Is it okay to eat butter now? “It’s not a sin,” says Steven Nissen, MD, chair of Cardiovascular Medicine at Cleveland Clinic. Dr. Nissen and other top cardiologists want you to know that things are changing in our view of diet and heart disease.
Indeed, the new federal government-commissioned Scientific Report of the 2015 Dietary Guidelines Advisory Committee includes some surprising departures from previous advice. Old beliefs have been overturned and new research avenues opened. Some controversies have heated up. Things are moving fast.
In case you missed something, Health Hub shares this roundup of the latest developments in our understanding of diet and heart disease.
Okay, take a deep breath. We’re going to talk about cholesterol.
High-levels of cholesterol in the blood are strongly associated with coronary artery disease in patients of all types and ages. If you have a high level of cholesterol in your blood, you need to work with your doctor to make it lower, or face a higher risk of heart attack, stroke or other cardiovascular event.
But here’s the big news – you may not have to give up high cholesterol foods like butter, beef and bacon.
Many kinds of fat
“High cholesterol is a metabolic condition that can only be moderately influenced by diet,” says Dr. Nissen.
“Most circulating cholesterol is produced by the liver. Dietary cholesterol accounts for only about 15 to 20 percent of blood cholesterol. Changing the diet typically has only a modest effect on serum cholesterol levels.”
According to the above-cited Scientific Report, “Available evidence shows no appreciable relationship between consumption of dietary cholesterol and serum (blood) cholesterol.”
Down with no-fat diets
Dr. Nissen is strongly opposed to highly publicized low-fat diets that supposedly reverse coronary artery disease.
“You can use a bit of butter to flavor your food,” he says. “Moderation is key. There are a lot of reasons to hedge your bets, but you don’t have to absolutely avoid saturated fats. You just want to keep them under control.”
There is one kind of dietary fat that Dr. Nissen and everyone else says you should by all means avoid: trans fats. Trans fats are found in many fast foods, junk foods and commercial processed foods.
Also known as hydrogenated vegetable oils, they are totally linked to heart disease and should be shown no mercy.
Why do experts sometimes change their minds about what’s good for you and what’s not? Because the science is always getting better.
“High-quality research requires meticulous methodology of the sort that’s evolved only recently with development of the randomized controlled trial,” says Dr. Nissen. “Research before the modern era relied mostly on observational studies, with all their inherent biases.”
One study that Dr. Nissen strongly endorses is the PREDIMED investigation, published in the New England Journal of Medicine in 2013. Looking at a high-risk population of 7,500 people, it found that a Mediterranean diet including extra virgin olive oil or nuts reduced the incidence of major cardiovascular events.
“This is a high-quality study that blows the low-fat diet myth out of the water,” he says. “It’s good news for people advocating a sensible, balanced and tasty diet. Go Mediterranean and enjoy life!”
High blood pressure raises the risk of heart attack, stroke and other deadly conditions. If you have high blood pressure, you need to work with your doctor to get it lower. But you may not have to give up salt.
For a long time, salt has dominated the popular view of high-blood pressure and its prevention. But a recent study of more than 8,000 adults found only a modest relationship between salt intake and systolic (the top number) blood pressure. This study found that most important modifiable risk factor for high blood pressure is body mass index – in other words: lose weight.
Red meat, eggs and dairy: Not off the hook
For generations, eggs and red meat have topped the list of foods implicated in cardiovascular disease because of their high levels of dietary cholesterol.
But the new science-led exoneration of fat described above would seem to let red meat and eggs off the hook. And it largely has, as regards fat. But a whole new line of investigation focused on intestinal bacteria is keeping eggs and red meat in the spotlight.
Going for the gut
Stanley Hazen, MD, PhD, Section Head of Preventive Cardiology and Rehabilitation at Cleveland Clinic, has published one study after another linking the metabolic product of bacterial digestion of substances found in red meat and egg yolks with development of pathologies ranging from atherosclerotic plaque to heart failure to chronic kidney disease.
According to Dr. Hazen’s findings, increased blood levels of a compound formed by gut microbes following consumption of foods such as red meat and egg yolks are associated with increased risk of adverse cardiovascular outcomes, including death, even when controlling for other cardiovascular risk factors and traditional blood test results.
A new bad guy
Briefly, here’s how it works: Red meat and eggs (plus some dietary supplements and energy drinks) contain choline and carnitine, which gut bacteria metabolize into TMA (trimethylamine).
TMA travels to the liver, where it is converted to TMAO (trimethylamine-N-oxide) and released into the bloodstream.
There, TMAO becomes a factor that promotes vascular inflammation and formation of unstable plaques in arterial walls. The influence of TMAO on cardiovascular disease is significant enough to have prompted Dr. Hazen to develop an assay to assess cardiac risk by measuring plasma TMAO.
Eat meat or not?
So what are the dietary implications of these findings? When Dr. Hazen did a study comparing 51 habitual meat eaters with 26 vegetarians or vegans (Nat Med. 2013;19:576-585), he found that the vegetarians and vegans had much lower concentrations of plasma TMAO than did the meat eaters.
But he notes that recommendations must await further studies. “While multiple studies with thousands of subjects show high levels of TMAO predict increased future risks for heart attack, stroke or death, studies haven’t yet directly tested whether lowering TMAO lowers cardiac risk,” he says.
For now, Dr. Hazen recommends moderation. “If you eat a lot of red meat, this study argues to consider cutting back,’’ he says, noting that the same goes for eggs.
Here’s where we stand
You can eat meat, eggs, butter, nuts, dairy and some oils in moderation. Add a little salt, if you like. Enjoy a Mediterranean diet.
Remember this: It’s not the fat in your food that’s going to give you a heart attack. It’s the fat on your body. Lose weight. Being overweight or obese raises your risk of heart attack, stroke, diabetes, cancers, and joint disease. Talk to your doctor about the best and safest way to do this.
Back to the future
In the 1973 movie Sleeper, Woody Allen plays a health food store owner who awakens from suspended animation into a future world where scientists have reversed the current wisdom and now consider deep-fried foods, steak, cream pies and hot fudge to be the real health foods. The joke always gets a big laugh. But it seems we have moved somewhat in that direction, at least where some fats are concerned.
One thing we know for certain is that dietary recommendations will continue to be fine-tuned as scientists continue to study food’s complicated effects on health.