I’d like to say at the outset that I like fruits and vegetables. Even if they weren’t supposed to be good for you I would eat them. I might even eat them if I heard they were a little bit bad for you; that’s how much I like them.
And if I had to cut them almost totally out of my diet—which I did when, in my young adulthood, I went on the very-low-carb Stillman diet for a while—I would not only miss them terribly but I would dream about them.
Yes, I used to dream about fruit.
So it always astounds me when people talk about low-carb diets as being so great. “I can eat eggs and bacon every day! And then a big steak and some gooey cheese for dessert!” Although I like to eat all those things too, the thought of eating them or their equivalent every day, for nearly every meal, fills me with dread.
That said, I realize other people have vastly different desires. But I’ve long thought that the long-standing food wars about what’s good for you and what’s not rest at least partly on people’s idiosyncratic food preferences.
That brings us to today’s article in the NY Times by George Johnson, which is being hailed as knocking the common wisdom that fruits and vegetables are so very good for you.
The article limits itself to criticizing the viewpoint that fruits and vegetables confer some particular benefit in protecting against cancer. But it’s interesting that many commenters seem to generalize it to mean or to imply or to insinuate that there’s no health benefit of eating fruits and vegetables, period (see some of the commentary on this thread for examples of what I’m talking about).
I offer the caveat that attempts to link nutrition and food intake to diseases or health are fraught with peril, whatever the truth about foods and health might actually be. They tend to rely on self-reports about diet, which are certainly suspect, and tend to be about correlations, which can hint at causation but certainly do not prove it. So all diet suggestions for the general public should be taken with (forgive the pun) a grain of salt.
That said, Johnson is talking about something that science (as opposed to popular lore) had been backing off from: the idea that diet has a lot to do with whether one gets cancer or not. If you don’t believe me, see this, from the Harvard School of Public Health:
Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. Unlike case-control studies, cohort studies, which follow large groups of initially healthy individuals for years, generally provide more reliable information than case-control studies because they don’t rely on information from the past. And, in general, data from cohort studies have not consistently shown that a diet rich in fruits and vegetables prevents cancer.
For example, in the Nurses’ Health Study and the Health Professionals Follow-up Study, over a 14-year period, men and women with the highest intake of fruits and vegetables (8+ servings a day) were just as likely to have developed cancer as those who ate the fewest daily servings (under 1.5).
A more likely possibility is that some types of fruits and vegetables may protect against certain cancers.
A more nuanced claim, to be sure.
And although Johnson is very careful to limit his article to whether fruits and vegetables protect against cancer, the Harvard publication is pretty clear that whatever the case for cancer protection (and it’s weak at best), the evidence that fruits and vegetables can help protect a person’s cardiovascular health is much stronger:
There is compelling evidence that a diet rich in fruits and vegetables can lower the risk of heart disease and stroke. The largest and longest study to date, done as part of the Harvard-based Nurses’ Health Study and Health Professionals Follow-up Study, included almost 110,000 men and women whose health and dietary habits were followed for 14 years.
The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30 percent less likely to have had a heart attack or stroke.
Although all fruits and vegetables likely contribute to this benefit, green leafy vegetables such as lettuce, spinach, Swiss chard, and mustard greens; cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) make important contributions.
When researchers combined findings from the Harvard studies with several other long-term studies in the U.S. and Europe, and looked at coronary heart disease and stroke separately, they found a similar protective effect: Individuals who ate more than 5 servings of fruits and vegetables per had roughly a 20 percent lower risk of coronary heart disease and stroke, compared with individuals who ate less than 3 servings per day.
There is little question that, as with most health/diet studies of this design, there is the complication that there might be a lot of other things that are different about people who eat so many fruits and vegetables compared to people who don’t. Most studies attempt to control for confounding variables of this nature (such as exercise, for example), but let’s just acknowledge that it’s very hard to effectively do so.
All such studies are handicapped by this built-in flaw, and probably always will be. But that doesn’t mean we should toss them out, although you’re free to reject them if you want, and to eat whatever you want—life is for living, after all.