Fish oil caplets

In 2005, researchers published The Oxford-Durham Study. At the time, the study was not behind a paywall, but as of 2023 it is inaccessible with a journal subscription as you will see if you click the link. You will be able to see the abstract, however, and it alone is quite interesting.

The study hints at a potential linkage between an Omega-3 deficiency and dyslexia, or at least reading struggles, and points to possible benefits of fish oil supplementation for the dyslexic child.

The study didn’t specifically address dyslexia, but rather was aimed primarily at children with motor skills problems which the authors refer to as DCD, or Developmental Coordination Disorder. Fortunately (from our perspective) they measured not only motor skills, but also the reading and spelling ability of each child in the study. In addition, they measured a third element, that being a child’s tendency to exhibit symptoms of ADHD, or Attention Deficit/Hyperactivity Disorder.

The reason I feel that this study can reasonably be interpreted to have implications for dyslexia is because of the confluence of symptoms of children in the study. That is, a majority of the children in the study exhibited symptoms in all three areas, motor skills, reading/spelling skills and attention. This fits with my perception of dyslexia being more than just a reading problem; that it is instead a broader developmental problem which manifests itself in many ways, though certainly not in the same way for every child.

A Brief Description of the Study

The study was designed primarily to see if a deficiency of Omega-3’s in the diet was a cause of DCD, or motor skill deficiencies.

Before you jump to the study (assuming you have access and choose to read the entire study) let me briefly describe what the researchers were trying to learn. They designed the study primarily to see if a deficiency of Omega-3’s in the diet was a cause of DCD, or motor skill deficiencies. Thus, when the groups were randomized, the main effort was to see that each group had similar overall motor skills.

However, and fortunately for us, they also measured their reading ability (using a word recognition test) and spelling ability. They also administered a form of the Conner’s test to get a measure of each child’s tendency to exhibit symptoms of ADHD. All three areas were examined.

The children were divided into two groups having similar motor skills characteristics. As a result, the reading ability of each group differed somewhat, but this actually makes the results even more startling (and I did find them startling, so I hope that an attempt is made to replicate their results by other researchers in time.)

Fish oil supplementation was used to provide the Omega-3 dosage because fish oil is an excellent, concentrated source and it is usually tolerated well. Group one, called the active group, was administered fish oil daily for three months while Group Two received a similar pill containing olive oil. Then, three months later, measurements of all three areas (DCD, reading/spelling and ADHD) were again taken at which point Group One continued on the fish oil while the placebo group (Group Two) also was given fish oil. After another three months all of the children again had measurements taken in all three areas being studied.

Discussion of Specific Results

The researchers were surprised, and I suppose disappointed, that they found no significant effect of fish oil supplementation on DCD, or Developmental Coordination Disorder, i.e., motor skills deficits. They say that there was anecdotal evidence sufficient to make them question how they measured motor skills in the study, but nonetheless, the two groups performed similarly.

Motor Skills Results

To acquaint yourselves with the way the results were reported, here is a link to the table in the study describing the motor skills results. It will open in a separate tab or window so you can tab back and forth as I discuss the results here. (Again, you will need access.)

Table Describing Motor Skills Results

Now, look at the fourth line of numbers labeled “Total Impairment” and starting with the number 15.6. (The number in parentheses is the standard deviation. Just ignore it for our purposes.) Next to the 15.6 is a 15.2. If you check the column headings you’ll see that 15.6 was the mean score of the Active Group and 15.2 was the mean score of the Placebo Group. Remember, the Active Group got fish oil over the next three months and the Placebo Group got olive oil (and therefore no Omega-3’s.)

Essentially, both groups started out with about the same scores (out of a possible maximum impairment of 40, if you take the time to read the footnotes under the table.)

Now, look at the next two numbers, which are 13.1 and 12.1, indicating that both groups showed improvement and if anything the placebo group improved even more than the active group (which got the fish oil.) Note: The lower the score, the less the impairment.

Ignore the next two numbers which are statistical measures and look at the last two, 10.4 and 10.0 respectively. These measurements were taken at six months after both groups had been on fish oil for the second three months of the study period. Note that both groups again improved to about the same degree.

In fact, the bottom row of figures indicates just how close the two groups remained to each other and how much both improved during the study period. At the beginning of the study, both groups were in approximately the bottom 6 percent regarding motor skills (5.8 and 5.9) and by the end of the study both had improved to about the 20th percentile (19.5 and 20.0) of the general population.

Why they improved at all, and why they improved at the same rate are both mysteries and if this is all the study’s authors had evaluated we would probably have heard no more of it. (One hypothesis: Something common to both the olive oil and the fish oil resulted in the improvement.)

Now, remember that they also evaluated ADHD and reading/spelling. I’m going to cover the ADHD results first because of my hypothesis that dyslexia is a developmental condition that covers more than just reading difficulty. Hence, a causal factor of reading struggles should also be a cause of other developmental difficulties, including possibly ADHD.

ADHD Results

First, here is a link to the table in the study describing the ADHD results. It will again open in a separate tab or window so you can tab back and forth as I discuss the results here.

Table Describing ADHD Results

Now, recall that I said that the study’s authors were primarily evaluating DCD, or motor skills deficits, so that is how the groups were both selected and randomized. It turned out that when the children were selected on the basis of weak motor skills, the study also ended up with a heavy concentration of children who exhibited ADHD-like symptoms (and, as will be discussed later, also with reading problems to an extent.) This goes along with my thinking that what we call “dyslexia” is really better characterized as a broader developmental delay affecting more than just academics.

Anyway, the table of ADHD results is much more confusing, so let’s just focus on the last line which is the score for the composite ADHD which combined both hyperactivity and attentiveness. A score of 50 is considered average for the general population (if I understand it correctly) and since the standard deviation is 10 according to the note in the table heading, this means that two thirds of the general population would score between 40 and 60 on the Total ADHD test. Note that the scores for the Active Group and the Placebo Group started out at 64.6 and 63.7 respectively. Thus, the Active Group (the group that got the fish oil first) was a bit more hyperactive than the Placebo Group.

Because ADHD and reading/spelling were secondary measures, not all children in the study necessarily demonstrated poor performance on the ADHD scale

One thing to bear in mind is that because the selection method to be in the study was that a child must have demonstrably poor motor skills, and because ADHD and reading/spelling were secondary measures, not all children in the study necessarily demonstrated poor performance on the ADHD scale. Some were very likely quite normal in this regard. This will be even more obvious when we get to the reading/spelling results next.

Anyway, if you look at the next set of numbers, 59.5 and 62.7, you will see that the Active Group dropped 5.1 points on the scale (from 64.6 to 59.5) while the Placebo Group dropped only 1.0 point (from 63.7 to 62.7) a significant difference in effect. (The <.00001 figure a couple of columns over indicates that there is only a 1 in 100,000 chance that the groups statistically performed the same.)

Also, note for future reference the numbers in parentheses, which all fall quite close to a value of 11 to 12. This is a measure of how widely varying the results among the children were. Note the stability of that measure at beginning, three months and six months and between both groups, as I will discuss it later in the reading/spelling context.

At six months, when both groups were given fish oil for the preceding three months, both groups improved their ADHD measurements. The Active Group dropped another 2.0 points (from 59.5 to 57.5) and the Placebo Group dropped 3.1 points (from 62.7 to 59.6). In other words, the Active Group continued to improve on this measure, and the Placebo Group made even greater gains, presumably because they finally had the benefit of the fish oil supplementation.

Finally, note that although the Active Group started with a higher score (64.6) than the Placebo Group (63.7), they ended with a lower score (57.5 versus 59.6) again presumably because they had the benefit of six months of fish oil supplementation while the Placebo Group only had three months of it.

It would appear that the longer the treatment, the better the result, at least up to six months.

Summarizing, the first three months demonstrated that the two groups differed in significantly in results, whereas the second three months demonstrated that the control group (the Placebo Group) could achieve the same benefit if given the fish oil treatment. Furthermore, it would appear that the longer the treatment, the better the result, at least up to six months.

In fact, if you read the text of the study you will find the following statement (CTRS-L refers to the ADHD measurement method): “At 3 months after treatment, only 24 children (23.5%) still had CTRS-L scores that placed them in the clinical range for ADHD. Among those receiving active treatment, 7 of the initial 16 no longer fell into this category; in the placebo group, only 1 of 16 improved in this way.

Now let’s move on to the results obtained in reading and spelling.

Reading/Spelling Results

Bear in mind that the children in the study were not selected because of reading and/or spelling issues. They were selected because of motor skills deficits. They were also randomly grouped in a manner that balanced the two groups on the basis of those motor skills deficits, and not on their reading/spelling abilities.

Here is the table that reports the reading and spelling results, and it is quite surprising. Again, you will need access to the study. However, you should be able to understand the results by reading the description below, just as you could in the two discussions of results above.

Table Describing Reading/Spelling Results

There are three main columns, each with an Active and Placebo Group, as with the other two tables. Measurements were taken at the start, and at three months and at six months. And there are two measurements, a reading score (which was a word identification task) and a spelling score.

A reading age of 100 indicates that a child is reading at his age level (actually, identifying individual words at his age level.)

The first challenge is to understand what is meant by Reading Age so let’s look at the first number for the Reading Age of the Active Group, that being 93.6 (with a standard deviation of 18.6, that being the number in parentheses.) If you read the full study you’ll find that the children varied in age from 5 to 12 years old. A reading age of 100 indicates that a child is reading at his age level (actually, identifying individual words at his age level.) The way a standard deviation works is that it tells you the range in which two thirds of the sample population falls. Thus, two thirds of the children had reading ages that fell between 75 (93.6-18.6) and 112.2 (93.6+18.6)

Again, remember that these children weren’t selected because they couldn’t read or spell. It just turns out that they had somewhat below-average scores as a group. In fact, a fairly large percentage of them could read better than average. A score of 112 would indicate that a child was reading twelve months (or one full year) above his age level and fully one sixth of the Active Group may have fallen in the range above 112. Similarly, one sixth of them should have fallen below the 75 level or fully two years and more behind.

Also, because the groups were randomized and formed on the basis of motor skills, the reading scores at the start of the study differed considerably between the two groups. In fact, the Placebo Group was almost an average group, starting with an average reading score of 99.8.

The Active Group went from 93.6 to 103.2, catching up to the Placebo Group by making a gain of 9.6 months in reading age in just three months

Looking across under the three months column you will see that the Placebo Group improved to 103.2, indicating that they made 3.4 months of progress in three months, or about as you would expect for an average class of average readers. However, the Active Group went from 93.6 to 103.2, catching up to the Placebo Group by making a gain of 9.6 months in reading age in just three months! Note for future reference that their standard deviation also rose significantly.

The .004 number a couple of columns over means that there is only a 4 in 1000 chance that the two groups actually didn’t differ in results statistically. In other words, there was a very high probability that they were measuring a real difference.

Looking at the last two columns, you’ll see that when both groups were on fish oil, both groups made nearly identical gains, with the Active Group gaining an additional 10.8 months in reading age to 114.0 in three months (for a total gain of 20.4 months in six months actual time) and the Placebo Group gaining 12.8 months in reading age to 116.0 now that they were also getting fish oil capsules. Also, notice that both groups’ standard deviation jumped again, reaching 34.1 in both groups. (More on this later.)

I’ll leave it to you to examine the Spelling results, noting only that the gains were less, which one would expect since reading ability generally precedes spelling ability unless the curriculum is specifically geared to teaching spelling prior to reading, as very few are. Nevertheless, you will note the same pattern of gains when on fish oil, and the same increase in the standard deviations of both groups when on fish oil.

Possible Implications of the Large Rise in Standard Deviations

It's likely that the fish oil was of even greater benefit than the numbers indicate for some of the children in the study and of much less benefit (possibly even of no benefit) for others.

While the fish oil apparently caused a large increase in reading and spelling ability in both groups, the rise in the standard deviations that accompanied those increases raises a cautionary note. What very likely happened is that the fish oil was of even greater benefit than the numbers indicate for some of the children in the study and of much less benefit (possibly even of no benefit) for others in the study. This would explain the large increase in the standard deviation. For example at the end, the reading age of the Active Group had two thirds of the children scoring between 79.9 (114.0-34.1) and 138.1 (114.0+34.1) so one sixth of the group scored below 79.9. In other words, the whole group didn’t improve together at approximately the same rate. Nor did the slower readers catch up to the better readers, for then the standard deviations would have gone down, not up, as the reading ages clustered closer together.

An Unavoidable Conclusion

Fish oil, or presumably Omega-3 essential fatty acid supplementation, appears capable of enabling rapid gains in certain language skills in some, but by no means all, children. It is not even obvious from the results of this study that fish oil benefited the weaker readers at all, though it is hard to believe that was the case since it would have been quite apparent to the study’s authors as they viewed the raw data.

This study's results suggest that every parent should consider fish oil supplements or some other means for boosting the Omega-3 in their children’s diets (and their own diets too, for that matter) but that it is probably not the answer for all children with dyslexia. In some cases, however, it just might be a key missing piece of the puzzle we call dyslexia.

It's also worth considering whether the fish oil used contained vitamin D3, though it's unlikely since most fish oils sold today do not appear to contain D3. Cod liver oil does, but as discussed elsewhere, the heavy concentration of vitamin A in cod liver oil might override the beneficial effects of the vitamin D3 it contains.

The companion article to this one, More Evidence Nutrition Matters, discusses a study that assessed the impact on certain reading skills after supplementation with a multi-vitamin. As with this fish oil study, a subset of the children had a particularly positive response.