In this lecture, we're going to look at our third macro-nutrient, which is dietary protein. As a review, each gram of dietary protein that you eat in your diet contains 4 calories per gram. It's similar in caloric contribution to carbohydrates. In the United States, and in most developed countries, protein deficiency, is very rare. 2/3 of the protein, in the diets of people in the United States, come from animal foods. Meat, poultry, seafood, eggs, and dairy. In the developing world, the, the mix is a little bit shifted. In the sense that, the developing world countries tend to rely more heavily on plant proteins. We know that, as a population's economic status improves, there's a consequent increase in the proportion of animal protein that they consumed. And you'll see, that animal proteins tend to have more of those unhealthy fats, contribute more to overweight and obesity. So it's unfortunate that, the more developed or rich a country becomes, actually, the poorer their diet becomes. What does protein do in our diet, or in our body? Protein does a number of things. The enzymes in your bodies that are required to make chemical reactions occur are actually proteins. Your hormones, your antibodies and transport proteins are all examples of proteins as well. Protein helps you to maintain your fluid and your electrolyte balance. It maintains acid base balance, promotes the growth, the maintenance and the repair of your body tissues. It also gives you energy 4 calories per gram and in certain cases can actually provide you glucose through the process of what is called gluconeogenesis. New meaning neo meaning new and genesis meaning to make. Your body can although it would prefer not to break down dietary or body proteins in order to make glucose. Amino acids are the building blocks of proteins and amino acids are linked together by what we call peptide bonds.If you have 2 amino acids joined together that's a dipeptide, 3 amino acids joined

together is a tripeptide and more than 3 is what's called poly peptide, again amino acids are linked by what are called peptide bonds. Here you see an example of amino, of an amino acid. An amino acid contains an amine group. And amine means nitrogen containing. So your proteins are unique and different from carbs and fats in the sense that they're the only macronutrient that contains nitrogen. You got your amino group here. An acid group here and a hydrogen group here. All amino acids have those same three components. What makes an amino acid unique is what's called its side chain. A side chain is unique to each amino acid. Amino acids are the building blocks of proteins.There are essential and non essential amino acids. When we study nutrition if we say something as essential what that means is that has to be consumed in the diet because your body can't make it. So, we got 9 essential amino acids and when you eat different plant or animal proteins, they contain a mix of those essential amino acids, Okay, you have to eat those in your diet because your body doesn't have the ability to make them. There are 4 nonessential amino acids which if you eat the right mix of essential, your body uses components of those in order to make the nonessential amino acids inside your body. We also have what hare called conditionally essential amino acids or conditional amino acids. The Institute of Medicine and the Food and Nutrition Board in the United States say that these. 8 amino acids are ordinarily made by the body. So they're ordinarily non-essential amino acids. Except in time of illness or stress, they become what are called conditionally essential amino acids. Your body can, although it would prefer not to, utilize the proteins in your body to be broken down to provide energy. Now in a perfect situation when you are healthy you get the majority of your calories from carbohydrates. But if for whatever reason perhaps you are on a very restrictive diet, if you

didn't get enough calories to meet your body's needs, your body would break down it's body protens. And that would happen because you don't actually store amino acids. There is no storage mechanism for amino acids. You store extra carbohydrate as glycogen and if your body's glycogen stores get full up, then you start storing it as fat. If you have excessive amounts of protein in your diet, your body can't store those amino acids. Nitrogen makes up about 16% of the weight of protein. And that's similar to the Earth's atmosphere. So if you have an individual who weighs 170 pounds, that body is made up of about 16% protein. So, about 27 pounds plus water makes up 70% of that rest of that body weight. Half of your body's total protein is used to form your skeletal muscles. So its important that you eat the right mix of dietary protein, so that your body can promote the optimal ability to build body proteins inside of you. Protein is the only macro nutrient that contains nitrogen. Nitrogen is in the amino group. This is the amino group, meaning that it's nitrogen-containing. The process of de-amanization is what your body goes through in order to remove that amine or that nitrogen containing component. Nitrogen plays an important role and is a big component of your urea. Urea is a waste product which your body excretes in your urine. So your body uses the nitrogen for a number of different processes to build body proteins. But at the end of the day it really essentially is a waste product. Carbon, hydrogen, and oxygen can be broken down in order to produce ATP, which is the form of cellular energy, or it can be used to make glucose or fatty acids. We would prefer again, that you get the majority of your calories from carbohydrates but in extreme cases, if you do need to use protein, to provide your body with energy, it can be done, although it occurs in a relatively, metabolically, inefficient way. In our diets we get protein from both

animal, and plant sources. Dairy foods contain protein, milk, yogurt, and cheese. Animal flesh from things like poultry, meat and fish do, as do legumes, nuts, and eggs. Grains contain a little bit of protein, although they tend to be incomplete proteins, and an incomplete protein is one that does not contain all of the essential amino acids. Vegetables also have incomplete sources of protein, but you get a few grams of protein here and there from different vegetables. We say that soy is the only non-animal complete source of protein. Again, a complete protein is one that provides you with all of the essential amino acids. Sometime you hear people say, well I've heard that there's other non-animal sources of protein. Soy is not the only one. What about foods like quinoa, buckwheat, hempseed and amaranth. These are very high protein grains that also, in some situations, can be considered to be complete proteins. They do contain all of the essential amino acids but after you eat them and digest them, all of those essential amino acids are not actually available to your body for use. So, there's a scale called the Protein Digestability Corrected Amino Acids Scale and quinoa, buckwheat, hempseed, and amaranth while again they're very high protein foods don't register 1.0, which is a complete protein on that scale. So they're certainly good sources of protein, but it is safe and most health professionals and scientists would agree that soy continues to remain the only complete source of protein that's not an animal protien. Animal sources of protein. We said they come from milk. A cup of milk gives you 8 grams of protein. An egg gives you about 6 grams of protein. And 3 ounces of meat gives you about 20 grams of protein. So in a very small amount of animal foods in your diet, you actually can amass a pretty decent amount of protein. But that's not the only place you get protein in your diet. Plants also give you protein.

Now, the serving sizes of plants give you less grams of protein per serving. But the reality is, is that most people in the developed world eat too much protein. One slice of bread gives you 2 grams of protein. A 1/2 cup of beans, somewhere between 6 to 10 grams. A 1/2 cup of rice, cereal, or pasta, 2 to 3 grams, and then 1/4 cup of nuts or seeds is 5 to 10 grams, so you can see that per serving, the plant foods generally have less protein. But again, most of us don't need as much protein, and in turn we don't need as many animal foods as you might have previously thought. What are the recommended serving sizes for proteins? You go to a steak house, and you sit down and sometimes the smallest steak you can order is 8 ounces, a fillet. Occasionally you can get a 6 ounce petite fillet. But did you know that you really only need about 2-3 ounces of cooked lean meat. Things like poultry and fish, to get in some cases, almost half of the amount of protein that you need in a day. Half a cup of dried beans is a serving, 1 egg, 2 tablespoons of peanut butter, 1 ounce of cheese. And if you're curious what an ounce is, it's about the size of a domino or if you buy pre-packaged sliced cheeses it's the, that size as well. That's 1 ounce. 2-3 ounces of soy protein, soy beans are meat alternatives. These are all what we call a serving size. A protein. How much protein do we need? Well, 10-35% of your total calories, should be coming from protein. If you're significantly under 10, you're probably not getting all of the essential amino acids you need. And if you're way over 35, it means you're probably not getting enough fat or enough carbohydrates. In the United States the average person eats somewhere between 12 to 18% of their calories from protein. Protein needs vary dependent upon what life stage you're in. As a percentage of your body weight, when you're young, a baby, a child, and even

an adolescent, you're growing at a more rapid rate than you are when you're pretty well developed as an adult. So you can see that in the developmental stages of life, as a function of grams of protein required per kilogram of body weight, needs are higher in the earlier stages of life. By the time you're an adult, 18 years and older provided that you're not pregnant or breastfeeding, you need 0.8 grams of protein for every kilogram of body weight that you are. Then during pregnancy and breastfeeding. Protein needs for females go up. But most adults, we say the RDA, which is the recommended dietary allowance for protein, is .8 grams per kilogram. And in case you're not sure, 1 kilogram is equal to 2.2 pounds. So take a moment to figure out, for yourself, based on the .8 grams per kilogram. How many grams of protein you need per day? There are certainly other scientific bodies out there, besides the Institute of Medicine, and protein recommendations vary and tend to be a little bit controversial. Older adults who are engaged in resistance training might actually have higher protein needs, 1 to 1.3 grams per kilogram. Athletes tend to be on the higher side as well. 0.9 to 1.3 grams per kilogram. So, in addition to the life stage that you're at, your activity level, how much exercise you do, what disease state you have, these all may increase your dietary protein needs. The British Department of Health and World Cancer Research Fund recommends and puts specific guidelines out there for how much meat we should be eating. We know that excessive amounts of protein from animal foods, contributes a lot of other nutrients that we don't need so much of. This groups recommends no more than 2.5 ounces of red meat per day, and no more than one pound of red meat per week. There are certain groups that need higher protein. Vegans, vegetarians, older people with lower calorie intake levels. They might all need more protein than some of these international bodies

recommend. There are groups that might actually need less protein. For people that have gout, they are recommended to eat not only less red meat. But also less poultry and fish, no more than 4 to 5 ounces per day. Other populations that might need less protein include people with kidney disease who may need to restrict their dietary protein dependent upon what level of kidney disease they have. Let's do a sample calculation together. Let's say we have a 30 year old male who weighs 172 pounds. That's 78.2 kilograms. The RDA for protein for him would be 0.8 grams of protein per kilogram of body weight. So I'd like you to take a moment to figure out, using that RDA, how many grams of protein per day. Should this guy have? Using the information that we are provided, he's 18 or older, so his RDA for protein is 0.8 grams per kilogram. He weighs 78.2 kilograms, so if we multiply those two factors together, we see that he needs about 63 grams of protein per day. So 63 grams of protein. What does that mean? What does it look like and how may he put together a meal plan to make sure he gets enough but not too much protein? So I've put together just a sample menu to show you how someone like this gentleman might achieve the goal of 63 grams of protein. And what I want you to see, is that with a variety of foods, and a not too heavy reliance on animal foods, you can quite easily meet your protein needs. For breakfast if he has a egg with a slice of whole wheat toast and a pear, he gets 9 grams of protein. At lunch he has cup of lentil soup, a cup of long grain rice, and a cup of boiled greens for another 16 grams. He gets hungry after lunch so he brings or goes to get a snack of a cup of low-fat yogurt plus a cup of berries. Dinner, a very, very small amount of chicken breast in let's say a noodle soup dish that he's having. So he gets a little bit of protein from the noodles. Has a side of carrots, and a little bit of protein. Protein.

Just 2 ounces gives him actually 17 grams of protein. And then after dinner he's hungry for a snack so he gets himself a half a cup of ice cream. So again the only meat that he really had in the day was 2 ounces of chicken breast. But with the contribution of all the little bits of protein that he got from the different plant sources he was very easily able to reach his goal of 63 grams of protein a day. Now in reality, most people don't eat like that. Especially in the developed world. In the western world, we tend to have an over-reliance, on animal proteins. A typical western diet might look like this; guy wakes up late for work, goes to the drive through, gets Mcdonalds. He has 2 sausage McMuffins with eggs, for 42 g of protein. Not to mention a whole bunch of sodium and saturated fat. For lunch, he doesn't take the time to bring his own lunch, so he runs out to the deli, and gets a deli club sandwich with cheese, for 57 grams of protein. For snack, he gets hungry, he grabs some chips with some processed cheese on top of them. And for dinner he decides, oh, I've been kind of unhealthy today, I'm going to go for a chicken breast. And he gets himself a big, fat, 8 ounce chicken breast for 68 grams of protein, plus some rice and broccoli. After dinner, he stays up too late watching TV, or playing video games, and so he gets hungry, and he goes for a bowl of cereal and puts a cup of milk on it. In that day, the guy ate 194 grams of protein. Now he only needs 63 grams of protein so he ate 131 extra grams of protein that he really didn't need. That protein doesn't just disappear. That contributes calories, right? 4 calories per gram of protein times 131 calories is roughly 524 extra calories a day that he didn't need. If he kept that pace up, he would be expected to gain about a pound of weight a week because he's regularly consuming 500 extra calories a day. So one of the problems with excessive protein consumption is that it contributes excessive calories to many people, who frankly just don't need.

Need them. So, what does the research say about protein? There's actually a lot of misperception and misconception out there regarding protein. One poll that was done, consumers, 48% of consumers said that they're trying to eat more protein. 69% say that they want to eat more protein, because it helps them feel full. And another 60% believe that a high-protein diet Can help with weight loss. Well is that true? A study that was done by French researchers and published in the journal Cell, showed that, protein, yes, it is a satiating macronutrient. And we hear that sometimes. Protein and fat help promote satiety. They make you feel fuller for longer. The notion is, if you feel fuller for longer, you won't go and overeat. But what is this mechanism attributable to? Well, when you digest dietary protein, this modulates the activity of molecules called mu-opioid receptors. We'll call them MORs or MORs. These are the same receptors that your body uses in response to things like morphine. More send signals to your brain when you eat dietary protein. Telling your intestine to release glucose. Glucose suppresses your hunger, suppresses your appetite. And should result in reduced intake. In this study done by the French researchers, they showed that mice who were genetically engineered to lack these receptors failed to show signs of feeling full. When they were fed high protein meals. So how does this translate to humans? Well, we know that a diet that's high in protein and high in animal protein increases cardiovascular disease risk. In the Nurses Health Study, an analysis of 84,000 women who were age 30 to 55 years old, who didn't have any real underlying health conditions, were followed for 26 years. Thus researchers learned that red meat not surprisingly was associated with a higher risk of a coronary heart disease. Well what the researchers also found was that the risk for heart disease was reduced by thirteen to thirty percent if the women would just shift their dietary protein intake and the shift what that

need was that if they ate less animal meat and more nuts, low fat dairy, poultry and fish. So leaner sources of protein and more. Proteins, it actually reduced their risk of heart disease. Another study that was done in 2010 also looked at the effect of protein intake and health. This was an analysis of almost 44,000 Swedish women who were age 30 to 49 years. Years. And they were followed for about 16 years. They were given extensive dietary questionnaires, which helped the researchers learn a little about what they ate on an average basis. What the researchers found was that for every 1 point increase in protein consumption on a 10 point scale, this was associated with the 4% increased risk of having a cardiovascular event. Each 2 point increase, on a 20 point protein to carbohydrate scale, was associated with a 5% higher risk. Basically they found that, the association was stronger, in women, where the protein was primarily from animal sources. So what this tells you, is that in the western society, western countries, we tend to give, this health halo to protein. We think that protein builds muscle, which it plays a role in, the rebuilding of muscle after physical activity, but protein is not this be all, end all wonderful macronutrient. We need a little bit of protein. Protein. Most of us eat too much of it. In the developed world, most of us not only get too much protein. But the fact that we're getting it from animal sources, as opposed to the healthier plant based sources of protein is also increasing our risk for cardiovascular disease, and other sorts of chronic disease. If you're interested in learning more, here's a few slides about protein from the CDC, the Food and Agricultural Organization, the United States Library of Medicine, and then also the UCSF Patient Eduction provides you healthy ways to increase calories and protein, if that's what your body needs.