A study conducted by scientists at the Fred Hutchinson Cancer Research Center and Ohio State University concluded that increased blood levels of the omega-3 fatty acids derived from fatty fish or fish oil raise the risk of prostate cancer, particularly the more aggressive form of the disease. One critic of the study, Joie Meissner, a naturopathic physician from LifeChangeMedicine, states that there are numerous methodological shortcomings to this study that lead her to question its validity. Meissner was skeptical of the outbreak of news stories about the study and decided to do more digging. The Intelligent Optimist interviewed her to find out more of her thoughts on the way that the study was conducted and the validity of the results.
What are omega-3 fatty acids? What are their perceived benefits?
“Omega-3 fatty acids are polyunsaturated fats that are necessary for sustaining life. These fatty acids are essential, meaning that the body cannot produce them and so we must obtain them from our diets. Foods like fish, fish oil and flax seed oil are rich sources of omega-3 fatty acids.
“Inflammation plays a major role in many disease processes, and omega-3 fatty acids are thought to reduce inflammation. There is strong evidence that increased intake of omega-3 fatty acids reduces the risk of certain cardiovascular conditions such as coronary heart disease and there is promising evidence that increased omega-3 intake may be beneficial for a number of other health conditions including neurological conditions such as bipolar depression and attention-deficit hyperactivity disorder (ADHD) and for inflammatory diseases like rheumatoid arthritis, asthma, and many others.”
What were your initial thoughts about the results of the study on how omega-3 fatty acids were linked to prostate cancer?
“When I first heard it announced on the news I was very skeptical of the media’s presentation of the study, but wanted to look into it further. The more I looked into the study the more convinced I have become that the study is not capable of providing any scientific evidence that omega-3 fatty acids are involved with the development of prostate cancer.”
What makes the study flawed?
“There are a surprising number of serious methodological shortcomings in the study. Some of these significant deficiencies include the following. The scientists, lead author Theodore Brasky and his colleagues, did not document the participants’ intake of omega-3 fatty acids such as whether the men in the study were taking fish oil supplements or eating fish. There are some important reasons to believe that the blood testing that was used in the study did not reliably establish the men’s omega-3 intake throughout the duration of the study.”
“Researcher William Harris, who is an expert research scientist in the field of fatty acid research, has pointed out some of the study’s profound methodological faults. Harris used data from the famous Framingham Heart study, to compare with data used in Brasky and co-worker’s study. The Framingham study looked at common characteristics that contribute to cardiovascular disease including dietary fatty acid intake. Professor Harris’ calculations reveal that the men in the Brasky et al. study had blood levels that were too low for them to have been taking fish oil supplements or eating high amounts of fish or other omega-3 rich foods at or prior to the time their blood was tested.
“Because there is no reliable evidence that the men in the study were taking fish oil or eating high amounts of omega-3 rich foods like fish, media reports that this study proves that fish oil causes prostate cancer are completely unfounded.
“Harris points out another weakness in the study’s methodology namely that differences in the omega-3 blood levels of the men who were not diagnosed with prostate cancer, the control group, compared to the men who were diagnosed with prostate cancer are too small to be meaningful. Something like metabolism or basic genetic differences can account for these slight differences in their blood levels, rather than the amount of omega-3s in their diet.”
Are there any helpful observations this study made?
“If anything, this study brings to our attention the need to understand that the ways that scientific research is conducted can be so flawed that we cannot rely on studies with such severe flaws. On the positive side, researchers may be able to learn from the influx of critical analysis that is likely to result from this study. These critiques may also help researcher design better future studies.”
Are there ways we can distinguish between an accurate study and a flawed one? Are there "warning signs" the general population can look out for?
“Common sense can play a part. For example, humans have been eating fish throughout recorded history and in countries like Japan, the population has a much higher omega-3 intake than in the United States yet these populations have significantly lower rates of prostate cancer. But in general, it’s hard for the laymen to know about the detailed flaws of a study’s methodology; they’re not scientists nor physicians, but they can look out for certain things like what the previous body of research has shown and check to see if the news reports of the study weighthe benefits against the risks. The public can ask what is the evidence that this is harmful or beneficial for me? because it depends on how something will affect individuals with different health conditions.
“When reports on new, controversial studies offer just a sound bite, it makes it easy to jump to conclusions without examining all the evidence. Taking the time to get more information will go a long way to making the best health decisions.”
Joie Meissner is currently working on an upcoming article on the Brasky and colleagues study. Find out more here.
A note
The Intelligent Optimist asked Theodore Brasky for his reaction to Meissner’s findings. He states that participants were asked about their regular diet and supplement use, but that they specifically examined blood levels of fatty acids. The study was performed explicitly for this reason because there is a lot of error in asking people to recall their regular diet. He points out that his team compared the rate of developing prostate cancer among men in the highest level of omega-3 compared to the lowest. The difference translates to about 1 serving of fish/day, much more than the estimates Harris gave according to Meissner. He furthermore mentioned that “if the study were fatally flawed, it would not have passed anonymous review by our peers, nor would it have been published by the editors of the Journal of the National Cancer Institute.”
Photo: Gwen
