This viral message listing supposed health benefits of butter over margarine (also the basis of previous questions about health impacts of trans fats and whether margarine is similar to plastic) makes this claim, among many others:

Eating butter increases the absorption of many other nutrients in other foods.

Everything I can find suggesting any biological mechanism for this suggests that it is to do with fat-solubility of certain vitamins - for example, HowStuffWorks has this to say:

Dietary fat, which comes from the food you eat, is crucial to the absorption of the fat-soluble vitamins, which includes vitamins A, D, K and E

However, even if this is exactly true (which isn't clear - Howstuff works appears to source this claim from Natural News, which says it is from "a study in the Americal Journal of Clinical Nutrition" but fails to mention details like, say, the title of that study), this logic would apply equally to margarine as it does to butter. Indeed, the Natural News article says that the published study compared canola oil-based salad dressing to fat free salad dressing.

So: is there any evidence for the claim that eating butter increases nutrient uptake, in any way that doesn't also apply to (or is somehow more effective than) margarine?

  • 2
    Mercola makes many outlandish claims (so many that we have a tag for him, go figure)...
    – Sklivvz
    Aug 18 '15 at 13:37
  • 1
    @Sklivvz ... duly noted. I've replaced the reference to Mercola with one to HowstuffWorks, which is probably only marginally more credible, but at least doesn't say enough bizarre things to have its own tag here or a Wikipedia page all but denouncing it as quackery.
    – lvc
    Aug 18 '15 at 14:33
  • The actual research (Carotenoid absorption from salad and salsa by humans is enhanced by the addition of avocado or avocado oil and Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection) from which this claim (cuarts.columbia.edu/category/heart-disease) might have been adapted from is discussed here-wsj.com/articles/SB115499279665729249 Aug 20 '15 at 5:23
  • For more on butter read this too-ncbi.nlm.nih.gov/pubmed/25004639. Aug 20 '15 at 5:32

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