Identify the Most Suitable Sources of Protein and Their Costs for the Dr. Poon’s Metabolic Diet Program

The objective of the Dr. Poon’s Metabolic Diet Clinic is to help patients improve their obesity related medical conditions through lifestyle modifications. One of the modifications is nutrition. Patients are counseled on the importance of the essential nutrients and to avoid the foods that promote obesity and disease. Human must ingest protein to survive, but protein can be expensive. Patients who have limited food budgets may find it hard to maintain a high protein, low carbohydrate lifestyle. Furthermore, not all protein sources are equal in their biological values. This study tries to identify protein sources that have good biological values and are relatively inexpensive, so our patients can utilize their food budget wisely.


Background
In human nutrition, there are essential amino acids and fatty acids that human have to consume directly, in order to stay healthy. They are "essential" because humans cannot synthesize them from other nutrients. Cows have four stomachs and can convert grass into muscle. Humans lack the ability to build muscle from eating grass. The lean body mass determines our metabolic rate, and most of the low calorie diet plans may not provide enough good quality protein to maintain the lean body mass. Losing muscle leads to slowing in the metabolic rate and eventually slows down the rate of weight reduction and/or result in weight loss plateau. The vast majority of patients are classified as obese due to excess body fat and not over lean body mass; hence, it is important to design a diet plan that will help patients to lose fat weight and preserve or gain lean muscle mass. The daily requirement of protein intake in the general public is about 0.6 to 0.8 g per kg body weight. This requirement will go up for patients who have low lean muscle mass to start with, or patients who do lots of exercise. While there are essential amino acids and fatty acids, there is no essential sugar or starch. There is energy starvation due to the lack of food but there is no such a thing as carbohydrate energy malnutrition. Eating a diet that is high in carbohydrate and low in protein will lead to protein energy malnutrition. Since protein is the main structure of human hair, a diet that is low in protein can lead to excessive hair loss. This is particular true for the ultra-low calorie diet plans.
What is considered as a good quality protein? Protein that can easily be digested by humans and contains the optimal qualities and ratio of the essential amino acids will be considered as a good quality protein. The building blocks of proteins are called amino acids. There are 22 common types of amino acids in the human body (Table 1), and 11 of these are classified as non-essential, because they can be synthesized by the human body from substrates such as carbohydrate, fat and other amino acids. We do not need to consume protein to synthesize these non-essential amino acids. There are 9 essential amino acids and two partial-essential amino acids. These are amino acids that cannot be synthesized by humans from other nutrients, so direct ingestion is needed. Inadequate ingestion of these essential amino acids will lead to poor muscle growth or repair, hair loss, impaired immune response to infections etc. The Amino Acid Score [1] (AAS) is a way to rank the quality and quantity of different protein sources. An AAS that is over 100 is considered a complete protein. The lower the score, the lower is the protein quality.
Food that has low AAS can be mixed with other foods that have complementary amino acids profiles to improve on the overall AAS. This is important in patients who are vegetarian, as vegetarians rely on protein sources that are incomplete and have low AAS.

Non-Essential Amino Acids Essential Amino Acids
Alanine Isoleucine In order for a protein source to score an AAS of 100, the amino acids profile has to satisfy the minimal requirement listed in Table 2. Most protein sources contain some essential amino acids. If any one of the essential amino acids is missing in the protein source, it will have an AAS of 0.
Essential Amino Acid Amount of Amino Acid in mg/g of protein

Isoleucine 25
Leucine 55 Lysine 51 Methionine + Cysteine 25 Phenylalanine + Tyrosine 47 Threonine 27 Tryptophan 7 Valine 32 Histidine 18 In addition to worrying about the quality of the protein source, patients also need to look at the quantity of protein in the product. Although the protein found in potato qualifies as complete, the quantity of protein in potato is very low.
In order to provide all the essential amino acids needed for the whole day, an average adult needs to consume 9 large baked potatoes per day 2 . Nine large baked potatoes contain about 500 g of sugar and starch which is equivalent to 125 teaspoons of sugar. Consuming nutritive protein is only part of the goal of Dr. Poon's diet plan. The main objective of plan is to minimize the intake of nutrients that are harmful to the patients' health and/or causes weight gain.

The Theory Behind the Dr. Poon's Diet Plan
Dr. Poon's diet can be classified as a high protein diet which also includes a good amount of omega-3, omega-6 and high fiber vegetables. The diet limits the intake of sugar, starch, bad fat and sodium. Patients are allowed to eat until full and no calorie counting is needed. Table 3 outlines the general limitations of certain micro-nutrients in the different phases of the diet. On Phase 1 of the diet, the amount of sugar and starch (net-carb) is kept to below 1 g per serving to force the body to maintain normal blood glucose levels via gluconeogenesis. During gluconeogenesis, fat and muscle are metabolized, leading to fat and muscle loss. The good news is that more fat than muscle is lost.
There are no diets that can only burns fat and not muscle; hence, it is of vital importance to consume enough good quality protein to repair and replace the muscle lost. Not enough intake of the good quality protein will lead to lean muscle loss and slow down on the metabolic rate. On Phase 2 of the diet, the limitation on net-carb is reduced and allows 5 g of net-carb per serving. This will provide more food options for the patients, while continue to lose weight. On Phase 3, the maintenance phase, 10 g of net-carb per serving is allowed. As shown in Table 3, the amount of fat and salt per serving are at the same levels, irrespective on the diet phase. There is no explicit limit on the amount of protein and fiber that one can consume; but patients are instructed to stop eating when full. There is no set hour of the day that patients should stop eating either. The theory is that even when the patients ingest protein before sleep, protein usually ends up depositing in the muscles. Exercise is encouraged as it helps to maintain or increase muscle mass.
 Net-carb less than 1 g on Phase 1  Net-carb less than 5 g on Phase 2  Net-carb less than 10 g on Phase 3  Sugar alcohol less than 10 g  Total fat less than 6 g  Total saturated fat less than 2 g  0 trans fat  Sodium less than 170 mg  No limit on protein and fiber The diet does not require the patient to count calories, and yet, there is no evidence that patients over-consume protein, because protein induces satiety. It is not how much our patients eat, but what they eat, that allows them to lose weight and improve health. As long as the calories are coming from the right sources, they will end up at the right places. There are no essential carbohydrates and there is no minimum daily intake of bad fats or added salt in human nutrition.

Objective of the Study
Some of our patients have very limited financial resources. Even though Dr. Poon's diet program does not charge any user fees, patients with limited incomes find it difficult to afford high protein intake, since protein is more expensive than other nutrients. It is the objective of this study to identify good quality, inexpensive sources of protein, so that patients can maintain this lifestyle on any budget.

Method
Nutritional compositions were obtained from the USDA website and nutritiondata.self.com. Prices of the individual food items were obtained from local supermarkets and nutritional stores in the Greater Toronto Area. These prices represent the regular prices in Canadian dollars, and not the sale prices. Food items can be either fresh or frozen.

Result and Discussion
The minimum daily requirement for protein intake is 0.6 g of protein per kg of body weight. If the patient is on a low calorie diet and goes into a catabolic state, the requirement may have to increase to 0.8 g of protein per kg of body weight. For a 100 kg patient, in order to spare muscle wasting, the patient should consume 60-80 g of protein per day. Remember, 60 g of protein does not mean 60 g of meat since only about 20% of meat is protein by weight, with the remainder being mostly water weight. Although the diet plan does not set a limit on the number of meals the patient should eat per day, most patients eat three meals per day. If the patient consumes 20 g of good quality protein per meal, the minimum daily protein requirement will be achieved, therefore, any food item that can provide 20 g of good quality protein per meal, and fulfill the requirements of net-carb, fat and salt will be considered as a protein source good for this diet (Table 5).   There are other good quality proteins (AAS of 100) available that are not listed above; however, they also contain excess net-carb, bad fat and/or sodium, such that patients can only consume a small quantity on Phase One or Two (Table 6). Patients cannot rely on these proteins as their main sources on Dr. Poon's Diet. For example, the diet only allows 2 g of black bean on Phase One due to its high net-carb content (47 g per 100 per of black beans). The 2 g of black beans contains only 0.4 g of protein, which is far from the 20 g of protein that patients should be consuming per meal. Patients would need to consume 93 g of black beans in order to achieve the 20 g of protein goal. Even on Phase Two, only 11 g of black beans is allowed; hence black beans are not considered a suitable protein source, even though it is a complete protein.
The maximum serving size of soybeans is 36 g on Phase One, which is way below the 152 g needed to provide the 20 g of protein goal; however, because the net-carb limit is increased to 5 g per serving on Phase Two, 179 g of soybeans is allowed on the Phase Two diet plan. This 179 g of soybeans will provide the patient with the 20 g of protein needed to stay healthy. Egg white is a good source of protein with AAS of 145. However, because of the sodium content is slightly high, the amount of egg white allowed is limited unless the patients have no water retention or hypertension.     There are some foods that contain some protein, but the quality of protein is poor, so even though they can be consumed in this diet program, they cannot be considered as a good source of protein (Table 7).   This diet plan allows patients to consume unlimited amount of green leafy vegetables and some low net-carb vegetables. As shown in Table 9, these plant foods contain good amount of potassium and also calcium. There will be no problem in meeting the minimum requirement of these two minerals. The diet program monitors the patient's vitals and biochemistry closely. Blood tests were ordered when patient lost 10% of the original weight. There was no case of pathologically low potassium level related to the diet reported so far.  This diet program does not allow any fruits or juices on Phase One due to their high net-carb contents, and patients sometimes worry about potassium deficiency. It is a common misconception from the general population that fruits are the only good sources of potassium. One medium size banana contains 422 mg of potassium, which can easily matched by the leafy vegetables and protein rich foods (Tables 8 and 9), while the banana contains 24 g of net-carb, which is equivalent to 6 teaspoon of sugar. Dairy products are not allowed on Phase One because they contain sugar and bad fats. One cup of homo cow's milk (244 g) provides 276 mg of calcium, but it also contains 12 g of lactose which is equivalent to 3 teaspoons of sugar, whereas unsweetened soy milk can provide 300 mg of calcium, with only 1 g of net-carb. Some milk have higher calcium contents, but those are fortified with extra calcium, which is like drinking regular milk and take a calcium pill on the side. Tables 8 and 9 show the calcium contents of different food products and dairy products do not own a monopoly on calcium. Milk protein only has an AAS of 85 and is not a complete protein.
The cost of food items per 100 g were found by visiting the local supermarkets and health food stores. Since we know the macronutrient composition of these food items, using the USDA site and the nutritiondata.self.com site, the cost per 20 g of protein, per food item, can easily be calculated (  The best protein source for the Phase One diet should be one that has AAS of over 100, relatively inexpensive, more than 20 g of protein, less than 1 g of net-carb, less than 6 g of fat, and less than 170 mg of sodium per serving. The daily minimal requirement for good quality protein is about 60 g. If the patient consumes 100 g of chicken meat three times a day will be an equivalent to 60 g of protein per day. The AAS of chicken is 134 (Table 5). One hundred grams of chicken meat contains minimal net-carb, 2.9 g of fat and 77 mg of sodium. Three servings of 100 g of chicken meat cost a total of $1.20. Using pork chop as another example, the patient needs to consume 88 g of pork chop to yield 20 g of protein.
The AAS of Pork Chop is 150 (Table 5). Eighty eight grams of pork chop contains minimal net-carb, 2.3 g of fat and 55 mg of sodium. The cost of pork chop equivalent to 60 g of protein is $1.95. Patient was told to remove the visible fat before consumption which will lower the fat content even more.
Gelatin is an animal product derived from collagen. Although it is mainly protein and inexpensive, the AAS is 0 meaning that it lacks many essential amino acids in its composition. Gelatin is allowed on Phase One but cannot be counted as a protein source due to poor nutritive value. Another product that is allowed on the Phase One diet which contains good amount of protein but low AAS is pea protein shake. Soy protein shake and whey protein shake have better quality protein than the pea protein shake. Soy protein shake is much cheaper than the whey protein shake.
There are many kinds of soy and whey protein shakes on the market. Patients are reminded to look for the one that is low in net-carb, fat and salt. If the shake comes in a powder form, patient should make the shake with water, unsweetened soy milk or almond milk only. Fruit smoothie is not allowed on the diet because fruits will increase the net-carb count of the protein shake.
Peanut butter was invented by a doctor long time ago to provide a source of protein to the elderly who had dental problem and cannot chew meat. Peanut butter was considered as a meat substitute. Peanut butter contains protein but is too high in fat for Phase One consumption. A product called PB2 took the peanut butter and removed most of the fat content and resulted in a peanut butter powder with higher protein content and less fat. However, the AAS is only 55 which limit its nutritional value. High fat and some net-carb After patients lose 10 pounds of fat and water on average, they will be given the Phase Two diet plan, which increases the net-carb per serving to 5 g. However, the amount of fat and sodium remains the same. Patients should continue to lose weight on Phase Two. The Phase Two diet does not provide more nutrients than Phase One, but it provides more choices for the patients. It is mainly designed to help patients to satisfy their cravings. On Phase Two, legumes are allowed in small amounts. Legumes can be classified as carbohydrate with some protein and fat, they are not pure proteins. Soybeans have the highest protein content of all the legumes and also has the highest AAS of 132. Black beans, chickpeas and kidney beans are also complete proteins (AAS over 100). All other legumes mentioned in Table 12 are incomplete proteins with AAS around 85. While consuming a combination of the incomplete proteins can complement each other and result in a complete protein dish, the net-carb content, however, is still too high (except the soybeans) for this program. Therefore, only 2 tablespoons of legumes are allowed per serving on Phase Two.
Nuts have high fat and net-carb contents. They also have a good amount of potassium and calcium. Other than cashew which has an AAS of 100, all other nuts are classified as incomplete protein. The worse one is macadamia nut which has an AAS of 4. Macadamia nut is the most expansive per gram of protein of all nuts.
Small amount of dairy products is allowed on Phase Two. The amount of dairy product allowed is determined by the amount of net-carb and fat in the product.
On the Phase Three diet, small amount of starch (10 g of net-carb per serving) is allowed. Table 13 shows food items that are allowed on Phase Three. These food items contain some protein, but the quantity of protein in these products is too low to make an impact on the daily protein requirement. Proteins from whole wheat flour, semolina, peanut butter and rice milk have low AAS. Even the food items that have high AAS, such as Quinoa and imitation crab have too many net-carb, which limits the serving size. Phase Three items are included mainly for enjoyment, and cannot be considered as good sources of protein in this diet plan.  can substitute the animal protein with some legumes, to lower the overall cost. For example, 60 g of protein from whole chicken, pork tenderloin and soybeans can drop the cost to $1.40 per day. Patient should try to eat fish at least twice a week for its omega-3 and omega-6 content. Similar study will be done in the future to identify inexpensive food products with good omega-3 and omega-6 contents.