April 23rd, 2014

Is eating fruits and vegetables good for you?

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.

15 Responses to “Is eating fruits and vegetables good for you?”

  1. blert Says:

    What you’re really looking at is the inherent flaw of multi-variate analysis.

    In the hard sciences, every attempt is made to reduce the equation to as few variables as possible, typically just one.

    After a lot of stumbling around, a determinist connection is revealed by nature.

    E = mc^2 and all the rest.

    In highly complex systems (humanity) it’s not possible to dial in on just a few variables.

    None the less, soft scientists go through rituals of mimicking hard science.

    The results are ALWAYS spongy.

    Not to fear: funding is sure to follow; and that was the whole purpose of the endevor in the first place.

    The original super scientists (Newton) did so because the effort was its own reward.

    Today, science is — for most — just a hustle.

    We see the same thing in medicine. It used to be that to be a doctor was no path to riches; just screwy hours and blood and guts.

    Today, medicine attracts hustlers.

    Mothers goad their kids on to medical college because of the lucre, plain and simple.

    In a prior era, they wanted their sons to be bankers or businessmen.

    You get what you pay for. Watch out.

    As an exemplar: Barry, himself. A ‘paid for’ creature.

    Without AA stimulants, Barry would not be winging it in Air Force One.

    &&&

    You just can’t trust any of these pop sci articles.

    The writing is to standard, the science is shaky in the extreme.

  2. vanderleun Says:

    When it comes to vegetables my all time favorite is fresh moist grass when it comes in its natural thick juicy steak container.

  3. Ray Says:

    Just remember, you can’t prove causality with statistics. Causality is a deterministic process and statistics deals with random processes, i.e. processes that have more than one outcome and the outcome is unpredictable. Flipping a coin, tossing a pair of dice and drawing a card from a deck are all random processes.

  4. Doom Says:

    I’m still calling bunk on the benefits of vegetables. I would have to see what else was screened before giving them any credence. Sure, I don’t eat vegetables. Yes, my heart is bad. But it was from a virus, and is actually in exceptional health for having been as damaged as it was by the virus attack(s).

    People who eat more vegetables, and fruits, for example, are generally more health conscious. Meaning, they exercise, the have limits on this and that, and some other things. Unless that was part of the control, their study is useless.

    By the way, the reason I first became a, mostly, carnivore, was for my own health and fitness interests. More protein and fat, compared to carbs, simply allowed me to strength train much more successfully, before my heart got et by little monsters anyway. So… it was actually fitness related. I’ve never, and still don’t, have a reason to change. Given the givens, I am in exemplary health. I look at the other guys at the heart transplant clinic and wonder. Even the woman at the front desk, almost every time, asks if I am in the right place. Fifteen of the last twenty visits she has informed me that THIS clinic is for Hearth Patients. Forgetful dolt! Gah. Still, I try to take it as a compliment. Well, and lately, to not laugh at her.

    Having said all that, I don’t mind almost any vegetable or fruit, and still include it when I have enough going on, or it is available. Basically, in my condition especially, though just being human, almost anything that is edible, qualifies as nutritious, and is readily available… might at least get nibbled. I try to stick to unprocessed foods, just cooked whole, or even raw. Other than that the sky is the limit, if for my own efforts it’s usually just meat as I can’t shop often enough to keep fresh fruits/veggies on hand.

  5. parker Says:

    People tend to eat the foods they ate growing up. For us that means plenty of fruits and vegetables on a daily basis. However, I ignore all studies about diets, specific foods, and the of and on benefits of coffee, eggs, etc. Eat what you like.

  6. Mrs Whatsit Says:

    parker: yes. And I go one step further: maybe I like fruits and vegetables (and I do) BECAUSE they happen to be good for my particular metabolism. Maybe somebody else who cannot bear the thought of broccoli is reacting reasonably to some kind of message from that person’s metabolism that broccoli is not good for that person, even though it is for me. We aren’t fungible. Or at least, we do not know in any scientifically provable manner that we are. If my body likes tangerines and tells me to eat them, why then, I should eat tangerines. If yours tells you not to, then by all means don’t. There are plenty of other healthy choices in 21st century America.

    My guess will be that you and I will both live about as long as we are supposed to, about as healthily as we would have anyway, without regard to the specific volume of broccoli or tangerines or coffee or eggs that each of us ingests. The real problem would be famines that prevented us from eating ANY fruits and vegetables at all, or that forced us onto herbivorous diets with no cheese and eggs. Barring that — I can’t believe that moderation, adjusted for individual preference, can harm, or for that matter particularly benefit, anybody.

  7. RigelDog Says:

    Low-carb does not have to mean low vegetable! You poor thing!! An extreme version, such as Atkins induction phase, can mean only having a handful of veggies per day. But I lost a bunch of weight and got all blood levels to a perfect level by cutting out starch and sugar. And even then not to crazy lengths…I would have salad dressing or ketchup with a bit of added sugar; some breaded chicken. No starch/sugar meant LOTS of veggies and some fruit too, along with meat, nuts, and dairy.

  8. parker Says:

    Mrs Whatsit,

    I have been involved in vegetable gardening from an early age because I grew up on a farm where we produced 95% of what ended up on the table. My wife is not a farm girl, but her family also had a vegetable garden. We don’t grow 95% of what we eat, but we do grow on our double lot, a wide variety of vegetables, and preserve much of our late summer and fall harvest by canning and drying; and we have a root cellar which allows us to have winter squash, potatoes, parsnips, and turnips well into late spring. Routinely we ferment about 5 gallons of vegetables each year.

    We also have a sour cherry tree, 2 apple trees, a pear tree, and raspberry and gooseberry patches. Our town allows ‘urban’ poultry so we have 4 chickens and 2 ducks; Great egg producers and every 3 years all are slaughtered and placed in the freezer as the cycle begins again. We’re pretty famine resistant what with squirrel and rabbit meat thanks to a .22 pellet rifle, and I take 2 deer every year during the shotgun and black powder season. ;-)

    May we all live our allotted span with a light heart, surrounded by grandchildren and good neighbors. So say we all.

  9. Geoffrey Britain Says:

    ‘Is eating fruits and vegetables good for you?”

    Of course they’re good for you. They are the primary sources of essential vitamins, minerals and other essential elements that animal products cannot provide. Meat and dairy products in moderation are good for us as well. We are omnivores, as our teeth and digestive system prove, not carnivores or herbivores.

    That so basic a subject is still discussed is a reflection of just how far we’ve fallen educationally and in common sense. And RigelDog has the right of it with our over consumption of starches, sugar and salt. If you regularly crave it, it’s a sure sign of imbalance in that area.

  10. RickZ Says:

    Keep the fruit and pass the Brussels sprouts.

    I’ve hated fruit my whole life (except for bananas [which no longer taste like banana]). Only after I left home did I realize that my digestive system does not like skins, be it apple or eggplant, or those tiny little seeds on the outside of some fruit (I hate watermelon not just for the flavor but because of all the damn seeds). I also hate the pith in many fruits (stringy indigestible crap). But I love me some orange zest (and lemon and lime as well) and I use a squeezer and strain the juice. I use both in my cooking, and not just Chinese. Lemon zest is a great topping on my soy sauce-lemon juice-butter braised Brussels sprouts, along with some toasted sliced almonds.

    I find fruit boring as well. I also hate boring cooked vegetables and have made it my life’s work to make ‘unboring’ vegetables, sliced carrots cooked in beef broth/bouillon with powdered coriander and cumin being a good example.

    As Emeril always says, ‘I don’t know where you come from, but my water doesn’t come flavored’.

  11. Fausta Says:

    Due to blood sugar issues, I’m on a very low-carb diet, but I eat huge amounts and varieties of non-starchy vegetables, & some low-glycemic fruit, like berries.

    It’s a very healthy diet, btw.

  12. Nick Says:

    My suspicion is that “fruits and vegetables” includes fries and potato chips. We have every reason to believe that some fruits and vegetables, prepared well, have a lot of nutrients including some that help prevent cancer. Some don’t. Potatoes and (iirc) a lot of melons are on the high-end of popularity and the low-end of nutritional value. The person who gets a good mix of healthy food, including healthy fruits and vegetables, is probably going to be healthier.

  13. Nick Says:

    Oh, how could I forget lettuce? The work-horse of the salad bar, containing almost nothing that’s good or bad for you. Primarily serves as a salad-dressing delivery device.

    I wonder how many of those 8+ fruits and vegetables people are counting Skittles. Because seriously, 8+?

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