Our food choices and preferences, and our
idea of what is or is not food, are strongly determined by social and cultural influences.
Let me show you some of the things I normally eat in Italy, and that I like a lot. This
is a horse steak, pretty common in Europe. This is a steak and kidney pudding, one of
the national dishes in the UK. This is a french boudin noir, made with pork’s blood. This
is deep-fried breaded brain, so soft and creamy and delicious. This is fegato alla veneziana,
beef liver with onions. This is a french “terrine” made with chicken livers and hearts. That’s
me eating a spleen and lung sandwich in Palermo, Sicily. Down there it is a very popular sandwich,
made with calf lung and spleen, a squeeze of lemon juice and melted cheese.
This is a vietnamese market selling bugs and larvae, cheap, good quality proteins. I did
try them once, but it took me a lot of effort. I do however like snails, and frog legs, both
traditional foods in northern Italy. For food much like for anything else, the
idea of what is considered normal or appropriate, is a product of our culture. Slaughtering
a dog for food is not any more cruel than slaughtering a cow, yet the though of eating
dog meat or cat meat, which is normal in many areas of china or vietnam, may repulse you
much like many indians would be disgusted at the thought of you eating cow meat, which
they consider sacred. Trying exotic dishes like mealworms, snake, or the yummy fish eyeball
sushi that you see in this picture, is an individual choice, but respect for the habits
and traditions of other cultures, in the kitchen much like in every other area, is indispensable
(doveroso). What we are going to do now is take a a quick
survey of the major food groups that constitute our typical Western diets. Please note that
this is not a complete classification of food items. We are just going to quickly go through
the main food categories to which we will refer many times during this course, so that
we know what we are talking about. We will also say a few words for each of them just
to familiarize a little, but by no means this is intended to be a complete nutritional evaluation
of these foods: that would require a separate course on its own! Let’s start with plant foods. Fruits and
vegetables are a very heterogeneous group of edible plant products. It is a category
that makes more sense from a nutritional and commercial point of view, but it is quite
arbitrary from a botanical perspective. When we say fruit, for example, we actually only
refer to sweet fruits. Eggplant, cucumber, bell peppers and tomatoes are all fruits,
botanically, but because they are less sweet, we call them vegetables. The name vegetable
can also refer to other part of the plant, for example leaves like spinach, roots like
carrot, flowers like broccoli, bulbs like onion, underground stems, or tubers, like
potatoes, and many more. Plants can also be eaten at different stages of the growth cycle,
for example, most plants can be eaten as sprouts. Of some plants we also eat the seeds. Seeds
belonging to the family Leguminosae are called legumes, and they have very particular nutritional
characteristics, so in nutrition we treat them as a separate category. The edible seeds
of other plants, that are not legumes, are just called nuts and seeds, and they also
constitute a separate nutritional category. A very particular type of fruits are those
belonging to the family Gramineae. These fruits are dry and fused with their seeds, and they
are called caryopses. We call them grains or cereals, and nutritionally they constitute
yet another category. Fruits are very rich in water and fiber, contain
little or no fat, small amounts of proteins, variable amounts of carbohydrates, mostly
simple sugars, and then organic acids, some vitamins, minerals and other bioactive compounds
such as polyphenols. As the fruit ripens, its organic acid contents decrease and its
sugar content increases. The composition of vegetables is very similar to that of fruit,
but they have less sugars, so their caloric value is even lower. They also, provide a
lot of water, fiber, and micronutrients. Keep in mind however that although we often associate
the word vitamin with fruits and veggies, they do not provide all of the vitamins we
need. Vitamins C, provitamin A, vitamin K, and some B vitamins such as folic acid are
abundant in fruits and vegetables, but other vitamins such as vitamin D, vitamin E or other
B vitamins are scarce or absent. Some vegetables also have a lot of the pigment
chlorophyll, which makes them green. There are some particular fruits and vegetables
that have unique nutritional composition so they need to be treated separately. For example,
some of them are starchy, meaning they contain a lot of complex carbohydrates, for example
potatoes, sweet potatoes, bananas and cassava. Some other are fatty, because they contain
more lipids, for example avocados, olives, or coconuts. This is the nutrient composition
of an apple with skin, as you can see it’s mostly water, with a significant amount of
carbs 12% and some fiber, which you mostly lose if you peel it. This is lettuce, and
now it’s really mostly water, with a little carb, protein and fiber. This is a banana,
again lot of water but also 20% of carbs which includes the starch, some proteins and fiber.
And this is a potato with its skin, water, 15% of carbs misty starch, 2% of proteins
and 2% of fiber, again, if you remove the skin you lose the fiber which is why you should
never peel a potato. You also have noticed that none of these plant foods had significant
amounts of lipids. Nuts and seeds are much more energy dense
than fruits and vegetables, because they have much less water. They have a lot of good quality
lipids, and good quality proteins. They also provide a lot of fiber, the amino acid arginine
which is cardioprotective, essential fatty acids, polyphenols, and many vitamins and
minerals including vitamin E and several group B vitamins.
Walnuts, hazelnuts, almonds, pistachio nuts, macadamia nuts, cashew nuts, pecan nuts, brazil
nuts, pine seeds, sunflower seeds, pumpkin seeds, flax seeds, sesame seeds, chia seeds
and poppy seeds are all members of this category. Peanuts grow undergrounds and are technically
legumes because they belong to the family leguminoseae, but nutritionally they are closer
to nuts and seeds so we put them in this category as well.
Let’s have a look at the composition of walnuts, as an example. You can see that 65%
of its weight is made of lipids, whereas only 6% is water. There’s an excellent 15% of
proteins, 7% of fiber and 7% carbohydrates. These are sunflower seeds. There’s a little
bit less lipids, but still more than half, a lot more proteins, 21%, and then again fiber,
water, and carbs are around 10%. These are peanuts. About half of their weight
is lipids, they have much more proteins, 26%, and water, fiber and carbs all slightly below
10%. We use the word “cereals”, or “grains”,
to identify to kernels of plants belonging to the family gramineae. These are actually
a particular type of fruit, which is fused with the seed and we call caryopsis. The most
common are wheat, corn, rice, oats, barley, millet, and rye. Although the word cereals
reminds many people of the box of breakfast cereals, keep in mind that a slice of bread,
a bowl of rice, or a serving of pasta, are all cereals as well. Anyway in this course,
to avoid confusion, we will mostly use the word grains to refer to this category.
Each kernel of grain is composed of four different parts: the husk, the bran, the endosperm,
and the germ. The husk is the outer shell of the kernel, it is mostly made of fiber
and it’s generally inedible so it must be removed. The bran is a second, inner shell,
it’s made primarily of insoluble fiber but it also has B vitamins, phytochemicals and
minerals such as iron, chromium, and zinc. The germ is the internal seed made primarily
of unsaturated lipids, it is very rich in vitamin E to protect them from oxidation,
and it also has B vitamins and phytochemicals. The endosperm is the largest part of the kernel,
and it is made primarily of starch, although it also contains some proteins, a little bit
of fiber and some vitamins. When we talk about whole grains, we refer
to kernels to which only the outer inedible husk has been removed.
When the kernel underogoes a milling process to also remove the fiber rich bran and the
lipid rich germ, leaving only the starchy endosperm, we obtain a refined grain. Later
in this course, we will discuss the huge nutritional difference between whole grains and refined
grains. In the grain category we also put the so-called
pseudo-grains, which are not grains botanically because they don’t belong to the family
gramineae, but they have very similar nutritional value. Some common psudo-cereals are buckwheat,
quinoa, and amaranth. Again let’s make a couple examples, here
we have whole brown rice, 73% of its weight is starch, 12% water, 8% proteins, 3% lipids,
and 4% fiber. This is pasta made with refined wheat, almost 80% of it is carbs, 6% water,
11% proteins, 1% lipids and 3% fiber. This is bread made with whole wheat flour,
43% of it is water, bread is much more moist than pasta, the rest is 34% carbs, 13% proteins,
7% fiber because this is whole, and 3% lipids, again because it’s whole and has the lipid
fraction of the germ. When we say legumes we usually refer to the
seeds of plants of the family leguminoseae, such as beans, peas, chickpeas, lentils, broadbeans
or soybeans. However sometimes the whole fruit of these plants is eaten, for example green
beans, or the sprouts such as alfalfa sprouts. Legumes are excellent sources of proteins
and starch. They are a great source of group B vitamins and they provide a lot minerals
such as iron, calcium, potassium, and many other. Also, legumes are an excellent source
of dietary fiber, both soluble and insoluble. On the whole, they are a very precious food
group and it’s a shame that a lot of people hardly ever eat them.
This is the composition of dry lentils, 30% of their weight is carbs, 26% proteins, 30%
fiber, 1% lipids and the rest is water. These are soybeans, you notice they have an exceptional
amount of protein, 36%, then 20% lipids, which is also way more than other legumes, but them
they have less carbs, 21%, 9% fiber, and the rest is water. Mushrooms are technically not vegetables because
they are not plants at all, they are a special type of fungus. Once more, in nutrition we
ignore the biological taxonomy and we can consider edible mushrooms to be vegetables
because they share most nutritional characteristics. A similar case goes for edible seaweeds. They
are large, edible marine algae, so they are not plants at all, but practically we can
consider them to be vegetables, although they do have some unique nutritional characteristics,
and particularly they are the best dietary sources of the mineral iodine. Let’s now move on to animal foods. Their
main strength is that they provide a lot of high quality protein, and they are the only
sources of vitamin B12. They also provide more zinc, copper and vitamin D than plant
foods. With the word meat we normally refer to the
muscle of animals, be it beef, pork, chicken, turkey, lamb, rabbit, and many other. Other
organs such as the liver or kidneys, are also commonly eaten, but because they have very
distinct and generally superior nutritional value than muscle meat, we put them in a separate
group and refer to them as organ meats. Other meat products, such as processed meats or
cold cuts, also have separate nutritional characteristics and should be considered separately. Let’s look at a veal steak. 76% of it is
water. There’s no fiber and negligible amounts of carbohydrates. About 21% is high quality
protein, and 3% is lipids. This is after all visible fat has been trimmed off, otherwise
its lipid content would be a lot higher. There is also some iron, copper, zinc, potassium
and group B vitamins. This is pork ham, the thing you notice it that it has a much higher
fat content. Excessive meat consumption is detrimental
for many different reasons. Because it provides a lot of protein but it’s poor in fiber,
it promotes the selection of unfavorable gut bacteria, and increases the risk for colon
cancer. The fact that it provides many saturated fats is a concern for cardiovascular risk.
Preserved meat or cold cuts have some extra concerns such as a lot of added salt, and
the use of not so desirable additives such as nitrites and nitrates or polyphosphates.
The good thing about organ meats is that they provide a lot more vitamins and minerals because
these organs tend to store them more than the muscle does. For example, compared to
a T-bone steak, and equal amount of calf liver provides provides a ton of vitamin A, way
more group B vitamins including more than twenty times more vitamin B12, double the
iron, more zinc and manganese, a hundred times more copper, and more than twice as much selenium. Let’s now look at fish. Technically it’s
still meat, just of different animals. But once again, our classification is mostly based
on nutritional characteristics, not on biological taxonomy.
Compared to meat, fish is easier to chew and digest because its muscle fibers are softer.
Another distinctive characteristic of fish is its lipid composition. The fat of fish
is of a much better quality than the fat of meat, because it’s less saturated and has
a lot of good omega-3 polyunsaturated fats, although as we will see, grain-fed farm-raised
fish is not necessarily as good. Fish also has more iodine and selenium than
meat. Small fish eaten whole also provide a lot of calcium from their bones, and vitamins
vitamin D and A from the their liver. Unfortunately, fish is highly susceptible
to environmental pollution and can easily accumulate heavy metals and other contaminants.
Also, fish easily deteriorates with storage and high temperature cooking, as its unsaturated
fat easily get oxidized. Let’s make a couple of example for fish
as well, this is salmon, it’s 74% water, 20% proteins, 6% lipids, no carbs, no water.
Salmon is a fatty fish, let’s now look at sea bass, you see it has less lipids, 2%,
18% protein, and the rest is water, and again of course, no fiber, no carbs. On we move to eggs. Almost all birds make
eggs, and many of them are edible, but if we say eggs without specifying the species
they come from, we refer to chicken eggs. I believe eggs are the best among all animal
food: they are excellent sources of high quality protein and their fat is of way better quality
than meat or milk. Eggs are often viewed with suspect because they have some cholesterol
in the yolk, but as we will learn soon, cholesterol content in food has very little to do with
blood cholesterol levels, and there are other way more important dietary strategies to control
blood cholesterol, so there is no reason whatsoever to limit consumption of eggs for this reason
and even individuals with high blood cholesterol if they have a generally balanced diet can
happily eat two eggs a day every day. An egg has 76% water, 13% protein, 10% lipids, very
little carbohydrates and of course no fiber. Eggs are also good sources of group B vitamins,
vitamin A, iron, and zinc. And then, we have milk and dairy products.
If we say milk without specifying the animal it comes from, we are referring to cow milk.
Whole milk contains 89% water, 3% protein, 3% lipids, 4% carbohydrates mostly as lactose,
and no fiber. Fat in milk is not of the best quality, so if we drink it regularly we should
definitely go for the low fat version of it. As we will see later in this course, however,
drinking many glasses of milk every day is not as healthy as many people believe, it’s
not good for your bone health and it may increase your levels of inflammation.
Two major dairy products made from milk are cheese and yogurt.
Cheese can greatly vary in composition but in general it concentrates proteins and lipids
from milk, while losing water and lactose. Because cheese is very energy dense and it
concentrates a lot of saturated fat, excessive consumption should be avoided. This swiss
cheese, for example, has only 41% of water, and 28% of lipids, 27% of proteins and 4%
of carbs. Yogurt is another important dairy product
from milk fermentation. Plain white yogurt is an excellent food because it contains live
health-protective bacteria that improve the bacteria population of our gut with positive
outcomes for our general health. Unfortunately, as we will see, many commercial yogurts contain
obscene amounts of added sugar and become a totally unhealthy food.