We'll begin this lesson by talking about the essential nutrients that our body needs in order to be physically active and to just survive, and we'll also talk about the role of vitamins and minerals in the body, and at the end of this lesson we'll talk about how to read food packaging so that you can be an educated and informed consumer about the foods that you're putting into your body.
The definition included on this slide of nutrition is from the American Medical Association, and it focuses mainly on the biochemical and physiological functions of food within our body.
So, I'll quote it here: "The science of food, the nutrients and the substances therein, their action, their interaction, and balance in relation to health and disease, and the process by which the organism ingests, digests, absorbs, transports, utilizes, and excretes food substances." So that's the definition of nutrition.
But simply put, when we talk nutrition, we're concerned with studying the food we eat, and how our bodies use this food for fuel. And so that's what we'll talk about for the rest of this lecture.
One thing that's missing from the definition that we just covered from the American Medical Association are the factors that affect the choices that we make about the food that we put into our bodies. So eating allows us to supply our bodies with the fuel needed to sustain life and carry out our daily activities, but eating is not a simple behavior, and in fact, it's quite complex. There are many reasons that we eat. And we eat in many different situations, so it's quite common behavior.
And you can see pictures on this slide of many different situations in which we eat. So, on the bottom right you can see a school cafeteria of trays. When you're growing up as a kid you're eating in the cafeteria. There's a holiday meal picture. The type of cultural setting certainly can affect the foods that you eat, the choices you make about your food. You can see there are examples of extreme eating—the hot dog contest featured here on the picture on the slide and also celebrations—like birthdays, weddings—things where we celebrate we often make different choices about our food. So, eating is something that is affected in the choices we make when we're eating, something that's affected by personal, social, and cultural factors.
And so in this lecture we'll talk about the essential nutrients and the role they play in our bodies, but we're also going to talk about eating because, ultimately, that's how we fuel our body and get the nutrition that we need.
So there are three main functions of nutrients in our body, and the first of these is simply to provide energy. And we get that from essential nutrients, and we'll talk about what those are in the next few slides. But essentially, when we talk about calories in food, we're talking about a unit of energy. A calorie is simply a unit of energy. And without these, our bodies don't function, so we need these to allow our body to function properly.
The second function of nutrients in our body are to regulate body processes. So some of these include temperature regulation, and this is done mainly by vitamins, minerals, and the water that is also in our bodies.
And finally, the third nutrient function is to maintain, repair, and grow nearly all the cells in our body. So they're being replaced constantly, and we need nutrients in order to help with this process.
On this slide you can see the classes of essential nutrients. We have two different classes: the macronutrients and the micronutrients. And the major difference here is that the macronutrients are providing calories, or energy, and the micronutrients are not providing energy to the body, but they do still play an important role. So in the macronutrients you have proteins, fats, and carbohydrates, and we'll talk about each one of these in detail, and then the micronutrients you have vitamins, minerals, and water. And these are all considered essential nutrients because your body does not make them fast enough or doesn't make them at all in order to be able to function properly.
The first macronutrient that we'll talk about are proteins. And the major function of proteins in our body are growth and maintenance of tissues. And so oftentimes people think only of muscle growth when they think of protein, but the reality is the role of proteins in our body goes well beyond building muscle. So, for example, proteins are integral in building hemoglobin and antibodies in your body.
There are four calories per gram of protein, four units of energy. Remember that that calorie is simply a unit of energy, and proteins are made up of amino acids. And although there are over 20 amino acids that are important for our bodies, only nine of those are essential, meaning that they must be obtained from food because they can't be made in the body.
It's recommended that adults get about 0.8 grams per kilogram of ideal body weight of protein. So, for a 150 pound person, that would be about 54 grams of protein per day. For a 200 pound person, that would be about 72 grams of protein per day, and the reality is, in our culture meeting your protein requirements is pretty easy. And we also know that active athletes might need a little bit more protein, so 1 to 1.5 grams per kilogram of your ideal body weight.
But, it's important to note that excess protein does not necessarily equal bigger muscles. If you have excess protein, you eat extra calories as protein, that your body does not need or process, it's stored as fat because it's not as easily used as a body source of energy. So, eating more protein does not necessarily translate into bigger muscles like many people often think that it does.
And we're using ideal weight here because protein is not needed for fat tissue—only to build lean tissue.
So where do we get the protein that we need for our bodies? Protein comes in many, many different sources, and the first sources that often pop into people's minds are meat, milk, eggs, and fish, but it's important to note that protein needs can be met by eating non-animal products as well, or by combining animals and non-animal products.
So some ways to get protein sources that are not animal products include beans, tofu, lentils, and some grains such as quinoa and bulgar. Click on the link here, and you can see lots of great sources of vegan forms of protein.
Our second macronutrient, which is also an essential nutrient, are carbohydrates. And the major function of carbohydrates is to be an energy source for the body.
And oftentimes carbohydrates get a bad rap when people talk in the popular media about diet, but as you'll see, carbohydrates play a very important role in our body, and namely they're that preferred energy source. They have the same calories per gram as proteins, and they're classified into two different types: simple and complex.
And the simple carbohydrates are mono and disaccharides. Saccharide simply means sugar, or sweet. So, simple carbohydrates just have one or two sugar molecules, and complex carbohydrates have three or more sugar molecules, and those are called polysaccharides.
So, examples of monosaccharides are glucose (or your blood sugar) and fructose (the sugar that's found in fruit).
Examples of disaccharides would be sucrose (or your table sugar), lactose (which is milk sugar). And so for lactose, for example, you have the combination of glucose and galactose together, and so you have two different sugar molecules that are working together.
Your complex carbohydrates you're going to have things that people often associate with being carbohydrates such as your starches and your fibers.
Dietary fiber is a term for a diverse carbohydrate polysaccharides of plants that cannot be digested by the human stomach. So, essentially, it's a special type of carbohydrate. And there are two forms of this: insoluble fiber and soluble fiber. And although it's not listed as one of the essential nutrients in our bodies, fiber intake has been associated with many health benefits, such as reduced risk of heart disease and diabetes.
And so like I said, there are two different forms—insoluble and soluble. The insoluble helps with elimination, keeps your colon healthy. In other words, it helps to keep you regular. It keeps things moving through your digestive system and through your colon.
The soluble fiber binds with cholesterol in your intestines and prevents it from being absorbed into your body. So instead of being absorbed, that cholesterol gets excreted, which is much better for you overall.
The sources of dietary fiber are numerous, but oftentimes fruits, vegetables, whole grains, nuts, legumes, and many more.
Because carbohydrates are the body's preferred source of energy, the dietary recommendation is that you get about 55 to 60 percent of your total daily energy intake, or the total calories that you take in each day, from carbohydrates. And about 20 to 35 grams of fiber.
But the key with that 55 to 60 percent is that most of those should come from complex, not simple, carbohydrates. So we're talking about those polysaccharides not the mono and disaccharides.
It's okay to have some of the mono and disaccharides in your diet, but most of your 55 to 60 percent of carbohydrates should come from complex carbohydrates, such as those whole grains and fruits and vegetables.
There are many different sources of carbohydrates. And the goal with eating carbohydrates is really to eat many of the foods that you see listed here on the sides. So, vegetables, fruits, whole grain breads, as opposed to avoiding highly processed foods, such as crackers, soda, other sugary drinks, white bread. All of those things are carbohydrates, but they contain much more simple carbohydrates than the complex carbohydrates.
I've attached a link here to the Harvard School of Public Health recommendations for good sources of carbohydrates to distinguish between some of your better choices for carbohydrates and some of the poorer choices for carbohydrates.
The third category of macronutrients are fats, and fats are found both in foods and inside our bodies. They are more energy dense than both carbohydrates and proteins, so fats have nine calories per gram, compared with the four calories per gram that we saw with carbohydrates and proteins, and there are four categories that I'll talk about here.
The first are triglycerides. Most of the fat that's stored in our body is stored in the form of triglycerides.
The second category is cholesterol, and the interesting thing about cholesterol is that people often think of cholesterol in the terms of context of your health and thinking about how to avoid getting high cholesterol, and people worry about it because the body makes all the cholesterol it needs. And cholesterol is very important for many processes in your body, but a recommendation is to limit cholesterol intake because you don't need to eat cholesterol; it's not an essential nutrient because your body makes all that it needs to function properly.
The third category of fats are phospholipids, and these, this is a type of fat that's present in every cell of the body and allows fats to be suspended in your bodily liquids, like water and blood.
The final category here are trans fats, and trans fats are a manmade creation. They're formed by processing vegetable oils through a process called hydrogenation. And you find these in many margarines and other processed foods. So, check your labels. These are very harmful to your body. Although they are unsaturated, they operate in the body like saturated fats, and so they increase risks for cardiovascular disease, and really they're manmade in order to make foods that would typically be liquids, such as margarines, into a solid product, and oftentimes it's done to increase shelf life and improve flavor over a longer period of time. So although it does those things, it is not good for our health.
Fats have multiple roles in our body. And essential fatty acids (there are a couple of them listed here, omega-6 and omega-3) are fatty acids that we must get from our food because our body does not produce them.
So, you're seeing a trend here. Every time we talk about essential nutrients or macronutrients we're talking about things that the body either does not make at all or doesn't make in great enough quantities to be used by the body.
And so your essential fatty acids—the linoleic and linolenic acids essential fatty acids—help with blood clotting, regulating blood pressure, and triggering immune responses among many other things. So these are integral to get into your diet.
Fats are also used for insulation and protection in your body. So you can think about fats as protecting you from extreme cold. They also provide protection for your vital organs.
And finally, fats are used to transport vitamins, which we haven't talk about yet, but you have fat soluble vitamins (like A, D, E, and K) that must be transported using fat that's in the body.
It's recommended that adults get about 20 to 35 percent of their total daily calories from fats and less than 10 of that percent from saturated or trans fats. And, really, even less if you can help it. You want to get most of your fats in the unsaturated form and very few from either saturated or trans fats. So the way to get these good fats or the unsaturated fats would be by eating nuts, oils (such as olive, canola, peanut oil). All of those are great ways to get your unsaturated fats.
And the dietary recommendation for cholesterol is to limit your cholesterol intake to less than 300 milligrams per day. And so that sounds like, oh, that's pretty easy, right? Well, there's about 200 milligrams of cholesterol in one egg! So you can see that it's very easy to eat high levels of cholesterol in a typical Western diet. And so, the guidelines are really to limit your cholesterol intake because your body already makes all of the cholesterol that it needs.
Alright, so where do we get our sources of fats? On the left side of the screen here you can see some better choices for getting your fat intake—your daily recommended value. You can see an avocado (which is actually high in fat, but also pretty good for you), walnuts (pictured here), olive oil; so those are all pretty good choices for getting fat into your diet.
On the right side you have some choices that are probably not as good. You have the saturated fats, the marbling you can see in the steaks that are on the grill here, again saturated fats in butter, you have shortening products like Crisco, and then you have your ice cream and your chocolate. Again, animal products often have those saturated fats. Non-animal products do not have the saturated fats.
Alright, so we're moving on to the micronutrients now, and here you see the first two micronutrients—vitamins and minerals. And vitamins are essential organic substances needed by the body to perform highly specific metabolic processes in the cells.
There are two different types here—water soluble and fat soluble. The water soluble vitamins dissolve in water, like the name suggests. They can be excreted by the body if you consume too many, which just essentially means you pee it out.
The fat soluble vitamins must be stored in the fat within your body to be transported throughout the body. And high levels of these vitamins, usually that occur through supplementation, can be toxic because they're not excreted like water soluble variables.
The best way to get both of these types of variables is to eat a balanced diet. Most people (there are some cases where vitamin supplementation is important and good), but the best way to really make sure that you're getting all the vitamins and the minerals that you need is to eat a balanced diet.
And so some examples of roles that vitamins play in the body are folic acid, for example, helps with the synthesis of DNA and other molecules, thiamine, which is a B vitamin, helps with the breakdown of food molecules, and vitamin K helps with blood clotting, so there are many, many other examples. You're not responsible for knowing exactly what each vitamin does, but you are responsible for knowing the different types of vitamins within your body—the water soluble and the fat soluble.
Minerals are essential inorganic substances that are vital to, again, many of your bodily functions. So, some examples of minerals in your body would be calcium (which obviously helps with the formation of bones and teeth), iron, sodium (which helps with your water balance in your body and your nerve function). So these, again, are just a few examples of the important roles of vitamins and minerals in our body.
The final micronutrient that does not provide any energy but certainly is very, very important to many bodily functions is water. And as many of you probably know it makes up about 60 percent of the body's weight, and water's involved in virtually every process in your body. It's recommended that we get about six to eight 8-ounce glasses of water a day. More is perfectly fine and probably even good for you. In particular, if you're being physically active, then you'll need to drink more than that six to eight glasses per day.
So we're going to switch gears here. In the final few slides we'll talk about concepts that are important for planning a nutritious diet. And the first of these is your nutrient-calorie benefit ratio. And simply what we mean here is the amount of nutrient per energy unit or per calorie, so how many nutrients are your getting per calorie. And ideally, we want nutrient-dense foods, meaning you want the most nutrients with the fewest amount of calories. So you want a lot of bang for your buck here, if you will. A lot of nutrients for as few calories as possible.
So, for example, if we compared two foods, let's compare green leafy vegetables on one hand that have lots of vitamins and minerals in them, compared to a candy bar. The green leafy vegetables are going to have tons of nutrients and very few calories, compared to the candy bar that's going to have very few nutrients and high calories. So you're green leafy vegetables, in this case, would have a much higher nutrient-calorie benefit ratio.
The second concept that's important for planning a nutritious diet is to understand the dietary reference intakes. And here we're talking about the recommendations that are given to all adults in our country about what you should be eating and how much you should be eating of these particular nutrients.
And so the recommended dietary allowances were originally designed to prevent nutritional deficiencies. But, nutritional deficiencies are much less of a problem now than they used to be, and so there are currently lots of revisions going on to these recommended dietary allowances where we're focusing on how to eat in order to prevent chronic disease, not just to prevent deficiencies. And so we still want to prevent deficiencies, but we're incorporating now the idea of a concept of using food and healthy eating to reduce your risk for chronic diseases, as opposed to originally when we were just trying to prevent those deficiencies, which are not as big of a problem anymore.
Just like our government published recommendations for physical activity, they also make dietary guidelines. And I'm not going to go over all of these here on the slide because they're in your text, and you should also read this section in the text if you haven't already. But, the dietary guidelines include everything from food safety practices when handling food to engaging in physical activity to help maintain or achieve a healthy weight, and limiting fat and sodium intake. Other things include alcohol and caffeine in moderation because there's some evidence that both have benefits if they're not done in excessive amounts. And so to learn more about the dietary guidelines for Americans, you can click on this link here, you can click on the picture, and that'll take you to the dietary guidelines, and you should be very familiar with these guidelines.
Again, another source, if you're trying to plan a nutritious diet, is ChooseMyPlate.gov, and this is again, the government's suggestion for what our plates should look like, essentially, when we sit down for a meal. And you can see that about three-quarters of the plate is covered with vegetables, fruits, and grains, and a much smaller portion is covered in protein, just about one-quarter of the plate. And then also some dairy on the side. And so, check out ChooseMyPlate.gov. You'll be able to look and see what some examples are of meeting these requirements, and just see what our government recommends for planning a nutritious diet.
Being able to read the nutrition facts label that's provided on any manufactured food in the US (it's required to be on any manufactured food), so reading that nutrition label and in addition to that, the ingredient list that's on that packaged food is so important for helping to plan a nutritious diet.
And, so like I said, all manufactured food in the United States is required to have these labels for you, the consumer. But, the labels are no good if you don't read them. For example, if you look at the nutrition facts, a few things that you want to pay attention to, or you should be able to look at pretty easily—the serving size on the package. Oftentimes there are multiple servings in a box or a bag of packaged food, and you need to know how much you're eating and what fat, cholesterol, sodium, carbohydrate, all of your nutrients are in that one serving. If you eat multiple servings, you also need to adjust your nutrition information accordingly that's provided on the label. And so there's more information about how to do this in the book.
Also on this nutrition fact sheet you'll find the calories. Again, these are calories per serving, so understanding these calories can help you stay in your energy balance, which we'll talk about in the next chapter. All of the macronutrients are included on this nutrition facts panel, so your fats, your carbohydrates, and your protein are all included, and you should pay particular attention to not only how much fat is there in the product but is it saturated fat, is it unsaturated fat, is it trans fat. You should also pay attention to the type of carbohydrate you're eating. Is it considered fiber or sugar? Obviously higher fiber and lower sugar would be better. So, that's the nutrition facts panel.
If we're talking about the ingredient list, the simplest way to judge an ingredient list would be to look for the number of ingredients on that list. In most cases, fewer ingredients in a processed food is probably going to be better. Again, that's not across the board, but in most cases.
So, for example, let's compare these two lists. Both are peanut butter, okay? So, you have your list on the left, and for this we'll just look at the ingredients; we won't look at the nutrition facts. The list on the left is peanut butter and contains two percent or less of salt. So you basically, in your peanut butter, have peanuts and salt. On the right you have many more ingredients. And what you see there, any time you see any kind of, the word "hydrogenated," you know that there are trans fats in that product, so the ingredients list helps you figure out whether there are trans fats in that product, even if you see zero trans fats. (And we'll talk about that on the next slide—why they can say zero trans fats and also list some trans fats in the ingredient list). But if you compare these two lists, you have a better idea of what is in the food that you're eating. And ideally, to be an educated consumer and to eat healthy, you need to understand what is in the food that you are eating.
Another important thing to be aware is that the health claims that are provided on packaged foods in our country are regulated by the United States Food and Drug Administration, or the FDA. So you can see some examples here of health claims that are included on our packaging, and these are things that are so common that it's oftentimes we don't even realize that we're seeing it so much.
And so, on the package of bacon at the top you see "30 percent lower fat". Well that means something. On the lean burgers you have "1/3 less fat". On the broccoli you see "organic" and the Near East wheat salad you see "100% natural."
The claims made on our packaged food are regulated by the FDA. I should say there are certain claims that are regulated by the FDA.
So some common ones include "free." Free could be substituted with "no," "zero," or "without." And that usually comes with other words, such as "fat free." So when a product says "fat free" that means something, and it means something consistent. It means that the product has less than 0.5 milligrams of fat per serving.
Another example—something that has "no sugar" or claims to have no sugar means that it has less than 0.5 grams of sugar per serving. And so, although these are very small amounts, you still need to be aware of what these phrases mean because packaging is marketing, and the manufacturers want to sell you a product, so you need to understand what you are putting into your body.
Another example would be "low." Low could be substituted with "little" or "few." So, for example, "low fat." These are foods that can be eaten frequently without exceeding the recommendations for that particular nutrient.
And, so for example, "low fat" would be less than three grams of fat per serving. It still has some fat in it.
Another common claim, and you see this on cereals a lot, is "a good source." So, if a product claims to be a "good source" of calcium, for example, it must contain 10 to 19 percent of your daily recommended value in one serving. And so, my point here is not that you need to know all of these specific values, but rather that you understand that the claims made on our food products mean something. So be educated about what the package is telling you and what it's not telling you, and you'll be a better consumer for it.
So if you're thinking to yourself right now, "Wow, this is really confusing! I'm not even sure I know how to eat well!" don't stress about it. Eating can be really easy, and in eating, as often we don't think of it like this, but eating can be a very visual experience. So if you look at this slide, you'll look on the left and you see fish and chips. Everything on the plate is brown. Although it's probably very tasty, it's not very colorful. If you look on the right, you see lots of different colors;reds, greens, peppers, strawberries, some carrots, lots of different colors, oranges. The left side you have this yellowish brown, monochromatic, probably processed, fried food. On the other side you have this beautiful, colorful, unprocessed, and unrefined food. And so, if you use your visual cues to eat, clearly the right hand side is a much better option. It doesn't mean you can never have fish and chips. Moderation is key in everything. But let your eyes be your guide. Eat lots of colors in your diet, and I guarantee you you'll have a healthier diet than if you eat monochromatic meals. So, if you're really confused, ultimately, put lots of colors on your plate, and you'll be better off than you would be if you had lots of yellow, brown, fried food. So these are just a few tips on how to plan a nutritious diet, but there's certainly lots more in your book and lots of good information on the web, some of which I've provided here for your reading.
