Fish intake might improve antidepressant response

Approximately half of the people suffering with depression don’t respond to SSRIs. Recently a group of Dutch researchers discovered that adding fish oil to antidepressants increases the response rate.

According to a lead researcher they saw that depressed patients had an altered metabolism of fatty acids, and this altered metabolism was affected by stress hormones. In the experiment the researchers planned on examining the relationship between depression and fatty acids, and hormones such as cortisol.

They took 70 patients with depression and compared them to 51 healthy controls, by measuring their fatty acid levels and cortisol levels. They then gave the depressed patients 20mg of an SSRI daily for 6 weeks, and in those who did not respond to the SSRIs the dose was gradually increased up to 50mg/day. Fatty acid and cortisol levels were measured during the trial.gel capsules

They found that the MDD patients who didn’t respond to the SSRI also tended to have abnormal fatty acid metabolism, so they checked the dietary habits of all those taking part in the trial. Fatty fish is rich in fatty acids, such as the well-known Omega-3 DHA. So the researchers looked at the amount of fatty fish in the diet of all involved in the trial. They categorised the patients into 4 groups, according to their fatty fish intake, and they found that those who took the least fish tended to respond badly to anti-depressants, whereas those who had most fish in the diet responded best to anti-depressants. Those who ate fatty fish at least once a week had a 75% chance of responding to antidepressants, whereas those who never ate fatty fish had only a 23% chance of responding to antidepressants.

There were a couple of problems with this study. For one thing the study was on the small side and should be replicated with a larger one. A second problem is that the researchers appeared to know the fatty acid status of the depressed patients so they might have subconsciously altered the depression scores in order for their hypothesis to be proven correct. How the depression scores were measured is unclear from the article.

Andrew Stoll was one the first researchers to notice the antidepressant effect of fish oil. He theorized that fish oil might effect the composition of nerve cell membranes and consequently neurotransmission. Barry Sears, author of ” The Zone”, was another researcher who mentioned that stress could effect the type of fatty acids. They both probably inspired this study. I did not read the original article so if you are curious you will have to pay for the article through ECNP.

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Not all fish supplements created equal

I have been taking a variety of fish oil supplements( Twinlab, Now) since 2003 and I believe, for the most part, that they were helpful, howevergel capsules I couldn’t say for certain. Recently I came across some information that is new to me. A website PsychEducation mentioned that if you purchase fish oil the amount of EPA should be 60 percent of the total amount of Omega-3 fatty acids per/pill.  A fish oil pill with less than that percentage acts more or less like a placebo. I found it difficult to discern this from some of the brands since some don’t give you much detail.

big review of all these studies and more suggests that the ratio of EPA to DHA (the two omega-3 fatty acids) really matters. Their analysis shows that of these two omega-3’s in each pill, at least 60%  must be EPA. Less than that and it does not work better than a placebo; in fact in several studies, less than 60% EPA was worse than a placebo.

The Mayo Clinic gives fish oil a grade of C due to the fact that results of various studies have been mixed. I’m not sure if the information from this latest review has been taken into account?