If medium-chain fatty-acids are so good for us, how come human milk is mostly made of long-chain fatty-acids? Is there a difference between children and adults in terms of nutritional needs?
It is my understanding that medium-chain fatty-acids (especially abundant in coconut oil) are easily digested and utilized as a source of energy, and thus considered a great choice in general, but especially for people with digestive, metabolic, and neurological problems.
Now, I have found this quote "The milk fats of man, dog, and guinea pig, [are] largely made up of long-chain fatty acids... The milk fats of cow, sheep, and goat, [are] rich in short-chain acids... Horse milk, ... contains large amounts of medium-chain fatty acids..." (Source: http://www.jlr.org/content/8/5/473.abstract)
Short- and medium-chain fatty acids are similarly digested: "[s]hort-chain fatty acids, just as medium-chain fatty acids, are taken up directly to the portal vein during lipid digestion, in contrast to long-chain fatty acids, which are packed into chylomicrons and enter lymphatic capillaries and enter the blood first at the subclavian vein." (Source: http://en.wikipedia.org/wiki/Short-chain_fatty_acid)
How is it possbile that human milk has a less-than-ideal fat composition when compared to that of horse/cow/goat? Or is the hype around medium-chain fatty-acids exaggerated? Or am I getting something wrong?
Human milk does have short- and medium-chain fatty acids. They represent almost 10% of total calories. That corresponds to about 2 tbsp/day coconut oil for an adult.
That's approximately what you would ingest if you use coconut milk or oil for all your cooking and some of your sauces.
No one would say you should get most of your calories from these fats. But a few tablespoons a day is probably healthful.
Higher doses make a diet ketogenic which can have therapeutic value in certain diseases, especially neurological disorders.
Like all macronutrients, how "good for us" something is depends on the dose. There are diminishing returns as quantity increases.
Sheep, cows, horses, and goats are born and need to be able to stand and move quickly. Dogs, guinea pigs, and human babies are born quite immobile. Evolution most likely determined the fatty acid profile of the milk of migrating herd animals.
A New fat Taxonomy
LCSFA - long chain saturated fatty acids - best
Monunsaturates - Oleic acid from animal fats and olive oil - good
n-6 PUFA - Technically essential but in huge excess due to technology - bad
n-3 PUFA - necessary to balance excess n-6 but otherwise bad - contextual
MCT - Medium chain saturated fats - good in reasonable amounts
NTF - Natural trans fats like vaccenic and rumenic acid - good
ATF - Artificial trans fats like Elaidic acid -not found in nature - bad
The preceding would be the chemically based, "nutritionist" taxonomy. But we can construct a real-food based taxonomy by recombining the nutritionist elements into a 6 part scheme like this...
Grass finished ruminant animal fats. LCSFA and Mono in roughly equal amounts. Same small amounts of n-6 as IRAF, but more n-3 to balance. More NTF. Best.
Industrial grain-fed ruminant animal fats - LCSFA and Monounsaturates in roughly equal amounts with smaller amounts of PUFA - may be deficient in n-3 PUFA. Has less NTF. good
Non-ruminant animal fat. Highly variable. Has LCSFA but may be very high in n-6 and if grain fed poor in n-3. More sensitive to diet of the animal than IRAF or GRAF. fair if pastured but poor otherwise. Think factory chicken.
Temperate plant oils. Artificially abundant due to technology. excess n-6, effectively no n- 3. Some MUFA. Little LCSFA bad
Tropical Plant Oils. Coconut and Palm oils. Good source of MCT and/or LCSFA - lower in n-6 and n-3. These are also made available by processing technology, but their content is better than TemPO. Good.
Frankenfats. TemPO chemically modified by hydrogenation. Very bad - avoid completely.
I hope I have convinced you that the macronutrient label of "fat" as in "high fat" is or "low fat" diet is metabolically not very useful. Keep this in mind when you read anything at all in the literature about "fat".
Perhaps you can help me change the nutritional language game by using my new fat taxonomy and resisting the old one, even if you disagree with my judgements about their nutritional merit.
When you discuss diets or ways of eating, you can use language like "I eat PaNu, a high GRAF, low TemPO diet".
Or, "PaNu is a high GRAF, low TemPO, low NRAF, zero FF way of eating". PaNu is "low fat" in regard to TemPO and n-6 PUFA, but very high fat in regard to LCSFA, Mono and GRAF.
Or "Dr. Davis advocates a diet free of wheat, but unlike PaNu it is low GRAF and IRAF, but high TemPO and high n-6 PUFA". Davis is "low fat" in terms of animal fats, but "very high fat" in terms of n-6 PUFA.
We'll deal with "Carbohydrates" and offer a new taxonomy for them in Part II.
"No animal drinks the milk of other animals."
yes they do, dogs and cats. wild animals do not drink milk because it is not available to them. when given choice it is possible that many other carnivores and omnivores would not object consuming milk.
and rats do not mind cow milk as well.
not trying to say something definitive, but just wondering:
you posit that "medium-chain fatty-acids are so good for us" - is that really so? does the fact that they "are taken up directly to the portal vein during lipid digestion" signifies that they are necessarily "good" for us?
what if the body just desperately tries to get rid itself of the stuff as soon as possible?
Having been investigating the benefits (or otherwise) of medium chain fats and in particular coconut oil you might find these links interesting.
Man made MCT's are used to treat certain illnesses, and one trial showed benefits of MCT's in a controlled study.