Why the Variety of Your Protein Sources Matters

Why Protein Variety Is Important In LineSometimes the simple story is good enough. I’d venture to say that simple is usually good enough, particularly when it comes to health. A good diet? Eat lots of plants and animals, don’t eat so many carbs, and stop being scared of natural fat. Training? Lift heavy things, move around a lot at a slow pace (constantly, if you can swing it), go really fast once in awhile, and enjoy what you do. Lifestyle in general? Get some sun, be with your tribe, get into nature as often as possible, inject meaning, laugh, love, and live. There—that gets you most of the way. Simple, right?

Another common piece of advice is “eat protein.” And yeah, that’s true. We need protein to survive. It’s probably the most essential nutrient in existence because we can’t make it ourselves. But sometimes digging a little deeper pays off.

Not all protein is created equally. Protein is composed of up to 20 different amino acids. Every protein source contains some or all of those amino acids in different proportions, so each source of protein really is different. When we digest protein, what our body actually absorbs and utilizes are those amino acids. Each one plays a different role in the body, from building and repairing various tissues, performing vital metabolic processes, acting as progenitor for essential compounds, and even regulating gene expression. We need amino acids to live.

We need some amino acids more than others. We can synthesize or convert some of the amino acids we need, but there are 9 amino acids that we cannot make or convert. These are the essential amino acids, and we must consume foods that contain them.

Another category is the conditionally essential amino acids. These are the amino acids that we can synthesize or convert, but certain conditions and contexts increase our requirement for them. In many cases, people don’t eat enough of these conditionally essential AAs. They are therefore essential for most people. 

For the most part, animal-based protein contains adequate concentrations of all the essential amino acids. Furthermore, animal muscle meat is roughly identical in amino acid composition. Whether you eat chicken thighs, lamb chops, pork loin, salmon filets, or ribeye, you’ll be getting the same basic pattern of amino acids in your diet—including all the essentials. The same thing goes for almost all animal-derived foods, like eggs and dairy. They’re all complete proteins—they provide the essential amino acids.

Plant proteins are incomplete–they’re usually missing one or more of the essential amino acids. That’s why cultures that rely heavily on plant protein end up with staple food combos carefully curated to provide all the essential amino acids, like beans with rice or beans with corn.

Eating a variety of protein sources ensures you’re getting all the amino acids you need to perform basic physiological processes. So here are a couple reasons why balancing your protein intake from different sources is important.


I’ve written about this before. The crux of the matter is this:

Most animal proteins are high in methionine, an amino acid critical for growth and development and overall robustness but also implicated in unchecked growth of cancer cells. The calorie restriction with optimal nutrition (CRON) crowd tends to avoid methionine like the plague, pointing to animal studies in which animals on high-methionine diets die earlier and get more cancer and other degenerative diseases than animals that restrict methionine.

What I and people like Denise Minger have suggested is that glycine—an amino acid found abundantly in connective tissues but not in muscle meat—can counter the anti-longevity effects of methionine. A study (the abstract of which is sadly no longer free to view; wonder why) from 2011 found that giving glycine to rodents on a high-methionine diet extends lifespan and emulates the effect of methionine restriction.

If that’s true in humans, then expanding our protein intake to include both muscle meats (methionine) and connective tissue (glycine) will make us healthier.

And although scientists haven’t looked at the topic very closely yet, we have inklings that glycine is important for humans. In one recent study, the relationship between red meat and diabetes was abolished after controlling for low-glycine status. People with low glycine levels and high meat intakes were more likely to have diabetes; people with higher glycine levels could have higher meat intakes without any issues. In another study, low circulating levels of glycine also predicted diabetes risk

We do know that glycine is a conditionally essential amino acid. We can make it from proline, but evidence shows that we can’t make enough to cover all the tasks glycine performs. So if we want to sleep better at night, maintain the structure and integrity of our ligaments, tendons, and cartilage, keep our skin taut and firmand balance out our methionine intake, we’d better start eating skin, tendon, bone broth, and other gristly bits.

Increasing protein variety to include collagenous materials will balance out our meat intake and make us healthier.

Plant Protein

If we’re gonna have to eat animal protein or assemble complex combinations of plant proteins that provide all the requisite amino acids, why eat plant protein at all? Why not just eat a few ounces of steak instead of the perfect proportion of rice and beans?

Variety can be good for its own sake. Some people get bored eating the same thing every day. Opening up an entirely different genre of protein—plants—will only increase variety.

And as I laid out a couple weeks ago, legumes—the most popular and dense source of plant protein—offer other advantages: prebiotic fiber, minerals like magnesium, copper, and manganese, and vitamins like folate and B1.

Plus, plant protein is usually cheaper than animal protein. Obtaining a portion of your protein from plants offsets the cost and allows you to focus on quality protein from grass-fed and pasture-raised animals. A pound of steak doesn’t offer any distinct advantages over 3/4 pound of steak with a half cup of black beans. If anything, the latter offers a bit more nutrient variety.

Increasing protein variety to include plant sources allows more freedom when planning meals, offers fiber, minerals, and vitamins we can’t easily get from animals, and makes it easier to afford high-quality animal protein.

Nutrient Co-riders

Another reason to vary your protein intake is that different sources of protein are accompanied by different nutrients. A mussel might give you similar amino acids as a chicken thigh, or a cup of yogurt, but the similarities end there. The mussel provides manganese, selenium, a ton of B12, and some folate.  The chicken thigh provides less B12, some niacin, a little more magnesium. The yogurt offers probiotics and calcium. You’re better off eating some of all three rather than an equal amount of one.

Eating a variety of protein sources grants access to different co-riding nutrients.

Like for Like

Some traditional medicine systems have a concept called “like for like.” If you want to improve your masculine vigor, you eat tiger penis. If you want to promote kidney health, you eat stir fried pork kidneys. That sorta thing.

Is there anything to it, or is that superstitious mumbo jumbo?

While I can’t speak to the libidinous merits of consuming tiger penis, I can speak to the benefit of some other examples.

Livers are extremely high in folate and choline, two important nutrients for liver function.

A lamb brain is full of omega-3 fats. A 3 ounce portion of cow’s brain has a full gram of omega-3s. Since we need omega-3s for optimal brain development and function, eating an animal’s brain can help our brains.

Animal skin is made up of collagen, the densest source of glycine. Our bodies use glycine to build and repair collagenous tissues, including skin, cartilage, tendons, and other connective bits. Eating skin can improve the health and appearance of your skin.

A can of bone-in sardines contains easily-digested bone. Compare that to another bone friendly food, dairy. You’re getting all of the bone, not just the calcium. If there are any nutrient co-factors that help bone mineral density, they’re probably contained in the bone itself—the bone that you’re eating. I haven’t found any studies examining the effect of eating bone-in sardines on bone mineral density or osteoporosis, but I bet it helps.

If you’re just eating the same cut of steak every day, you’ll miss out on the “like for like” mechanism.

To sum up, protein variety is important for many reasons:

It helps you obtain all essential and conditionally essential amino acids.

It helps you balance out methionine intake with glycine.

It increases the range of co-riding nutrients you obtain.

It makes it easier to afford higher-quality, pasture-raised, and grass-fed animal products.

It increases food variety and makes your diet more enjoyable and sustainable.

It allows you to follow the “eat like for like” rule when applicable.

What are some other good reasons to vary your protein intake?

Thanks for reading, everyone. Take care!


About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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61 thoughts on “Why the Variety of Your Protein Sources Matters”

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  1. As always, excellent laid out article. I’m wondering, would a collagen protein supplement be just as effective as drinking bone broth? I do consume bone broth but not on a regular basis. However I use two scoops of collagen protein in my breakfast smoothie every mourning.

    1. I think the scoops on collagen would do the trick. I’m aware of the “methionine needs to be balanced by glycine”. Besides bone broth and skin, I take 1000mg Trimethylglycine (TMG) daily in hopes of reducing the possible side effects of meat consumption. It also lowers homocysteine. Not sure if that amount is effective. Keeping protein intake in the moderate range is necessary also.

    2. Don’t forget the “co-riders”. Your body uses co-enzymes and vitamins to work with the amino acids and proteins.

  2. It makes sense to eat a wide variety of protein, and I can’t imagine our ancestors hunted an animal and only ate the lean muscle. In fact, I know my grandparents and parents had a diet rich in organ meats. I do regularly eat liver pate, skin on meat and bone and fish broth.

    1. How about if the skin is roasted is it still good or is it too cooked?

  3. I’ve never been able to get very worked up over studies conducted on animals for the simple reason that animals aren’t people. Studies conducted with people aren’t much better because people lie. Rodents are honest, but their dietary needs are different from ours. I do agree that eating a variety of protein is probably best, as opposed to homing in on one or two things and sticking with them to the exclusion of other types of protein. I’m guilty of doing that when it comes to animal protein. I don’t like organ meats and seldom eat lamb or veal.

    1. Perhaps you didn’t eat the right kind of lamb’s meat. The “unadulterated” kind is quite smelly (identified by a big and fatty tail) and turns many people off. Inquire about the one that was crossbred. It’s is very mild and gentle in flavor and unlike it’s predecessor, there’s nothing like a skewer with a few nuggets of grilled fat from the tail.

  4. I know since going primal I crave different sources of protein. I fully believe that these cravings go along with the primal lifestyle as your body’s signals are not interrupted as with the SAD, and when eating primal your body sends intrinsic signals that can lead you to your next food source for the specific nutritional content. A few years back the thought of eating sardines was enough to elicit a gag reflex. Nowadays I love sardines and include them in my diet probably about once a week. I also love dark meats and include the skin (as opposed to skinless chicken breasts only). I also hunt whitetail deer and eat the meat, fat and marrow. Primal living makes eating fun and gives it a sense of purpose as well.

    1. with me, but no one seems interested! As a former long term vegetarian, I used to be totally grossed out by people eating meat of the bone, or eating the chicken skin. Now I roast chicken just so I can have first dibs at that crispy skin, and actually tried ribs for the first time in my life last week. And I have learned that I actually enjoy chicken livers. Can’t say the same about beef liver, but I at least tolerate it. Love broadening my horizons!

      1. just saw the top part of my reply got cut off up there. I had mentioned how I was also grossed out by sardines, and now I love them. Always trying to get people to hop on the sardine bandwagon with me!

        1. I know! I’ll eat a can of them while I’m sitting on the couch with my wife and she hates the smell of it! Can’t get her to try a bite but my 8 year old son loves them!

          1. I also buy the roasted sardine. It does not smell bad. Love it. Start her with that.

    2. Eating this way has turned me into a bizarre foods aficionado. I’ve tried everything from various organ meats to every animal I can find that walks, flies, swims, or slithers. Can’t say that there have been any I disliked. These days, boneless, skinless chicken breast or lean pork loin may be the only meats I dislike – too dry and bland.

  5. Strange. Doesn’t Mark’s get-started book say “no beans”?. I went to a lot of trouble looking for recipes for “no-bean bean soup”. And I hadn’t bumped into a retraction nail now. Are beans now “good”?

    1. That’s one of the things most of us love about Mark. He’s never complacent, always questioning and is willing to change course if evidence suggests he should. Read his piece on legumes from last week. He’s still not saying go whole hog on them, but a few small servings could benefit you if your digestion agrees.

      1. Southern people, black and white, almost always cook beans with scrap pork of some kind. My choice has always been smoked pork necks (or turkey necks) which are high in collagen; others prefer to use pig tails, also collagen-rich.

        I’ve long suspected that the real problem with beans is potential mycotoxin content. This can be reduced by the same technique which reduces gassy mucopolysaccharides: boiling beans for five minutes, turn off and walk away for an hour, drain and rinse, then cook.

        As a descendant of Cherokees, Mexicans, and numerous generations of poor whites, I always considered beans sufficiently paleo for me.

    2. Beans? What aboout the rice? Aren’t grains “hazardous stuff”?

    3. I’d like to know this too. I thought beans were Paleo no-no. I’ve long taken the position that white rice is no big deal, but I considered it a paleo cheat.

      1. Mark’s method has always seemed like his own take on or variation of paleo to me, and he does seem more willing to question everything – including paleo dogma – if the research presents itself. White rice has been on the meh-it’s not so bad list for a while now, except in the hard core anti-grain crowd. As I understand it, brown rice is still frowned upon, though.

      1. If they agree with you. MDA’s previously referenced article does point out that legumes should be properly soaked and cooked, not just from a can you open and heat up. Personally, I love beans, but they don’t love me, so I just stay away from them (have not experimented with different beans though). Rice I can eat on rare occasions. I find I don’t miss rice, but there are some recipes that just seem better on a little rice. And I’m talking like 1/4 cup.

  6. It is the 9 essential amino acids that make the difference– we make the other 11 if enough protein is eaten. Protein sources are digested into peptides and amino acids- peptides are the most common items absorbed– and the body doesn’t care where they come from – just eat enough protein – well above the so called RDA

  7. I just finished dinner which included roasted lamb’s shoulder, baby sweet potato and salad, accompanied by a small glass of Sangiovese wine (in celebration of the new year), so I’m not going to get my self worked out over the mention of Black beans 🙂 But no question about it; verity of protein and other key foods, is the key to good health

    And since I started my day with “Chile rocket fuel latte” with 2 tbs of collagen, I think I’ll be fulfilled all the requirements.

  8. Great Lakes Gelatin has a huge glycine profile. I mix a little with water and butter to always make a little sauce if I’m having muscle meat (steak). That way I know I’m getting the glycine to counteract any negatives.

  9. My problem with this is that I don’t like eating meat. I hate it. I like chicken but I am a picky eater. So don’t expect me to eat chicken bones or skin. Any suggestion?

    1. Make your own bone broth and you can drink it instead. It may sound scary but bone broth is really just amazing stuff. Full of great flavor. I slow cook a whole chicken, take the meat off then cook the bones on low with 1 tbsp apple cider vinegar. Don’t forget the vinegar. It is necessary to get a good amount of gelatin formed. Cook for 24 hours and you have liquid gold.
      It keeps in the fridge for about 3 days. I take a scoop of it and mix with hot water first thing in the morning instead of coffee.

  10. I’m curious about the collagen/gelatin/glycine content of ground meats vs. their wholesome counterparts. Since ground beef, for example, usually contains connective tissue (etc.), could it be considered a more well-balanced source of various proteins (assuming it’s the grass-fed, well-educated, impeccably-mannered stuff, of course)?

  11. This articles make sense; eat multiple sources of protein similar to the way one would eat a variety of veggies. I just have to find where to buy tiger penis…

    1. I eat pork rinds almost every night. Don’t forget the guacamole dip!

    2. Made a nice bone-in ham, with the skin on for Thanksgiving last weekend (Canadian). First time I’ve had cracklings since I was a kid. So. Freakn’. Good! I had to fight my mom for them. Of course, the whole time my dad was telling me how bad it is for you (while he was sipping on his third can of Coke for the evening)

      1. I had quite a few of those. my dad was a pork producer (small farm). Delicious.
        I’m Canadian too.

  12. I think the key to this discussion is not that we need to eat a crazy amount of protein, but more to the fact that we need to eat a variety of ‘quality’ protein. Organic Grass fed meat from rotational pastured livestock. That being said I still think that we should eat mostly plants.

  13. Really great article Mark, thanks. I’ve followed this philosophy for a long time and can testify to its benefits.

  14. I’m trying to achieve ketosis but I’m pretty sure I’m being scuppered by the protein I eat. I think a lot of it is being converted to glucose by my liver and driving up my insulin levels. I know this because I’m T1 diabetic and even though my carb intake is near zero (ok so its < 30g/day) I still have to inject about 50 units of insulin a day to keep my blood glucose levels within normal limits.
    Am I doing something wrong? And can anyone tell me how the body 'decides' what to do with the protein it ingests – muscle/organ maintenance/repair, or gluconeogenesis?

    1. Protein is, indeed, converted to glucose. I’ve read reports ranging from 55 to 65%. It converts slowly but you can still use these approximate percentages to adjust your serum glucose levels.

      1. I don’t know how much it actually helps but I take Chromium Picolonate and R-Lipoic Acid which supposedly has an effect on glucose levels.

    2. There is a keto summit on for another 18 hours or so. Several of the presenters talk about a keto diet and diabetes. If I recall correctly, I believe one said excess protein intake will turn to glucose. What is excess will vary with individuals. http://ketosummit.com/replay Some of the presenters were speaking with a lot of technical jargon, others, not so much.

    3. Ciaran, what else are you eating? What kind of protein do you eat? What evidence do you have that ketosis is beneficial for T1D? (It might not be.) Years ago I administered a medical keto diet for my son based on guidelines from Childrens Hospital, and I doubt that it would be meat protein that’s keeping you from achieving ketosis. However, it’s usually necessary to limit portion size of both protein and carbs.

      1. I usually skip breakfast (because I’m not hungry), then have something like a leafy salad with olives, ham, cheese, mayo for lunch, then meat or fish with above ground veg for dinner. At the weekends I have a good cooked breakfast (but no bread or beans) and skip lunch (again because I’m not hungry). I confess also to having a wine addiction, say 5 bottles a week (eek!). The reason I assumed ketosis was beneficial for T1D was the same I thought it was beneficial for everyman. As long as I inject enough insulin to keep my blood glucose within the normal range I figure I should be fine.

        In the last few hours (after being T1D for 32 years and being in regular touch with a diabetes consultant) I have been informed on another forum that protein DOES require insulin to pass through the cell wall, and also that protein stimulates the pancreas to secrete glucagon, which causes the liver to release glucose into the blood. So this metabolic pathway definitely explains my relatively high insulin dose.

        So I suppose my question is whether I should reduce the protein absolutely, or whether I should build more muscle (I’m not exactly ‘ripped’) which could just as easily reduce my need for insulin, since there are some muscle cells that use glucose without the need for insulin? Or both?

        1. First, with the wine, you are ingesting more carbs that you need a day especially with a high blood glucose. Please somebody correct me if I’m wrong, I’m not a Dr. , if you want to heal you need to eat/drink lower carbs. for a while, 1/2 cup of wine is the maximum per one sitting or even 1/4 cup until your sugar stabilized at normal. Also, ensure your carbs have fiber to slow down the absorption.

  15. I understand that organ meats produce specific peptides when digested that provide “information” to support organ function — so eating organ meats to support your organs makes sense. I have just returned from a French supermarket, where I came across liver, kidneys, lungs with heart attached, sliced ox heart, marrow bones, pigs brains, ox tail, and that is all I can remember! All these foods are standard fare in a French home.

  16. What do you think about casein and albumin? Casein have many drawbacks, it seems. Okay?

    1. Lamb hearts FTW. Serve them on skewers for a Valentine’s day dinner. 🙂

  17. If I just eat ribeye steak, I should have excellent ribs and eyes, right? This is worth exploring…
    As to the like-for-like, liver has become pretty easy to purchase and consume since I discovered the raw liver smoothie. But I have yet to find a source of brains that doesn’t include the entire head of the animal. I only want three ounces, and I’d prefer not to need a hatchet to get it.

  18. Please, do NOT eat animal brains, especially bovine brains, EVER. Any mammal can have prion disease, testing is not sufficient to always catch it, and brain is the highest-risk tissue to consume.

  19. Good read, but I’m not so sure about the “like for like” bit. I mean, in some areas, I’m sure there’s truth to it. But isn’t that also where we get the “eating fat makes you fat” mantra?

  20. Mark, I applaud your encouragement of legumes/beans!! I am on what I consider a whole traditional diet, but not low carb diet, so not Paleo, with lots of whole foods, mostly plants and just a little fish (sardine, herring wild caught shrimp), ~96% plant-based.

    I can tell you adding legumes to the diet is one of the best things I have done. It is superb for your gut, stabilization of blood sugars, and provides essential nutrients not found in most animal sourced protein such as niacin, riboflavin, magnesium and lots of antioxidants. I would add that chia and hemp seeds, as well as Nori seaweed are also great protein sources, and in the case of chia (and sardines and herring) a good calcium source for those not eating any dairy. Nori seaweed also adds a bit of EPA omega-3 to the diet, without any mercury or other toxins that come with fish.

  21. Hi Mark. In one of your post you have mentioned about consuming a dozen of eggs a day. Considering the Methionine content in one boiled egg accounts for 27% of rda, a dozen would account to 324% rda. Won’t that be a health risk?

  22. Protein, nutrients, fiber all do come in beans….. but those damn legumes stuff me up!!! I digest way better when I have no legumes and no grains.