The results are pretty clear – fruit consumption has no significant effect on mortality.
The bar charts figure below shows what seems to be a slight downward trend in mortality, in the 35-69 and 70-79 age ranges, apparently due to fruit consumption.
As it turns out, that slight trend may be due to something else: in the China Study II dataset, fruit consumption is positively associated with both animal protein and fat consumption. And, as we have seen from previous analyses (e.g., this one), the latter two seem to be protective.
So, if you like to eat fruit, maybe you should also make sure that you eat animal protein and fat as well.
Do we know the ranges of daily fruit consumption of many cultures?
ReplyDeleteSo at least it doesn't seem positively associated with mortality, eh?
ReplyDeleteI'm curious, because, while I'm convinced of the deleterious effects of refined fructose on human health, I haven't been able to turn up any study that finds poor outcomes for people who consume fruit. There has been a lot of anti-fruit sentiment on various paleo-type blogs, but this seems to be jumping to conclusions based on refined fructose that may not apply to fruit.
As a parent, I'm pretty successful in limiting sugar, and there is no HFCS or soda in our lives, and juice only on special occasions, but I don't want to fret about my kids eating whole fruit (which they love) if there are no grounds for doing so.
Hi John. There is data out there, but it is usually hard to compare different cultures like that, because there are so many other factors.
ReplyDeleteThis China Study II sample has some good things going for it. It has a decent amount of variation in fruit consumption, and the range is not that small – 0 to 219 g/d.
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ReplyDeleteHi Helen. I’ve never seen any convincing evidence that the fructose-glucose combination found in fruits is anything but benign. Under glycogen depletion, it actually makes the liver a “sponge” as far as blood sugar is concerned. That is, under glycogen depletion, it seems to be health-promoting.
ReplyDeleteThis is interesting, because in most HG populations that I know of, older people seem to engage in very little glycogen-depleting activities. That is perceived as something that the young folks should do. And the concept of strength training (and exercise in general) is nothing but a joke to HGs.
I’ve seen somewhere the idea that plants “trick” animals into dispersing seeds by sneaking disease-promoting fructose into fruits.
Well, that is not how evolution works. If that were the case, animals would probably have evolved an aversion to fructose.
The organisms involved in evolutionary “arms races” are moving targets. And plants’ genes certainly don’t undergo mutations faster the genes that code for traits in animals.
Well this does support the food combining principle that fruit and animal meat are compatible in a meal.
ReplyDeletefats/fruit, meat/fruit/ =Good
carbs/fruit =bad
"I’ve seen somewhere the idea that plants “trick” animals into dispersing seeds by sneaking disease-promoting fructose into fruits.
ReplyDeleteWell, that is not how evolution works. If that were the case, animals would probably have evolved an aversion to fructose."
I totally agree and also am doubtful of the "we've been tricked" argument. We want fructose-containing foods for some reason that is beneficial to us. I do think the rarity/seasonality argument has a little bit going for it, but the rarity of native fruit varies from place to place.
Having soluble fiber - plus other substances in fruit such as vitamins, minerals, and polyphenols - along with your fructose changes how it is absorbed and handled by the body. Some of it is fermented by gut bacteria into acetic acid before it even hits your bloodstream. And Stephan Guyenet, I'm sure you're aware, just did a thing on polyphenols and hormesis - and their attendant health benefits. I think there may be effects of polyphenols and other "phytonutrients" apart from that, but that was a good argument in their favor.
The arguments to ditch fruit because of studies finding harm from refined fructose remind me of the anti-egg hysteria brought on by studies of rabbits eating refined cholesterol.
I did have a Chinese medicine specialist warn me once against too much fruit because it's "very yin." That argument makes more sense to me. It does make me feel "too yin" if I eat too much of it and not enough other stuff of substance.
Vance - A little fructose actually makes glucose utilization more efficient, because it's a stronger stimulant of the glucose-sensing enzyme glucokinase than glucose alone. (Glucokinase tells your pancreas how much insulin to make.) A lot of fructose, though, isn't great for glucose metabolism, or for your liver. So a bit of fructose with your starch may be a good thing - just have a dab of honey with your porridge, not the other way around.
I'm posting this comment while having my evening snack. At y elbow are some slices of very shap cheddar, some blackberries, anda glass of petite sirah.
ReplyDeleteGiven that the French do rather well on plates of fruit and cheese washed down with a good wine, it doesn't surprise me a bit that you're getting these results.
The Paleo types might not approve (Fruit? Alcohol? Dairy?), but frankly I don't find the Paleo hypothesis all that much more compelling than the cholesteol theory of heart disease.
Although lipophobia and Paleo might seem miles apart, they share some characteristics. One is reasoning to conclusions from assumptions that may or may not be valid. Another is a simplistic proposed mechanism that is easy to sell to the public.
In both camps, I seem to hear people saying: Well, that's fine in practice...but can't you see that it just doesn't work out in theory?
Hi Ned,
ReplyDeleteIs it true that comsuming fructose with equal amounts of glucose is the safest combination? I believe that some fruits achieve this 50/50mix but not all. If I am correct about this, can you tell me why?
Let me also say that I have been enjoying you blog for a while now and appreciate your work.
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ReplyDeleteGood points Helen, thanks.
ReplyDeleteVance, in addition to what Helen said, I would also point out that: (a) fruits contains carbs, sometimes quite a lot of them; and (b) the healthiest people in this sample tended to consume a lot of rice as well. On (b), there is probably an overlap between moderate/high rice consumption and high fruit consumption.
ReplyDeleteHi David. Indeed, there seems to be a growing aversion to fructose in Paleo circles. It makes very little sense if we think of fructose from fruits, as fruits are probably the ONLY food that was “designed” by evolutionary pressures for animals to eat.
ReplyDeleteHi Alan. I don’t think a 50-50 split is really that important. What seems to be important is that it is hard to over-consume fructose from fruits. How many apples can one eat in one sitting?
ReplyDeleteAlso, it seems that the fructose in the fructose-glucose mix is also turned into glycogen by the liver, as long as liver glycogen “tank” is depleted: http://bit.ly/edzA7t.
Hi Samantha, thanks. Actually it is very low in my priority list to increase the readership of this blog. It keeps going up, but I’m not really interested in trying too hard. I have a full time job, and enough part time activities to keep me busy every single second I am awake.
ReplyDeleteOkay, here's my basic hypothesis.
ReplyDeletePeople and their crops and their diets coevolved. And, as you have shown the math, it really doesn't take millions of years of evolution for an adpative trait to spread through a population. Imagine how much faster things happen if they co-evolve.
But I think our ways of processing food, and our ways creating utterly new foods, have surged way beyond the co-evolutionary and cultural systems that existed before.
People are mixing things up in ways that never happened before.
A number of people have noted that there aren't many natural foods that are both high in carbs and high in fat. Yet I'm fine with fruit and cheese...
But easily digestible carbs and really crappy fats from Mars, ala a typical bag of potato chips? From the point of view of our bodies, Weird Food.
I've actually spent quie a bit of time in China, and even in the rural areas, people have been mixing up their diets in ways never heard of before Mao unified the country and, ahem, modernized.
I think low-carb works. I think Paleo works. I even think Ornish works, if you can stand it. But I think they only work because they drive our eating behaviors to what we think of as an "extreme"--and that extreme happens to exclude certain things or combinatiosn of things to which we aren't adapted.
Traditional Eskimos do fine. Traditional Cretans do fine. Traditional Kitavans do fine. Traditional Masai do fine. As I mentioned, even the French do pretty well.
The similarity? They aren't eating anything in combinations heretofore unseen, and aren't eating anything processed in a way my great-great grandmother wouldn't have recognized.
And, you're right: fruit is asking to be eaten. I refuse to accept the "tricky plant demon" concept that has become so widespread.
It is a good theory David.
ReplyDeleteAnother thing that I often hear is that modern fruits are bred to have a very high sugar content. While this may be sometimes the case, I am not sure that this goal has been achieved for many fruits.
There are several fruit varieties that look quite big compared with wild fruits, but that seems to be mostly due to water accumulation. This being the result of human engineering makes sense, since fruits are usually sold by weight.
If a fruit is big because of its having more water, its glycemic load will be lower than that of a smaller variety.
Hello, Ned, thanks for an interesting post.
ReplyDeleteFruits increase their sugars as they ripen. That's what refractometers are all about in the wine industry, they watch for the sugar content they need. And we all know that greener fruit is tart and it becomes sweeter as it turns its more natural colors and softness, think bananas, pears, even apples. I don't know about berries, although the firmer ones are usually tarter. The carbs will vary with the state of ripeness.
Good point Jean. Also, certain toxins present in green fruits are sometimes not present in ripe fruits.
ReplyDeleteI had to jump in with something that I thought would have been mentioned by now.
ReplyDeletePeaches and cream.
Such a tasty and "natural" combination. And it doesn't even have to be peaches. So many fruits are delicious with cream. The fat soluble vitamins aid in the absorption of nutrition contained in the fruit. A quilt free delight.
What seems to be important is that it is hard to over-consume fructose from fruits
ReplyDeleteEasy, with figs or dates and some other tropical fruits.
As a trivia point to illustrate that, before the use of maize to fatten ducks and geese livers, traditionaly (i.e. the Romans) figs were used for that purpose. It was so obvious that even the french word for liver (foie) is derived from ficatum the latin for fig.
http://fr.wiktionary.org/wiki/foie
Hi gallier2. I have on occasion eaten raw figs. I can’t eat many at once. Their gram-adj. sugar content is indeed higher than that of an apple; dried figs are a lot worse. Some numbers from nut.data:
ReplyDeleteRaw figs (100 g)
Sugars 16.3g
Apple (100 g)
Sugars 10.4g
Dried figs
Sugars 47.9g
We should also not forget that traditionally fruit was not consumed fresh, this is only a recent phenomenon due to cooling and transport. As fruits are seasonal and over-abundant only for a short time, people have invented methods to conserve them, dry fruits, syrups, jams and stews. Especially the Chinese markets are full of very sweet concentrated fruit candies that are 100% fruit. So my problem with the "healthy fruit" message is that people equate eating an apple and guzzling a litre of organic apple juice, which has the sugar content of 30 apples.
ReplyDeleteThe message that fructose is always metabolized to fat first before it can be used as energy is imho not emphasized sufficiently. Add in the snacking culture where adipose tissue are never sollicited and you have a disaster happening.
Question, did the China Study make a difference between fresh fruits and concentrated form?
i hope this is the start of a trend that knocks out the fruit-as-candybar nonsense.
ReplyDeletefat consumption just isn't enough.
good blog.
Hi gallier2, again. Fructose ingestion leads to lipogenesis only when glycogen stores are replenished, and I think most people underestimate the size of glycogen stores, even in the liver.
ReplyDeleteI suspect that one can consume a significant amount of sucrose at once, say 50 g, and none of that will go past the liver if liver glycogen is depleted, as long as one is free from any disease.
This article exemplifies somewhat what I am saying:
http://www.ajcn.org/content/48/2/240.abstract
The problem starts when people do things like consuming foods rich in refined carbs and sugars that are essentially empty calories. Those foods are not satiating, are low in important micronutrients, and prevent the body from tapping its fat reserves. Hunger regulation is messed up, and people consume them with glycogen stores full, at times when they should not be hungry.
Hi Shel. Thanks for stopping by and commenting.
ReplyDelete"There are several fruit varieties that look quite big compared with wild fruits, but that seems to be mostly due to water accumulation. This being the result of human engineering makes sense, since fruits are usually sold by weight."
ReplyDeleteYes indeed. Follow the money!
I love tomatoes (which, of course, are actually a fruit rather than a vegetable.) And they seeme to have many health benefits--though some shun any of the nightshade family (including potatoes and eggplant) because of the solanine content. But the ancestral tomato, insofar as they have been able to find it in the wild, is a pretty nasty little berry...to humans. Chances are it was intended to be spread by birds, but through selective breeding we've made peace with it.
ReplyDeleteHot peppers are an interesting case. The capsaicin is probably an anti-feeding mechanism, but it seems to be directed at mammals. Birds take no notice of it's "heat" and gobble down peppers as soon as they ripen. When we lived in Hawaii, we always had pepper plants and cherry tomato plants popping up in our yards because of bird droppings.
But even though capsiacin may prevent us from overeating hot peppers, it doesn't seem to mean that they are bad for us. In fact, capsiacin seems to have a number of health benefits.
Life is complex, innit?
Thanks David for your great insights, as always.
ReplyDeleteJust a clarification on my second comment in response to Gallier. The 50 g of sucrose I mentioned will be broken down to about 25 g of fructose.
Those 25 g will be used by the liver to make glycogen, if liver glycogen is depleted, and none will be used for lipogenesis.
Sorry, but I don't think the study you gave contradicts my point about fructose metabolism.
ReplyDelete1) The study does conflates fructose and glucose in the CHO category without breaking up the numbers between the two. It is thus impossible to conclude which contributed to glycogen and how much.
2) The glycogen store is full on the 1st day of CHO overfeeding, indicating that de novo lipogenesis starts quickly. It's measured on day 2 of CHO overfeeding.
3) Basic biochem shows that there's no* pathway from fructose to glycogen synthesis.
http://www.medbio.info/Horn/Time%201-2/carbohydrate_metabolism%20March%202007a.htm
* Not entirely true as fructose can be phosporylated by hexokinase but because it has a 30 times lower affinity to it than to glucose it nearly never happens.
Here the relevant citation of the Horn page:
One might think that fructose could be converted to glucose and stored as glycogen. This has been suggested many times by health faddists. However, the balance of insulin and glucagon after a meal rules this out. Gluconeogenesis is turned off, glycolysis races forward and fructose is converted to fatty acids. This is the most likely explanation for the increased triglyceride levels found after in people who use "normal amounts" of sugar. Sugar consumption has increased from about 8 kg/year to over 50 kg/year in many societies during the past 150 years. Genetically, we are designed to consume far less! Today's "normal" sugar consumption is, genetically seen, far from a normal sugar intake.
The study doesn’t differentiate among sugars, but given the amount of CHO taken, it is hard to believe that all of the fructose possibly present was converted to fat.
ReplyDeleteSee also this post covering an in vitro study with rat liver tissue: bit.ly/edzA7t.
You might be right for the first few hours until hepatic glycogen is saturated, thing that happens quite rapidly. Muscle glycogen does take longer but doesn't incorporate fructose. You're right also to say that after workout, fructose is a good thing. The problem is that a general encouragment for the general population of over consumption of fructose is not absolved by that, as normally people have 100% liver glycogen all the time. The CHO overfeeding shows it quite clearly, as long as there is de novo lipogenesis (and it starts within the first day of CHO overfeeding), there is no fat mobilisation from tissues and the generated fat along with the dietary fat is used instead and as the metabolism changes to glucose as primary fuel (to get rid of it), less and less of the fat generated and ingested can be used. So fat accumulation is the consequence.
ReplyDeleteMy point is that, at large us overweight westerners are in this state 99% of the time and giving a freepass to fructose because in the 1% of time it is useful, is an error.
Hi Gallier. We are in full agreement that overconsumption of fructose is bad. In fact, overconsumption of almost anything, even water, is bad.
ReplyDeleteOur liver glycogen tank is not full all the time. Once it is replenished, it goes down at about 5 g per hour, to supply the needs of the brain and other tissues that use only glucose (red blood cells). That slow release is mediated by glucagon secretion. See this post: bit.ly/ftES8Y.
So if you fast for 8 h your body will use about 40 g of glycogen. The fructose+glucose combination in two small apples will fall short of replenishing that, but not by much. No liver lipogenesis in this case.
Two cans of regular soda will be overconsumption, and will make one fat indeed, after only 8 h fasting since a meal that fully replenished liver glycogen.
But if you fast for 30 h, even two cans of regular soda will fail to cause liver lipogenesis.
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ReplyDeleteIn fact, it seems more and more disgusted with fructose ancient world. This makes little sense if we think that fructose from fruit, fruit may be the only food to eat animals evolutionary pressures this is "design."
ReplyDeleteThis is really interesting because it's strange even though when they are really aware with those things, on the other hand I didn't know those facts about fruits...
ReplyDelete