Just when you thought it was safe to go back to the breakfast table: eggs are in the news again, and this time the news ain’t good. This week the nutritional research ouija board people once again asked the eternal question:
And the answer (for this week) is:
Many readers of this blog know that this is definitely not my first eggs rodeo. I follow egg news very closely and make sure Fit is a Feminist Issue followers are always informed of the latest in good-egg-bad-egg research. Here are some of my previous forays into ovo-journalism:
Tracy has also written often on food morality: not demonizing foods, avoiding all-or-nothing thinking about nutrition.
Okay, time to give y’all the 411 on the newest egg nutrition results. There is a serious question that nutrition researchers have been wrestling with for decades: what, if any, relationship is there between dietary cholesterol intake and mortality risk? The answer is (as it always is in real science, especially nutrition science): it’s complicated. Here’s some background from the New York Times coverage of the new study, that came out in JAMA on Friday:
Eggs are a leading source of dietary cholesterol, which once was thought to be strongly related to blood cholesterol levels and heart disease. Older studies suggesting that link led to nutrition guidelines almost a decade ago that recommended consuming no more than 300 milligrams of cholesterol daily; one egg contains about 186 milligrams.
Newer research questioned that relationship, finding that saturated fats contribute more to unhealthy levels of blood cholesterol that can lead to heart problems.
The latest U.S. government nutrition guidelines, from 2015, removed the strict daily cholesterol limit. While eating as little cholesterol as possible is still advised, the recommendations say eggs can still be part of a healthy diet, as a good source of protein, along with lean meat, poultry, beans and nuts. Nutrition experts say the new study is unlikely to change that advice.
So what’s new about this study? Here’s what CNN had to say about it:
The researchers examined data from six US study groups including more than 29,000 people followed for 17½ years on average. Over the follow-up period, a total of 5,400 cardiovascular events occurred, including 1,302 fatal and nonfatal strokes, 1,897 incidents of fatal and nonfatal heart failure and 113 other heart disease deaths. An additional 6,132 participants died of other causes.
Consuming an additional 300 milligrams of dietary cholesterol per day was associated with a 3.2% higher risk of heart disease and a 4.4% higher risk of early death, Zhong’s analysis of the data showed. And each additional half an egg consumed per day was associated with a 1.1% higher risk of cardiovascular disease and 1.9% higher risk of early death due to any cause, the researchers found.
Here’s where things get a bit interesting and more complicated. News sources are not consistent in their reporting of these results. The New York Times said this about the results:
The researchers calculated that those who ate 300 milligrams of cholesterol daily — about 1 ½ eggs — were 17 percent more likely to develop heart disease than whose who didn’t eat eggs.
So which is it? Eating 300mg of dietary cholesterol a day, or 300mg MORE of dietary cholesterol (than what?) a day is bad for me? I think the New York Times got it wrong this time.
I went to the original paper, which is long (15 pages, a lot for a medical journal), and has loads of tables with loads of data. In the discussion section (which is always what you want to read when tackling these technical papers), they raise a bunch of issues that bear directly on how to interpret their results, how to understand their results in contrast with eggs-good research results, and what they think is really going on with respect to eggs, dietary cholesterol consumption, and mortality risk:
- previous meta-studies have been all over the place, finding positive, negative and no correlations between more frequent (more than one a day) egg consumption and risks of death from various diseases.
- Apparently egg consumption has been associated with low physical activity, smoking, and “unhealthy dietary patterns” (according to the paper). So it’s hard to separate egg consumption effects from these other effects.
- The associations found between egg consumption and mortality risk were modest, but statistically significant.
- Researchers claim a dose-response effect of egg consumption, which means the more eggs you eat, the higher the effect.
Their discussion raised some questions for me:
- Do the researchers think there is a “safe/normal” intake amount of dietary cholesterol? They say the mean intake in the US is 289mg/day, and that taking in 300mg more per day (which would be 1.5 eggs, including half the extra yolk) increases all-cause mortality. But what is their nutritional goal here?
- When researchers say egg consumption should be reduced, what do they have in mind for its substitutes? Eggs are a big source of animal protein, and lots of other sources have more saturated fat, which has its own scary back story.
- As always, I am wondering to what extent statistical or research significance translates to clinical or medical significance?
- All eating happens in social and cultural and economic contexts– if you ask people to reduce eating X, will substituting Y make things better or worse?
What do you think, dear readers? Is this new egg news throwing a monkey wrench into your brunch plans? Are you vegetarian or vegan and don’t care? Is this a reason to increase our vegetarian or vegan eating? Are you inclined to just turn the page and dismiss the nutritional research as a mass of confusion? Should we short-sell egg futures (I don’t know what that means, exactly, but I think it sounds business-y)? I’d love to hear from you.