Dear Mark: Collagen or Glycine, Keto and Gallstones, Raw Liver, Stevia Itching, and Gaining Muscle, Losing Fat

For today’s edition of Dear Mark, I’m answering five questions taken from this Twitter thread. First, does collagen offer anything special above and beyond glycine? Second, what’s the relationship between keto and gallstones? Third, do I recommend eating raw liver, and why or why not? Fourth, why does one reader’s scalp itch when eating stevia? And finally, what’s the best way to lose fat and gain muscle at the same time?

Let’s go:

If collagen is broken down into amino acids in the gut before being absorbed, is it just the amino acid profile (i.e. high glycine) that makes it so beneficial? Anything else?

Glycine is a major reason why we need collagen in our diets, but it’s not the only one.

When you feed people collagen derived from pork skin, chicken feet, and cartilage, many different collagenous peptides appear in the blood. You don’t get any of these from isolated glycine:

Proline-hydroxyproline, a peptide with protective effects on osteoarthritic cartilage degradation.

Glycine-proline-hydroxyproline, a peptide that makes it into the blood and turns into proline-hydroxyproline, which makes it into the skin.

Collagen peptides have beneficial effects above and beyond glycine alone—although glycine is great for balancing out methionine intake from muscle meat consumption. It’s also been used in several studies to improve multiple markers of sleep quality.

A family member has a complicated health history including cancer and wants to eat keto. But, now she finds she has gallstones. Any thoughts on a good way to attack this complicated issue?

Has your family member already gone keto? Did going keto come before the gallstone reveal?

If so, that’s actually normal.

The primary role of the gallbladder is to collect bile from the liver, concentrate it into potent super-bile (my term), and release the concentrated bile to break up incoming dietary fat into smaller molecules that lipase can attack and digest. Dietary fat is the biggest driver of gallbladder emptying.

If the gallbladder isn’t regularly emptied, gallstones can form. Usually made of hardened cholesterol, gallstones are quite common and often produce no symptoms. Problems arise when normal gallbladder emptying flushes out a stone small enough to make it into but too large to pass through the bile duct and a blockage occurs. Gallstones can also directly damage the walls of the gallbladder, leading to cholecystis, or gallbladder inflammation.

A high-fat diet can exacerbate or even uncover gallstone issues by increasing gallbladder emptying. Remember: the more fat you eat, the more often you empty your gallbladder—and everything in it.

But high-fat diets don’t generally cause gallstones to form. They only reveal pre-existing ones. The biggest risk factors for gallstone formation are:

  • high intake of high-glycemic carbohydrates.
  • High estrogen levels, which concentrate cholesterol deposition in the gallbladder. This is why women, especially pregnant women and/or those taking hormonal birth control, are more likely to have gallstones.
  • Obesity, which also increases cholesterol levels in the gallbladder.
  • Weight loss, with a caveat: high-fat weight loss diets reduce and even prevent gallstone formation. In fact, when you compare people who lose weight on a low-fat diet to those who lose it on a high-fat diet, research shows that 45% of the low-fatters develop gallstones while none of the high-fatters develop them.

Once the gallstones are all clear, keep up with the keto eating, as eating more fat will keep your gallbladder regularly flushed and clear of stones.

Is Raw Liver safe to eat?

I’ve eaten raw liver before. I know people who eat raw liver. I can’t recommend it, however, because I don’t know what kind of liver you have access to. Who raised the animal? What did it eat? What were the processing conditions?

But because I know people are going to try this…

Freeze it first for several days.

Buy from a trusted source.

Buy only liver from well-raised, grass-fed, organic animals.

If it looks unhealthy, it probably is. I would never eat a pale, flaccid liver with ugly spots, cooked or raw.

Don’t eat raw (or even medium) pork liver. A huge percentage of pigs carry the Hepatitis E virus, which is transmittable to humans and concentrates in the liver.

Why does stevia make my scalp itch?

Stevia can be an allergen actually. It’s not very common, but as more and more people use stevia, more will be revealed to have an allergic reaction.

I’d just skip it.

Is it possible to gain muscle and lose weight with properly timed IF around workouts?

It is possible, although you may not actually lose weight, but rather body fat (which is better).

The best way I’ve seen people do it is the classic Leangains method.

Fast from 8 p.m. to 12-1 noon.

Fasted workout in the afternoon, perhaps with a little BCAA or whey isolate before the workout. Lift heavy, compound movements.

After the workout, walk for 20 minutes. Brisk pace to utilize all the free fatty acids swimming around.

Then eat. If you’re going to eat carbs, do it in this meal and keep the fat low-to-moderate. Load up on protein.

Eat as much as you like until 8 p.m.—the end of your eating window. Favor protein and, again, if you’re eating carbs keep fat lower than usual.

Maintain the fasting period every day. On rest days, eat low/no carb and higher fat. Protein always high. Go for walks on rest days.

That’s it. That usually works really well, but it presupposes you have a flexible schedule and can actually train in the afternoon whenever you want. Your mileage may vary—though it will work at any time.

Muscle gain won’t be as rapid as it would drinking a gallon of milk a day, eating pizza smoothies, and cramming ice cream made with whey protein at night, but it will minimize fat gain and perhaps even help you lose fat as you gain muscle. No guarantees, but it’s the best method I’ve seen.

That’s it for today, folks. Thanks for reading, take care, and be sure to leave a comment down below if you have any questions.

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.

If you'd like to add an avatar to all of your comments click here!

27 thoughts on “Dear Mark: Collagen or Glycine, Keto and Gallstones, Raw Liver, Stevia Itching, and Gaining Muscle, Losing Fat”

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Hi Mark,

    I always heard that Hemp protein was easily digestible and well tolerated by the body. I however get VIOLENTLY ill when ever I consume anything with even a bit of hemp protein. I tried to research hemp allergies and other conditions on this but haven’t found anything. Any thoughts?


    Michael Beaver

  2. It’s just n=1, but I’ve eaten raw liver, as well as heart and kidney, for 9 years now, with no ill effects. But I do buy grass-fed beef organs directly from a farmer who I’ve known for years.

    I started eating liver raw when I discovered, during a class on traditional pig slaughtering/butchering techniques, that liver has a very mild taste raw. It’s only when you cook it that it gets that gag-me taste that I can’t, well, gag down.

    I actually use my food processor to blend 2 parts liver, 1 part heart, 1 part kidney to make a paste, which I freeze in ice cube trays, about 1 oz per cube.

    Each morning I pop a couple cubes into a glass of warm water, sometimes add a dash of cream, then gulp it down. Little or no liver taste, and I have my organ meats for the day.

    I’d like to add spleen to the mix, but haven’t found a source yet.

    1. I have found really high quality spleen from white oak pastures (google them for their website). I do similar to you – I make a smoothie every night of liver, heart, kidney, spleen, collagen, and lemon.

    2. @Cheyenne – I’m glad to hear I’m not the only one doing this! I usually get such strange (and disgusted) looks when I describe the process that I generally don’t talk about it.

      @Matt – I wish I could say something definite, but I developed my current routine over the same 10 years I’ve been paleo, which is also a developing lifestyle. So it would be tough to separate out my organ consumption vs. other paleo lifestyle changes. I just know that I feel much healthier at 60 than I did at 40.

  3. I’m confused about the fasting schedule — how do you train fasted in the afternoon if you eat at noon or one?

    1. You eat after you train, so you train at noon or a little before as described, then eat your first meal. May not be exactly at 12 or 1, but it works the same. He didn’t find the best way to describe it for those that want to nitpick details. You should check out lean gains that he drew it from for more info.

      1. Not trying to nitpick details, i just wasn’t sure if he was saying that eating at noon or one, then training in the afternoon, say at 4, would be considered fasted. I certainly wouldn’t call that fasted, but wasn’t sure if that’s what he was saying.

        1. No, that would not be training fasted.

          You take a protein supplement (BCAAs or EAAs traditionally) 10-15 minutes prior to training, just to start protein synthesis when you’re lifting.

          Then you eat afterwards.

  4. Hi Mark. Thanks for the discussion on whey vs collagen fuel vs collagen peptides. I was having trouble knowing which was for me, appropriate grams per day, and also cost effective way to balance it all. I’m a 78 yr old female who went keto six months ago after being a vegetarian for decades.Went grain free and gave up garbonza beans! Lost 30 lbs, feel great, walk twice a day, eat flank steak fixed in an iron skillet, and have a big ass salad for lunch/brunch several times a week. Thanks for the Primal books. I’m counting on keto to keep the mind going.

  5. My partner was just diagnosed with cancer and we are looking at the carnivore diet and IF. Only thing I’m concerned about is the fact he is slim already (we both are and always have been- I went carnivore for my IBD and have found relief but did lose some weight I really didn’t want to as a side effect)

    What is your opinion on carnivore for cancer? And how would you optimise it? Would love your insight.


    1. Check out the protocol being used in Hungary by PaleoMedicina. You can also find papers and talks online by their medical director, Zsofia Clemens, including from this year’s Carnivore Conference. I’d include all the links, but I don’t want my comment to be held up. Best of luck to you both.

  6. It should be noted that the Leangains protocol was developed by the Swedish fitness professional Martin Berkhan.

    His website is here:

    There are many free articles about fitness and nutritional science available. Berkhan is very much science based, which is how he came to develop this method. He was very frustrated with the typical bodybuilding advice to eat “six small meals per day”, which is something I think this community can relate to.

    He also has a book, though I haven’t read it.

    I’m not actually sure if conventional bulking offers any benefit over Leangains at all in muscle building. Muscle tissue growth is demand driven, and while it does require energy intake as you can imagine you get hungry. I haven’t seen any research which suggests it can’t build muscle as effectively. Leangains may in fact be superior because circulating growth hormone is higher in the fasted state.

    I am an IF paleo/primal/keto/LCHF/whatever eater, and normally eat two meals per day without hunger. But on lifting day, with the same restricted feeding window (6-8 hours depending on the day) I get ravishingly hungry within two hours of eating. And the meals I eat are larger as well.

  7. Hi mark!
    I saw the article in regards of the gallbladder…indeed I was one with stones in gallbladder and had to have it removed due to having gallbladder attacks weekly…my questions would be without the gallbladder now and being on keto (high fats) will that make my liver over work or damage my intestines! Thank you for all the good information

    1. The advice I’ve seen on this is that generally it’s fine, just don’t do huge boluses of fat. Like, skip the fat bombs. If you don’t already take a bile salt you may find that helpful, especially if you are getting gut cramps and fatty, floating, smelly poopoos.


    Does anyone know or have evidence that the following quote at the link is true?

    “In addition, collagen falls apart at temperatures above body temperature, turning it into plain gelatin — yes, the stuff in Jell-O. At these higher temperatures — when added to hot coffee, for example — collagen’s molecular structure melts, diminishing or even negating the desired health benefits”

    Or this one?

    “What about bone broth? Despite the hype, the notion that the collagen in bone broth will somehow become collagen in your body is just wishful thinking. In fact, the ingredients that are supposed to make bone broth superior are not that special, and likely during preparation the collagen has been melted.”


  9. So excited to have found you. I’m down the rabbit hole with all things keto and this information.

    Does collegen powder bread my fast?

    Do you drink anything special in the morning besides coffee?

    What vitamin supliments are you taking daily iif any?

  10. I used to do the raw liver thing. I would buy grass fed beef liver from a local farmer and cut into small cubes then freeze. In the am I would take one or two cubes out of the freezer and let them soften just a bit, then swallow whole (because there was still a liver taste…ugh) What I noticed was increased energy and stamina. It was pretty amazing. It hasn’t been as easy to get to the market lately, but now I’m thinking about starting this up again.

  11. In regard to raw liver. I grew up on a small farm where my dad raised a couple of beef cows every year and would slaughter them to supplement our grocery’s. His being a butcher by trade I guess it seemed like the natural thing to do. As a kid he would always try to get us kids to eat fried liver which I detested. One time when he was slicing some frozen liver, the best way to slice it, I asked out of curiosity what it tastes like, so he cuts off a small piece and says, “here try it”. Much to my surprise it wasn’t as bad as the fried stuff. Now as an adult I have my own small farm and raise my own beef and although I am not a butcher I do supplement my diet with my own farm raised beef. One of the things I have noticed about liver and heart to a lesser degree is that the fresher it is the better it tastes, cooked or raw, so if I like to get my organ meats in the freezer as soon as possible after being harvested from the animal. Actually this is probably the way our ancestors consumed them as well eating the organ meats fresh and then packing the rest pack to camp for curing and smoking.

  12. I tried drinking some powdered instant kratom tea and that gave me some itchiness. I’m guessing that’s from whatever in it being an opiate receptor agonist.
    I’d like to try it again in a higher dose and by itself too to get a more accurate idea of how it affects me since I was buzzed on a mix of stuff that night.

  13. Does it mean the more often fat is eaten, the gallstones will be emptied from the gallbladder eventually please?

  14. I take Collagen and I would like to know if it is bad or good for my gallbladder because I have gallstones and Idontwant it to get worse.

    1. I too would like to know the answer to this question, as I have gall stones, and would like to start taking collagen protein, but am unsure if it is wise due to the gall stones