I recently wrote about a study that found no overall reduced risk of cancer via consumption of fruits and vegetables.
Heart attacks and cancer are the first and second leading causes of death in the developed world.
So just why, again, are we supposed to be eating our fruits and vegetables?
Here’s most of the abstract written by the epidemiologists:
This Review summarizes the evidence for a relationship between fruit and vegetable consumption and the occurrence of coronary heart disease…Most of the evidence supporting a cardioprotective effect comes from observational epidemiological studies; these studies have reported either weak or nonsignificant associations. Controlled nutritional prevention trials are scarce and the existing data do not show any clear protective effects of fruit and vegetables on coronary heart disease. Under rigorously controlled experimental conditions, fruit and vegetable consumption is associated with a decrease in blood pressure, which is an important cardiovascular risk factor. However, the effects of fruit and vegetable consumption on plasma lipid levels, diabetes, and body weight have not yet been thoroughly explored. Finally, the hypothesis that nutrients in fruit and vegetables have a protective role in reducing the formation of atherosclerotic plaques and preventing complications of atherosclerosis has not been tested in prevention trials. Evidence that fruit and vegetable consumption reduces the risk of cardiovascular disease remains scarce thus far.
What do they mean by controlled prevention trials? Here’s an example. Find 20,000 people with similar characteristics. Randomly assign half of them to eat significantly more fruits and vegetables, and make sure they do it. The other half eats their usual way, and make sure they do it. Analyze the entire group’s health and food consumption after 10 years and see which half has more or less heart disease.
Such a study is very difficult and costly. Even if the fruit and veggie group had less heart disease, someone would argue that the heart benefit was gained because of what they cut out of their eating to make way for the fruits and veggies! “They quit eating Cheetos; that’s why they had fewer heart attacks.”
Fruits and vegetables don’t prevent heart disease, according to these researchers.
Fruits and vegetables are components of overall healthy diet patterns such as the Mediterranean diet, the DASH diet, and the “prudent diet.” Is it possible they reduce the risk of stroke, the second leading cause of death? I’ll leave that for another day.
I’m starting to think if I read enough nutritional literature, I won’t know anything with certainty.
Dauchet L., Amouyel, P., and Dallongeville, J. (via MedScape). Fruits, vegetables and coronary heart disease. Nature Reviews Cardiology, 6 (2009): 599-608. doi: 1011038/nrcardio.2009.131