Animal or Plant? How to Pick Your Protein
Friday, June 17, 2011
LifeTime WeightLoss in Andrea McDaniel, Nutrition, Protein, vegetarian

Written by: Andrea McDaniel, MS, Registered Dietitian, Certified Sports Nutritionist & Personal Trainer, Columbia Life Time Fitness

The question of whether animal or plant-based protein is better is a highly debatable subject.   Is one healthier than the other? Will one help with weight loss more than the other? In order to answer these questions, it is important to compare the quality, nutrients, and metabolic effects of the two sources of proteins.

Here is a list of the common sources of each protein:

Health Benefits:

When it comes to health, protein is a critical component. Proteins form our organs, our hair, our nerves and muscles, and help assemble into hormones. In fact there are about 50,000 different proteins.  Each protein is made up of a combination of 22 amino acids, the nutritional building blocks of a healthy body. Of the 22 amino acids, eight are considered essential, meaning they cannot be made by the body, and must be obtained from food sources. 

Protein Quality

This is one thing that sets animal-based protein apart from plant-based protein: they are all complete proteins (containing all eight essential amino acids).  On the other hand, with the exception of soy, plant-based proteins lack at least one essential amino acid. Plant-based proteins can be combined so they become “complete.” 

For example, beans lack the essential amino acid methionine and rice lacks lysine; by eating them together makes a complete protein source. Complete proteins are very important because of the health benefits associated with each essential amino acid. Here are some examples:

  1. Branched-chain amino acids (isoleucin, leucine, and valine) benefit blood sugar management and growth hormone production[i],[ii]
  2. Lysine benefits production of antibodies, hormones, and enzymes
  3. Methionine benefits hair, skin, and nail health; detoxification of heavy metals
  4. Threonine benefits digestive health
  5. Tryptophan benefits immune system and brain health, helps with relaxation, reducing anxiety and depression[iii]
  6. Tyrosine benefits thyroid function[iv]

What about Soy?

As mentioned, soy is the only plant-based protein that is considered complete.  It is often used as a primary source of protein for vegans and vegetarians. However, there is still a lot of debate on its health benefits. 

Soy contains a component called isoflavones, considered a class of phytoestrogens, which means they mimic estrogen in structure but are weaker. One side of the debate argues this is good, especially for women in menopause, as it helps establish normal estrogen levels during a time they are decreasing. However, high concentrations of isoflavones over time can have a significant and can exert a toxic effect (i.e., estrogen dominance) on organs with estrogen receptor sites, such as the breast, uterus, and thyroid.[v] 

This potential isoflavone overload is especially a concern with many modern processed soy products, such as burgers and cheese. Studies have shown that 30 grams of unfermented soy consumed per day can affect thyroid function and is strongly linked to a host of autoimmune diseases, such as Hashimoto’s thyroiditis.[vi],[vii]  Bottom line: Although soy is a complete protein, a high intake of processed, unfermented soy products may cause more harm than good.

Nutrient Quality

In addition to amino acids, it is important to consider the other nutrients that accompany these protein sources. Plant-based protein sources have an important nutrient not contained in animal-based protein sources, which is fiber. Beans, legumes, and flaxseed are great sources of fiber.Fiber helps maintain bowel health and regularity, binds to help release toxins in teh body and helps balance blood sugar levels.

On the other hand, animal-based proteins are the riches sources of the following nutrients:

  1. B-complex vitamins: B vitamins play a crucial role in the body, and its requirements for them dramatically increase during periods of stress, illness and physical activity. The body cannot store B vitamins - thus, they are needed on a daily basis.
  2. Iron: Iron is important in maintaining a healthy immune system, thyroid function and energy production.
  3. Zinc: Zinc is essential for optimal growth and repair, immune function, wound healting and maintenance of muscle mass.
  4. Omega-3 fatty acids: Both plant and animal-based protein sources contain omega-3 fatty acids.  The difference is that many plant-based sources contain omega-3 fatty acids in the form of alpha linoleic acid (ALA) (see Omega-3 Is Essential to Your Diet). ALA has to be broken down in the body to form the essential fatty acids and often yield a much smaller amount of them in the body. The richest source of essential fatty acid is from fatty fish, such as wild salmon. Quality meat sources can also provide omega-3s.  For example, meat from grass-fed animals has 2-4 times more omega-3 fatty acids than meat from grain-fed animals. This is also true for poultry. This is also true for poultry. Eggs from pastured hens can contain as much as 10 times more omega-3s than eggs from factory hens.[viii]

Weight Loss

The impact of plant-based versus animal-based protein sources on weight management are the other nutrients that accompany them, such as carbohydrates, fat, and fiber.

Carbohydrates. One of main reasons for weight gain or an inability to lose weight is excess carbohydrate intake (see Low Carb Tops Low Fat…Again). The problem with many plant-based proteins is that they also contain carbohydrates. 

For example, for one serving of grains (rice, quinoa, oats), there are roughly 3 grams of protein and 15 grams of carbohydrates.  Beans, legumes, and lentils will contain more protein (8 grams), but also come with 15 grams of carbohydrate. On the other side, most animal-based protein sources contain trace amounts of carbohydrate. 

The exception is dairy; 1 serving (e.g., 8-oz. milk or 6-oz. yogurt) contains 8 grams of protein and 12 grams of carbohydrate. Relying solely on plant-based protein will increase carbohydrate intake.   

Fat and fiber. Fat and fiber both provide fullness and satisfaction, thus helping curb appetite.  Moderate amounts of healthy fat can be found in plant-based sources, such as nuts and seeds.  Quality animal-based protein sources, such as grass-fed beef, wild salmon, and organic eggs are also good sources of fat. As already mentioned, plant-based sources, such as beans, legumes, and flaxseeds are great sources of natural fiber. 


Both animal-based and plant-based protein sources provide health and weight loss benefits.  A combination of the two, with a focus on quality is key.  Animal-based protein sources are complete, while careful combining of plant-based protein sources is necessary to receive all the essential amino acids. When it comes to weight loss, carbohydrates that accompany many of the plant-based protein sources can add up and compromise weight loss efforts. 

One way to obtain a complete amino acid profile, without the added carbohydrates is by using a vegan protein powder, such as VegaMax.  VegaMax contains superior plant-based proteins sources: split pea isolate and rice protein isolate, which combine to create an amino acid profile comparable to whey protein. Lastly, it is important to choose both animal and plant-based protein sources that are in their original state (raw nuts versus candied nuts), in whole form (whole grain brown or wild rice versus whole grain bread), are ideally organic (grass-fed versus grain-fed beef).

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.



[i] Qin L-O.  Higher Branched-Chain Amino Acid Intake Is Associated with a Lower Prevalence of Being Overweight or Obese in Middle-Aged East Asian and Western Adults. J. Nutr. 2011; 141: 2 249-254

[ii] Mobbs CV.  Impaired glucose signaling as a cause of obesity and the metabolic syndrome: the glucoadipostatic hypothesis. Physiol Behav. 2005;85:3–23

[iii] Hudson C, Hudson S, MacKenzie J. Protein-source tryptophan as an efficacious treatment for social anxiety disorder: a pilot study. Can J Physiol Pharmacol. 2007; 85(9):928-32

[iv] Green, W. Effects of 3-nitro-L-tyrosine on thyroid function in the rat: an experimental model for the dehalogenase defect. Environmental Health Perspectives Supplements. 2002; 110(3)

[v] Chorazy PA, Himelhoch S, Hopwood NJ, et al. Persistent hypothyroidism in an infant receiving a soy formula: case report and review of the literature. Pediatrics . 1995;96:148-150.

[vi] Jabbar MA, Larrea J, Shaw RA. Abnormal thyroid function tests in infants with congenital hypothyroidism: the influence of soy-based formula. J Am Coll Nutr . 1997;16:280-282.

[vii] Ishizuki Y, Hirooka Y, Murata Y, Togashi K. The effects on the thyroid gland of soybeans administered experimentally in healthy subjects. Nippon Naibunpi Gakkai Zasshi; 1991:20 67:5 622

[viii] Lopez-Bote, C. J., R.Sanz Arias, A.I. Rey, A. Castano, B. Isabel, J. Thos (1998). "Effect of free-range feeding on omega-3 fatty acids and alpha-tocopherol content and oxidative stability of eggs." Animal Feed Science and Technology 72: 33-40.

Related Posts Plugin for WordPress, Blogger...

Article originally appeared on LifeTime WeightLoss (
See website for complete article licensing information.