Category: omega-3

Science in Action: Omega-3 (more memory results)

Seth Roberts3 Comments

Several weeks ago I compared flaxseed oil (high in omega-3) and olive oil (low in omega-3). I’ve posted results from a balance task and a memory-scanning task. I also measured what is called digit span — the number of digits you can remember perfectly after one presentation. It is a widely-used measure of short-term memory. In my test, the digits were shown one by one for 1 second each on my computer screen. A few seconds after the last one, I had to write them down in order. If I was 100% correct the next trial had one more digit than the last. If any of my answers were wrong, the next trial had one fewer digits than the last. The test continued until there had been six “reversals” — right answers after one or more wrong answers, or wrong answers after one or more right answers. The measure of performance is the mean of the six reversal points. It estimates the list length at which I have a 50% chance of being correct.

Here are the results:

flaxseed oil vs. olive oil

Performance was better with flaxseed than olive oil (t = 2.5, one-tailed p = 0.01). The difference — the omega-3 effect, you might say — was quite a bit weaker than what I saw with balance and memory scanning. My guess is that the relative insensitivity of this task comes from two features: 1. Binary measures. Each trial is measured right or wrong; whereas with the memory-scanning and balance task, each trial yielded a duration (many-valued). 2. Slow. Each trial takes about 30 seconds; it takes about 10 minutes to get six reversals.

Guide to my omega-3 posts.

Injury-Causing Falls: The New Scurvy?

Seth RobertsLeave a comment

In an article about aging in this week’s New Yorker, Atul Gawande writes:

The single most serious threat she faced was not the lung nodule or the back pain. It was falling. Each year, about three hundred and fifty thousand Americans fall and break a hip. Of those, forty per cent end up in a nursing home, and twenty per cent are never able to walk again. The three primary risk factors for falling are poor balance, taking more than four prescription medications, and muscle weakness. Elderly people without these risk factors have a twelve-per-cent chance of falling in a year. Those with all three risk factors have almost a hundred-per-cent chance.

Could the cause of so much falling be too little omega-3? My omega-3 research suggests that more omega-3 quickly improves balance and that current levels in most places are far below optimal.

Does Omega-3 Affect the Brain?

Seth Roberts3 Comments

The last three data sets I’ve posted — one from Tim Lundeen, two from me (here and here) — provide evidence that omega-3 affects the brain. The evidence has several good features:

1. Two people.

2. Three tasks.

3. Two ways of varying omega-3.

4. Strong effects (that is, large t values).

5. Easy to obtain.

Does omega-3 affect the brain? This is a good place to start a research project because there is a reasonable chance the answer to the question “does omega-3 affect the brain?” is yes.

The placebo/expectations explanation — which, based on the lack of effect of placebos in most studies, is implausible to begin with — has trouble with several facts: 1. The initial discovery was a surprise. 2. Tim’s results involved comparison of two plausible doses. 3. Tim had earlier found that dose increases had no effect. 4. Tim’s results had a pattern I have never seen (and thus Tim couldn’t have expected). 5. My results had two different time courses.

Even more interesting than the idea that how much omega-3 we eat might affect how well our brains work are two more subtle ideas that are also becoming plausible: (a) the average diet (very low in omega-3) is very suboptimal and (b) improvement can be noticed quickly and easily.

In the latest U.S. government nutrition guidelines, there is no omega-3 requirement.

Directory of my omega-3 posts.

Science in Action: Omega-3 (flaxseed oil vs. olive oil, continued)

Seth Roberts3 Comments

I posted a few days ago about the different effects of flaxseed oil (high in omega-3) and olive oil (low in omega-3) on my balance. There was a big difference. If omega-3 affects one measure of brain function (balance), it should affect many other measures of brain function. The whole brain is made of the same stuff (neurons, etc.).

Which brain measures are most sensitive to omega-3? The more processing/time the better, I assumed; so I looked for tasks that, like balance, involve continuous processing for most of the test period. This led me to try a paper-and-pencil version of Saul Sternberg’s memory-scanning task. (Sternberg’s use of this procedure is described here.) On each trial I memorized a list of three digits (e.g., 2, 3, 7); then as fast as possible marked each of 100 digits (20 digits/row in 5 rows) according to whether they were in the list or not. I made a line under the digit if it was in the list, through the digit if it was not. I did five trials per day.

Here is an example of the test materials and my marks:

example of memory-scan test

The other side of the page had two more sets of digits.

Here are the results from the same flaxseed/olive oil experiment I discussed a few days ago:

flaxseed oil vs. olive oil

There was a huge difference between the flaxseed oil and olive oil condition: t > 7.

Curiously the time course is different from the balance results. In the case of balance, when I switched from flaxseed to olive oil my balance slowly got worse. Nothing like that is apparent here. This might reflect a different mechanism or it might be due to the vast difference in how much practice I had had with each task. When this experiment began, I had had far more practice with the balance task than with the memory-scanning task.

Which Signs of Aging are Inevitable?

Seth Roberts1 Comment

In a New Yorker article titled “The Way We Age Now,” Atul Gawande writes:

With age . . . the gums tend to become inflamed.

As I posted a few weeks ago, my gums have recently become less inflamed — no doubt because of more omega-3 from flaxseed oil. For the first time in memory they are not inflamed at all. (My dentist was surprised. Hardly anybody improves, he said.) Could Gawande’s “with age” effect be due to not enough omega-3?

Science in Action: Omega-3 (flaxseed oil vs. olive oil)

Seth Roberts17 Comments

As I’ve described in previous posts, flaxseed oil (high in omega-3) seems to improve my balance. As I increased the daily dose, I found that 4 tablespoons (T)/day had almost the same effect as 3 T/day. To measure the effects of omega-3, I plan to use 3 or 4 T/day flaxseed oil — which presumably produces near-optimal omega-3 levels — as a baseline for measuring the effect of other things.

For my first comparison I chose olive oil: widely believed healthy, but low in omega-3. (And recommended by me in The Shangri-La Diet.) I used an ABA design: several days flaxseed oil, several days olive oil, several days flaxseed oil. In all conditions, I took 2 tablespoons of the oil at about 10 am and 2 tablespoons at about 10 pm each day. I measured my balance at about 8 am the next day. Each daily test consisted of 30 trials. Each trial consisted of balancing on one foot on a board atop a metal cylinder (pictures). The score was how long before I lost my balance and put the other foot down.

Here are the results.

flaxseed oil vs. olive oil

While drinking the olive oil, my balance slowly got worse. When I returned to flaxseed oil, my balance quickly returned to its previous level. Very clear difference between the oils, F (2,40) = 18, which corresponds to a tiny p value and t about 5.

A possible explanation is that when the concentration of omega-3 in the blood is low, the omega-3 in cell membranes slowly “evaporates” into the blood. When a cell’s membranes lose omega-3, it doesn’t work as well.

Effects of SLD and Flaxseed Oil

Seth RobertsLeave a comment

A reader (Josh Mangum) writes:

The flavorless calorie diet lets me drop weight whenever I need to. I was usually 10-15 lbs overweight and up to 25 lbs when under stress. Both my parents are overweight so I was worried that I would put on weight under stress and not take it off. My dad especially has followed the pattern of gaining a few pounds a year his whole adult life and is now about 75 lbs overweight. Besides the obvious advantages of losing weight now it’s really nice that I don’t have to worry about being very overweight in the future.

Flax oil is more subtle. I think it’s improving my sleep and mental ability. For sleep I’ve noticed being rested and having more vivid dreams. There seems to be a dosage effect. One night I tried 6 tbls of flax oil, had very vivid dreams and felt very rested the next day. The other thing that seems consistent with it working is that I can go back to sleep for a couple hours after waking at 7 am if I’m still tired. Previously I was never able to go back to sleep whether I woke at 2 am or 7 am.

I write software and notice that it seems easier while I’ve been using flax oil. It seems to be easier to hold large problems in my head and work though them than previously. I don’t notice much effect on how often I’m “insightful” or “clever” though. So rather than being smarter it seems like being adequately smart more often. This is subtle though and it could be the phase of the project or my outlook or just better sleep. Maybe the effects are just the result of coming out of the shorter foggier San Francisco winter days.

Omega-3 and Arithmetic (several analyses)

Seth Roberts4 Comments

In a recent post I described Tim Lundeen’s arithmetic data. He found that increasing his daily dose of DHA seemed to increase the speed at which he did simple arithmetic. Here is the graph:

Tim Lundeen's arithmetic data

I didn’t bother to do any statistical tests because I thought the DHA effect was obvious. However, someone in the comments said it wasn’t obvious to them. Fair enough.

If DHA has no effect, then the scores with more DHA should be the same as the just-preceding scores with less DHA. There are practice effects, of course, so I analyzed the data after practice stopped having an effect: After about Day 40. (And I left out days preceded by a gap in testing — e.g., a day preceded by a week off.) Thousands of learning experiments have found that practice makes a difference at first and then the effect goes away — additional practice doesn’t change behavior.

If I do a t-test comparing low-DHA days (after Day 40) with high-DHA days, I get a huge t value — about 9. If you’re familiar with real-life t values, I’m sure you’ll agree that’s a staggeringly high value for a non-trivial effect. The model corresponding to this test is indicated by the lines in this figure:

Tim Lundeen's data

The red (”more DHA”) points don’t fit the line very well, which suggests doing an analysis where the slopes can vary:

Tim Lundeen's arithmetic data

There is still a huge effect of DHA, now split between two terms in the model — a difference-in-level term (t = 4) and a difference-in-slope term (t = 3).

But this analysis can be improved because based on thousands of experiments I don’t believe that the less-DHA line could have a positive slope, as it does in the model. Or at least I believe that is very unlikely. So I will constrain the less-DHA line to have a slope of zero:

Tim Lundeen's arithmetic data

Now I get t = 8 for the difference in slopes and t = 4 for the difference in level. This is interesting because it implies that more DHA not only caused immediate improvement but also opened the door to more gradual improvement (indicated by the slope difference). DHA changed something that allowed practice to have more effect.

That’s a new way of thinking about the effects of omega-3 — actually, I have never seen any data with the feature that a treatment caused a practice effect to resume — so I have to thank the person who claimed the difference wasn’t obvious.

Omega-3 and Arithmetic (evaluation)

Seth RobertsLeave a comment

When I read an empirical scientific paper I ask four main questions:

1. How clear is the effect or correlation? Generally measured by p values.

2. How clear is the cause of the effect?

3. How much can we generalize from this?

4. Assuming we can generalize, how much will this change what anyone does?

The overall value is something like the product of the answers. Most research gets a modest score on #1 (because a high score would be overkill and, anyway, the low-hanging fruit has been picked) and a low score on #4. Experiments get a high score on #2, surveys a low score.

Tim Lundeen’s little experiment that I described a few days ago, in which he found that a higher dose of DHA improved his arithmetic ability, gets a very high score:

1. The effect is very clear.

2. It’s an experiment. Because the variation was between two plausible doses of a food supplement, I doubt it’s a placebo effect.

3. The subject, the treatment, and the test are “ordinary” — e.g., Tim does not fall into a special group that might make him more likely to respond to the treatment.

4. Who wouldn’t want to improve how well their brain works?

From the point of view of a nutrition scientist, I’d guess, the effect is shockingly clear and direct. Experimental nutrition with humans almost always measures correlates of disease (e.g., correlates of heart disease) rather than disease. To me, an experimental psychologist, the results are shockingly useful. Practically all experimental psychology results (including mine) have little use to most people. The clarity of the effect does not quite shock me but I’m very impressed.

Omega-3 and Arithmetic (continued)

Seth Roberts14 Comments

Tim Lundeen, a Bay Area software developer, previously posted here about what happened when he increased his daily dose of DHA (an omega-3 fat in fish oil) from 400 mg/day to 800 mg/day: The next day, the speed with which he did simple arithmetic (e.g., 7 + 3) increased. At that point he had only four days from the high-DHA condition. Now he has two months. Here it is:

Tim Lundeen's arithmetic data

The y axis is the total time taken to do a set of 100 simple arithmetic problems.

Bottom line: The improvement continued, at roughly the same level. Very good evidence for an effect.

Tim had earlier found that doses of 200 and 400 mg/day of DHA had no apparent effect.

My main posts about omega-3.