Tuesday, November 11, 2014

Proteins: Vegetarians and Omnivores

I think the slightly "brisk" tinge in the air and the recent palm tree trimming event that happened outside our apartment signals the onset of fall here in San Diego, California. Other than that, the sun is bright, people swim in the outdoor pool, and I wonder why in the world I felt the need to move so many of my winter clothes from Ohio to California. As my first holiday season in Southern California approaches, I find my thoughts drifting to memories of snow covered Novembers, my grandmother's (disgusting) annual beef tongue, Thanksgiving turkey, and vegetarians. 

"09-03 NFlaWildTurkeys" by Tim Ross - Own work. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:09-03_NFlaWildTurkeys.JPG#mediaviewer/File:09-03_NFlaWildTurkeys.JPG


I decided to focus this week's topic on protein, amino acids, protein recommendations in the United States, and vegetarianism.  


 Some facts about protein

Proteins are large, complex molecules that are found in the cells of all living things. The human body is made up of thousands of proteins. Proteins contain nitrogen (N), carbon (C), hydrogen (H) and oxygen (O).
  • Some functions of protein
    • Provides nitrogen (in the form of amino acids)
    • Growth and maintenance of cells, muscle and tissue
    • Enzymes
    • Hormones
    • Antibodies
    • Fluid and electrolyte balance
    • Acid-base regulation
    • Transportation of nutrients
    • Blood clotting
  • DNA contains the instructions that guide protein synthesis. RNA translates the message so synthesis can happen.   
  • Thousands of amino acids connect together in a specific order to form proteins. The bond that forms between two amino acids is called a peptide bond.
    • Peptide bonds are a type of bond that connects the carboxyl group of an amino acid (COOH) with the amino group of another amino acid (NH2). Water is released and a CO-NH peptide bond is formed. 
  • All of our proteins are made from 20 different amino acids.
Amino Acids
Amino acids are the building blocks of proteins. All amino acids share the following characteristics
    • a central carbon (C, highlighted in blue);
      An amino acid
    • an amino group, nitrogen = NH2 (highlighted in green);
    • a carboxylic acid group (COOH, highlighted in yellow);
    • and a side group that is denoted by "R" (highlighted in pink).
      • The side group distinguishes each amino acid from other amino acids.
      • The side group influences the shape of the protein that is formed and the function of the protein.
  • There are 11 nonessential amino acids (NEAA)
    • Also called dispensable amino acids
    • The human body makes these amino acids
  • There are 9 essential amino acids (EAA)
    • Also called indispensable amino acids
    • The human body cannot make these 9 amino acids at all or cannot make enough of them to support our biological needs 
      • We absolutely have to eat foods that contain proteins with these 9 amino acids 
    • The 9 EAA are
      • valine   
      • isoleucine
      • leucine
      • lysine
      • methionine
      • phenylalanine
      • threonine
      • tryptophan
      • histidine
These twenty amino acids come together in different and specific combinations to make all of the different proteins in the body.

Dietary Guidelines for Americans

 In 1990, the National Nutrition Monitoring and Related Research Act mandated that the Secretary of Health and Human Services and the Secretary of Agriculture revise and publish a new set Dietary Guidelines for Americans every five years. The DGA focus on health promotion and disease prevention for all Americans two years and older. The DGA influence how federal nutrition and health dollars are spent. They also impact industry trends. 

The 2010 DGA emphasize that Americans 
  • increase intake of fat-free or low-fat milk and milk products;
  • choose a variety of protein foods - lean meat and poultry, eggs, beans, soy, nuts, and seafood;
  • and replace solid fats with unsaturated fats. 
Here is a a sample list of lean protein sources Protein Foods - MyPlate.   
SuperTracker (MyPlate.gov)  is one way you can access free meal ideas based on the Dietary Guidelines for Americans. You can enter in your age, gender and physical activity level to get recommendations customized to you. 
Protein needs
  •    In terms of calories, protein should make up 10-35% of the calories in an adult's diet. 
    • An individual's protein requirement can be calculated based on body weight. In health (not during times of growth, injury, illness, burn), adults need 0.8 grams of protein per kg body weight. 
    • In general, adult women need about 46 grams of protein per day and men need about 56 grams of protein per day.
  • During pregnancy (which is a period of growth) a woman's protein needs increase by ~10-15 grams a day. 
  • Endurance athletes may need 1.2 – 1.7 g/kg healthy weight. 
    • This is a practice endorsed and recommended by some branches of science and medicine and not by others. 
    • Mental stress, physical labor, recreational weekend sports do not require an increase in protein intake.
  • Most people in the United States eat more than the recommended amount of protein. Excess protein cannot be stored as protein. Excess protein will be stored as fat.
  • Vegetarians may need to consume more protein to meet their full protein needs. 
Vegetarians

People choose vegetarian diets for a variety of reasons.  
  • Religious belief
  • Political or ideological reasons
  • Ethical reasons
  • Personal preference
  • Health
  • Economics 

There are many different "branches" of vegetarianism. Below are the official classifications of different vegetarian diets.
  • Vegan: Vegans eat a plant-based diet. They do not eat any animal products. Vegans do not eat meat, fish, poultry, eggs, or dairy. Vegans get all of their protein from plant-based sources.
  • Lacto-vegetarian: Lacto-vegetarians eat a plant-based diet that also includes dairy products. Lacto-vegetarians get their protein from plant-based sources and from dairy (milk, cheese, etc.)
  • Lacto-ovo vegetarian: Lacto-ovo vegetarians eat a diet that is rich in plant-based foods and also includes dairy products and eggs. Lacto-ovo vegetarians get their protein from plants, dairy (milk, cheese, etc.) and eggs.
  • Semivegetarian: Semivegetarians eat a plant based diet and occasionally eat poultry and fish. These vegetarians often do not eat red meat. These vegetarians usually consume dairy and eggs.
  • Vegetarian: This is a broad term that encompasses vegan, lacto-vegetarian, lacto-ovo vegetarian, and semivegetarian. 
These terms provide a common ground for discussion and are used to organize different types of vegetarian eating plans. In reality, "vegetarian" and "vegan" are the most common terms used to refer to vegetarian diets. These terms are used quite broadly and refer to a diet plan that derives most if not all of its protein from plant sources. 

 If you are considering incorporating more plant proteins into your diet, going with "meatless Mondays" or becoming a vegetarian, you might be interested in the article Tips on Switching to a Meatless Diet by Sharon Denny, MS, RDN, posted at the Academy of Nutrition & Dietetics website, eatright.org.
Protein Quality

Complete proteins are considered "high quality" proteins because they provide all 9 EAA (essential amino acids) at levels that adequately support human needs.
  • Complete proteins come from animal sources
    • Dairy
    • Eggs
    • Meat, fish, poultry
  • Two complete proteins from plant sources
    • Soybean, quinoa
"Edamame - boild green soybeans" by Kanko* 


 "Quinoa cuit" by Vult.


Incomplete proteins are considered "low quality" proteins. These proteins are "low quality" because on their own they cannot provide all 9 EAA at levels that adequately support human needs. 
  • Plant proteins, except for soybean and quinoa, are incomplete proteins

 "You Complete Me" - Complementary Proteins



All plant proteins, except for soybean and quinoa, are low in at least one essential amino acid. In other words, nearly all plant proteins have at least one limiting amino acid. 

    • A limiting amino acid is an essential amino acid that is not present in an high enough amount to adequately support protein synthesis in the human body. 
    • Different plants are limited in different EAAs. This can be overcome by pairing foods together.
      • Complementary proteins need to be eaten in the same day but do not have to be eaten during the same meal. 
    • The act of pairing two plant proteins together, each with a different limiting amino acid, is called protein complementation. Beans and rice are a famous complementary pair of protein sources. 
      • As you can see in the chart below, beans are limited in methionine but contain enough lysine. Rice lacks lysine but has enough methionine. 
      • When beans and rice are paired together, they complete each other. Beans and rice are complementary pairs.

  • Vegetarians, particularly vegans, may need to eat more total protein in order to meet their overall protein requirement because proteins need to be paired. 
    • For example, a woman who follows a vegan eating plan may need 45 grams of protein per day. However, because all of her protein comes from plant sources, she may need to eat 65 grams of protein per day to get all of the amino acids that are needed. This can be done easily with plant sources and without excess calories. 
    • A benefit of plant proteins is that they do not contain cholesterol or saturated fat (unless it has been added during food preparation).
  • It is not necessary to consume complementary proteins during the same meal, but it is important to eat them during the same day.
Vegetarian Diets throughout the Life Span

 Choosing plant-based proteins is healthy and sustainable at all ages. It does require planning and attention in order to be certain that all 9 EAAs are provided every day. It also requires a bit of extra attention to make sure that all other nutrient needs are met. These needs vary with age. The resources below provide some insight about things to consider for different age groups. 

 As mentioned above, it is not necessary that limited amino acids be paired together during the same meal, however, this is often a convenient and logical way to approach meal planning, especially in the beginning phases of adopting a vegetarian diet.

The Academy of Nutrition and Dietetics has some useful resources available for parents of toddlers, children, and teens that are vegetarians. 

Some resources:



Image attribution:

"Edamame - boild green soybeans" by Kanko* - Flickr. Licensed under Creative Commons Attribution 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Edamame_-_boild_green_soybeans.jpg#mediaviewer/File:Edamame_-_boild_green_soybeans.jpg

 "Quinoa cuit" by Vult... -i..C Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons -http://commons.wikimedia.org/
htwiki/File:Quinoa_cuit.JPG#mediaviewer/File:Quinoa_cuit.JPG
Is a high-protein diet harmful?


1. One concern and potential risk associated with high protein diets is that the protein consumed in these diets tends to come from animal sources rather than plant sources. The extra protein usually displaces intake of plant-foods. Increasing the intake of protein from animal sources while decreasing intake of plant foods increases the likelihood that the diet won't provide enough fiber, vitamins, or phytochemicals (plant chemicals). 

2. Diets that are high in protein are more likely to be high in saturated fat and cholesterol. Diets high in saturated fat and cholesterol increase the risk of cardiovascular disease, hypertension, and type two diabetes. 

3. High intake of processed red meat is associated with an increased risk of colon cancer. 

Anyone with kidney disease should discuss protein with their health care provider. 
Final Thoughts

  • A comprehensive discussion about protein, health and disease can be found at the Harvard School of Public Health - Nutrition Source website.
  • Dietary protein does not build muscle. Exercise (specifically strength training / weight lifting)  builds muscle.
  • Eating more dietary protein than the body needs leads to excess. Dietary excess gets stored as fat. Excess nitrogen is lost because it cannot be used. It will get excreted in the urine.
  • There are many kinds of vegetarians. There is no right or wrong way to be a vegetarian. There is no right or wrong reason to be a vegetarian. 
  • A vegetarian diet can meet the nutrient needs of people of all ages and all fitness levels.
  • Athletes in training may have higher protein requirements, but not all scientists and medical professionals agree about this.

 A Few Other Resources

Posted by
Labels: