, I don’t think salt restriction can work for me. From now on I will ensure that I get sufficient salt on a daily basis.

Summary

These are the main points I learned during the experiment, from most to least interesting.

1. Salt restriction caused impaired thermoregulation. In hot weather, my cardiovascular system was not able to sufficiently lower my body temperature. This resulted in an elevated heart rate and hypethermia (up to 101.5 degrees in one instance). This can be dangerous, so be careful if you try this at home.

2. No clinically meaningful change in blood pressure. Systolic pressure was unchanged, though salt loading may have caused a small rise in diastolic pressure. This does not rule out long term negative effects from chronic salt loading (see discussion below), but it does show that, as previously discussed, my kidneys seem to basically work and can regulate my blood pressure through the maintenance of fluid and electrolyte balance in response to changes in my sodium intake.
3. Salt reduction may increase susceptibility to skin infections. Three days into the salt restriction phase, I came down with what was probably a staph infection in my right eyelid. This responded to antibiotics but it came back once I went off them. Since adding back salt I have had no problems with skin infections and no more antibiotics.
4. Possible strength loss. I did not perform well in the gym on my usual strength training program.
5. My taste for salt adapts quickly to restriction and loading. I experienced no cravings even when my sodium intake was too low. I can’t just “listen to my body”. Likewise, while the salt loading phase was difficult for the first two or three days, my taste rapidly adjusted to the added salt.
6. Bodyweight changes. I experienced substantial changes in body fluid levels (e.g. 6 pound weight gain within two hours of the transition from the salt restriction to the salt loading phase).

Conclusion: A low carb paleo diet must include added salt (for me). Can others do without? Perhaps, and some scientists such as Loren Cordain and Tim Noakes (e.g. this podcast episode 18 at 1:03:50) seem to think they can. Skip ahead to read my further musings on this question.

Study Design

The experiment had three phases. First, I did a one week lead-in phase (phase I) where I made no changes to diet or salt consumption. The purpose of phase I was to establish a blood pressure baseline through daily morning measurements (see Measurement Methods below).

This was followed by a three-week sodium restricted phase (phase II) during which I did not add any salt to my food. In addition, during phase II only, I avoided naturally salty foods such as shellfish. My sodium intake during phase II was limited to the sodium in the foods I was eating. Note however that there were one or two restaurant meals per week during this time where I was not able to strictly control for added salt. Sodium consumption on phase II was estimated to be between 800mg and 1000mg per day. phase II was originally scheduled for two weeks, but was extended due to the aforementioned infection and antibiotic use.

Finally, phase III was a salt-loading phase during which I added an additional 5 grams of sodium to my diet, for a total of nearly 6 grams of sodium per day including the sodium naturally occurring in my food. The supplemental salt during phase III consisted of hand harvested French Celtic sea salt (Eden Foods, Inc.) and was measured daily on an AMW-1000 digital scale. Because the Eden French Celtic sea salt is approximately 1/3 sodium by weight according to the label, the 5 grams of supplemental sodium per day was provided by approximately 15 grams of sea salt. Note that different varieties of salt will contain different percentages of sodium by weight. Sea salts vary significantly due to variations in residual water content (not, as commonly assumed, by the presence of other minerals). Please consult the label or a friendly analytical chemist for guidance.

The diet throughout this experiment consisted of meat, fish, eggs, coconut oil, butter, and non-starchy vegetables. In addition, I typically consumed a banana, an ounce (28g) of almonds and a bit of dark chocolate each day. Potassium intake was fairly consistent at around 4 g/day. Table 1 shows a typical day’s macronutrient intake. Given the macronutrient ratio, I believe it is likely that the diet was ketogenic.

Table 1. Approximate daily macronutrient intake.

Macronutrient
grams
 calories percent (calories)
Carbohydrate
50
 200 6.6%
Protein 155 620 20.5%
Fat 245 2205 72.9%
Total 3025
100%

 

Measurement Methods

I measured blood pressure daily first thing each morning while seated, with the cuff of an Omron HEM-711 placed on the left upper arm over the brachial artery. I followed guidelines described by Agena et al (see Chart 2 of the linked paper). Each day’s blood pressure value was determined by averaging the first three measurements taken that morning.

My first measurement of the day was typically higher than the average of the second and third measurements (systolic: +5, diastolic: +4, average over all three phases). This is referred to as the “alarm reaction” and is related to the more commonly known “white coat syndrome”, where the presence of a doctor elicits a stress response and therefore an innacurately high blood pressure reading. My alarm reaction seems to be due to the fact that I get slightly stressed out about seeing what my blood pressure is, even when I measure it myself. Therefore I experience a slight rise in blood pressure while waiting to see the first reading each day. I kept all three readings for this experiment. My “true” normal blood pressure is on average slightly lower than these results which include the first “alarm” reading.

Results

I summarized my qualitative findings in the executive summary above. If you skipped that because you are not an executive, you can go back and read it now. Below are graphs showing my blood pressure and bodyweight during the three phases.

Figure 1: Possible mild elevation in diastolic blood pressure during the salt loading phase. Each point is the average of the three morning blood pressure readings for the day. Red = phase I, green = phase II, blue = phase III. Curves from ggplot2 “geom_smooth()” using default parameters.

 

Figure 2. No change in systolic blood pressure.

 

Figure 3: Bodyweight.

Figure 3 shows my daily bodyweight, measured each morning before consumption of any food or fluids. Note that my previous health goal (the 415 deadlift) involved an intentional increase in bodyweight and therefore significant excess calorie consumption. My current diet is lower in calories and Figure 3 therefore should show a long term downward trend in bodyweight.

Salt restriction clearly resulted in a rapid decrease in bodyweight over the first few days of phase II. There appears to be a stabilization towards the end of the salt restricted phase. The salt loading in phase III produced a very large initial weight gain, followed again by stabilization around the same level seen at the end of the salt restriction phase. As salt is primarily stored in bones and extracellular fluids, an increase in salt would be expected to correspond to an increase in extracellular fluid (since the body’s bone mass should change slowly). The bodyweight changes shown in Figure 3 therefore reflect changes in extracellular fluid levels. While salt loading at the levels used in phase III produced a large acute change in body fluids, this was restored to normal over approximately 5 days.

Since my extracellular fluid volume was evidently restored within 5 days, it is not surprising that salt loading had no significant effect on my blood pressure. What is somewhat surprising was that there was no evidence of a temporary increase in blood pressure during the few days in which my extracellular fluid volume was in fact elevated. This suggests that there is an additional regulatory element working to restore blood pressure homeostasis at a shorter time scale than the dominant kidney-fluid mechanism previously discussed on the blog here.

Thanks to Mako Hill for guidance with ggplot2, without which these plots would look less nice.

Discussion

This experiment demonstrated to me that a low carb paleo diet with no added salt is potentially dangerous for me. Impaired thermoregulation is a big deal and would have been a life-threatening issue if I had to hunt for my food in a hot climate. Not only was my body temperature elevated in warm weather, but my pulse was elevated as well, suggesting my cardiovascular system was unable to restore my body temperature to normal. I’m clearly not salt sensitive, and I do not function well with a low salt diet. However, genetic studies suggest the ancestral human genotype is associated with high levels of salt sensitivity and ability to function with very low sodium intakes. How did humans evolve these traits? And why don’t I seem to have them?

A Faustian Kidney Bargain

Susumo Watanabe has proposed in interesting hypothesis about the evolution of sodium metabolism in hominids. The theory is laid out in a 2002 paper called “ Uric Acid, Hominid Evolution, and the Pathogenesis of Salit-Sensitivity,” published in the journal Hypertension. It goes something like this. At some point during the evolution of our common ancestor with gorillas and chimpanzees, a series of mutations inactivated the gene for urate oxidase, an enzyme that breaks down uric acid. As a consequence, we have much higher blood levels of uric acid than other mammals. These mutations seem to have occurred between 24 and 8 million years ago, during the miocene, when our ancestors were believed to be subsisting primarily on fruits and leaves. This diet would have been exceptionally low in sodium. Since there is evidence of multiple independent mutations in this gene in multiple primate lineages, it is thought that mutations deactivating urate oxidase were strongly selected.

In rats, uric acid raises blood pressure acutely, but also causes renal vascular disease via renin/angiotensin systems. This over time makes the rats more salt sensitive. If there is very little salt available, salt sensitivity can be a good thing. Watanabe argues that, where salt is scarce, high uric acid is beneficial (via multiple pathways) for preventing blood pressure from going too low.

In addition to causing kidney disease, high uric acid causes other problems, like gout, and is associated with heart disease. So this looks like an engineering tradeoff with a number of downsides, but some benefits in the context of a miocene diet that was even lower in sodium than the lowest current estimates for paleolithic diets. The organism with this adaptation is supposed to partially destroy its kidneys on purpose in order to maintain sufficiently high blood pressure. This miocene environment is long gone. However, it is much easier to break a gene than to put it back together. Our urate oxidase gene has been broken more than once and it would take quite a long time to fix it.

It’s kind of a crazy theory. I’m not sure I believe it but it is interesting to think about.

Some Hypotheses

During this experiment, I was eating almost exclusively meat, fish (often with bones), eggs and vegetables, plus added calories from butter, coconut oil and olive oil. The diet was grain, legume and dairy free and, as mentioned, possibly ketogenic. This would be considered by many online diet and health personalities to be a good low carb paleo diet, even though of course processed fats like butter and coconut oil are not Paleolithic foods.

So I want to discuss a few possible ways to resolve the apparent impossibility of eating this way without added salt.

Hypothesis 1: Low Carb, Low Crab, or Low Salt: choose any two

I have been eating a low carb diet, and my experiment suggests that, in that context, low salt is not a good idea. It is possible that a healthy human diet can be either low in carbohydrates or low in salt, but not both.

A great deal of evidence suggests that ketosis was not the norm for our paleolithic ancestors (see e.g. Kuipers et. al. 2012 for a thorough review of paleolithic diet research). In fact it would have been quite a struggle for me to eat this sort of macronutrient ratio without modern refined fats such as butter and coconut oil. Or ready access to marine mammal blubber (but then again the Inuit are not my paleolithic ancestors).

In contrast to the online paleo diet scene, most low carb diet advocates seem to line up behind the recommendation for ample supplementary salt. My result accord with that clinical experience. Low carbohydrate diets are usually said to have a diuretic effect in this community, at least in the initial stages (e.g. M.R. Eades, Jenny Ruhl). It is possible that my problems were caused by the interaction between diet-induced ketosis and salt restriction, and I would have done just fine without salt if I had some more carbohydrates. This hypothesis would be straightforward to test.

In order to keep my sodium intake sufficiently low during the salt restriction phase, I had to remove shellfish such as oysters and mussels from my diet. Crab is also salty and makes for a handy pun. It seems likely that daily shellfish consumption would have pushed my sodium intake into the healthy range. While shellfish does not get much attention these days in the paleo club, there is ample support (again see Kuipers et. al.) that it was an important contributor to actual paleolithic nutrition.

Hypothesis 2: Humans must drink blood. Or eat salt.

File this one in the “ teen paranormal romance” department. This hypothesis states that the ancestral human diet was not as low in salt as commonly assumed.

Sodium is the body’s primary extracellular cation, and most of it is located in the blood and other extracellular fluids. A pint of blood contains about 1.6 grams of sodium (see, e.g., these livestock reference ranges for blood sodium). That much blood per day should have been more than enough to push me into the healthy range of sodium consumption. On the other hand, salt depletion set in pretty quickly for me (probably 3-4 days), so this hypothesis assumes that fresh blood was consistently available to inland populations that did not have ready access to shellfish or sea water.

I find this hypothesis intriguing because of the fact that my putative ancestors were commanded not to drink blood (Genesis 9:4, Leviticus 17:13, Deuteronomy 12:15-16), and that salt is used in this tradition specifically to remove blood from meat before it is eaten. Presumably blood drinking was outlawed because it was thought to spread diseases and not because of tacky pop-culture connotations. Were my ancestors salting their meat not just for its preservative qualities, but also to make up for the reduction in sodium intake due to their prohibition on drinking blood?

Hypothesis 3: I’m Not (Genetically) a Paleolithic Human

Some say the human genome has hardly changed in the past 10,000 years. However, the hard evidence points to a number of significant evolutionary changes since the advent of agriculture, the classic example being lactase persistance (see Cochran and Harpending 2009 for a thorough argument on the rapidity of recent human evolution). Genes associated with hypertension and salt sensitivity are also apparently under strong evolutionary pressure. Alan Weder discusses this in an article published in 2007 in the journal Hypertension about evolution and hypertension. It is worth reading as an example of excellent science writing.

My experiment clearly demonstrates that I am not salt sensitive. This is not surprising given my European ancestry. As discussed by Weber, the genetics of salt resistance seem to correlate with adaptations to colder climates. It seems possible that in the course of such adaptation, my ancestors lost the ability to function optimally on a low salt diet.

Is a High Salt Diet Safe?

It is possible that, as much of mainstream medicine believes, a high salt diet actually is unhealthy over the long term. There is nothing in this experiment that contradicts that belief. Just because I am resistant to the short term blood pressure effects of salt loading, that does not mean I am immune to whatever long term negative effects a high salt diet may have. While epidemiological studies have their problems, it seems unwise to discount their findings altogether.

Edward Frohlich has argued that, notwithstanding the fact that most people’s blood pressure does not respond to acute increases in sodium intake, sodium is nevertheless responsible long-term for increases in blood pressure. He argues that excess salt causes kidney damage over time (as with uric acid this is mediated by renin/angiotensin systems), resulting long-term in an increase in blood pressure. While much of this research is based on studies done on rats (including those of the “ spontaneously hypertensive” variety), this line of thought is worth looking into and I will continue to do so.