Dr. David L. Katz, MD, MPH, FACPM, FACP, FACLM is Director of the Yale University Prevention Research Center and a nationally recognized authority on nutrition, weight control, and the prevention of chronic disease. He is the author of Nutrition in Clinical Practice: A Comprehensive, Evidence-Based Manual for the Practitioner (three editions) and Disease Proof: Slash Your Risk of Heart Disease, Cancer, Diabetes by 80% or More, among other volumes. His scientific paper, "Can We Say What Diet is Best for Health" (Annual Review of Public Health, 2014), received more than 85,000 downloads, becoming the most downloaded article in the journal’s history. In addition, Dr. Katz led the scientific expert panel that developed the ONQI® (Overall Nutritional Quality Index) algorithm, which powers the NuVal® Nutritional Scoring System. Shoppers at about 2000 supermarkets nationwide can consult displayed NuVal product scores ranging from 1 to 100 to help them make the healthiest food purchases possible in those stores.
HHN: You discuss in Disease Proof that all of us have the ability to drastically slash our risk of heart disease, cancer, diabetes, and more, just by practicing 3 lifestyles habits: 1. consuming a healthy diet, 2. getting adequate physical activity, and 3. not smoking. As you report, a Centers for Disease Control (CDC) study of 23,000+ adults found that those who did all 3 lifestyle habits had a marked 82% reduced risk of dying in the 5-year study period.
How did that CDC study define "healthy diet," and today how would you define it? What would you say are the most important healthy diet "to dos" and "not to do’s" based on the nutrition science known to date?
DK: The evidence that these 3 lifestyle practices can prevent 80% of disease is stunningly strong, voluminous, and consistent, deriving from just about every imaginable methodology, over the past 20 years. And one of the beautiful things about it is just how simiple the prevailing measure of good diet proves to be.
In the 2009 study you mention, the researchers defined a healthy diet as "habitual intake of vegetables, fruits, and whole grains." That was it. They just asked people, "Do you routinely, [pullquote-right] "The evidence that 3 lifestyle practices can prevent 80% of disease is stunningly strong." [/pullquote-right] every week, include vegetables, fruits, and whole grains as part of your diet?" If the answer was "Yes, most days of every week I eat those foods," your diet was good, and if the answer was "No," your diet was not so good. That’s the incredibly simple, fundamental foundation of a healthy diet—in contrast to the din and discourse in our culture about whether health is all about gluten or grains or GMO. Disease was 80% less in people who got this diet plus physical activity plus not-smoking right than people who got them wrong.
I would define a healthy diet in much the same way. If your diet is mostly composed of vegetables, fruits, and whole grains—plus, I would add beans, nuts, seeds, and drinking water—you cannot go too far wrong.
Does your diet need to be high in fat or low in fat, or somewhere in between? The short answer is yes, it needs to be one of those [pullquote-right] "Some of the world’s best diets are high in fat and others are low in fat." [/pullquote-right] options. Of the world’s best diets—those associated in large populations, across a span of generations, with a combination of longevity and vitality—some, such as traditional Mediterranean diets, are high in fat, and others, such as traditional vegetarian diets and Asian diets, are low in fat.
In essence, then, the best diets are not only simple but broadly defined. You don’t have to follow one diet or cuisine for health. You have lots of options.
And having these choices is really important. To habituate healthy eating, you need to be able to pick the diet that works best for you and your family. You need to be able to love the food that loves you back.
Diet Changes the Human Body
HHN: Can you explain what will happen within our body if we follow these healthy diet prescriptions?
DK: In simple terms, 3 main pathways wear our bodies down:
But at the same time, we need all 3 to live. I’ll explain.
[dropcap]1[/dropcap] Inflammation: Our bodies are constantly battling hostile forces—viruses, bacteria, parasites, etc. How it sends off the foreign marauders and then repairs what’s needed basically works the same way as a big house project. The first step is always deconstruction: stuff gets knocked down. Then, after deconstruction, comes reconstruction.
So whenever there’s a bodily injury, cut, or fracture, the damaged site has to go through demolition—and inflammation does the job. [pullquote-right] "How our bodies send off foreign marauders and then repair what’s needed basically works like a big house project." [/pullquote-right] White blood cells flood in. Some of them are like PacMen, actually chewing up damaged tissue. Others release what are essentially chemical weapons in the form of various molecules which erode the damaged tissue. Later, other cells go in and do the repair work.
In short, inflammation is continuously performing two vital functions for us: tissue repair and defensive warfare against foreign marauders.
[dropcap]2[/dropcap] Oxiation is also part of the body’s same defense system. The white blood cells release a variety of oxygen-free radicals, which are oxygen molecules combined chemically with other molecules in a way they can bind to proteins. As a result, they can bind to the surfaces of bacteria and viruses, thereby inactivating those marauders.
Unfortunately, however, excessive inflammation and oxidation damage the body:
- Too much inflammation—where the body’s immune system mistakenly initiates an inflammatory response even though there’s no apparent inflammation to fight off—can lead to chronic disease.
- With too much oxidation, those defending white blood cells will also corrode the surface of other cells. Basically, oxidation is rust. When oxidation is excessive, our white blood cells bind to other cell surfaces via proteins in our blood (which contains iron) and rusts them. Biological rust then distorts the essential protein molecules.
When inflammation and oxidation are disproportionate, they contribute to all major chronic and neurogenerative diseases, expedite [pullquote-right] "If we didn’t have inflammation or oxidation, we would immediately succumb to foreign invaders." [/pullquote-right] wear and tear on the body, and accelerate the aging process on the cellular level. Yet, if we didn’t have inflammation or oxidation, we would immediately succumb to foreign invaders and be incapable of repairing the damage done to our bodies every day.
So the key here is balance.
Now, the modern Western diet, excessive in saturated fat, sugar, and starch, has been shown to increase inflammatory molecules in the blood and oxidation, hastening aging.
But a healthy diet has been shown to mitigate inflammation and oxidation damage, restoring both to their "sweet spot." [pullquote-right] "The modern Western diet has been shown to hasten aging." [/pullquote-right] And once your vital organs are healthier, they perform their jobs better—filtering and cleaning your blood better, transporting nutrients and oxygen to your organs better—which makes your body healthier still. All this consequently slows the aging process.
HHN: How do we know on a cellular level that an unhealthy diet hastens aging and a healthy diet lengthens life?
DK: We can measure this in various ways, but the best one may be the length of our telomeres, which are the caps at the end of our chromosomes. There’s a strong correlation between the length of telomeres and life expectancy: the lengthier our telomeres, the longer our life expectancy. They’re essentially like a timepiece at the end of our chromosomes, counting out how much time we have left for our cells to remain healthy.
Telomeres get shorter with excessive inflammation, oxidation, and age. But when you adopt a an optimal diet, you line up that "sweet spot," telomeres tend to lengthen.
Of course, sufficient physical activity and not smoking are vital as well. All these are at the bedrock of influencing the fundamental health of the human body.
The Skinny on Saturated Fat
Honest Health News: Let’s dig now into the nuances of foods we’ve been told not to eat, which can be considerably more confusing. The new dietary guidelines for Americans advise us to reduce our sodium intake and to limit calories from saturated fats, added sugars, and cholesterol. Beginning with saturated fat—Is the takeaway from all the research really as simple as "reduce all saturated fat from your diet"?
DK: If you aggregate all the evidence from animal, cell culture, observational epidemiology, and human intervention studies on outcomes such as atherosclerosis (disease from plaque build-up inside the arteries), coronary disease, high LDL cholesterol, and so on, they line up. Saturated fat looks pretty damning.
That said, not all saturated fat is the same. Saturated fat is a class of fat, with diverse members, and not all kinds have been associated with disease. For instance:
[dropcap]1[/dropcap] Stearic acid, a long-chain saturated fat that predominates in dark chocolate, is well established to be innocuous. It doesn’t promote inflammation or oxidation. It doesn’t advance arthrosclerosis.
Now, just because stearic acid is harmless does not mean it’s good for us. I’ve never considered harmlessness the benchmark for optimal nutrition.
It turns out, though, that dark chocolate is good for us, because it’s extremely rich in bioflavinoid anti-oxidants, magnesium, fiber, and a beneficial protein called arginine. The stearic acid allows allows these other benefits to come through.
[dropcap]2[/dropcap] Lauric acid is another saturated fat, short-chain, that predominates in coconut. It also appears to be harmless, although the evidence is somewhat less well-developed than that for stearic acid.
So, if people are getting most of their saturated fat from unsweetened cocoa, or cacao beans to be more accurate, everything is fine. And if they’re getting most of their saturated fat from coconut, they may be fine as well.
HHN: Now, the research shows that saturated fat in conventional, processed, antibiotic-containing meat and dairy is harmful to the body—but do we know for a fact that saturated fat from grass-fed meats or dairy, from healthfully raised animals, is equally harmful? Could it be that the saturated fat is interacting with other elements in processed conventional meat/dairy and then doing damage?
DK: We don’t know whether the harm would be the same if people only ate meat and dairy from optimally raised animals. [pullquote-right] "We all need to stop focusing on nutrients for health." [/pullquote-right] My guess is that we would see much less harm. There’s still likely to be harm, though, because, to go back to our prior discussion, it’s very well-established that most saturated fat is inflammatory, and excess inflammation is not good for the body.
In effect, then, we could put error bars around the saturated fat conclusion and say: Saturated fat may be a problem in part because of the particular foods which contain it.
But on another level I also have to say: It doesn’t really matter. Because, as far as I’m concerned, we all need to stop focusing on nutrients for health. We’ve been doing this for decades, and it’s only brought us harm:
- We talked about cutting more fat, but we didn’t eat more broccoli; we ate fat-free cookies and got sicker and fatter.
- We talked about cutting carbs, but we didn’t eat more wild salmon; we ate low-carb brownies and got fatter and sicker.
The focus on saturated fat is just one example of a replication of the follies of history.
HHN: Why do you believe focusing on saturated fat is "a replication of the follies of history"?
DK: Earlier in this interview we discussed that "harmless doesn’t mean helpful." So, even if it turns out that organic, grass-fed meats and dairy aren’t particularly harmful, you certainly are not going see the anti-inflammatory, anti-oxidizing, anti-aging benefits provided by vegetables, fruits, whole grains, beans and seeds.
Here’s another way of explaining it. The NuVal food scoring system, which I helped create, is the only [pullquote-right] "Even if it turns out that organic, grass-fed meats and dairy aren’t particularly harmful, you certainly are not going see anti-aging benefits." [/pullquote-right] the system scientifically proven to prevent chronic illness, based on the medical literature. Food items in participating supermarkets are rated from 1 (least healthy) to 100 (the healthiest). To arrive at scores, we factored in the 30 most influential nutrients for human health; each product’s "good" nutrients (fiber, vitamins, minerals, etc.) are divided by its "bad" nutrients (saturated fat, sodium, sugar, etc.).
So, for example, compare NuVal’s healthiest meat vs. beans for protein:
The 4 Healthiest Meats
TURKEY, BREAST, SKINLESS 73
CHICKEN, BREAST, SKINLESS 57
BEEF, ROAST, ROUND, TOP 55
PORK, CHOPS, FRESH, TOP LOIN 48
4 Healthy Beans
BLACK BEANS 100
GARBANZO BEANS 100
KIDNEY BEANS 100
These— and a number of other beans— get perfect 100 scores, because besides containing protein, they are also rich in healthy nutrients, such as fiber, omega-3, vitamins, and minerals.
From this broader perspective, while saturated fat has some relevance, any single nutrient variable is the wrong topic. The right topic is: What foods should people be eating if they care about their health?
Clarity on Cholesterol
HHN: With that said, many people do remain confused about cholesterol, for good reason. The new dietary guidelines cite "strong evidence" that eating patterns which limit dietary cholesterol are linked to a lower risk of heart disease, and recommend eating as little dietary cholesterol as possible—but no longer provide a specific cholesterol target (formerly under 300 mgs). Also, some foods you yourself have acknowledged as healthy, such as sardines and salmon—ranked 94 and 93 out of 100 respectively on the NuVal nutritional rating system—are quite high in cholesterol:
The 5 Healthiest Fish
SALMON, ATLANTIC 93
CATFISH (BASA, PANGASIUS, SWAI) 91
TUNA, SKIPJACK 91
DK: Given the way most people in the world are eating now, I personally believe that variation in dietary cholesterol is not a major determinant of any health outcome. Isolated cholesterol, as far as I can tell, has minimal discernable effects on health.
Now, there is debate here. Some colleagues I trust and admire point out, "Yes, but, if you have an optimal vegan diet and then you add dietary cholesterol to it, your LDL and overall blood cholesterol go up."
That may very well be, so if we ever arrive at the point where most Americans are eating an optimal vegan diet, we can revisit this discussion. Right now, as I see it, it’s mostly a distraction.
Now, cholesterol is the same molecule no matter what food it appears in. But, akin to our earlier discussion, the real difference between the cholesterol in one food and another is everything else going on in those foods.
So yes, there are cholesterol-rich healthy foods, such as sardines and salmon, which contain high levels of omega 3 fatty acids, which have been shown, among other things, to protect against heart disease. Eggs are another example of a high-cholesterol that is extremely concentrated in a wide variety of nutrients.
It’s also instructive to view cholesterol and saturated fat through the lens of the Stone Age diet. This native diet is relevant. [pullquote-right] "The real difference between the cholesterol in one food and another is everything else going on in those foods." [/pullquote-right] The bodies of any species need to be well adapted to the diets available to them, because species that cannot adapt will not survive and propogate. So, what do we know about our human ancestors ate 50,000 years ago?
Admittedly, it’s very hard for most of us to remember what we ate yesterday, and thereby damn near impossible to speak with certainty about 50,000 years ago, so we’ve got pretty wide error bars around the particulars of the Stone Age diet. Still, we do know a lot about the basics. And it’s pretty clear that
- cholesterol was a significant component, coming from bone marrow, organ meats, and eggs;
- saturated fat was not a major source of human calories, because there wasn’t much of it around in the Stone Age.
HHN: If our Stone Age ancestors were eating meat, how could their diets be low in saturated fat?
DK: Today, about 35% of the calories from grain-fed beef cattle, the kind of beef most people eat, come from fat, and much or most of [pullquote-right] "The kind of meat our Stone Age ancestors ate is closest to today’s antelope meat, and almost none of its fat is saturated." [/pullquote-right] that fat is saturated. However, according to paleo-anthropologists, the kind of meat our Stone Age ancestors ate is closest to today’s antelope meat. Now, only about 7% of the calories in our antelope meat come from fat, almost none of it is saturated fat, plus quite a bit of it contains omega 3 fatty acids.
So, in effect, when people talk about eating meat today just like our ancestors did, they’re really talking night and day.
The real takeaways here are that our ancestors' diet was relatively high in cholesterol and fairly low in saturated fat. One could then surmise that the human body is adapted to run pretty well on a cholesterol-rich diet, provided that it is also fairly low in saturated fat.
Salt Certainties & Surprises
HHN: Let’s now zero in on salt/sodium, another area with conflicting stances. Current U.S. dietary guidelines say Americans should limit daily sodium intake to 2,300 mg, but the American Heart Association recommends a 1500 mg daily maximum, and some experts say there isn’t sufficient evidence for the latter recommendation. Is it really important to monitor our sodium intake? And, if so, how can people do this practically, with which guideline?
DK: The evidence is clear that excess sodium is a liability. The principal concerns are heart disease, hypertension, and stroke, as well as osteopenia, or thinning of the bones.
Excess sodium stresses the heart, so it figures in cardiomyopathies, which are essentially distortions of the heart wall muscle. These, in turn, can contribute to heart disease and heart failure.
As for hypertension and stroke, my colleagues at the Center for Science in the Public Interest maintain that 150,000 Americans die prematurely [pullquote-right] "There's an association between high sodium intake and low bone mass, perhaps because calcium tends to travel along with sodium out of the body." [/pullquote-right] do with every year from stroke, due mostly to hypertension, due mostly to excess sodium. Frankly, I don’t know whether the figures or associations are that clean, but excess sodium intake certainly figures into stroke, and even if we put wide error bars around the numbers, it’s still a major calamity.
Also, excess sodium is associated with an increased loss of sodium in the urine, and calcium tends to travel along with sodium, thereby out of the body. So there’s an association between high sodium intake and osteopenia (low bone mass) and potentially with osteoporosis and its related fractures.
HHN: Where do you stand on the maximum quantity question?
DK: I stand in the place of pragmatism. To me, whether 1500mg or 2300 mgs per day is optimal is secondary to the fact that right now, [pullquote-right] "No matter whether the maximum quantity of daily sodium is 1500mg or 2300mg, most of us are consuming way the hell too much." [/pullquote-right] which most Americans are consuming well over 3000 mgs of sodium a day—and some up to 6,000 mgs! So, practically speaking, no matter what the "right" number is, which we don’t know yet, most of us are consuming way the hell too much. Excess sodium is a clear and present danger.
Here’s the easiest way to take action and lower your numbers: 80% of the sodium in the typical American diet has nothing to do with the salt shaker [pullquote-right] "Eighty percent of the sodium in the typical American diet has nothing to do with the salt shaker and everything to do with processed food where the salt was already added." [/pullquote-right] on people’s kitchen tables, and everything to do with processed food where the salt was already added. Plus, for the most part, the problems with these processed foods go way beyond salt. They tend to be made of quick-loading carbohydrates which rapidly break down into sugar and the wrong kinds of fat. They’re also usually replete with artificial colorings and flavorings, preservatives, and high concentrations of added sugar.
The breakfast cereal aisle is a perfect example. No one seems to realize that most leading breakfast cereals are more concentrated in sodium than anything in the salty snack aisle.
HHN: Most breakfast cereals really have more salt than potato chips?
DK: Yes. In a typical breakfast cereal mix, let’s say a cereal with multi-colored marshmallows, the salt has to compete with 47 other ingredients, including absurd amounts of sugar. When you’re in competition for flavor, it takes a lot of sodium to make a meaningful difference in taste.
In contrast, if your salty snack is potato chips and the recipe has 3 ingredients—potatoes, oil, and salt—you don’t need that much sodium for the salt flavor to stand out.
You should see the sodium content of Cheerios. Or Pop Tarts. Astronomical!
These cereals, in contrast, are excellent options:
Top 5 Cold Cereals (As Available in Participating Supermarkets)
|ARROWHEAD MILLS ALL NATURAL NATURALLY NUTRITIOUS ORGANIC PUFFED KAMUT CEREAL 99|
|SIMPLY FIBER BENEFIT NUTRITION ALL NATURAL CRUNCHY O’S CEREAL MADE FROM BRAN, WHOLE GRAIN WHEAT & WHOLE GRAIN CORN 99|
|KELLOGG’S MINI WHEATS UNFROSTED WHOLE GRAIN WHEAT CEREAL 93|
|ARROWHEAD MILLS ORGANIC SPROUTED MULTIGRAIN FLAKES 93|
|POST 100% NATURAL WHOLE GRAIN WHEAT SHREDDED WHEAT ORIGINAL BIG BISCUIT 91|
Top 5 Hot Cereals (As Sold in Supermarkets Carrying NuVal Ratings)
|QUAKER OAT BRAN HOT CEREAL 100|
|HODGSON MILL PREMIUM QUALITY MULTI GRAIN WITH QUINOA & FLAX HOT CEREAL 100|
|UDI’S STEEL CUT OATS CURRANTS, FLAX & CHIA 98|
|LOVE GROWN FOODS SUPER OATS CHIA SIMPLY PURE HOT CEREAL BLEND 97|
|BOB’S RED MILL 100% WHOLE GRAIN QUICK COOKING BULGUR WHEAT 94|
HHN: Recent studies indicate that different individuals respond differently to the same foods. Might optimal sodium intake also vary from person to person?
DK: Even a single person’s optimal intake may change depending upon what else he or she eats—again, human physiology being more subtle [pullquote-right] "A person’s optimal sodium intake may change depending upon what else he or she eats." [/pullquote-right] than just "What did this one nutrient do?" What may matter more, in part, is the ratio of consuming sodium to potassium. If our diet is very rich in potassium, a bit more sodium may be fine, and if our potassium intake is lower, we may be better off with somewhat less sodium.
And yes, it’s quite possible that people have different optimal sodium intakes. The following example is still a matter of debate, but I think it’s worth telling:
The Africans being brought to America on slave ships were treated horrendously. Those who survived the voyage arrived at the brink of starvation and dehydration.
Generations later, today’s African Americans seem especially prone to high blood pressure.
One theory is that many African Americans are descended from those slaves. On the slave ship, if you couldn’t withstand deep dehydration, you died. Therefore, those who survived had to have been particularly robust in weathering dehydration. This means they were good at hanging on to salt, which hangs on to water.
High salt retention was a critically important biological adaptation if you were being dehydrated to death on a slave ship, but it’s not such a good trait if you’re living today in the United States in the land of Golden Arches.
Still, no matter who you are today, the same greater guidelines apply. If you eat a diet comprised predominantly of fruits, vegetables, whole grains, beans, nuts, and seeds, and drink water, guess what? Your sodium intake is going to be fine. Your potassium intake will likely be high, and everything else will mostly sort itself out.
HHN: So, if we took away all the processed foods and people were basically getting their salt from a salt shaker, would we even be having this conversation?
DK: We wouldn’t need to have this conversation, for 3 reasons.
[dropcap]1[/dropcap] Our taste buds are adaptable little fellas. When they can’t be with the foods they love, they pretty readily learn to love the foods they’re with. Stated in more scientific terms, familiarity is a very potent driver of taste preference.
[dropcap]2[/dropcap] is tolerance, a key element of addiction, in which the more you get, the more you need. While whether food is addictive is a matter of debate, [pullquote-right] "If we’re bathing our taste buds in absurd amounts of sodium even when we’re eating foods that aren’t supposed to be salty, the amount of salt it takes for us to feel satisfied goes up and up and up." [/pullquote-right] it’s been established that people who eat lots of sugar need more sugar to enjoy sweetness, and people who consume excessive salt need ever more to enjoy saltiness. So, if we’re bathing our taste buds in absurd amounts of sodium even when we’re eating foods that aren’t supposed to be salty, the amount of salt it takes for us to feel satisfied goes up and up and up. Instead, if we’re getting salt only from a salt shaker, our salt sensitivity goes up, meaning it takes less to stimulate and satisfy our taste buds, and we will simply prefer and use less salt.
[dropcap]3[/dropcap] No one would be inclined to shake as much salt as the amount engineered into processed factory food. To reach the 1,500 mg daily maximum per the American Heart Association without eating packaged food, you’d have to shake about ¾ teaspoon of salt, and to reach the 2300 mgs daily maximum per the U.S. Dietary Guidelines, you’d have to shake an entire teaspoon.
So yes, I think the conversation goes away where people use a salt shaker as they wish and are not eating foods engineered with absurd amounts of sodium.
All of this withstanding, as we’ve discussed, it’s time for us to stop fixating on what individual nutrients are good and bad for our health, and start applying what science has taught us about how to eat for a long and vital life.
That is a largely-plant-based diet comprised mostly of vegetables, fruits, whole grains, beans, nuts, and seeds. We are best nurtured from nature.by