Dear Mark: Liver for Babies, Flax Seed, and MCTs with Fruit

Cooked LiverFor today’s Dear Mark, I’ve got a three-parter. First I discuss the suitability and proper dosage of grass fed beef liver for babies and toddlers. It’s definitely a good choice, but you do have to keep a few parameters in mind to do it right and do it safely. Next, I discuss flax seed. Is it a good choice? Does it have health benefits beyond the meager conversion of alpha-linolenic acid into longer-chain omega-3s? Finally, I explore what happens when you eat medium chain triglycerides – the fats most prevalent in coconut oil – with fruit or other carb sources. Good, neutral, or certain death?

Let’s go:

Hi Mark!

How much cow liver is safe for a 14-month-old? We cooked up some high quality, grass-fed liver from a local farm here in NY, and our daughter LOVES it. Should we be worried about vitamin A or iron, or limit her intake?



First of all, great job! If your 14 month old is digging liver this early, you’ve probably got a very adventurous, non-fussy eater on your hands. Cultivate and encourage this attribute.

Second, while the recommended upper limit for kids aged 1-3 is  2000 IU of preformed vitamin A (retinol, the type in animal products) per day, you probably don’t need to worry too much. That’s a little less than a half ounce of beef liver. How much is she eating, and is it every day?

You can probably go higher than that, too, since true vitamin A toxicity requires really high intakes, vitamin D increases the upper limit and reduces the toxicity of vitamin A, and supplemental vitamin A seems to be more problematic than food-based vitamin A (at least in regards to causing birth defects during pregnancy). If your kid is getting sun, taking vitamin D, or eating a good amount of vitamin D-rich foods like sockeye salmon or sunbathing mushrooms, she’ll be able to tolerate higher levels of vitamin A and more beef liver. Heck, she won’t just tolerate higher levels, she’ll actually require more vitamin A to balance out the vitamin D.

I wouldn’t worry about the iron content. Babies and toddlers actually need more iron than older kids due to their rapid growth. If anything, most parents and pediatricians fret about their kids getting sufficient levels of iron in their diets. Plus, the iron in liver is way more absorbable (and less constipating) than supplemental iron, so it’s the preferred form.

I’d stick to about a half ounce to an ounce per feeding if you’re feeding regularly. Don’t give beef liver every day, and make sure she’s getting vitamin D somehow.

You could also try mixing in pastured chicken livers, which are higher in iron and folate but much lower (while still being “high enough”) in vitamin A than beef liver. They’re also much milder, for all you parents with pickier, more squeamish kids.

Just keep the polar bear liver away from your daughter and I think you’ll do just fine.

Hi Mark,

The university of Manitoba recently published a finding on a study of long term flax consumption that concluded earlier this year.

It’s a pretty interesting read as I know you’ve written articles about flax consumption on the site before.


I agree – that is an interesting bit of research. Flax seed does appear to lower blood pressure in people with hypertension. Let’s take a look at some other recent evidence to see how flax stacks up.

  • In 2013, researchers compared the metabolic and lipid profile effects of flax seed oil to those of olive oil in healthy, young adults who were habitual olive oil users (not abusers, mind you). They found no significant differences in biomarkers, except for greater levels of of alpha-linolenic acid (ALA) in the flax group and lower c-reactive protein (CRP, a marker of inflammation; lower is better) in the olive oil group.
  • Flax seed was able to lower cardiovascular disease markers in a recent RCT, but it was in comparison to wheat. Doesn’t take a whole lot to beat wheat. Another study comparing flax seed to “wheat germ placebo” (hell of a placebo!) had merely a “limited effect on apolipoprotein metabolism.”
  • Flax may also modestly lower testosterone, which is good when you have prostate cancer, but probably bad if you’re an otherwise healthy male. However, high levels of ALA in the blood are a risk factor for the occurrence of prostate cancer, as I’ve written previously, so we may be dealing with a “good if you have it, bad if you don’t” type thing.

So, it’s not bad. Better than wheat (big deal), but the primary benefits seem to revolve around the effect on hypertension. Other effects are modest. And most evidence suggests that, in humans, conversion of the plant omega-3 ALA into EPA and DHA (which have the most beneficial effects in us) doesn’t happen very efficiently; women are better at it than men, especially if they’re pregnant.

If you’re going to use flax, milled flax seed seems to be the ideal form. The oil is way too unstable, the whole seeds are nigh impossible to digest, while the milled flax seed protects the oil, contains prebiotic fiber, and can be fully digested.  The initial study you sent found that milled flax was the most beneficial form. You can buy your seed pre-milled or mill the whole seed yourself.

Hi Mark,

Fully entrenched in the primal food lifestyle both personally and professionally I have a question regarding coconut and carbs. Given the preferential burning of MCT in coconut as energy, what happens metabolically when you combine coconut via cream, milk flakes or oil with carbohydrate? Will even less carbohydrate be used for energy as you tick along in the day and therefore cause greater conversion to triglyceride or will glucose still win out in the race for conversion to energy? We keep our carb load low but as a larger number of recipe ideas creep out combining coconut and whole fruits, dried fruits and honey I am interested in the level of fall out from this combination.

Thank you for providing a resource that has answered countless questions for me already via your search function.



I suspect coconut oil/MCTs pair quite nicely with moderate amounts of carbs/fruit for several reasons:

1. The traditional diets of Pacific Island people tend to be fairly high in both coconut fat and carbohydrates (whether through sweet potatoes or fruit) and they manage to maintain good health. Famously, the Kitavans eat by all accounts a high-carb diet and obtain most of their saturated fat through coconuts. 69% of their calories come from carbs (mostly starches with some fruits) and 21% come from fat (mostly coconut with some fish).

On the other side, you’ve got the Tokelau obtaining 63% of their calories from coconut (yes, all their calories), 13% from starchy taro or breadfruit, and 3% from sucrose while showing almost zero evidence of cardiovascular disease or obesity. Moreover, the way they consume their coconut is to cook the starches in coconut cream. So these guys aren’t doing cyclical ketogenic diets or anything where their coconut oil is separated from their carbs; they’re eating their moderate amounts of starches immersed in a bath of MCT-rich coconut fat.

These accounts don’t prove anything, but they do suggest it’s possible for coconut and carbs to coexist amicably.

2. There’s some evidence that consuming medium chain triglycerides with your carbohydrates can reduce the blood glucose response and improve body fat metabolism. In one study (PDF), MCTs reduced post prandial blood glucose levels compared to other types of fats when eaten with carbs. Another study found that the addition of two tablespoons of coconut oil per day to a “balanced, hypocaloric diet” reduced abdominal fat in overweight women. Seeing as how “balanced” invariably means “moderate-to-high-carb” and the control group had identical dietary instructions except to use soybean oil instead of coconut oil, the latter seems safe enough.

3. Typical ketogenic diets prescribe extremely low levels of carbohydrate in order to induce ketosis. That’s how the clinicians treating epilepsy do it, and it’s how most regular folks attempting to reach ketosis do it. It’s also how fasting causes ketosis. However, you can also induce ketone production by consuming medium chain triglycerides or coconut fat on top of your regular diet. And, according to a series of animal and human studies, the benefits of ketones persist even with carbs in the diet:

What’s all this mean? I think you should go ahead and try out the combination. If it doesn’t work, you’ll know it because you’ll gain weight and suffer other negative symptoms. If it does work, you’re in luck because coconut milk poured over frozen berries is an amazingly delicious treat.

That’s it for today, guys. Thanks for reading, and keep the questions coming!

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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29 thoughts on “Dear Mark: Liver for Babies, Flax Seed, and MCTs with Fruit”

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  1. Mark,
    I think you’ll find this interesting so wanted to share:
    I have been eating Paleo for 17 months now. Whenever I want a biscuit or pancakes, etc. I use almond meal and sometimes coconut flour. I was adding ground flaxseeds to my smoothies, sprinkling sunflower seeds on my salads, and eating macadamia nuts among others as snacks frequently throughout the week. Well, I went to the doctor for a Complete Blood Panel and found out that not only did I gain weight in the form of fat but I also had a huge imbalance of Omega-6 to Omega-3 ratios. My doctor told me to cut out all nuts, seeds and their derivatives such as almond butter. These were having a negative effect on my health. I now eat NO nuts or seeds in any form, and will return in 3 months to see if this has improved my health.
    So, if people are gaining fat on Primal/Paleo eating, this could surely be the cause!

    1. Your comment is interesting and has reinforced what I’ve known all along: that fat (or fatty foods) will indeed make you fat if you eat enough of it. Fat by itself might not cause weight gain, but nobody eats nothing but fat so the jury is still out on that theory. When eaten in combination with various other foods, such as grains or starchy vegetables, too much fat from nuts, seeds, butter, coconut oil–whatever the source–will definitely cause weight gain.

      When I first went Paleo the weight melted off in nothing flat–40 pounds of it. In fact I started worrying that I would get too thin. I started adding a baked potato loaded with butter or sour cream to my diet twice a week. The weight loss stopped immediately.

      I wasn’t aware of the potential for omega-6/omega-3 imbalance. Thanks for mentioning that.

    2. You might want to lay off all peppers except the yellow bell type–surprisingly, they’re higher in Omega-6 than Omega-3, and the yellow ones are neutral (good as it gets) when eaten raw.

      Any of the green-colored herbs/spices are FREAKIN’ high in Omega-3, so use those to offset any fears about Omega-6 overdose. All it takes is 1 teaspoon.

      What I do: hone your veggie list down to the ones with the highest amounts of Omega-3 in them (, combine them with high Omega-3 meats (grass-fed meat, eggs, dairy, or fish), and use a high Omega-3 herb or spice on them. That way, each meal is loaded with enough Omega-3 as to offset the nuts, fake olive oil, or flax meal I may take in.

      1. Love your comments, thanks for this info on Omega-3 and veggies. I’m struggling with a 5 pound weight gain over winter along with some unwanted stress (robbing me of my sleep) UHG……
        Thanks again Wenchypoo (where’s your website? LOL)

      2. Wow, you can’t be serious about worrying about the fat content of bell peppers (or any veggies).
        The fat content of 100 grams of bell pepper is <0.1 grams. That's less than 0.1%.
        That amount of Omega 6 won't do a bit of difference unless you are eating several pounds of bell peppers a day, in which case you have other issues to deal with…

    3. I once did a no-grains, no nuts, no dairy, and no exercise diet, and lost about 20 lbs. and quite a bit off my LDL cholesterol. This “winging it” diet was my first foray into anything Paleo-like. Then I went all in–full Paleo after that.

    4. I would check your overall calorie consumption. Smoothies, biscuits, pancakes? Sounds like you’ve fallen into the trap of if it’s “paleo” it must be healthy. Humans like junk food in all forms and paleo/primal eaters are no exception. Those bread substitutes and dessert treats are supposed to be every once in while items – not everyday fare. Grok didn’t make pancakes – he ate real food in it’s existing form – meat, plants, some nuts.

    5. If you read what Mark says in PB he does stress not to go ‘nuts’ on nuts, apart from Macadamias which are low in omega 6 (my salary restricts those in excess anyway!).

      Think about it; ‘in the wild’ nuts aren’t easy to get at in bulk – you’d have to climb trees & then crack the shells.When I was a child, at Christmas time, we had a big bowl of nuts in shells on a side table; I’d start cracking away but usually got bored of it quite quickly – Imagine that now with no tools except for a couple of stones and I’m sure you wouldn’t be doing it day in, day out. A handful here & there as a snack especially if your getting plenty of O3 in the rest of your diet is no problem.

      Remember people, Primal is supposed to be easy – don’t replace calorie counting with O6 or Carb counting etc

      Remember to the rules, 80/20, variety – Grok on with no problems!

  2. Somewhat related – made some ridiculous chicken liver, bacon and rosemary pate this weekend. No one would eat it and said it was gross 🙁 more for me?! Any tips for getting people on liver?

    1. Many people, me included, don’t like the taste, smell, or texture of liver. Combining that with the knowledge that the liver is a filter for toxins really kills any desire to eat it. Doc, my tip would be to eat liver if you like it and not concern yourself about whether anyone else likes it or not.

      1. Mark has done a good piece about the “liver stores toxins” myth. The liver does filter out toxins, but it’s a chemical filter that sends toxins back out to be eliminated, not a physical filter like a coffee filter, that traps and holds things.

        There are lots of recipes online for mixing liver into spicy dishes like chili or meatballs, so folks who don’t like it get some of the nutrition and none of the taste.

        1. Wow, I have never thought to mix liver into spicy dishes. I try so hard to eat beef liver, but I can’t get past the taste and the texture (the texture is starting to be less of an issue over time, fortunately). I will have to try mixing it in spicy dishes for a change. Thanks for mentioning that.

    2. Soak chicken livers in milk overnight, then make pate the way the French do… with an enormous quantity of butter. I also up the quantity of port and sherry.

      1. I’m not a big liver lover either, but I am trying to eat more of it. I just tried something new; I shaved some frozen liver into some homemade broth and added vegetables. I thought it was absolutely delicious, I will be doing this often. The liver simmering in the broth made it incredibly tender. I’m sure there are recipes out there, but I must confess I haven’t heard of liver soup before 🙂

  3. Mark

    You don’t mention the phytoestrogen aspect of Flax Seed oil. I’ve read a deal about this being beneficial in peri-/menopause in evening out effects of falling oestrogen (and thereby increased ratio of testosterone to oestrogen) believed to be instrumental in some of the symptoms associated with this phase of life.

    I’ve been taking a tablespoon of organic cold-pressed Flax Seed oil for a few weeks now and noticed some positive changes (as for stability, the bottle says store in fridge, which I’ve been doing, and this is cold-pressed so should be unmodified and stable I would imagine if stored properly?). (I also dropped the caffeine to one black tea bag a day which is believed to cause painful breast tissue).


  4. High Energy, thanks for the comment, I have had similar issues with flax seeds, and nuts; weight gain and a puffy tongue?! (not an allergy though) I guess we just aren’t supposed to eat these things by the bag! I’m a bit wary of flax in general, it doesn’t seem like much of a ‘food’ if you have to mill it and process it to be remotely edible. Think I’ll get my omega 3’s from fish oils and steer clear of omega 6. Great post as always!

  5. The only flax seed i consume is sprouted…wouldnt that make it far more digestable?

    1. It would contain more Omega-3 in sprouted form, that’s for sure.

  6. And I was feeling bad about my treat. Fried apply slices to carmelization, add cinnamon and pour coconut cream on it warm. Yum. I just sat down to something new, I mixed 3 Stevia’s with a can of sour cherries and poured coconut cream and milk over it. Next time I will remove the liquid. Yeah, processed cherries.

  7. Looks like my dinner tonight – sweet potato topped with shredded chicken, zucchini, broccoli and a coconut milk curry sauce – gets the MDA seal of approval.

  8. Milled flax seed does things to my stomach that not even gluten and dairy can lay claim to…

  9. Does anyone have a reference for ketogenic diets- what % of fat-carb-protein to start with?

  10. Flax has very high levels of phytates. Chia is a better option

    1. There are also sprouted flax seeds available (which I use). Pura Vida products makes an excellent sprouted flax seed powder which stays shelf stable and does not rancidify even outside of the fridge due to the antioxidants and phytate removal from their sprouting process. Their product is called Sprout Revolution sprouted flax seed powder, and I would highly recommend it. Sprouted chia seed powder is also available.

  11. I would think a baby would naturally know when to stop eating liver before any level of toxicity got even close. Even I seem to naturally know when I’ve had enough liver, without even having to push it out onto my chin.

  12. To those who are struggling with liver it’s worth pointing out that it comes in different tastes and different textures. Just by way of example if you eat meat what are you eating – chicken, beef, lamb, venison, wild boar or pheasant that’s been hung for two weeks (very strong and smelly). The best liver to try is calf’s liver then lambs liver – mild and less grainy. Beef liver can be tough and not so delicate in flavour. For me lambs liver is the best – delicate flavour and not grainy. The secret is to take out any sinew and slice it evenly. Flash fry it quickly so it’s still pink throughout. A bit like squid – cook it too long and it goes tough and tastes like cardboard. Liver and bacon is a firm favourite here in the UK – well for those of us that were bought up on it that is. Hopes this helps a little.

  13. Hi Mark

    Firstly hope your well and alls good. Just wanted to drop a comment to say thanks really love the Daily Apple and have recently purchased The Primal Blue-Print love it!!! All the best.

  14. So I hope someone can answer my question here:
    I’m getting confused as to how serious the omega6-omega 3 & “keep PUFA low!” argument really is. I see some people advising against avocados, etc. and even chicken or pork due to the omega 6/PUFA content.
    I find that I naturally prefer nuts, avocados, olives/olive oil, poultry and fatty fish (i.e. salmon, sardines, etc) for my fat intake over the more paleo-endorsed sources of fat like beef, coconut, and eggs. However, these foods are higher in PUFA. Is it really necessary to be careful about even natural sources of PUFA? It’s making me contemplate whether I should follow my natural taste preferences or consciously try to shift my fat intake towards more saturated fat.