The skeptical cardiologist was somewhat disheartened to read the New York Times headline today that the PREDIMED study was flawed. I frequently reference this landmark randomized trial of the mediterranean diet when I’m citing the cardiovascular benefits of nuts and EV olive oil.
Science mag summarizes the problem which prompted a re-analysis of the study:
A months-long inquiry by the Spanish researchers and NEJM staff uncovered that up to 1588 people in the trial hadn’t been properly randomized: Some were assigned to the same diet as someone else in their household (a common feature of diet studies, but not reported in the original paper). Others, who lived in a rural area, were assigned to different diets based on the clinic closest to them—for example, one group had to pick up a liter of olive oil each week. “The investigator realized he couldn’t get people to travel as far as they needed so he made his study ‘cluster randomized,’” by clinic rather than by individual, Drazen says.
Here’s what I wrote about nuts and the PREDIMED study when I first started distributing Dr. P’s Heart Nuts to my patients.
The skeptical cardiologist has finally prepared Dr. P’s Heart Nuts for distribution. The major stumbling block in preparing them was finding almonds which were raw (see here), but not gassed with proplyene oxide (see here), and which did not contain potentially toxic levels of cyanide (see here).
During this search I learned a lot about almonds and cyanide toxicity, and ended up using raw organic almonds from nuts.com, which come from Spain.
I’ll be giving out these packets (containing 15 grams of almonds, 15 grams of hazelnuts and 30 grams of walnuts) to my patients because there is really good scientific evidence that consuming 1/2 packet of these per day will reduce their risk of dying from heart attacks, strokes, and cancer.
The exact components are based on the landmark randomized trial of the Mediterranean diet, enhanced by either extra-virgin olive oil or nuts (PREDIMED, in which participants in the two Mediterranean-diet groups received either extra-virgin olive oil (approximately 1 liter per week) or 30g of mixed nuts per day (15g of walnuts, 7.5g of hazelnuts, and 7.5g of almonds) at no cost, and those in the control group received small nonfood gifts).
After 5 years, those on the Mediterranean diet had about a 30% lower rate of heart attack, stroke or cardiovascular death than the control group.
It’s fantastic to have a randomized trial (the strongest form of scientific evidence) supporting nuts, as it buttresses consistent (weaker, but easier to obtain), observational data.
Despite the statistical flaws PREDIMED is still an important study demonstrating the benefits of nuts. PREDIMED was the best randomized trial data we had for nuts but there are tons of observational data which are very consistent and show a strong association between increased nut consumption and reduced mortality..
Consequently, I made up a new batch of Dr. P’s Heart Nuts in honor of the survival of PREDIMED and will be distributing them to patients today.
The skeptical cardiologist found himself reading a cookbook the other day, something he heretofore had avoided. Cookbooks somehow seem archaic and, I presumed, exclusively the domain of the women in my life. My mother had loads of them, hiding their food-stained bindings behind a cabinet door in my childhood kitchen. Whereas I can stare longingly at all manner of books on bookstore shelves, I scrupulously avoid the cooking section, finding nothing that intrigues or attracts me in their heavily illustrated contents.
The eternal fiancee’ of the skeptical cardiologist (EFOSC), I believe, had requested I find the recipes for several dishes we (more accurately, she) could prepare the next week and had headed off to Whole Foods or Nordstrom Rack or Pier 1 (all of which, strangely and conveniently sit side by side).
After receiving directions on where these mysterious tomes resided, I grabbed the cookbook that looked the most interesting: Ruhlman’s TWENTY: 20 Techniques, 100 Recipes, A Cook’s Manifesto. Instead of searching for recipes I ended up being distracted by Chapter 2: Salt: Your Most Important Tool.
In Chapter 2, Ruhlman makes the bold statement that “if you don’t have a preexisting problem with high blood pressure and if you eat natural foods-foods that aren’t heavily processed-you can salt your food to whatever level tastes good to you without worrying about health concerns.”
In the Lancet article, the authors did a pooled analysis of four large prospective studies involving 133118 patients in 49 countries. They studied the relationship between salt consumption, measured by 24 hour urine excretion of sodium (because what goes in must come out) and the incidence of cardiovascular disease and death over about 4 years.
Patients without hypertension who excreted more than 7 grams/day of sodium were no more likely to have cardiovascular disease or death than those excreting 4-5 grams/day.
In fact, in both normotensive and hypertensive groups, sodium excretion of < 3 g/day was associated with a significantly (26% higher in normotensives, 34% in hypertensives) increased risk of cardiovascular disease and death.
The only group that would appear to benefit from lower sodium consumption was the hypertensive group which excreted 7 g/day of sodium and when compared to the hypertensive group that excreted 4-5 g/day of sodium had a 23% higher risk of CV death and disease.
If we have to worry about anything with salt consumption, this study (and others) suggests that it is consuming too little salt.
The only group that need worry about too much salt consumption is those who have hypertension and who consume a really large amount of salt. Since the average American Average consumes 3.4 grams per day of salt, very few of us are consuming over 7 g/day. Despite this, The American Heart Association continues to stick by its totally unjustified recommendation that sodium levels be no higher than 1,500 mg/day, and other organizations recommend sodium levels below 2,300 mg/day.
What Kind of Salt Should We Consume
Ruhlman recommends coarse kosher salt, preferably Diamond Crystal or, if that’s not available, Morton’s.
Why? Because “salt is best measured with your fingers and eyes, not with measuring spoons.”
“Coarse salt is easier to hold and easier to control than fine salt.”
He feels that salting is an inexact skill and one should always salt to taste.
“When recipe includes a precise measure of salt, a teaspoon, say, this is only a general reference, or an order of magnitude–a teaspoon, not a tablespoon. You may need to add more. How do you know? Taste the food.”
These words were music to my ears as I am an advocate of serendipity, chaos and creativeness in the kitchen. When I make a frittata, as I did this morning, I measure nothing precisely; not the butter and olive oil used to sauté, the bell peppers, onions and garlic; not the milk mixed with the eggs; not the cheese sprinkled on top; not the time spent in the oven or even the heat; and most assuredly, not the salt and pepper.
At the end of the frittata creation process I took a bite. It was delicious but it needed something: a touch more salt. I sprinkled some David’s kosher salt on top and tried again, Perfection!
Although I have hypertension, I know (see discussion here) that my salt consumption is way below 7 grams/day and, if anything, based on the most recent studies, I should be worrying about too little sodium in my diet.
Spend a day or two accurately tracking your consumption of salt to educate yourself. I found this app to be really helpful. I’ll expand on this in a future post.
Recognize that not everybody needs to follow a low salt diet. If your blood pressure is not elevated and you have no heart failure you don’t need to change your salt consumption.
If your blood pressure is on the low side and especially if you get periodic dizzy spells, often associated with standing quickly liberalize your salt intake, you will feel better.
If you have high blood pressure, you are the best judge of how salt effects your blood pressure. In the example I gave in a previous post, my patient realized that all the salt he was sprinkling on his tomatoes was the major factor causing his blood pressure to spike.
The kidneys do a great job of balancing sodium intake and sodium excretion if they are working normally. If you have kidney dysfunction you will be more sensitive to the effects of salt consumption on your blood pressure and fluid retention.
If you are following a Mediterranean diet with plenty of fresh fruits and vegetables you are going to be in the ideal range for both potassium and sodium consumption.
When individuals discover that they have abnormal cholesterol readings they are often told to initiate lifestyle changes to try to correct them.
Based on what physicians and patients have been taught over the last twenty years, the likely dietary change recommended and the easy , first step is likely to be to cut back on dairy fat.
After all, it’s a pretty easy transition to start using skim milk and non fat yogurt because these line the supermarket shelves and have been filled with chocolate or added sugar to taste more palatable.
You might miss the great taste that butter adds to bread or cooking but for your health you would be willing to switch to non butter spreads and cut down on the cheese in your diet because based on what you have heard from numerous media sources this is a giant step toward reducing your cholesterol numbers.
Unfortunately, it is a horribly misguided step.
Although, the switch to low or non fat dairy lowers your cholesterol numbers, it is not lower cholesterol numbers that you want: what you want is a lower risk of developing stroke or heart attack or the other complications of atherosclerosis.
Let me repeat: Don’t worry about your cholesterol numbers, worry about your overall risk of developing heart attack or stroke.
Due to 30 years of misinformation, the concept that lowering your cholesterol means lower risk of heart disease has become firmly entrenched in the public’s consciousness-but in the case of dietary intervention this has never been documented.
I take care of a 69 year old woman who has an abnormal heart rhythm and chest pain. As part of her evaluation for chest pain we performed a coronary CT angiogram (CCTA) which showed advanced but not obstructive atherosclerotic plaque in her right and left anterior descending coronary arteries.
This lady was not overweight, followed a healthy diet and exercised regularly. Her mother, a sedentary, heavy smoker, suffered a heart attack at age 54.
Her PCP had obtained lipid values on her 6 months before I saw her which were abnormal but the patient had been reluctant to start the recommended statin drug because of concerns about side effects.
After seeing her CCTA I advised that she begin atorvastastin 10 mg daily and aspirin to help reduce her long term risk of heart attack, stroke.
She decided without telling me not to take the statin, again due to side effect concerns, but started the aspirin, and began to pursue what she felt were healthy dietary changes.
When I saw her back in the office she told me “I don’t eat butter or cheese anymore and I’ve switched to skim milk.” She had substituted olive oil for butter.
Here are her lipid values before and after her dietary changes (TC=total cholesterol, LDL= bad cholesterol, HDL=good cholesterol, trigs=triglycerides)
Date TC LDL HDL trigs ASCVd 10 year risk
3/2015 275 173 72 149 7.9%
10/2015 220 122 43 274 8.3%
At first glance, and especially if we focus only on the total and bad cholesterol, this appears to be a successful response to dietary changes: a 29% reduction in the bad cholesterol and a 25% drop in the total cholesterol.
However, although the LDL or bad cholesterol has dropped a lot, the HDL or good cholesterol has dropped by more: 40%!
This is the typical change when patients cut out dairy fat-the overall ratio of bad to good cholesterol actually rises.
In addition, the pattern she has now, with a low HDL and high triglycerides is typical of the metabolic syndrome which is recognized as likely to contribute to early atherosclerosis: so-called “atherogenic dyslipidemia.”
When I plugged both sets of numbers into the ASCVD 10 year risk calculator app (see here) her estimated 10 year risk of heart attack and stroke had actually increased from 7.9% to 8.3%.
Hopefully, this anecdote will reinforce what population studies show:
There is NO evidence that dairy fat consumption increases risk of cardiovascular disease (see here)
Finally, my patient is another example of an inherited tendency to development of premature atherosclerosis: her diet, exercise, body weight were all optimal and could not be tweaked to lower her risk.
Such patients must deal with the cardiovascular cards they have been dealt. If they have advanced atherosclerosis, as much as they may dislike taking medications, statins are by far the most effective means of reducing their long term risk of heart attack and stroke.
The other night I had the best cioppino I have ever had. I’ve had variations of this wonderful tomato-based seafood stew all over the world (including the legendary bouillabaisse in Marseilles) but I left my heart with the Dungeness crab cioppino served at Sotto Mare Oysteria and Seafood restaurant in North Beach, San Francisco. It makes sense, since cioppino was invented by Genoan fishermen from the SF Bay Area in the 19th century who threw together the freshest catch from their day at sea.
The recipe for Sotto Mare’s cioppino is actually available online as follows:
¼ cup olive oil
1 tsp. crushed red chile flakes
8 cloves garlic, finely chopped
3 cups fish stock
1 ½ cups whole peeled tomatoes in juice, crushed
10 leaves basil
1 lb. cod, cut into 2″ chunks
1 lb. cleaned calamari, bodies cut into ½″-wide rings
12 oz. medium shrimp, deveined
12 oz. bay scallops
16 clams, cleaned
16 mussels, cleaned
2 2-lb. Dungeness crabs or snow crab legs, halved
Kosher salt and freshly ground black pepper, to taste
It involves a lot of shellfish: calamari, shrimp, scallop, clams, mussels, crabs and I think a large part of what made it so good was the freshness of the shellfish obtained from the nearby Pacific Ocean.
Shellfish, Dietary Cholesterol and Cardiovascular Risk
Shellfish contain a lot of cholesterol and many of my patients have been told to minimize or avoid shellfish, especially shrimp, due to concerns they will exceed the (completely arbitrary) 300 mg daily limit suggested by the American Heart Association and the USDA nutritional guidelines.
There is no scientific basis for being concerned about the amount of cholesterol one consumes when eating shellfish (or for any food for that matter, as I previously wrote about with regard to eggs here)
But there are definitely warnings out there on the internet and traditional new media from seemingly responsible authorities.
“Since our bodies make plenty of cholesterol for our needs,we do not need to add any in our diet. Cholesterol is found in all foods that come from animals: red meat, poultry, fish, eggs, milk, cheese, yogurt, and every other meat and dairy product. Choosing lean cuts of meat is not enough; the cholesterol is mainly in the lean portion. Many people are surprised to learn that chicken contains as much cholesterol as beef. Every four-ounce serving of beef or chicken contains 100 milligrams of cholesterol. Also, most shellfish are very high in cholesterol. All animal products should be avoided for this reason. “
The Physician Committee for Responsible Medicine appears to be a front for vegan-promotion. They go on to state that every 100 mg of cholesterol you consume raises your cholesterol by 5 mg/dl and that
“Every time you reduce your cholesterol level by 1 percent, you reduce your risk of heart disease by 2 percent. For example, a reduction from 300 mg/dl to 200 mg/dl (i.e., a one-third reduction) will yield a two-thirds reduction in the risk of a heart attack”
A Fox News publication simultaneously extolls the virtues of shrimp consumption (noting that “three ounces of shrimp (or about seven medium-sized shrimp) has a mere 84 calories, 1g of fat, and an impressive 18g of lean protein” and that they are a great source of selenium, “an antioxidant that fights cancer-causing free radicals in your body”) and warns you against eating it (“If you are watching your cholesterol, it’s best to go easy on shrimp because four large shrimp have 42.5mg of cholesterol”)
Other publications advise those with high cholesterol or higher risk of heart disease to choose low-cholesterol varieties of shellfish over shrimp.
The Science Supporting Shrimp
Let’s look at what is actually known about consuming shrimp and shellfish.
A study of over 13,000 subjects (the ARIC study) found no increased risk of cardiovascular disease in the high shellfish consumers versus the low shellfish consumers.
A study in 1996 compared consuming a diet with 300 grams (about 10 oz.) of steamed shrimp/day (providing 590 mg of cholesterol daily) versus a baseline diet of 107 mg/ cholesterol in 18 individuals without cholesterol problems. The shrimp consumers compared to baseline had a 7% higher LDL or bad cholesterol but a 12% higher HDL or good cholesterol. Thus, the ratio of total to good cholesterol went down. We now know that this ratio is a much more important risk marker for cardiovascular disease than the total cholesterol. Triglycerides dropped significantly when subjects were consuming shrimp versus the baseline, low cholesterol diet.
A 1990 study looked at multiple different types of shellfish substituted for meat, cheese and eggs, and found that oyster, clam, crab and mussel diets (with lower cholesterol and higher omega-3 fatty acid profiles) lowered VLDL triglycerides and VLDL cholesterol. These shellfish diets, except for the mussel diet, also lowered LDL and total cholesterol. Shrimp and squid had no effect on the lipid profiles.
Benefits of Shrimp and Shellfish Consumption
I’ve focused on shrimp in this post because it has the highest cholesterol content of all shellfish and therefore is the most likely to be considered bad for heart patients or patients with high cholesterol. I’m presuming if I can convince you that shrimp are heart healthy, then you will believe that all shellfish are.
Take a look at this chart of the nutrient composition of shrimp and you can understand that, once you eliminate unsubstantiated fears of the cholesterol content, this a great food.
I am not a big advocate of examining the macronutrient composition of foods in order to predict their health benefits. This approach to nutritional science resulted in the development of highly processed low-fat monstrosities that currently sit in boxes and bags and line the most prominent parts of supermarket shelves. The overall effect of foods on the cardiovascular system depends on an incredibly complicated interaction of food components, bacteria in the gut and genetic predispositions: areas we are only beginning to understand. However, for those readers who are concerned about such things there is reassurance.
Start with the fact that there are no carbohydrates in shellfish: since carbs and added sugar are likely the biggest culprits in our obesity epidemic, shrimp and shellfish are great tools in helping to manage weight. Shrimp have a very high percentage and quality of protein content for muscle building.
Some avid shrimp promoters insist that shrimp should be consumed regularly to reduce the risk of both cancer and heart disease. The fat in shrimp is mostly polyunsaturated fat with a high ratio of omega-3 to omega-6 which is considered optimal . Eating 100 ounces of shrimp daily gives you 180 mg of EPA and DHA (considered the most important of the omega-3 fish oils for heart health) daily, close to the 250 mg daily the USDA recommends for most adults.
Astaxanthin has been found to be a potent natural antioxidant, exceeding ten times the antioxidant activity of β-carotene and 500 times that of α-tocopherol. The astaxanthin level of wild shrimps has been reported to vary between 740 and 1400 μg/100 g in edible meat portions.
If I were a vegan or vegetarian I would consider slipping shrimp into my dishes instead of tofu.
The cioppino recipe above doesn’t add a lot to the shellfish and fish: a little olive oil and tomatoes, basil and garlic-these things are not going to jack up the calories, sugar or fat content.
Depending on how you cook shrimp, the resulting dish will have markedly different nutrient composition compared to the raw nutrients listed above.
Breading and deep frying the shrimp takes 3 oz from 60 calories to 206 and the fat grams from 1 to 10. I suspect that you or your body will figure this out and eat less later. Given the fairly low fat and carbohydrate content of the Sotto Mare cioppino, I am ashamed to admit, I ate that whole bowl pictured above (which the menu said could be shared between two).
The SOSC doesn’t share my love of cioppino; she ordered the linguine with clam sauce. Three ounces of clams have only 26 mg of cholesterol but it seems to me the majority of calories in this dish are coming from the carbs in the pasta and whatever the composition of the sauce is. In any event, the SOSC pronounced it the best she has ever had.
Mercury in Shellfish
The level of mercury is a concern in all the fish that we consume. Fortunately a recent study from Maine University found that shrimp is very low in mercury. This included varieties from Thai shrimp farms, Maine shrimp farms and the Gulf of Mexico. In comparison to other types of fish, shellfish are universally on the low end of the mercury level graph as shown below.
Fear neither the cholesterol nor the mercury in shrimp and consume your cioppino with gusto and without guilt!