The Omega Ratio

The theory advanced by Dr. Lands and Hibbeln is that the ratio of omega-6 to omega-3 fatty acids in the diet is the crucial factor for mental and physical health, rather than the absolute amount of each. Omega-6 and -3 fats are essential long-chain polyunsaturated fatty acids. The number refers to the position of the double bond near the methyl end of the carbon chain.

The ratio of omega-6 to omega-3 (hereafter, n-6 and n-3) in the diet determines the ratio in tissues. Since these molecules have many cellular roles, it doesn't stretch the imagination that they could have an effect on health. Hunter-gatherer and healthy non-industrial cultures typically have a favorable ratio of n-6 to n-3, 2:1 or less. In the US, the ratio is currently about 17:1 due to modern vegetable oils.

DHA, a long-chain n-3 fatty acid, is concentrated in neuronal synapses (the connections between neurons) and is required for the normal functioning of neurons. n-6 fats compete with n-3 fats for space in cellular membranes (which have a fixed amount of total polyunsaturated fat), so a high intake of n-6 fats, particularly linoleic acid, displaces n-3 fatty acids. Lower tissue levels of DHA and total n-3 correlate with measures of hostility in cocaine addicts. Feeding mice a diet high in linoleic acid increases aggressive behavior, and increses the likelihood of rats to kill mice.

If the ratio of n-6 to n-3 in the diet predicts psychiatric problems, we'd expect to see an association with n-3 intake as well. Let's take a look:

This is homicide mortality vs. n-3 intake for 24 countries, published here. The association is significant (p> 0.001) even without correcting for n-6 intake. Of course, one could see this as a cloud of points with a few well-placed outliers. Here are some closer associations from the same paper:

It's clear that both a high n-6 intake and a low n-3 intake correlate with negative psychiatric outcomes. Together, the data are consistent with the hypothesis that the ratio of n-6 to n-3 impacts brain function. Dr. Hibbeln and Dr. Lands do not claim that this ratio is the sole determinant of psychiatric problems, only that it is a factor.

Now to address the big criticism that was brought up by very astute readers of the last post, namely, that the data were purely correlative. Believe me, I wouldn't even have posted on this topic if I didn't have intervention data to back it up. In addition to the animal data I mentioned above, here are more studies that support a causal role of fatty acid balance in psychiatric problems:
Most of those were placebo-controlled trials. If we can see a significant effect of n-3 supplementation in short-term trials, imagine how well it would work as a long-term preventive measure.

The Omega Ratio

The theory advanced by Dr. Lands and Hibbeln is that the ratio of omega-6 to omega-3 fatty acids in the diet is the crucial factor for mental and physical health, rather than the absolute amount of each. Omega-6 and -3 fats are essential long-chain polyunsaturated fatty acids. The number refers to the position of the double bond near the methyl end of the carbon chain.

The ratio of omega-6 to omega-3 (hereafter, n-6 and n-3) in the diet determines the ratio in tissues. Since these molecules have many cellular roles, it doesn't stretch the imagination that they could have an effect on health. Hunter-gatherer and healthy non-industrial cultures typically have a favorable ratio of n-6 to n-3, 2:1 or less. In the US, the ratio is currently about 17:1 due to modern vegetable oils.

DHA, a long-chain n-3 fatty acid, is concentrated in neuronal synapses (the connections between neurons) and is required for the normal functioning of neurons. n-6 fats compete with n-3 fats for space in cellular membranes (which have a fixed amount of total polyunsaturated fat), so a high intake of n-6 fats, particularly linoleic acid, displaces n-3 fatty acids. Lower tissue levels of DHA and total n-3 correlate with measures of hostility in cocaine addicts. Feeding mice a diet high in linoleic acid increases aggressive behavior, and increses the likelihood of rats to kill mice.

If the ratio of n-6 to n-3 in the diet predicts psychiatric problems, we'd expect to see an association with n-3 intake as well. Let's take a look:

This is homicide mortality vs. n-3 intake for 24 countries, published here. The association is significant (p> 0.001) even without correcting for n-6 intake. Of course, one could see this as a cloud of points with a few well-placed outliers. Here are some closer associations from the same paper:

It's clear that both a high n-6 intake and a low n-3 intake correlate with negative psychiatric outcomes. Together, the data are consistent with the hypothesis that the ratio of n-6 to n-3 impacts brain function. Dr. Hibbeln and Dr. Lands do not claim that this ratio is the sole determinant of psychiatric problems, only that it is a factor.

Now to address the big criticism that was brought up by very astute readers of the last post, namely, that the data were purely correlative. Believe me, I wouldn't even have posted on this topic if I didn't have intervention data to back it up. In addition to the animal data I mentioned above, here are more studies that support a causal role of fatty acid balance in psychiatric problems:
Most of those were placebo-controlled trials. If we can see a significant effect of n-3 supplementation in short-term trials, imagine how well it would work as a long-term preventive measure.

Vegetable Oil and Homicide

One of the major dietary changes that has accompanied the downward slide of American health is the replacement of animal fats with industrially processed vegetable oils. Soybean oil, corn oil, cottonseed oil and other industrial creations have replaced milk and meat fat in our diet, while total fat consumption has remained relatively constant. The result is that we're eating a lot more polyunsaturated fat than we were just 30 years ago, most of it linoleic acid (omega-6). Corn oil may taste so bad it inspires you to violence, but its insidiousness goes beyond the flavor. Take a look:


This figure is from a paper that Dr. Joe Hibbeln sent me recently, of which he is the first author. This followed an interesting e-mail conversation with Robert Brown, author of Omega Six: the Devil's Fat. He put me in touch with Dr. Hibbeln and Dr. William Lands (NIH, NIAAA), both of whom warn of the dangers of excessive linoleic acid consumption from modern vegetable oils. Dr. Lands has been researching the relationship between dietary fat and inflammation since the 1970s, and has been a critic of modern vegetable oils for just as long. Both Dr. Hibbeln and Dr. Lands were very generous in sending me a number of their papers. The figure above shows the homicide rate vs. linoleic acid consumption of five countries over the course of 40 years. Each point represents one year in one country. The U.S. has the distinction of being in the upper right.

I asked Dr. Hibbeln how he selected the five countries, and he told me the selection criteria were 1) available homicide and linoleic acid consumption statistics, 2) "first world" countries, and 3) countries representing a diversity of linoleic acid intakes. I'm satisfied that there was probably not a significant selection bias.

What's interesting about the graph is that not only does the homicide rate track with linoleic acid consumption across countries, but it also tracks within countries over time. For example, here is the same graph of the US alone:


And here is the UK, which doesn't suffer as much from the confounding factor of firearm availability:


I don't think we can draw any solid conclusions from this, but it is worth noting that epidemiological associations don't get much better. In the next few posts, I'll explore the data from intervention trials that support the hypothesis that excessive omega-6 consumption, and insufficient omega-3 consumption, cause serious problems for psychiatric and physical health.

Vegetable Oil and Homicide

One of the major dietary changes that has accompanied the downward slide of American health is the replacement of animal fats with industrially processed vegetable oils. Soybean oil, corn oil, cottonseed oil and other industrial creations have replaced milk and meat fat in our diet, while total fat consumption has remained relatively constant. The result is that we're eating a lot more polyunsaturated fat than we were just 30 years ago, most of it linoleic acid (omega-6). Corn oil may taste so bad it inspires you to violence, but its insidiousness goes beyond the flavor. Take a look:


This figure is from a paper that Dr. Joe Hibbeln sent me recently, of which he is the first author. This followed an interesting e-mail conversation with Robert Brown, author of Omega Six: the Devil's Fat. He put me in touch with Dr. Hibbeln and Dr. William Lands (NIH, NIAAA), both of whom warn of the dangers of excessive linoleic acid consumption from modern vegetable oils. Dr. Lands has been researching the relationship between dietary fat and inflammation since the 1970s, and has been a critic of modern vegetable oils for just as long. Both Dr. Hibbeln and Dr. Lands were very generous in sending me a number of their papers. The figure above shows the homicide rate vs. linoleic acid consumption of five countries over the course of 40 years. Each point represents one year in one country. The U.S. has the distinction of being in the upper right.

I asked Dr. Hibbeln how he selected the five countries, and he told me the selection criteria were 1) available homicide and linoleic acid consumption statistics, 2) "first world" countries, and 3) countries representing a diversity of linoleic acid intakes. I'm satisfied that there was probably not a significant selection bias.

What's interesting about the graph is that not only does the homicide rate track with linoleic acid consumption across countries, but it also tracks within countries over time. For example, here is the same graph of the US alone:


And here is the UK, which doesn't suffer as much from the confounding factor of firearm availability:


I don't think we can draw any solid conclusions from this, but it is worth noting that epidemiological associations don't get much better. In the next few posts, I'll explore the data from intervention trials that support the hypothesis that excessive omega-6 consumption, and insufficient omega-3 consumption, cause serious problems for psychiatric and physical health.

Water for the Pima

A few months ago, I published a post about the Pima Indians (Akimel O'odham) of Arizona. The Pima are one of the most heart-wrenching examples of the disease of civilization afflicting a society after a nutrition transition. Traditionally a healthy agricultural people, they now have some of the highest rates of obesity and diabetes in the world.

The trouble all started when their irrigation waters were diverted upstream in the late 19th century. Their traditional diet of corn, beans, squash, fish, game meats and gathered plant foods became impossible. They became dependent on government food programs, which provided them with white flour, sugar, lard and canned goods. Now they are the subjects of scientific research because of their staggering health problems.

I'm happy to report that after more than 30 years of activism, lawsuits and negotiation, the Pima and neighboring tribes have reached an agreement with the federal government that will restore a portion of their original water. Of the 2 million acre-feet of water the Pima were estimated to have used since before the 16th century, the settlement will restore 653,500. An acre-foot is approximately the personal water use of one household. The settlement also provides federal funds for reconstructing old irrigation canals.

Now we will see how the Pima will use it. Will they return to an agricultural lifestyle, perhaps with the advantages of modern technology? Or will they lease the water rights for money and continue to live off Western foods? Perhaps some of both. They are definitely aware that Western food is causing their health problems, and that they could regain their health by eating traditional foods. However, white flour "fry bread", sugar and canned meat have been around for so long they are also a cultural tradition at this point. Only time will tell which path they choose.
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