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The Importance of Protein
The word protein originates from the idea that proteins are central to life and the first nutrient. Vitamins – vita meaning life and amin meaning protein – got their name from the misconception that amino acids, the building blocks of protein, were the essential components for maintaining life.
Proteins are found in animals and plants, but the mixture of amino acids – the building blocks of the protein found from different sources – varies. As a result, there are 21 common amino acids consisting of 12 nonessential and nine essential amino acids. Essential amino acids are those that cannot be synthesized from other amino acids, but must be consumed in the diet. The usual way that nonessential amino acids are formed is by metabolism of other amino acids. All amino acids have a basic structure of an alpha-amino nitrogen and carboxylic acid.
Maintaining the amounts of protein in muscles and organs is essential to life and is the main objective of the adaptation to starvation. In fact, loss of more than 50 percent of body protein is incompatible with life. The protein is stored in organs and there is no labile compartment.
The Importance of Protein
There is evidence that modestly increasing the proportion of protein in the diet, while controlling total calorie intake, may:
* Improve body composition.
* Facilitate fat loss.
* Improve body weight maintenance after weight loss.
Mankind is very well adapted to malnutrition and starvation, and this adaptation is reflected both in the way the body stores energy and how it uses these stores of energy when food intake is reduced or eliminated altogether. In the average 70 kg (154 lbs) man:
* The largest store of calories is in the form of fat in adipose tissue with approximately 135,000 calories* stored in 13.5 kg (30 lbs) of adipose tissue.
*A dietary calorie is 1,000 calories or a kcal, but for simplicity will simply be noted as calories. You may also see dietary calories capitalized as “Calories.”
This storage compartment can be greatly expanded with long-term overnutrition in obese individuals.
There are approximately 54,000 calories stored as protein both in muscle and organs, such as the heart and liver. Only half of these calories can be mobilized for energy, since depletion below 50 percent of total protein stores is incompatible with life. In addition to being an energy source, protein plays a functional role in many organs, including the liver, and depletion is associated with impaired immunity to infection. In fact, the most common cause of death in an epidemic of starvation is typically simple bacterial pneumonia. Conservation of protein is an adaptation tightly linked to survival during acute starvation.
Meal Replacement Shakes and Weight Maintenance
Studies show that meal replacement shakes are a viable way to maintain weight, as recognized by the European Food Safety Authority, and that increasing the protein to about 30 percent of resting metabolic rate, as estimated by bioelectrical impedance, leads to greater loss of fat with retention of lean body mass.
What are the healthy carbs?
Carbohydrates are an important element in the diet, and many of the foods that are rich in carbohydrates are also rich in fiber and phytonutrients. Good carbs are simply fruits, vegetables and some whole grains. Carbohydrate needs should be met first by consuming five to nine servings per day of diverse and colorful fruits and vegetables, which provide a wealth of beneficial substances. If more carbohydrates are needed, they can be supplied by whole grains and legumes (e.g., beans). A low-carbohydrate diet restricts carbohydrate grams to such a low level that individuals consuming these diets cannot benefit from the many health benefits of fruits and vegetables.
Carbohydrates are made up of atoms of carbon, hydrogen and oxygen but no nitrogen, and are broken down into sugars, such as glucose and fructose. Undigested carbohydrates are eliminated from the body and are referred to as dietary fibers.
Hidden Simple Sugars
Simple sugars include glucose, fructose, lactose and sucrose. These are listed as sugars on food labels, while the so-called complex carbohydrates are not included in this list, despite their similarity to simple sugars. Simple sugars can be directly absorbed by the mucous membranes of the mouth. However, short-chain carbohydrates, such as maltodextrin or corn sugar, consist of 15 glucose units, which are hydrolyzed in the stomach by enzymes and acid into simple sugars. These are often called complex carbohydrates on food labels but act like sugars.
The digestion of starches begins in the mouth in the presence of salivary amylase. As with proteins, much of the digestion takes place on the intestinal mucosal villi, which have both digestive enzymes and specific transport systems for sugars.
Lactose and sucrose are combinations of two different sugars linked together. Lactose is made up of galactose and glucose, while table sugar or sucrose consists of glucose and fructose.
High-fructose corn syrup is made from corn by a process that ends with 55 percent free fructose and 45 percent free glucose, approximately equivalent to table sugar. The tastes of corn sugar, sucrose and fructose are different. Fructose, the sweetest-tasting sugar, is found in fruits such as oranges. Corn sugar tastes like pancake syrup and is the primary sweetener in colas in the United States. In some countries, such as Mexico, sucrose is used to sweeten colas and they taste distinctly different from their U.S. counterparts. The issue with corn syrup is not its chemical character but the huge amount in the diet. Due to government subsidization of corn, large amounts of corn syrup are used in many foods,including soft drinks, which results in extra calories added to the diet. Studies suggest that the obesity epidemic can be linked to the following:
* Consumption of large amounts of high fructose corn syrup (HFCS).
* Consumption of high-fat foods.
* A sedentary lifestyle.
Since dietary fibers are not digested, they do not contribute directly to the nutritive value of foods in terms of calories, but they have many effects on human physiology. Ancient man consumed a great deal of fiber, and this fiber resulted in numerous large, bulky stools that filled the colon and caused it to contract against a large volume load. Modern man eats a small amount of fiber, approximately 10 to 15 grams per day, compared to 25 grams per day in a healthy, plant-based diet and well over 50 grams per day in ancient diets.
Carbohydrates have a bad reputation, due in part to the recent popularity of so-called high-protein, low-carbohydrate diets for weight loss. Classifying foods as carbs, proteins or fats is misleading since few foods are composed purely of one macronutrient, and the quality of the food can vary significantly. A high-carbohydrate diet could be a plant-based, whole-foods diet with phytonutrient-rich fruits and vegetables at the base, with a moderate amount of whole grains and healthy low-fat proteins to balance nutritional needs. But, since sugars, refined flour products (such as white bread and pasta) and refined grains (such as white rice) are all considered carbohydrates, a diet that is based primarily on refined grains, while it could be low in fat, could also be very high in calories because these low-fiber grain foods are not particularly filling.
Individuals who consume a diet of this type may feel virtuous for avoiding fat, but they could easily gain weight on a diet based on refined grains. The recent popularity of a high-protein, low-carbohydrate diet came on the tails of the high-carbohydrate craze of 20 years ago, because people found they were gaining weight on bread, cereal, rice and pasta if they made no distinction between whole grains and refined products. Pasta, which had previously been considered good because it is low in fat, is now viewed as bad because it is often a refined flour product (there are whole grain versions available).
In sports nutrition, especially for aerobic exercises, large amounts of carbohydrates are used to provide energy that is burned in the course of exercise. In the Fitness Science section, this topic is discussed in detail.