The One Diet Shown To Prevent Heart Disease
Diets to prevent cardiac disease are rarely studied in randomized trials, and only one is backed by data
This is a post I published some years back, now re-edited and updated for subscribers who asked me about diet, health, and longevity.
The woman had sudden squeezing chest pains that traveled to her arm, and she was already in the ICU. But not as a patient. She was a nurse, and knew too well what the pain could mean. She informed her supervisor, walked to the elevator, and came down to the ER, where she described her symptoms to me with seasoned calm.
Hours later, tests in hand, we were relieved. Her pain was gone and it wasn't a heart attack. But fear lingered, and after a near miss she wanted an action plan. "What about the new diet?"
She was referring to the Mediterranean Diet which, it turns out, wasn't new even then. In the 1990s studies showed people assigned to a Mediterranean Diet after a heart attack had fewer heart attacks and died less than those assigned to an American Heart Association diet. But a newer study was making news because of the subjects—healthy men and women, with no heart problems. Like her.
It is a paradox that trials to prevent heart problems are usually done on people who already have them. Why? Math. People with heart disease have strokes and heart attacks at rates far higher than healthy people, which gives researchers something to improve upon. The chance a healthy nurse will suffer a heart attack or stroke is tiny, less than 1 percent. It's tough to prevent things that rarely happen, and trying to prove it mathematically means randomizing thousands of people, then following them for years.
Enter: the Mediterranean Diet study published in 2013, with more than 7,000 healthy people followed for five years. Those are unusual numbers, big enough to show convincingly that fewer heart problems (strokes, heart attacks, and deaths) occurred in the Mediterranean Diet group than people assigned to a low-fat diet. The newer twist—using it to prevent a first heart problem—extended the proof to healthy people like my ICU nurse for the first time.
There are very few randomized trials (the gold standard in research) testing diet for the prevention of heart disease, the world’s number one killer. Most studies are observational, watching and recording as people report their diet habits over years. Interesting data, but much less reliable. It’s the kind of data that leads to constant flip-flopping. Caffeine’s good! No wait, it’s bad. Drink red wine! No wait, it’s a killer. Never eat dairy. Wait… butter’s baaaack! Only the Mediterranean Diet has shown a potentially life-saving benefit in large-scale, long-term randomized trials. Everything else has either failed, or remains guesswork.
I recommended she start the Diet. Then she asked about statins. Her doctor had suggested the drugs a year before. Like the Mediterranean Diet, statins have been studied in both healthy people and heart patients. For some heart patients the benefits can trump the harms but in healthy folks not so much. In one large review the drugs reduced heart attacks and strokes by a relative 25 percent—almost as good as the 30 percent seen with a Mediterranean Diet. But experts everywhere seem to agree on the Diet, while there’s debate about statins for primary prevention. In one issue of the Journal of the American Medical Association prominent cardiologists took opposing views.
Why debate statins but love on the Diet? According to cardiologist Dr. Rita Redberg, then editor-in-chief of JAMA-Internal Medicine and author of the con view, it’s because with drugs there’s no free lunch. Muscle damage, liver problems, and diabetes all occur with statins. But not with a Mediterranean Diet. The only downsides are related entirely to the loss of some foods, but check out what that ‘sacrifice’ looks like. To me it has always seemed more like a vacation on the Riviera than a ‘diet’.
And now, a decade later, in March of this year, a drug company-backed group of researchers who for years published rosy reviews touting statin benefits, finally released their diabetes data. Long after the last patent expired on a statin in the US, the group confirmed what skeptics like Redberg knew all along: For many, including the great majority of healthy people, harms are more likely than benefits with statins.
Which clarifies Redberg’s point and highlights what's unusual about a Mediterranean Diet: It is a free lunch. No losers, just rare winners. Yes, rare: to be clear roughly 1 out of every 60 people who switches to the Diet avoids a heart attack, stroke, or death (far better than the 1 in 125 with statins). But when a benefit like that comes without any chance of medical harms, among heart therapies that is unique.
And better yet, it’s better than the balance of benefits and harms with statins. Which is why Dr. Redberg told me: "If the Mediterranean diet was a pill, it would be a blockbuster."