Traditional Preparation Methods Improve Grains' Nutritive Value

Soaking or Germinating Grains

The most basic method of preparing grains is prolonged soaking in water, followed by cooking. This combination reduces the level of water-soluble and heat-sensitive toxins and anti-nutrients such as tannins, saponins, digestive enzyme inhibitors and lectins, as well as flatulence factors. It also partially degrades phytic acid, which is a potent inhibitor of mineral absorption, an inhibitor of the digestive enzyme trypsin and an enemy of dental health (1). This improves the digestibility and nutritional value of grains as well as legumes.

I prefer to soak all grains and legumes for at least 12 hours in a warm location, preferably 24. This includes foods that most people don't soak, such as lentils. Soaking does not reduce phytic acid at all in grains that have been heat-treated, such as oats and kasha (technically not a grain), because they no longer contain the phytic acid-degrading enzyme phytase. Cooking without soaking first also does not have much effect on phytic acid.

The next level of grain preparation is germination. After soaking, rinse the grains twice per day for an additional day or two. This activates the grains' sprouting program and further increases their digestibility and vitamin content. When combined with cooking, it reduces phytic acid, although modestly. Therefore, most of the minerals in sprouted whole grains will continue to be inaccessible. Many raw sprouted grains and legumes are edible, but I wouldn't use them as a staple food because they retain most of their phytic acid as well as some heat-sensitive anti-nutrients (2).

Grinding and Fermenting Grains

Many cultures around the world have independently discovered fermentation as a way to greatly improve the digestibility and nutritive value of grains (3). Typically, grains are soaked, ground, and allowed to sour ferment for times ranging from 12 hours to several days. In some cases, a portion of the bran is removed before or after grinding.

In addition to the reduction in toxins and anti-nutrients afforded by soaking and cooking, grinding and fermentation goes much further. Grinding greatly increases the surface area of the grains and breaks up their cellular structure, releasing enzymes which are important for the transformation to come. Under the right conditions, which are easy to achieve, lactic acid bacteria rapidly acidify the batter. These bacteria are naturally present on grains, but adding a starter makes the process more efficient and reliable.

Due to some quirk of nature, grain phytase is maximally active at a pH of between 4.5 and 5.5, which is mildly acidic. This is why the Weston Price foundation recommends soaking grains in an acidic medium before cooking. The combination of grinding and sour fermentation causes grains to efficiently degrade their own phytic acid (as long as they haven't been heat treated first), making minerals much more available for absorption (4, 5, 6, 7). This transforms whole grains from a poor source of minerals into a good source.

The degree of phytic acid degradation depends on the starting amount of phytase in the grain. Corn, rice, oats and millet don't contain much phytase activity, so they require either a longer fermentation time, or the addition of high-phytase grains to the batter (8). Whole raw buckwheat, wheat, and particularly rye contain a large amount of phytase (9), although I feel wheat is problematic for other reasons.

As fermentation proceeds, bacteria secrete enzymes that begin digesting the protein, starch and other substances in the batter. Fermentation reduces lectin levels substantially, which are reduced further by cooking (10). Lectins are toxins that can interfere with digestion and may be involved in autoimmune disease, an idea championed by Dr. Loren Cordain. Grain lectins are generally heat-sensitive, but one notable exception is the nasty lectin wheat germ agglutinin (WGA). As its name suggests, WGA is found in wheat germ, and thus is mostly absent in white flour. WGA may have been another reason why DART participants who increased their wheat fiber intake had significantly more heart attacks than those who didn't. I don't know if fermentation degrades WGA.

One of the problems with grains is their poor protein quality. Besides containing a fairly low concentration of protein to begin with, they also don't contain a good balance of essential amino acids. This prevents their efficient use by the body, unless a separate source of certain amino acids is eaten along with them. The main limiting amino acid in grains is lysine. Legumes are rich in lysine, which is why cultures around the world pair them with grains. Bacterial fermentation produces lysine, often increasing its concentration by many fold and making grains nearly a "complete protein", i.e. one that contains the ideal balance of essential amino acids as do animal proteins (11, scroll down to see graph). Not very many plant foods can make that claim. Fermentation also increases the concentration of the amino acid methionine and certain vitamins.

Another problem with grain protein is it's poorly digested relative to animal protein. This means that a portion of it escapes digestion, leading to a lower nutritive value and a higher risk of allergy due to undigested protein hanging around in the digestive tract. Fermentation followed by cooking increases the digestibility of grain protein, bringing it nearly to the same level as meat (12, 13, 14, 15). This may relate to the destruction of protease inhibitors (trypsin inhibitors, phytic acid) and the partial pre-digestion of grain proteins by bacteria.

Once you delve into the research on traditional grain preparation methods, you begin to see why grain-eating cultures throughout the world have favored certain techniques. Proper grain processing transforms them from toxic to nutritious, from health-degrading to health-giving. Modern industrial grain processing has largely eschewed these time-honored techniques, replacing them with low-extraction milling, extrusion and quick-rise yeast strains.

Many people will not be willing to go through the trouble of grinding and fermentation to prepare grains. I can sympathize, although if you have the right tools, once you establish a routine it really isn't that much work. It just requires a bit of organization. In fact, it can even be downright convenient. I often keep a bowl of fermented dosa or buckwheat batter in the fridge, ready to make a tasty "pancake" at a moment's notice. In the next post, I'll describe a few recipes from different parts of the world.

Further reading:

How to Eat Grains
A Few Thoughts on Minerals, Milling, Grains and Tubers
Dietary Fiber and Mineral Availability
A New Way to Soak Brown Rice

Blood glucose variations in normal individuals: A chaotic mess

I love statistics. But statistics is the science that will tell you that each person in a group of 20 people ate half a chicken per week over six months, until you realize that 10 died because they ate nothing while the other 10 ate a full chicken every week.

Statistics is the science that will tell you that there is an “association” between these two variables: my weight from 1 to 20 years of age, and the price of gasoline during that period. These two variables are indeed highly correlated, by neither has influenced the other in any way.

This is why I often like to see the underlying numbers when I am told that such and such health measure on average is this or that, or that this or that disease is associated with elevated consumption of whatever. Statistical results must be interpreted carefully. Lying with statistics is very easy.

A case in point is that of blood glucose variations among normal individuals. Try plotting them on graphs. What do you see? A chaotic mess, even when the individuals are pre-screened to exclude anybody with blood glucose abnormalities that would even hint at pre-diabetes. You see wild fluctuations that, while not going up to levels like 200 mg/dl, are much less predictable than many people are told they should be.

Blood glucose levels are influenced by so many factors (Elliott & Elliott, 2009) that I would be surprised if they were as smooth as those in graphs that are frequently used to show how blood glucose is supposed to vary in healthy individuals. Often we see a flat line up until the time of a meal, when the line curves up rapidly and then goes down quickly. It usually peaks at around 140 mg/dl, dropping well below 120 mg/dl after 2 hours.

Those smooth graphs are usually obtained through algorithms that have statistical methods at their core. The algorithms are designed to generate a smooth representations of scattered or disorganized data points. A little bit like the algorithms in software tools that plot best-fit regression curves passing through scattered points (e.g., warppls.com).

The picture below (click on it to enlarge) is from a 2006 symposium presentation by Prof. J.S. Christiansen, who is a widely cited diabetes researcher. The whole presentation is available from: www.diabetes-symposium.org. It shows the blood glucose variations of 21 young and normal individuals, based on data collected over a period of 2 days. Each individual is represented by a different color. The points on each curve are actually averages of two blood glucose measurements; the original measurements themselves vary even more chaotically.

As you can see from the picture above, each individual has a unique set of responses to main meals, which are represented by the three main blood glucose peaks. Overall, blood glucose levels vary from about 50 to 170 mg/dl, and in several cases remain above 120 mg/dl after 2 hours since a large meal. They vary somewhat chaotically during the night as well, often getting up to around 110 mg/dl.

And these are only 21 individuals, not 100 or 1000. Again, these individuals were all normal (i.e., normoglycemic, in medical research parlance), with an average glycated hemoglobin (HbA1c) of 5 percent, and a range of variation of HbA1c of 4.3 to 5.4 percent.

We can safely assume that these individuals were not on a low carbohydrate diet. The spikes in blood glucose after meals suggest that they were eating foods loaded with refined carbohydrates and/or sugars, particularly for breakfast. So, we can also safely assume that they were somewhat "desensitized" (in terms of glucose response) to those types of foods. Someone who had been on a low carbohydrate diet for a while, and who would thus be more sensitive, would have had even wilder blood glucose variations in response to the same meals.

Many people measure their glucose levels throughout the day with portable glucometers, and quite a few are likely to self-diagnose as pre-diabetics when they see something that they think is a “red flag”. Examples are a blood glucose level peaking at 165 mg/dl, or remaining above 120 mg/dl after 2 hours passed since a meal. Another example is a level of 110 mg/dl when they wake up very early to go to work, after several hours of fasting.

As you can see from the picture above, these “red flag” events do occur in young normoglycemic individuals.

If seeing “red flags” helps people remove refined carbohydrates and sugars from their diet, then fine.

But it may also cause them unnecessary chronic stress, and stress can kill.

Reference:

Elliott, W.H., & Elliott, D.C. (2009). Biochemistry and molecular biology. 4th Edition. New York: NY: Oxford University Press.

Tender cuts of meat for the grill: Filet mignon and bison

Filet mignon is one of the tenderest cuts of beef. It is also one of my favorites. Filet mignon comes from the tenderloin area (see this picture), which is not a weight-bearing area and thus is very tender. The bison cuts I get here in South Texas are close in terms of tenderness, but not as tender, probably because they are from the round area.

One steak of either filet mignon or bison will yield about 100 g of cooked meat, with 30 g of protein and 10 g of fat. About half of that fat will be saturated and half monounsaturated (as in olive oil). It will provide you with plenty of vitamins (particular B vitamins) and minerals. Good amounts of selenium, phosphorus, zinc and potassium.

On the photo below (click on it to enlarge), the bison steak is at the top. The other pieces are all filet mignon cuts. They are all medium-cooked. I cooked two plates of these, for 6 people. All ate to satisfaction, with a side salad. The leftovers are delicious for breakfast in small amounts.

For the filet mignon, I think you really have to go to a specialty meats store (butcher) and make sure that they cut the smaller tail end of the tenderloin muscle. You will be paying a lot for it, so it makes sense to be choosy. Experience butchers will cut it right in front of you and won’t mind your choosiness.

Below is a simple recipe; simple like most of the recipes on this blog. I like my meals quick and delicious.

- Prepare some dry seasoning powder by mixing sea salt, garlic power, chili powder, and a small amount of cayenne pepper.
- Season the steaks at least 2 hours prior to placing them on the grill.
- Grill with the lid on, checking the meat every 10 minutes or so. (I use charcoal, one layer only to avoid burning the surface of the meat.) Turn it frequently, always putting the lid back on.
- If you like it rare, 20 minutes (or a bit less) may be enough.

These are as tender as any piece of beef can possibly get. No need for any tenderizer juices during seasoning. If you are doing both filet mignon and bison together, either eat only bison or bison first. Because once you taste the filet mignon, the bison cut may taste a bit hard!

For me the filet mignon is a 10-dollar per pound treat for special occasions. The price of the bison cut is about the same, at least here in Laredo, Texas, where I get it shipped from Dakota via my local supermarket. You can also get it online.

By the way, some folks like to say that bison is the “salmon of the prairie”. This is in reference to bison’s omega-3 content. Well, here is the polyunsaturated fatty acid composition of 100 g of bison steak: 29 mg of omega-3, and 197 mg of omega-6. For salmon it is 1424 mg of omega-3, and 113 mg of omega-6.

Salmon of the prairie or not, I love it!

Grains as Food: an Update

Improperly Prepared Grain Fiber can be Harmful

Last year, I published a post on the Diet and Reinfarction trial (DART), a controlled trial that increased grain fiber intake using whole wheat bread and wheat bran supplements, and reported long-term health outcomes in people who had previously suffered a heart attack (1). The initial paper found a trend toward increased heart attacks and deaths in the grain fiber-supplemented group at two years, which was not statistically significant.

What I didn't know at the time is that a follow-up study has been published. After mathematically "adjusting" for preexisting conditions and medication use, the result reached statistical significance: people who increased their grain fiber intake had more heart attacks than people who didn't during the two years of the controlled trial. Overall mortality was higher as well, but that didn't reach statistical significance. You have to get past the abstract of the paper to realize this, but fortunately it's free access (2).

Here's a description of what not to eat if you're a Westerner with established heart disease:

Those randomised to fibre advice were encouraged to eat at least six slices of wholemeal bread per day, or an equivalent amount of cereal fibre from a mixture of wholemeal bread, high-fibre breakfast cereals and wheat bran.

Characteristics of Grain Fiber

The term 'fiber' can refer to many different things. Dietary fiber is simply defined as an edible substance that doesn't get digested by the human body. It doesn't even necessarily come from plants. If you eat a shrimp with the shell on, and the shell comes out the other end (which it will), it was fiber.

Grain fiber is a particular class of dietary fiber that has specific characteristics. It's mostly cellulose (like wood; although some grains are rich in soluble fiber as well), and it contains a number of defensive substances and storage molecules that make it more difficult to eat. These may include phytic acid, protease inhibitors, amylase inhibitors, lectins, tannins, saponins, and goitrogens (3). Grain fiber is also a rich source of vitamins and minerals, although the minerals are mostly inaccessible due to grains' high phytic acid content (4, 5, 6).

Every plant food (and some animal foods) has its chemical defense strategy, and grains are no different*. It's just that grains are particularly good at it, and also happen to be one of our staple foods in the modern world. If you don't think grains are naturally inedible for humans, try eating a heaping bowl full of dry, raw whole wheat berries.

Human Ingenuity to the Rescue

Humans are clever creatures, and we've found ways to use grains as a food source, despite not being naturally adapted to eating them**. The most important is our ability to cook. Cooking deactivates many of the harmful substances found in grains and other plant foods. However, some are not deactivated by cooking. These require other strategies to remove or deactivate.

Healthy grain-based cultures don't prepare their grains haphazardly. Throughout the world, using a number of different grains, many have arrived at similar strategies for making grains edible and nutritious. The most common approach involves most or all of these steps:

• Soaking
  
• Grinding
• Removing 50-75% of the bran
  
• Sour fermentation
• Cooking
  

But wait, didn't all healthy traditional cultures eat whole grains? The idea might make us feel warm and fuzzy inside, but it doesn't quite hit the mark. A recent conversation with Ramiel Nagel, author of the book Cure Tooth Decay, disabused me of that notion. He pointed out that in my favorite resource on grain preparation in traditional societies, the Food and Agriculture Organization publication Fermented Cereals: a Global Perspective, many of the recipes call for removing a portion of the bran (7). Some of these recipes probably haven't changed in thousands of years. It's my impression that some traditional cultures eat whole grains, while others eat them partially de-branned.

In the next post, I'll explain why these processing steps greatly improve the nutritional value of grains, and I'll describe recipes from around the world to illustrate the point.


* Including tubers. For example, sweet potatoes contain goitrogens, oxalic acid, and protease inhibitors. Potatoes contain toxic glycoalkaloids. Taro contains oxalic acid and protease inhibitors. Cassava contains highly toxic cyanogens. Some of these substances are deactivated by cooking, others are not. Each food has an associated preparation method that minimizes its toxic qualities. Potatoes are peeled, removing the majority of the glycoalkaloids. Cassava is grated and dried or fermented to inactivate cyanogens. Some cultures ferment taro.

** As opposed to mice, for example, which can survive on raw whole grains.

Blood glucose control before age 55 may increase your chances of living beyond 90

I have recently read an interesting study by Yashin and colleagues (2009) at Duke University’s Center for Population Health and Aging. (The full reference to the article, and a link, are at the end of this post.) This study is a gem with some rough edges, and some interesting implications.

The study uses data from the Framingham Heart Study (FHS). The FHS, which started in the late 1940s, recruited 5209 healthy participants (2336 males and 2873 females), aged 28 to 62, in the town of Framingham, Massachusetts. At the time of Yashin and colleagues’ article publication, there were 993 surviving participants.

I rearranged figure 2 from the Yashin and colleagues article so that the two graphs (for females and males) appeared one beside the other. The result is shown below (click on it to enlarge); the caption at the bottom-right corner refers to both graphs. The figure shows the age-related trajectory of blood glucose levels, grouped by lifespan (LS), starting at age 40.

As you can see from the figure above, blood glucose levels increase with age, even for long-lived individuals (LS > 90). The increases follow a U-curve (a.k.a. J-curve) pattern; the beginning of the right side of a U curve, to be more precise. The main difference in the trajectories of the blood glucose levels is that as lifespan increases, so does the width of the U curve. In other words, in long-lived people, blood glucose increases slowly with age; particularly up to 55 years of age, when it starts increasing more rapidly.

Now, here is one of the rough edges of this study. The authors do not provide standard deviations. You can ignore the error bars around the points on the graph; they are not standard deviations. They are standard errors, which are much lower than the corresponding standard deviations. Standard errors are calculated by dividing the standard deviations by the square root of the sample sizes for each trajectory point (which the authors do not provide either), so they go up with age since progressively smaller numbers of individuals reach advanced ages.

So, no need to worry if your blood glucose levels are higher than those shown on the vertical axes of the graphs. (I will comment more on those numbers below.) Not everybody who lived beyond 90 had a blood glucose of around 80 mg/dl at age 40. I wouldn't be surprised if about 2/3 of the long-lived participants had blood glucose levels in the range of 65 to 95 at that age.

Here is another rough edge. It is pretty clear that the authors’ main independent variable (i.e., health predictor) in this study is average blood glucose, which they refer to simply as “blood glucose”. However, the measure of blood glucose in the FHS is a very rough estimation of average blood glucose, because they measured blood glucose levels at random times during the day. These measurements, when averaged, are closer to fasting blood glucose levels than to average blood glucose levels.

A more reliable measure of average blood glucose levels is that of glycated hemoglobin (HbA1c). Blood glucose glycates (i.e., sticks to, like most sugary substances) hemoglobin, a protein found in red blood cells. Since red blood cells are relatively long-lived, with a turnover of about 3 months, HbA1c (given in percentages) is a good indicator of average blood glucose levels (if you don’t suffer from anemia or a few other blood abnormalities). Based on HbA1c, one can then estimate his or her average blood glucose level for the previous 3 months before the test, using one of the following equations, depending on whether the measurement is in mg/dl or mmol/l.

    Average blood glucose (mg/dl) = 28.7 × HbA1c − 46.7

    Average blood glucose (mmol/l) = 1.59 × HbA1c − 2.59

The table below, from Wikipedia, shows average blood glucose levels corresponding to various HbA1c values. As you can see, they are generally higher than the corresponding fasting blood glucose levels would normally be (the latter is what the values on the vertical axes of the graphs above from Yashin and colleagues’ study roughly measure). This is to be expected, because blood glucose levels vary a lot during the day, and are often transitorily high in response to food intake and fluctuations in various hormones. Growth hormone, cortisol and noradrenaline are examples of hormones that increase blood glucose. Only one hormone effectively decreases blood glucose levels, insulin, by stimulating glucose uptake and storage as glycogen and fat.

Nevertheless, one can reasonably expect fasting blood glucose levels to have been highly correlated with average blood glucose levels in the sample. So, in my opinion, the graphs above showing age-related blood glucose trajectories are still valid, in terms of their overall shape, but the values on the vertical axes should have been measured differently, perhaps using the formulas above.

Ironically, those who achieve low average blood glucose levels (measured based on HbA1c) by adopting a low carbohydrate diet (one of the most effective ways) frequently have somewhat high fasting blood glucose levels because of physiological (or benign) insulin resistance. Their body is primed to burn fat for energy, not glucose. Thus when growth hormone levels spike in the morning, so do blood glucose levels, as muscle cells are in glucose rejection mode. This is a benign version of the dawn effect (a.k.a. dawn phenomenon), which happens with quite a few low carbohydrate dieters, particularly with those who are deep in ketosis at dawn.

Yashin and colleagues also modeled relative risk of death based on blood glucose levels, using a fairly sophisticated mathematical model that takes into consideration U-curve relationships. What they found is intuitively appealing, and is illustrated by the two graphs at the bottom of the figure below. The graphs show how the relative risks (e.g., 1.05, on the topmost dashed line on the both graphs) associated with various ranges of blood glucose levels vary with age, for both females and males.

What the graphs above are telling us is that once you reach old age, controlling for blood sugar levels is not as effective as doing it earlier, because you are more likely to die from what the authors refer to as “other causes”. For example, at the age of 90, having a blood glucose of 150 mg/dl (corrected for the measurement problem noted earlier, this would be perhaps 165 mg/dl, from HbA1c values) is likely to increase your risk of death by only 5 percent. The graphs account for the facts that: (a) blood glucose levels naturally increase with age, and (b) fewer people survive as age progresses. So having that level of blood glucose at age 60 would significantly increase relative risk of death at that age; this is not shown on the graph, but can be inferred.

Here is a final rough edge of this study. From what I could gather from the underlying equations, the relative risks shown above do not account for the effect of high blood glucose levels earlier in life on relative risk of death later in life. This is a problem, even though it does not completely invalidate the conclusion above. As noted by several people (including Gary Taubes in his book Good Calories, Bad Calories), many of the diseases associated with high blood sugar levels (e.g., cancer) often take as much as 20 years of high blood sugar levels to develop. So the relative risks shown above underestimate the effect of high blood glucose levels earlier in life.

Do the long-lived participants have some natural protection against accelerated increases in blood sugar levels, or was it their diet and lifestyle that protected them? This question cannot be answered based on the study.

Assuming that their diet and lifestyle protected them, it is reasonable to argue that: (a) if you start controlling your average blood sugar levels well before you reach the age of 55, you may significantly increase your chances of living beyond the age of 90; (b) it is likely that your blood glucose levels will go up with age, but if you can manage to slow down that progression, you will increase your chances of living a longer and healthier life; (c) you should focus your control on reliable measures of average blood glucose levels, such as HbA1c, not fasting blood glucose levels (postprandial glucose levels are also a good option, because they contribute a lot to HbA1c increases); and (d) it is never too late to start controlling your blood glucose levels, but the more you wait, the bigger is the risk.

References:

Taubes, G. (2007). Good calories, bad calories: Challenging the conventional wisdom on diet, weight control, and disease. New York, NY: Alfred A. Knopf.

Yashin, A.I., Ukraintseva, S.V., Arbeev, K.G., Akushevich, I., Arbeeva, L.S., & Kulminski, A.M. (2009). Maintaining physiological state for exceptional survival: What is the normal level of blood glucose and does it change with age? Mechanisms of Ageing and Development, 130(9), 611-618.

There are more geniuses among men than among women, and more idiots too

Deary and colleagues (2007) conducted an interesting study on differences in intelligence scores among men and women. In the context of this blog, this study highlights yet one more counterintuitive and intriguing aspect of Darwinian evolution, adding to points previously made in other posts (see here, and here). Evolution may look simple at first glance, but that is a bit of a mirage. In my opinion, to really understand it one has to understand the mathematics underlying it, a lot of which comes from the field of population genetics.

What makes the study by Deary and colleagues (2007) particularly interesting is that its participants were opposite-sex siblings. This helped control for the influence of environmental factors. The downside is that the effect sizes might have been decreased, because of the high gene correlation among siblings, so we could expect larger differences between unrelated groups of men women. The differences, as you will see, are not in overall scores, but in score dispersion.

Let us get straight to the point made by the study. On average, men and women seem to score equally well on intelligence tests. The main difference is that there is more variation in the scores achieved by men than by women, which leads to an interesting effect: there are more geniuses and more idiots among men than among women.

This does NOT mean that a man’s genius is of a higher order; just that there is a tendency for more men to be geniuses (and idiots) than women in any random population sample. The women who are geniuses can be super geniuses, like two-time Nobel Prize winner Marie Curie, the first PERSON to receive such an honor. Albert Einstein is said that have greatly admired her intelligence.

As an illustration of this score dispersion effect, Deary and colleagues (2007) note that: “… for example, in terms of indices of scientific achievement, men were awarded 545 out of the 557 Nobel prizes awarded for science.” On the “idiot” end of the scale: there are a lot more men than women in prison, and one common denominator of prison inmates is that they tend to score very low on intelligence tests. (This is not to say that all criminals have low intelligence; perhaps mostly the ones that get caught do.)

Having said that, it is important to acknowledge that there are multiple types of intelligence, and even multi-indicator intelligence coefficients are usually poor approximations of an overall measure of intelligence (if there is one). This does not invalidate the main point of this post, which is related to score variability.

The table below (from: Deary and colleagues, 2007; click on it to enlarge; full reference at the end of this post) shows scores obtained by men and women (1,292 pairs of opposite-sex siblings) in various subtests of the Armed Services Vocational Aptitude Battery (ASVAB) test.

Note that nearly all of the differences between means (i.e., averages) are significant, but the direction of the differences (captured by the signs of the Cohen’s d coefficients, which are measures of effect size) varies a lot. That is, on several subtests (e.g., “Arithmetic”) men score higher, but in others (e.g., “Numerical operations”) women score higher. It all comes down to men and women scoring equally well overall.

Now look at the columns showing the standard deviations (“SD”) for men and women. In all subtests but two (“Coding speed” and “Numerical operations”) the standard deviation is higher for men; in many cases significantly higher (e.g., 44 percent higher for “Mechanical comprehension”). The standard deviations are about the same for “Coding speed” and “Numerical operations”. What this means is that variability in scores is nearly always higher, often significantly higher, among men than among women. I prepared the schematic figure below to illustrate the effect that this has on the numbers of individuals at the extremes.

The figure above shows two (badly drawn) quasi-normal distributions of scores. (This post shows a better illustration of a normal distribution.) The red curve refers to a distribution with a lower standard deviation than the blue curve; the latter is flatter. Each point on a curve reflects the number of individuals obtaining a particular score, which would be indicated on the horizontal axis. The number of individuals with that score is on the vertical axis. As you can see, the numbers of individuals scoring very high and low (geniuses and idiots, if the scores reflected intelligence) are greater for the blue curve, which is the curve with the higher standard deviation (higher dispersion of scores). The farther one goes to the left or right (the extremes), the bigger this difference becomes.

What does this have to do with evolution?

Well, there are a few possibilities, two of which appear to be particularly compelling. Maybe this effect is due to a combination of these two.

One is that ancestral women, like women today, selected mating partners based on a wide range of traits. Ancestral men on the other hand, like modern men, focused on a much smaller set of traits (Buss, 1995). The end result is more variation in traits, generally speaking, among men than among women. This refers to traits in general, not only intelligence. For example, there seems to be more variation in height among men than among women.

The other possible explanation is that, in our ancestral past, staying out of the extremes of intelligence was associated with higher survival success in both sexes. It seems that the incidence of certain types of mental disease (e.g., schizophrenia) is quite high among geniuses. This leads to more deaths due to related issues – suicide, depression leading to the metabolic syndrome, etc. And this is today, where geniuses can find many opportunities to “shine” in our complex urban societies. In our ancestral past the cognitive demands would have been much lower, and so would the practical value of being a genius.

If staying out of the extremes has indeed enhanced survival success in our evolutionary past, then it is reasonable to expect more women to fit that pattern than men. As with almost any “thing” that enhances survival success, women (especially pre-menopausal) naturally have more of that “thing” than men (e.g., HDL cholesterol).

The reason is that women are more important for the survival of any population than men; today and 1 million years ago. A population of 99 women and 1 man can potentially generate 99 children every few years. Here inbreeding in subsequent generations will be a problem, but that is better than extinction. A population with 99 women and 99 men (or even 1,000 men) will not generate significantly more children.

Reference:

Buss, D.M. (2003). The evolution of desire: Strategies of human mating. New York, NY: Basic Books.

Deary, I.J., Irwing, P., Der, G., & Bates, T.C. (2007). Brother–sister differences in the g factor in intelligence: Analysis of full, opposite-sex siblings from the NLSY1979. Intelligence, 35(5), 451-456.

Interesting links

Media

Health Data Analysis with HCE
  http://youtu.be/fvGmBEaX-4E

Managing Multiple Health Variables with HCE
  http://youtu.be/CjbDduHt4z0

Ned Kock interviewed on Episode 477 of The Livin’ La Vida Low-Carb Show with Jimmy Moore
  http://www.thelivinlowcarbshow.com/shownotes/4180/477-ned-kock-low-carb-blogger/

Reality check

Many people fall prey to scams that are presented as valid alternative medicine options for diseases that are psychosomatic in nature. The sites below can be helpful in avoiding these scams.

Quackwatch
  http://www.quackwatch.org

Somatic symptom disorder
  http://en.wikipedia.org/wiki/Psychosomatic_Illness

Various health sites

Below is a list of links to web sites that deal with health issues in general. These have been moved from the previous “favorite links” area to this post so that some space could be saved on the main page of the blog. Some of these sites are excellent sources of research-based and reliable information. Others are somewhat light in content, but still interesting.

Alan Aragon
  http://www.alanaragon.com/

Animal Pharm
  http://drbganimalpharm.blogspot.com/

Ancestralize Me!
  http://www.ancestralizeme.com/

Anthony Colpo
  http://anthonycolpo.com/

Arthur De Vany
  http://www.arthurdevany.com/

At Darwin's Table
  http://darwinstable.wordpress.com/

Athletics by Nature
  http://gregcarver.com/blog

Barefoot Ted's Adventures
  http://barefootted.com/

Beef and Whiskey
  http://beefandwhiskey.com/

Big Muscles Fast
  http://www.bigmusclesfast.com/

Blaine's Low Carb Kitchen
  http://fittv.discovery.com/fansites/blaine/recipes/recipes.html

Blood Sugar 101
  http://www.phlaunt.com/diabetes

Bob Delmonteque

  http://www.bobdelmonteque.com/

Body by Science
  http://www.bodybyscience.net

Body Recomposition

  http://www.bodyrecomposition.com/

Brad Pilon's Blog
  http://bradpilon.com/

Canibais e Reis
  http://www.canibaisereis.com/

Cholesterol and Health
  http://www.cholesterol-and-health.com/

Colorado State University's Physiologic Effects of Insulin
  http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/insulin_phys.html

Conditioning Research
  http://conditioningresearch.blogspot.com/

Cooling Inflammation
  http://coolinginflammation.blogspot.com/

Cut the Carb
  http://www.cutthecarb.com/

David Mendosa
  http://www.healthcentral.com/diabetes/c/17

Diabetes Update
  http://diabetesupdate.blogspot.com/

Diet Doctor
  http://www.dietdoctor.com

Discover Magazine Online
  http://discovermagazine.com/

Dr. Bernstein's Diabetes Solution
  http://diabetes-book.com/

Dr. Gabe Mirkin
  http://www.drmirkin.com/

Dr. Michael R. Eades
  http://www.proteinpower.com/drmike

Dr. Nemechek's Integrative Medicine
  http://www.nemechekconsultativemedicine.com

Dr. Ron Rosedale
  http://www.drrosedale.com/

Entropy Production
  http://entropyproduction.blogspot.com/

Ernestine Shepherd
  http://ernestineshepherd.net

Evolution for Everyone
  http://scienceblogs.com/evolution/

Evolutionary Psychiatry
  http://evolutionarypsychiatry.blogspot.com/

Evolving Thoughts by John Wilkins
  http://evolvingthoughts.net

Exercise Prescription on the Net
  http://www.exrx.net/

Experiments in Lifestyle Design by Tim Ferriss
  http://www.fourhourworkweek.com/blog/

Fat Head
  http://www.fathead-movie.com/

Fit 2 Fat 2 Fit
  http://www.fit2fat2fit.com

Free the Animal
  http://freetheanimal.com/

Grassroots Health
  http://www.grassrootshealth.net/

Girl Gone Primal
  http://girlgoneprimal.blogspot.com/

Gnolls by J. Stanton
  http://www.gnolls.org

Health News Review
  http://healthnewsreview.org/

Healthcare Epistemocrat
  http://epistemocrat.blogspot.com/

Heretic
  http://stan-heretic.blogspot.com/

Homo Consumericus
  http://www.psychologytoday.com/blog/homo-consumericus

Hunt, Gather, Love
  http://huntgatherlove.com/

Hunter Gatherer
  http://hunter-gatherer.com/

Hyperlipid
  http://high-fat-nutrition.blogspot.com/

ItsTheWooo's The Scribble Pad
  http://itsthewooo.blogspot.com/

John Hawks Weblog
  http://johnhawks.net/weblog

Julianne's Paleo & Zone Nutrition Blog
  http://paleozonenutrition.wordpress.com/

Lean Gains
  http://www.leangains.com/

Low-Carb for You
  http://lowcarb4u.blogspot.com/

Lucas Tafur
  http://www.lucastafur.com

Mark's Daily Apple
  http://www.marksdailyapple.com/

Matt Metzgar's Blog
  http://www.mattmetzgar.com/

Maxwell Murphy
  http://maxwellmurphy.typepad.com/

Metabolism Society
  http://nmsociety.org/

Michael Barker's Type 2 Ketosis Prone Diabetes
  http://ketosisprone.blogspot.com/

Muscle and the City
  http://www.muscleandthecity.com/

MuscleHack
  http://www.musclehack.com/

My Carb Sane-Asylum
  http://carbsanity.blogspot.com/

My Carb Sane Chronicles
  http://carbsanitychronicles.blogspot.com/

Natural Messiah
  http://naturalmessiah.blogspot.com/

Nephropal
  http://nephropal.blogspot.com/

Nigee's Diet & Nutrition Blog
  http://nigeepoo.blogspot.com/

Nourishing by Heart
  http://lunchwithouted.wordpress.com/

Nutrition and Physical Regeneration
  http://nutrition-and-physical-regeneration.com/blog

Nutrition, Health & Heart Disease
  http://www.health-heart.org/

Omega-6 Fat News Commentary
  http://omega-6-omega-3-balance.omegaoptimize.com/

Paleo Clinic
  http://paleoclinic.blogspot.com/

Paleo Diet
  http://paleodiet.com/

Paleo Hacks
  http://paleohacks.com/

PaleoFitMD
  http://paleofitmd.tumblr.com/

Patrick Ward's Optimum Sports Performance
  http://optimumsportsperformance.com/blog/

Pay Now Live Later
  http://paynowlivelater.blogspot.com/

Philosophy of Weight Management
  http://philosophyofweightmanagement.blogspot.com

Prague Stepchild
  http://praguestepchild.blogspot.com/

Primal Montain
  http://www.primalmountain.com/c/blog/

Primal Wisdom
  http://donmatesz.blogspot.com/

Principle Into Practice
  http://principleintopractice.com

Protein Power
  http://www.proteinpower.com/

PāNu
  http://www.paleonu.com/

Rambling Outside the Box
  http://ramblingoutsidethebox.blogspot.com/

Ramblings of a Carnivore
  http://ramblingsofacarnivore.blogspot.com/

Raw Food SOS
  http://rawfoodsos.com/

Ray Peat
  http://raypeat.com/

Robb Wolf
  http://robbwolf.com/

Ron Brown's The Myth of Loose Skin
  http://www.bodyfatguide.com/LooseSkin.htm

Sandwalk by Laurence Moran
  http://sandwalk.blogspot.com

Scooby's Home Bodybuilding Workouts
  http://www.scoobysworkshop.com/

Seth Roberts's Blog
  http://blog.sethroberts.net

Skyler Tanner
  http://skylertanner.com

Sock Doc - Natural Injury Treatment & Prevention
  http://sock-doc.com

Son of Grok
  http://www.sonofgrok.com/

Spark of Reason
  http://sparkofreason.blogspot.com/

Stella Style
  http://stellastyle.com/

Survivorman - Discovery
  http://dsc.discovery.com/fansites/survivorman/survivorman.html

That Paleo Guy
  http://thatpaleoguy.com

The Carnivore Health Weblog
  http://www.carnivorehealth.com

The Daily Lipid
  http://www.cholesterol-and-health.com/cholesterol-blog.html

The Evolution & Medicine Review
  http://evmedreview.com/

The Heart Scan
  http://heartscanblog.blogspot.com/

The Healthy Skeptic
  http://thehealthyskeptic.org/

The Livin' La Vida Low-Carb Show
  http://www.thelivinlowcarbshow.com/shownotes

The Paleo Diet
  http://www.thepaleodiet.com/

The Paleo Diet Blog

  http://thepaleodiet.blogspot.com/

The Queso Files
  http://dibruno.blogspot.com/

The Weston A. Price Foundation
  http://www.westonaprice.org/

Theory to Practice
  http://theorytopractice.wordpress.com/

Vitamin D Council
  http://www.vitamindcouncil.org/

Vitamin D Wiki
  http://www.vitamindwiki.com/

Weightology
  http://weightology.net/

Whole Health Source
  http://wholehealthsource.blogspot.com/

Wikipedia - Strength Training
  http://en.wikipedia.org/wiki/Strength_training

Wildly Fluctuating
  http://wildlyfluctuating.blogspot.com/

Zero Currency, Moneyless World - By Daniel Suelo
  http://zerocurrency.blogspot.com/

Zeroing in on Recovery
  http://malpaz.wordpress.com/

Zoe Harcombe
  http://www.zoeharcombe.com/

180 Degree Health
  http://180degreehealth.blogspot.com/