Food For Thought: An Interview with Nutrition Scientist Dr. Paul Saltman
Department of Biology, University of California, San Diego,
by Sean Henahan, Access Excellence
We are barraged by the media with endless claims and
promises about the value or risks of what we eat and drink and
what we take in the way of dietary supplements. Where is the
science? I spoke with nutrition science authority Dr. Paul
Saltman, professor of biology at UCSD, and author of various
texts and popular books about the science of nutrition, in an
effort to separate some nutrition facts from food fiction.
We hear so many claims and promises about what's good for us and
so many pronouncements about what's bad for us to eat. How can a
person bring a scientific approach to the task of sorting
through all this information?
A: I have a basic premise when I teach about
food and nutrition. Food is metaphysics. What we eat, when and
how much, has much to do with our culture and religions, our
economic and social environment, with our age and lifestyle.
Although it provides the nutrients by which we live, food is not
in itself a science, it is a sensual experience required for
Nutrition, in contrast, is an exact science. It is
experimentally verifiable through the strategies of what is
known as total parenteral nutrition (TPN), i.e. intravenous
feeding. With TPN feeding all of the nutrients that a human
being needs from the time of infancy to the latter years one can
be maintained alive and well and growing without ever eating a
morsel of food or drinking a drop of liquid.
This is the science. We know there are 44 chemical nutrients
required for TPN. We understand what their chemistry is and what
their structures are. There is nothing esoteric or magic about
it. These nutrients are not kosher, not Szechuan or Cantonese,
not chocolate or vanilla, they are chemicals. These 44 chemicals
really constitute the true staff of life.
Humans have evolved relatively rapidly from a caveman existence
to the world of today. Can we learn anything about human
nutrition by looking at what our prehistoric ancestors ate? For
example, some people like to claim that we evolved while eating
a diet primarily composed of forage.
A: There is good news and bad news. Those of us
that have the luxury of adequate nutrition and supplies of clean
water and the ability to get rid of our wastes have a longer
lifespan and better health than do those who are less fortunate.
We've learned about agriculture, public health, even about
medicine. The bad news is that, in the developed nations at
least, when you have ample supplies of inexpensive foods that
taste good, we get obesity and the consequences of obesity,
which are enormous.
We have evolved. The Pima Indians evolved to meet the needs of
living in the desert. In their case genetic selection was for
those with the most effective metabolism and ability to conserve
scarce resources. Make available a 7-11 and a six pack of beer
to people with this genetic background and you've got people who
are very obese and very sick from heart disease and diabetes.
We are living longer and reproducing more. We have challenged
the planet because of the growing population, using energy and
resources in a way which frequently becomes deleterious, but
need not be. The issue is how do we balance this well being from
man commandeering the world versus the needs of the roughly
two-thirds of the population that do not get enough to eat.
The cave-man model of the primal vegetarian diet makes no sense.
It is Rousseau's notion of the noble savage. It is nonsense. We
should go back even before man, to chimpanzees. It is often said
that these beautiful primates, precursors of humankind, are
vegetarians. They are not. They love meat. Indeed, recent
research shows they will really hunt to get meat, and using a
human analogy, will use meat to beg for sex. We did not evolve
from a vegetarian culture. We became less vegetarian and more
dependent on meat in our diet as a consequence of being able to
raise via animal husbandry, animal sources of protein.
I believe obesity is the root cause of many forms of cancer,
heart disease and stroke and many other aspects of human
disease. But we are living longer now with our current diet than
Cro-Magnon ever did. The reason Cro-Magnon's didn't have a lot
of cancer is that they didn't live long enough to get cancer.
Some of the first scientific understanding of essential
nutrients came with the observation that a lack of certain
nutrients was associated with some disease states, for example,
scurvy. How has the study of nutritional deficiency contributed
to the science of nutrition?
A:One of the first cases studied carefully was
the case of polished rice and beri-beri in the Dutch East
Indies. Dr. Eichman found that polished rice caused this
terrible disease and that eating the rice polishings that had
been removed would relieve the symptoms of the disease. That was
a beautiful demonstration of a thiamine deficiency disease.
The subsequent isolation of the different vitamins led us to
understand through the vitamins (one of only six of essential
nutrients groups) some mechanisms of action of specific
nutrients. This led to a way of looking at nutrition considering
the mechanisms of water, calories, carbohydrates, fats,
proteins, amino acids, minerals. This is a whole different way
of knowing why and how these 44 nutrients are essential for the
human organism to thrive grow and reproduce.
Vitamins are only part of the story. For example it is equally
important that we understand the mechanisms of how calcium is
used, how potassium and sodium are in balance in terms of
electrolyte balance inside and outside a cell, and why magnesium
is required, and how phosphate serves the body. These are every
bit as important as knowing about vitamin C and its role as a
co-factor in the hydroxylation reactions of proteins.
Antioxidant vitamins get a lot of attention these days. Go into
a vitamin store and you will see promises of eternal youth. But
these promises are made on supposedly scientific grounds. What's
going on here?
A: Let me say unequivocally. There is no
unambiguous double-blind, prospective controlled experiment that
show that doses of antioxidants greater than those required by
the USDA allowances have any value as a protectors against
disease, or as curative agents once a disease occurs, other than
in the case of deficiency disease. The notion of mega-dosing
popularized by Linus Pauling with vitamin C, has yet to be
proven in an unambiguous fashion. That bothers me. If I believed
that there was data supporting the use of mega-doses of
antioxidants, I would be swilling E, and taking mega-doses of C
faster than anyone. However, I don't see that data.
We know oxidative damage occurs in tissues. I've studied the
role of iron and copper in nutrition. These elements are
required for life. but in excess or bound in wrong fashion they
can cause free radical damage. I believe vitamin C is an
antioxidant but I also know it can be a pro-oxidant under proper
circumstances and can cause extensive damage to cells and
Because I know that oxidative damage is bad doesn't mean that
anti-oxidants are good over and above what has been found to be
required in experimental studies.
Will it ever be possible to answer these claims one way or
another with scientific studies?
A: Yes, I believe so. Prospective studies with
antioxidants are underway. Science requires repeatable
experiments. If a nutrient is useful you will see an effect. We
went down into Durango, Mexico with Mexican physicians and
fortified the milk with iron and copper. We were able to
demonstrate in controlled double blind studies that in children
who didn't look anemic we could move hemoglobin concentrations
20% above where they started. This is a marked increase. We know
the better your hemoglobin levels, the more oxygen you deliver,
the better your myoglobins and cytochromes. This in turn
produces better vitality, health and growth.
The WHO has numerous programs to provide fortification and
supplements of essential nutrients.
A: These programs have emphasized the
importance of both micronutrients and macronutrients. There are
good examples where adding nutrients such as amino acids and
calcium have made a difference in public health.
Calcium is a good example of complementary nutrients. It's not
just a matter of taking calcium is it?
A: Prospective studies with calcium show that
if women take RDA amounts of calcium it will increase bone
density. Adding trace elements can add bone density for
post-menopausal women. These are facts demonstrated by
On the one hand, if women took 1000 mg of calcium per day with
or without vitamin D they will increase bone density. But, women
should also take vitamin D, fluoride, trace elements and get
exercise. And if post-menopausal, women should consult a
physician regarding hormone replacement therapy. All of these
factors play a fundamental role in health and maintenance of
Similarly, iron is much more effectively used when taken with
copper. If you add one copper for every ten irons, you can get
by with a lot less iron. We also know that sugar, organic acids
and other molecules in the diet enhance the uptake of the
various metal elements.
At the moment there is a new push at WHO to include long chain
polyunsaturated fatty acids (PUFAs) in formula Q: fatty acids.
LC-PUFAs and formula.
A: That is a small part of the fat problem.
Infants need PUFAs. We all do. The issue with formula is that
you want to mimic as much as possible what's in human mothers
milk. Everyone in the pediatric community agrees mothers milk is
the best way to sustain growth and development in the child. So
with formula the issue is, if the mothers' milk has PUFAs, so
should the formula.
Fat is often portrayed as the enemy for adults trying to eat a
healthy diet. Is fat all bad?
A: We live in world filled with fear of fats
and cholesterol. People and organizations proclaim that 30% fat
in the diet will make us healthy. Yet, when we go back to TPN,
the IV bag can contain as much as 55% calories in fat. People
receiving TPN do not get fat on this diet. They are not obese
and don't have heart disease. The French diet is about 45%
calories from fat, yet they have half the level of obesity, and
half the level of heart disease of this country.
The physics of calories states that all calories are equal. That
is a thermodynamic truth. A calorie from fat equals a calorie
So what's wrong with fat? Fat makes food taste good. When food
tastes good, you eat more. Eat more calories you get fat.
Obesity is the number one nutritional disease in USA. It is a
disease of self-abuse, with more calories in the than out. If we
eat more than we exercise, more than our basal metabolic rate
can sustain. we suffer the physiological detriments from that
obesity. If we could control obesity we would have major handle
on one of the biggest panoramas of health problems in America
There is some confusion about PUFAs. We know that these
essential fatty acids are required as precursors to make
prostaglandins and related compounds necessary for cell membrane
structure. In general PUFAs are said to make good fat, i.e.
high-density lipoprotein, where saturated fats make the low
density lipoprotein. Good guys, bad guys, we're back into
metaphysics. The point is that some fatty acids relate to the
balance between high density and low density lipoproteins.
However, the most important issue is your total glyceride
concentration in your blood stream. That is what correlates best
There are guidelines handed down from above on what constitutes
a healthy diet. What is a rational person to make of these
A: This is a very complicated question. Part of
me says bless the FDA and USDA for all of the research that has
taken place in the 20th century. This research has brought
nutrition to be an exact science and has given the term
'nutrition' meaning in this country in terms of developing the
well being of the people. Whether you are talking about six
basic food groups or four basic food groups, circles that look
like peace signs or triangles and pyramids, the notion that
people are concerned about the health of the nation is good.
But these guidelines have not been without problems. For
example, George McGovern's committee formulating the 'Diet for
a Healthy America' made terrible mistakes, scientifically as
well as intellectually in terms of the belief that you can tell
people what to eat and what to do and that's going to make them
better, healthier people. It's important to remember that
nutrition guidelines are made by committee.
Can't the public can be excused for being confused when the
government changes it mind every couple of years?
A: Yes, and the scientists change their minds
too. These mixed messages leave us terribly confused and makes
it even worse than before. This is why I'm doing the class. The
level of illiteracy in America is so great that we haven't got
enough knowledge to pose the questions properly and force the
governments and responsible health groups to produce evidence
for their claims. We believe the latest bumper sticker slogans,
the latest dogmatic statements. When these start to get into
conflict, people say the hell with all of it, I'm going to have
a hamburger and a malt and french fries, or at the other end of
the spectrum, bean sprouts and brown rice. What concerns me
above all is to give people a level of science literacy so they
understand where the science ends and the metaphysics begins.
This kind of grounding would allow people to make informed
decisions about their own lives. People need to know the
consequences of what they do, not believe in the magic of
either the hamburger or the bean sprouts. With this knowledge
anyone can make you own diet in your life that includes an
integrated intake of nutrients as food and/or supplements.
I believe in supplements. I believe the government has made
terrible mistakes in the past. For example, not recommending
folic acid supplements to pregnant women. I think it is obscene
when the government says food is the only way to get adequate
nutrition. That's wrong. If they were right, you couldn't have
TPN. Yes, it's right and healthful to have a good diet, if you
make selections predicated on your age, your lifestyle, your sex
and your genetics.
Our lifespan and general health are determined by our genetic
background, as are elements of our weight level and metabolism.
How do recent
discoveries about the "ob" and "fat" genes, and the gene
product "leptin" contribute to our understanding of nutrition?
A: The genetics is not really new. Scientists
have been studying genetically predisposed obese rats for 35 or
40 years, trying to understand what genes are at work and what
the gene products are. It turns out there are at least five and
possibly as many as ten or twelve genes involved. Do we know
that there is a genetic component in human weight? Of course.
Many twin studies have shown this.
The leptin research is fascinating. Leptin is the first gene
product we've identified, and we're still looking for others.
Now we need to find out if leptin affects satiety, basal
metabolic rate etc.
The question is, what's going on here? There is not a diet for
everyone. Rather, there is a diet for each one of us. There are
an infinite number of diets within the space defined by the
number of calories we need, adequate amounts of the 44 chemical
nutrients we need, and our age, sex, lifestyle and genetics.
Each one of these parameters is interdependent on each of the
If you are a bicycle rider in the Alps eating 10,000 calories a
day, I'm not interested in how many calories a typical human
should have each day, I'm interested in the needs of that bike
rider. If you are sitting on a couch channel surfing, your
calorie needs go down. Your basal metabolic rate changes with
age. Your genes affect your basal metabolic rate.
QUESTIONS FROM THE ACCESS EXCELLENCE FELLOWS AND THEIR
Some weight loss programs advise drinking several glasses of ice
water, with the explanation that water increases the metabolism
of fats. Is this true?
A: You burn fat with
oxygen and release energy. If you drink ice water, a small (but potentially significant) amount
of this energy would be used to raise the temperature of water to body
temperature. Drinking water is good for several reasons.
Water fills you up and so you don't eat as much.
Water is zero calories, and it's good nutritionally to drink
eight glasses of water.
After aerobic exercise metabolism is said to be higher for a
little while, is this true?
A: No question about it, it's true. The great
benefits of exercise are in terms of weight management and
cardiovascular health. When you exercise you require more
calories, you burn more energy. As you raise your energy up with
exercise, your body returns to its normal basal metabolic rate
slowly, over a period of about two hours. Depending on how much
you exercised, the amount of excess energy burned as this rate
goes down, since you are continuing to burn calories even though
you are resting. The most interesting aspect of exercise, not
fully appreciated by coaches is loss of appetite. Really good
exercise causes a loss of appetite. Top athletes often have a
problem eating enough to restore calories.
A teacher asks for clarification on how fat cells communicate
with other tissues in the body, and whether some foods make your
more fat than others.
A: The communication issue is not nearly as
important as the thermodynamic issue. The first law of
thermodynamics states "if you eat it and don't burn it, sit on
it". You sit on these calories stored as glycerides in your
adipose tissue. Some people have more fat cells than others,
meaning some may have a tendency to store it more easily than
others. But you won't store it if you haven't got it.
The notion that some foods are more fat-producing than others is
true, but only over and above the line of how many calories you
have to burn in order to maintain your basal metabolic rate. It
takes more energy to store carbohydrates as fat. But we don't
store much carbohydrate, less than a half a percent is glycogen.
So you may get a little benefit by eating carbohydrates. The
other thing is that carbohydrates fill you up, so you don't eat
Is it true when a person is exercising aerobically that they do
not use up stored glycogen at the same rate as if they were
A: Yes. The beauty of aerobic exercise in terms
of burning calories is that the optimally trained athlete will
burn 70% fat, 30% carbohydrates. But if you don't have the
oxygen, you are forced into a glycolytic pathway in which you
are forced to used carbohydrate stores, making your ATP by
glycolysis, not having adequate oxygen in effect to burn the
fats and carbohydrates through the Krebs cycle, which can
generate 13 times more ATP than can glycolysis.
However, there are other athletic events, such as sprinting,
that are anaerobic in nature. That is where you want to be able
to use energy the other way. You train for different muscles and
with different method.
A teacher asks about claims made in best-sellers about
antioxidants in terms of aging.
A: The evidence is clear that as animals age,
there is a deposition of more end products of oxidative damage
to cells, such as lipofuscin- a pigment that's made from lipids
and lipid derivatives. Also your burden of mutations increases
over time, and the repair mechanisms become less effective. But,
to say that I'm going to live forever with mega-doses of
antioxidant vitamins, there is no evidence for that. You will
live longer if you are not obese and you exercise and don't
abuse your body.
There is a lot of interest in performance nutrition products
geared towards athletes and would-be athletes. These power bars
and super drinks often boast ingredients such as complex
carbohydrates and amino acids that supposedly enhance
performance. Is there any scientific basis for these products?
A: These are high priced goods. What are they
selling you? Calories in the form of carbohydrates, fats,
proteins, along with vitamins, minerals. You can get all of
these in the supermarket. The best, cheapest amino acid
supplement is dry milk powder.
Your body has never seen a complex carbohydrate in its blood
stream. Every carbohydrate you have ever eaten has been broken
down to glucose and absorbed. Just as sugars are broken down to
fructose and glucose and absorbed. There is no difference. The
only think is that when you eat complex carbohydrates you
usually eat them with other foods and it fills you up.
But there is also the metaphysics of food again. If you eat a
power bar and you believe it will give you the mystical powers
of the super athletes that are endorsing it, then you will play
above the rim. It's part of psyching yourself up for an event.
If you are an athlete you want to make sure than your eating the
nutrients that are in the TPN bag. Many athletes are actually
low on calcium and low on iron. Why? Because their coaches say
don't drink milk because of the mucous, and don't eat meat
because of the karma. So where are they going to get calcium and
the trace elements?
A teacher who climbed Mt. Everest asks about the effects of
high altitude on metabolism. The teacher reports experiencing
reduced appetite and altered metabolism of what was eaten. Is
the metabolism less efficient because of reduced oxygen?
A: Absolutely. Oxygen is required to burn the
fuels of the body. The net result of this at low oxygen tension
is that you burn carbohydrates, which don't have much to spare,
then start burning down your protein, reducing your muscle mass.
Your entire respiratory system is compromised by low oxygen
tension. Your appetite is reduced because you are under severe
The sherpas in the Himalayas eat a very high fat diet. They
don't read the literature about carbo. loading, and they survive
much better than the climbers on the high carbo. diets Fat is
fuel, the high test variety.
One component of fat that gets much public attention is
cholesterol. Yet there seems to be some debate as to whether
reducing your cholesterol makes any difference, except in people
with genetic hypercholesterolemia. How does cholesterol fit into
A: It is true that people with high serum
cholesterol have a higher risk of heart disease. Two kinds of
people have high serum cholesterol. One kind has lousy genes
that can't control cholesterol synthesis. These people need to
be treated with drugs that lower endogenous cholesterol levels.
They also need to reduce weight. Similar pathways are involved
in making and storing lipids and making and storing cholesterol.
People on TPN have zero cholesterol in their bags. They make all
of their own cholesterol. The whole idea that dietary is the
causal link to high serum cholesterol is wrong. What is right
is- show me a high cholesterol food and I'll show you a high fat
food. You go for seconds and you're not working out, you've got
And yet talk to anyone on the bus and they think lowering
cholesterol is a good idea.
A: Right, because it says so on television. The
doctor and scientist types appearing on television are telling
people that cholesterol in the diet is a fundamental issue. It
is not. It is only an indirect issue.
The Mediterranean diet appears to contain the basic elements of
a well balanced, low fat diet. Can we learn about nutrition by
looking at the cultural phenomenon of food?
A: The ideal Mediterranean diet contains the
TPN nutrients in the form of the old basic four food groups. The
key to diets like the Mediterranean diet is the cultural
attitude that you don't eat a lot of it. It came about
originally for economic reasons but the attitude persists for
moderate consumption. In some poor areas they couldn't have rich
foods. Gluttony is not part of those cultures.
Look at the Japanese situation. Their native diet is very low
fat, but with an increase in Western fatty foods, we see an
increase in heart disease and obesity. The most nutrient dense
food in the supermarket containing all 44 nutrients and all four
food groups is a pizza. So its crazy to call pizza junk food.
Similarly, why call an apple a health food? What does it
contain? Very little in the way of nutrients. It comes down to
the same thing again, a balance of calories and nutrients
determined by your age, sex, and your lifestyle.
Part of the Mediterranean diet is a nice glass of wine. Is there
enough data now to conclude benefits from alcohol in the diet?
A: Basically, it appears that alcohol is good
for you in limited amounts, currently defined as between one and
three drinks per day. The evidence from prospective and
retrospective randomized studies is unambiguous. The evidence
shows that moderate alcohol consumption reduces the incidence of
coronary heart disease. It doesn't have to be wine and it
doesn't have to be red. The issue is alcohol. Alcohol acts to
reduce the time of blood clotting and thus prevent clot
formation in the vessels leading to the heart. Alcohol also
shifts the concentration of lipid density in favor of HDL.
Moreover, a couple of glasses of wine can reduce a lot of
psychological stress that can lead to hypertension. The bad
news is that some people can't handle one or two drinks.
Alcoholism is a serious disease. Again, this comes down to
individual awareness and decision making.
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Dr. Art Ulene