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Animal or Plant? How to Pick Your Protein

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:

  • Animal: chicken, turkey, pork, beef, lamb, buffalo/bison, seafood, eggs, and dairy
  • Plant: soy, beans, legumes, lentils, grains, nuts, and seeds

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.

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Reader Comments (13)

This article does not adequately address vegetable protein sources and it is incorrect. There are other complete vegetable proteins besides soy, namely hemp seeds, amaranth, buckwheat, quinoa, and spirulina.

June 19, 2011 | Unregistered CommenterRoss

Is there an animal source of fiber or a good fiber source that is free of carbohydrates? If there is I'd like to know.

June 19, 2011 | Unregistered CommenterTina

Most soy is now GMO - questionable at best. Also, not all organic beef is grass-fed. Grass fed (and finished with grass the last few months, one needs to ask) has better balance of omega-6 and omega-3s and is also lower in cholesterol than grain fed. As for carbs, sticking to veggies to augment protein is great for weight loss, just be careful of beets, carrots, tomatoes, anything that is higher carb for an evening meal...a meal that you will not work off.

June 19, 2011 | Unregistered CommenterRandy

Thanks for the information... however, please proofread for typographical errors. There are quite a few in this article.

June 21, 2011 | Unregistered CommenterAnita

Good thing there is a disclaimer at the end of the article, since animal protein's are linked to high cholesterol, cancer and hypertension.

June 21, 2011 | Unregistered CommenterC

I have to wonder who writes these articles for Lifetime. I have read several and each has had incomplete and incorrect information. I agree with Ross.You do not properly address complete plant proteins. Carbs are not the problem for weight loss with protein being the answer. There are many studies that High carb/low protein diets work as well - as long as they are complex carbs, While high protein, especially animal proteins have may other health issues. Too much protein taxes the body and causes inflammation in the body. Randy also makes a hugely important fact that most soy is GMO and even more importantly is the feed of the animal that is consumed. Standard/conventional methods of raising meat can be flat out dangerous to our health. This article does not answer the question that it set forth to do... Animal or Plant? How to Pick Your Protein. It seems more like an add for the last product stated "vegamax" Lifetime needs to provide more in depth and accurate information. This article. like many before, was a disappointment.

June 21, 2011 | Unregistered CommenterDina

@C: Actually, the idea that animal proteins cause high cholesterol, cancer and hypertension is one of those myths that won't go away. The cholesterol piece is addressed in another article here ( As for the meat and cancer issue, processed meats are linked to an increase in cancer risk, but unprocessed meats are not. Same thing for hypertension. High blood pressure would be more a result of processed meats containing a lot of salt, which could cause an acute rise in blood pressure. The meat-saturated fat-cholesterol-heart disease hypothesis just doesn't have the scientific support most people have been led to believe.

June 21, 2011 | Unregistered CommenterTom Nikkola

Randy: You're spot on about soy. It's hard to find a non-GMO source of soy in today's food products. Organic meats/poultry should not be raised with GMO feed, but it doesn't mean they're raised on a natural diet. Grass-fed beef, free-range chicken, etc. are the best way to buy beef, chicken, etc. As far as the beets, tomatoes and carrots, I wouldn't worry about people eating toomany of those. They have the reputation for being a high glycemic food, but they have so little total carbohydrate, they're unlikely to cause an issue, unless they're made as a juice instead of a whole food.

June 21, 2011 | Unregistered CommenterTom Nikkola

Great article. When it comes to weight loss everyones body reacts differently. Fats are my friend.

June 22, 2011 | Unregistered CommenterBrent

I need to clarify something for you. Rice and grains do have lysine but it is such a minimal amount that it is considered too insignificant. And, beans do contain methionine similarly. All plants have complete proteins. They are considered to have a missing amino acid only because it is a small amount. The original studies on rats are where the human needs for protein came about. Humans can actually get sufficient protein from a wide variety of sources in plant foods because humans actually have a lower need for protein than rats.

July 20, 2011 | Unregistered CommenterTreadmill Traci

i was a little taken aback by the statement that soy is the only complete vegetable protein... luckily Ross hit the nail on the head in the first comment... Quinoa was going to be my first example of a much better vegetable source that contains a complete protein... that statement is totally contrary to what I've been taught ... whats up LT? .... i will say this though, i'd rather see my children exposed to LTs push for health products that probably are mostly healthy, than expose them to the current widespread push for uneccessary pharmaceuticals, alcohol & an array of convenient, junk food... although, its too late... the soda companies have their grip on my children already

I Love LIfeTime Fitness

July 17, 2012 | Unregistered Commentercrystal

Hello Crystal, thank you for your comment and your understanding in Life Time's encouragement to help you and your family achieve and maintain optimal health. You are correct in that quinoa, by definition, is considered a "complete protein." It does contain all essential amino acids. It was not mentioned in the article as a complete protein SOURCE because it is primarily made up of carbohydrates and contains far less protein. 1 serving of quinoa contains ~25 grams of carbohydrates and ~4-5 grams of protein, which is only about 2-3 grams more than rice. So, although it may contain all of the essential amino acids, the amount of total protein (and amino acids) is small relative to carbohydrates AND compared to animal protein (7 grams of protein/ounce or ~25 grams for a 3-4 oz serving).

Soy protein was mentioned in the article to show that even though a plant-based protein (or any protein for that matter) may be a complete protein source, doesn't necessarily make it a quality protein option. As mentioned in the article and comments, there are other possible issues with soy, such as GMO's. There are also issues with non-organic, conventionally raised animal protein sources, such as the diet they are fed, in addition to possible hormones and antibiotics they are often given.

The main thing, is it is important to look at the food as a whole and not just categorize it as good or bad based off of 1 characteristic (i.e. compete protein or not). In addition, I couldn't agree more with you in that it is all relative to where you are at right now. Is quinoa a better option than convenient, junk food? Absolutely. But, when identifying protein sources it is difficult to place quinoa in there considering the fact that it contains far less protein relative to carbohydrates and relative to animal products. Does that make sense? Again, thank you for taking time to comment and express your concern... and support :)

July 17, 2012 | Unregistered CommenterAndrea McDaniel

Thanks for the clarification.

July 17, 2012 | Unregistered Commentercrystal

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