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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