Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the world of health. Nutrition. Exercise. Diet. Supplementation. If there’s something new, I look at the science behind them, and let you know whether it’s real or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
The question of the day is whether fish oil contributes to the development of atrial fibrillation in healthy individuals while reducing the risk of having a heart attack in people who begin taking fish oil after a person already had heart disease. British researchers recently published an observational study on over 415,000 subjects in the UK Biobank database who took a fish oil supplement. During a follow-up period of almost 12 years, they statistically demonstrated a 13% increased hazard ratio (a measure over time of how often a particular event happens in one group compared to another group) in the development of atrial fibrillation in subjects. Atrial fibrillation is a type of arrhythmia, or abnormal heartbeat, that can result in extremely fast and irregular beats from the upper chambers of the heart. In those subjects, there was a 5% increased risk of stroke.
The resultant impact was an attack on dietary supplements for being too easily available, leading to overconsumption, and questionable because of the lack of purity in dietary supplements. The Medscape Cardiology online section put out a video by a reputable researcher explaining who should take fish oil supplements. But if they’re so bad, why would she recommend them at all?
The other part of the results showed that if someone already had cardiovascular disease (CVD), the hazard ratio of developing major cardiac events was reduced if they took fish oil supplements. That’s why the expert made the video, taking the good and trying to make sense of it. Still, it gave the appearance of being a pitch for a pharmaceutical solution.
I’ll wager you have at least one question so here’s the answer. Yes, this study tested only supplement use (and dietary intake) upon entrance to the study and nothing the rest of the 11.9 years, just like the multivitamin study I recently talked about. But there’s so much more that I’ll cover on the problems with this study. Just so you know, I’m still taking my fish oil supplements so I don’t forget to say that later.
Let’s put the fish oil study from in perspective. The most important thing is that observational studies such as these cannot demonstrate cause and effect. That’s not just a way to weasel out of making definitive statements; it’s because that, while fish oil supplements are associated in some way with atrial fibrillation in people who have no diagnosed heart disease, it may be something else entirely that people who take fish oil supplements do that’s actually the culprit. Remember the hazard ratio (HR) was only 13%. What were the remaining 87% doing that was different?
As I see it, these were the problems with this research paper.
Just as in the multivitamin study, researchers collected a whole host of dietary data and didn’t use much of it; they adjusted for those who ate oily and un-oily fish, but that was it. Fruit intake, vegetable intake, fiber intake, and a whole lot more dietary factors that have been shown to limit the development of cardiovascular disease, were not considered. That may have impacted the HR.
The major problem was that they didn’t report the rate of AFib in those who did not take fish oil supplements. How can you not? What happens to those who do not take fish oil supplements could have provided comparison groups, which seems like a better analysis to conduct. No explanation. They just chose not to do it.
The final critique is that this study was conceived and executed by statisticians and epidemiologists. There were no nutrition experts on the team reported in the paper. I don’t know how that’s possible. If you’re considering a nutritional intervention, such as taking a fish oil supplement, there has to be someone who understands nutrition to consider other factors. It can’t be all statistics without thoughtful guidance.
The Big Question is How? How would fish oil supplements cause the development of AFib?
Research has shown that eating oily fish does not appear to cause AFib. Why would fish oil? The researchers cited a couple of possibilities having to do with an impact on the channels that control electrical pathways but overall, no one has given any explanation.
This was not the first study that has examined fish oil supplements in large studies and found some relationship with AFib; there are also several that show no relationship at all. In this case, we have to reserve judgment because we can’t prove things either way.
But I have more questions. Here are some of my thoughts and questions about fish oil and omega-3 fatty acids.
1. None of the research to date has focused on complete nutrient intake, and that may have an impact on fish oil utilization. I’ve suggested that before, but vitamins, minerals, and especially phytonutrients from food may have a role to play in how the body uses fish oil and all the fatty acids within it.
2. Speaking of the fatty acids, the omega-3s that are always mentioned are EPA and DHA. In reality, they make up a small part of the fatty acid distribution in fish oil. Could that make a difference? In other words, would the emphasis on those fatty acids impact how omega-3s are used in the body, positively or negatively, compared with straight fish oil?
3. The form of the omega-3 may be important when it comes to bioavailability. There are phospholipids, re-esterified triglyceride (rTG), TG, free fatty acids (FFAs), and ethyl-ester forms of omega-3s. Does the form matter?
4. This is just my opinion, but there’s something in fish that works to improve absorption of omega-3s. Maybe it’s the other fatty acids or maybe it’s the protein in the fish when we eat it. There’s no evidence that oily fish intake increases AFib, so why would the oils alone contribute to any issue unless something is impacting the form mentioned above?
That’s the way I see it. It’s also why I think eating a good diet will prove to be beneficial when taking fish oil. We’ll just have to wait and see.
What should you do? First, eat the healthiest diet you can and exercise regularly, because lifestyle is more important than supplements. Second, if you have already been diagnosed with CVD as I have—a stent more than 20 years ago—taking fish oil may be beneficial. If you’re under 60, it seems taking fish oil isn’t an issue and there’s no reason to stop. If you’re older than 60, should you begin to take fish oil supplements? It’s a matter of choice. Foe everyone else, I have to reserve judgment for now but I ‘ll keep my eye on this research for sure so when I know more, so will you. I’m out of time. This is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
BMJMED 2024;3:e000451.doi:10.1136/ bmjmed-2022-000451
