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I have seen some nutritional advice that claims that it is possible to absorb calories through the skin, from face products for example.

This sounds like nonsense to me, can anyone confirm that and explain why it would not be possible?

Just to clarify the question a little, it was specifically related to dieting to aid weight loss and therefore whether calories absorbed from face products etc should be avoided.

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    I don't have sources at hand right now, but I call BS, too. How should your skin be able to transfer those calories into your digestive tract? And the people working in fast food chains would all be overweight! :D – cularis Jun 22 '11 at 11:29
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    Do you have some sources of such claims? Please add them. – Konrad Rudolph Jun 22 '11 at 11:51
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    the human body can certainly absorb substances that have a caloric value through the skin (fats used in creams for example), but that caloric value would be of no use as nutrients as they will never reach the digestive tract. – jwenting Jun 22 '11 at 12:53
  • Maybe related: Here is a product, a hair washing lotion which contains Vitamins for the hair (Vitamin F, Provitamin B5) – user unknown Jun 22 '11 at 13:01
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    @cularis The nutrients don't need to get to the digestive tract to be used - they just have to enter the body. Nearby cells might use them, or if they get into the bloodstream then other cells in the body might use them. The digestive tract certainly breaks them down differently than if they are absorbed directly into the bloodstream, but they aren't magically inert simply because they haven't hit the intestines. The only relevant question is: Are there materials that can be absorbed through the skin which provide energy to cells in the body? Lots of compounds have calories and aren't lipids. – Adam Davis Jun 24 '11 at 15:18
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We know there are a wide variety of substances which can be absorbed through the skin and metabolized,(some which spring immediately to mind are nicotine, sunlight to make vitamin D, fentanyl) but research about whether or not calorically dense substances such as fatty acids can be successfully absorbed and used is still very preliminary.

There is some preliminary research indicating it may be possible to use transcutaneous absorbtion of lipids from certain oils as a nutrtional supplement in preterm babies.

Transcutaneous absorption of a mixture of coconut oil and meadowfoam oil in preterm babies has been successfully demonstrated for the first time. The variations observed in the amount and the number of marker fatty acids is probably due to the dynamic state of triglycerides which are continuously metabolized. Coconut oil has predominantly short chain and saturated fatty acids. These are normally present in the serum of an individual, diet being one of the important source

however, with regard to this particular data it is important to note:

The skin of the preterm neonate has increased permeability as compared to full term babies

Also, there is not yet a clear understanding of which fatty acids are best absorbed, indicating that some may absorbed at better rates than others possibly due to their structure

The fatty acids with two double bonds (C20 ∆5,13) appears to be better absorbed as compared to fatty acid with single double bond

Of course, the relatively modest effects shown in this study only indicate that there appears to be some evidence for a plausible mechanism by which this occurs. It's still a long way away from determining if it a reasonable and effective way to supplement nutrition.

Given that this study was performed on premature neonates, extrapolation of this data with regard to older children and adults seems unwise to me at this point. Also, it would seem unlikely that transient amounts found in the localized application of various lotions and creams would have any tangible effect, and would probably only be able to shown by taking repeated blood draws before and after the application of one of these creams or lotions. It certainly would not be likely to have any effects noticeable outside perhaps, of a laboratory specifically looking for a serological rise in a certain compound.

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    The skin doesn't absorb vitamin D; it absorbs sunlight, and uses that to create vitamin D – BlueRaja - Danny Pflughoeft Jun 23 '11 at 5:51
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    Nobody mentioned macromolecules such as fatty acids (though the mention of face products does suggest this). But humans do absorb calories through their skin. After all, calorie is merely a measure of energy and we readily absorb heat from sunlight, and this does get used in the cells’ metabolism (even if only indirectly). – Konrad Rudolph Jun 23 '11 at 20:24
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    @Konrad I found it interesting and thought it seemed to be what the question was getting at (I took "calories" to imply "calorically dense substances"), because of the way he mentioned face cream (as you noted). – Monkey Tuesday Jun 23 '11 at 21:09
  • That's funny I just read the back of my coconut oil jar which says it's made of 67% medium chain triglycerides (MCTs) which would make the part of this article that claims coconut oil is predominantly short chain triglycerides, incorrect. – user31918 Mar 24 '16 at 22:22

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