How much fructose can you safely eat?

Tuesday, November 17, 2009 16:23
Comments Off on How much fructose can you safely eat?

MPj04305460000[1] Q. I’m confused by conflicting things I’ve read about fructose.

[In this article], I read that:

When large amounts of fructose are ingested, they do “provide a relatively unregulated source of carbon precursors for hepatic lipogenesis.” In other words, if you eat too much fructose, the liver can make the excess into fat. 

But later in the same article, another scientist is quoted as saying:

There is no evidence that reasonable consumption of fructose in a typical diet has any adverse effect on the liver or that it produces more body fat than sucrose or glucose.

I’m confused. Should we be concerned about fructose actually being stored as fat?  And how much fructose would a typical person have to eat for fat conversion to begin?

A. Notice that whenever the negative effects or dangers of fructose are discussed, it’s always in regard to  “large amounts of fructose” or “too much fructose” or “when fructose is consumed in excess.”

If you eat too much of ANY nutrient, the excess will be stored as fat. Fructose may be converted to fat more efficiently than glucose but these fat stores are readily mobilized when energy is needed. Over the long term, body fat accumulates because we take in more energy than we spend.

Here’s an analogy I used in a recent episode of my weekly podcast

Your body stores energy (or calories) in a variety of formats and
places in your body. You store a little bit in your blood, a little bit
in your muscles, some in your liver, and the rest you store as body fat. It’s a little like storing your money in a number of places. You
probably have some in your wallet, possibly some more in your dresser
drawer, some in a checking account, and maybe the rest is in a money
market account. 

Your body alternately makes and burns body fat all day long,
transferring fuel in and out of its various accounts.  When you eat, energy is stockpiled in your body’s accounts. As you go through your daily activities, you draw down these reserves. Which account you withdraw energy from will probably
depend on how much you need and how fast you need it.

But just like with your money, regardless of which account you withdraw
from, you’re still spending the same amount. If you spend less than you
deposit, your net worth goes up. And when you burn fewer calories than
you take in, you’re going to gain body fat.

Is fructose really the problem?

While it’s true that our consumption of fructose has gone up dramatically, it has simply paralleled the increase in our intake of sugar (and calories). Even with the increased use of high fructose corn syrup, the proportion of sugar consumed as fructose has not changed significantly.  So, regardless of what happens when you feed huge quantities of pure fructose to lab rats, I think it’s a little silly to say that  the negative effects of too eating much sugar are because of fructose.

How much fructose can you safely eat?

In my opinion, if your intake of added sugar is not excessive and your total calorie intake is appropriate to your needs, you probably don’t need to worry about consuming too much fructose.

What’s excessive? The World Health Organization recommends limiting added sugars to 10% of calories (something in the neighborhood of 50g/day).  More recently, the American Heart Association has recommended limiting added sugars to 5% of calories. Both are well below the threshold where fructose consumption would be a concern.

What’s an added sugar? The WHO defines added sugar as concentrated sugars (white sugar, brown sugar, honey, maple syrup, etc.) that are used in processed foods and beverages, recipes, or at the table.  The naturally occurring sugars in fruits and dairy are not considered added sugars.

Can you eat too much fruit?  You can eat too much of anything. But no-one is claiming that excessive fruit intake is behind the rise in obesity or diabetes (although fruit juice might be another story). Reasonable intake in the context of a typical diet is two to four servings of whole fruit a day.

P.S. The entire artic

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