Monday, December 03, 2007

Fruit and vegetables in Holland

Another nice fruit and vegetable study, this time from the Netherlands.

This is an intervention study, tightly controlled and available in full text. It looks at, amongst other things, total plasma antioxidant capacity and the resistance to oxidation of LDL cholesterol. Subjects were divided in to various groups but the two of interest either ate nearly half a kilo of vegetables per day or just over 100g per day.

The results I found most interesting were that, despite marked increases in vitamin C and assorted phyto-antioxidants, there was no increase in total plasma antioxidant capacity and no increase in resistance to oxidation of LDL cholesterol in the high vegetable vs the low vegetable group.

To a fruit and vegetable sceptic this is pretty much as expected. The one thing that did surprise me was that the total antioxidant capacity was unchanged in all groups. Looking at the variations/substitutions made between the various groups makes me suspect that the fructose concentrations in all the diets was about the same. If they had been different then uric acid production would have made the high fructose group look better than it should have done. But the study was good, tightly controlled and avoided this pitfall which is so common in this type of work.

Another intervention study to refute the causality of epidemiological associations between fruit and vegetables and health.

Peter

2 comments:

al said...

The conclusion to this paper includes the statement "Increased vegetable consumption enhances plasma vitamin C and carotenoid concentrations, but not resistance of LDL to oxidation."

This study focused on carotenoids. Of course, there are other phyto chemicals.

I wonder -- are you aware of any studies where the effects of a high polyphenol diet (e.g. one with lots of green tea, pomegranate, berries, etc) on LDL oxidation resistance are characterized?

Peter said...

Hi Al,

There may be other studies but these people

http://www.ncbi.nlm.nih.gov/pubmed/17157175

aren't convinced and seemed to think that failure for correction of uric acid production is the prime reason for the fruit and vegetables hyperbole.

Never forget, plants hate you. I would accept from WHEL, WHI and PPT that the ones we actually eat do have trouble succeeding in hurting you, that's how come we can eat them. The rest will kill you; deadly nightshade, daturas, periwinkles, yew, opium poppies, hemlock, nux vomica, monkshood. Probably they all have lots of antioxidants!

Peter