This story failed to answer the questions that would have made the significance of these findings more readily apparent:
Without answers to these questions, it’s difficult to understand why the new study should supersede the current consensus.
The American Heart Association recommends consumption of polyunsaturated vegetable oils rich in linoleic acid almost without reservation. It put out a statement a few years ago emphasizing that even very high intakes of linoleic acid appear to be safe and beneficial. Some nutrition researchers have long questioned the evidence supporting these guidelines, noting that the studies involved variables besides linoleic acid intake (e.g. increased consumption of omega-3 fatty acids) that could have affected the outcomes. The study discussed here contributes important information to this debate, because it suggests that increasing linoleic acid alone (without also increasing intake of omega-3 fatty acids) is not beneficial and may well cause cardiovascular harm.
In the final analysis, however, it is unclear if this nearly 50-year-old study, which also has its share of limitations, will do much to change the current consensus on what fats you should eat. Important questions will remain, and the only way they will be answered definitively is with large new randomized studies that probably won’t be performed any time soon.
ADDENDUM ON FEB. 8: Consumer Reports has just published, “Fat facts and fiction,” written by Kevin Lomangino, who was one of our reviewers of this story.
The cost of vegetable oil with linoleic acid is not in question.
The story came close to a satisfactory rating here, but couldn’t stick the landing. It says that the omega-6 group “had a 17% higher risk of dying during the study period from heart disease, compared to 11% among the control group.” It meant to say that the omega-6 group had a 6% higher risk of dying (17% vs. 11%).
We realize that in many news organizations copy editors are disappearing. And of those still around, how many have the stats sense to catch something like this?
But that’s no excuse. Inaccuracy matters.
The overall thrust of the story was about harms of linoleic acid, so we’ll call this satisfactory.
The story says the study found “convincing” evidence of a link between linoleic acid and heart disease. That’s a justifiable statement, but we’d like to have seen some acknowledgment of the limitations that the study authors themselves point to in the paper, including the fact that the margarine consumed in the intervention group likely contained trans fats, which is known to increase cardiovascular risk.
In addition, as with the competing HealthDay story, there’s no real discussion of the evidence supporting current recommendations and how these new findings differ from that research. The story says that current recommendations are “based on a review of the available data,” but without a more complete description, it’s really impossible to fully understand why the new results are considered groundbreaking.
The competing HealthDay story did include a statement about the limitation of the study’s generalizability to broad populations.
There was no overt disease-mongering.
The story includes a comment from an American Heart Association spokesperson, who interestingly suggests that the new research may play a role in a re-analysis of the organization’s diet guidelines. That’s different than the stance taken by the spokesperson contacted by HealthDay, who hinted that the results wouldn’t have much effect on current recommendations.
Even a brief mention of other approaches to reduce cardiovascular risk, such as other lifestyle changes (e.g. quitting smoking), drug therapy, and surgery, would have earned a satisfactory here. It would have required only a few more words to do so.
As with the competing HealthDay story, there really wasn’t enough information about the fatty acid composition of different vegetable oils, including which ones are rich sources of linoleic acid (e.g. safflower oil and corn oil) and which ones have a balance of omega-3 and omega-6 fats (e.g. canola, soy). There’s still good evidence that the latter group are healthier than saturated fats. As with the previous criterion comment, it would have not taken much space to explain this to readers.
The story notes that the mortality findings of this study were previously reported in 1978, and that the cardiovascular findings are new. That’s more detail than HealthDay provided.
This story has enough original reporting that we can be sure it wasn’t based on a press release.