How much fructose can you safely eat?

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 article is well-worth reading.

Strange Science: Meat consumption increases risk of Type 2 diabetes

A new meta-analysis concludes that a diet high in meat increases your risk of Type 2 diabetes by 17%.  Eating a lot of so-called "red" meat was associated with a slightly higher increase (21%), and a high intake of processed meats increases your risk by a whopping 41%.

Media reports are quick to point out that this is just the latest in "an ever increasing list of bad news for red and processed meat."

In all of these studies, the division of meat into "red" and "white" seems totally arbitrary, as I discussed at length in this post: Meat and mortality: What does color have to do with it? 

In this particular case, the authors concede that the apparent association between meat consumption and diabetes risk could be explained by other factors. (So why exactly are we going to press with this result?)

A false association seems even more likely in this case than in the recent associations between meat intake and cancer risk or all-cause mortality.  At least there are plausible mechanisms to explain why high meat intake might increase cancer risk. For example, charred meat contains known carcinogens--although I hasten to point out that this has nothing to do with the "color" of the meat.

Diabetes is a disease of disordered carbohydrate metabolism. Meat is made up of protein and fat. How could eating more protein and fat increase the risk of diabetes?  Doesn't it seem more likely that there is something else about the lifestyle or dietary habits of people who eat large quantities of meat (especially processed meat) that might increase their diabetes risk? Are they also over-weight? Are they sedentary? What's their consumption of alcohol? Of high-glycemic foods? 

I'm keeping an open mind but pending more convincing data, I'm not sure I'm buying it.

Reality Check: Does candy turn kids into monsters?

Trying to rein in the amount of sugar kids eat is hard enough.  Having a plastic pumpkin full of candy in the house sure doesn't make it any easier.

There are plenty of compelling reasons to limit kids' intake of sugar. Candy is a source of empty calories that can displace more nutritious foods, lead to weight gain, and wreak havoc with insulin metabolism. (Type 2 diabetes used to be called Adult Onset Diabetes, but no more.)

But many parents are also convinced that sugar turns kids into little monsters--making them hyper-active, aggressive, or otherwise unmanageable. Yet the research fails to bear this out.

Is it all in parents' heads? 

Controlled studies have measured the effects of sugar consumption on behavior and cognitive performance and failed to find any connection. See for example this meta-analysis. There have even been interesting studies where parents were asked to observe kids behavior. When the parents thought the kids had eaten sugar, they reported changes in behavior--even when the kids had actually been given a placebo. See this article for more on the sugar-hyperactivity myth.

Just last month, there was an interesting new twist on this: Researchers found that kids who ate candy every day were more likely to be arrested as adults for crimes involving violence, as reported by AP News. The researchers hastened to add that the association is probably more complex than it sounds. It may be, for example, that individuals with poor impulse control eat more candy as kids and then commit more crimes as adults. 

What's a responsible parent to do?

Most parents settle for damage containment and try to strike a balance between nutrition concerns and letting kids enjoy this once-a-year festival. Rather than banning all Halloween candy (now who's the monster?), try to limit the amount that is collected and then dole it out slowly.  One small treat after a healthy meal isn't going to turn your kids into monsters.  Getting your kids up and moving--whether it's to rake leaves, play touch football, or even some Wii tennis--is also an effective way to mitigate the effects of a little extra sugar.  

Is Paleo the new Mediterranean?

The Mediterranean Diet has been king of the hill for the last several years. While low-carb and low-fat camps continue to trade jabs, each amassing roughly the same number of studies in its favor, the Mediterranean diet (which is neither) has risen above the fray, trumping every diet it's compared with in study after study.

Just last week, for example, I noted a study finding that the Mediterranean diet helped diabetics lose more weight and use fewer medications than a low-fat diet.

But I sense a shift of power (or at least of focus) in the works.  The "Paleo Diet" has been garnering a larger and larger share of popular attention and support as the latest Solution To All Our Problems.  And now the research community is beginning to test the theory, designing studies that pit the Paleo diet against other dietary prescriptions.

The caveman versus the shepherd

While the Mediterranean Diet hearkens back a couple of thousand years ago to a pre-industrial, agrarian era, the Paleo diet turns the clock back by ten thousand years and attempts to replicate a pre-agricultural, hunter/gather diet.  Grains, dairy, legumes, and oils--mainstays of the Mediterranean Diet--are off the table in the Paleo diet, which is based on lean meat, fish, fruits, vegetables, eggs, and nuts.

The two went head to head in a small study of patients with heart disease. Paleo pinned Mediterranean to the mat, yielding greater improvement in glucose tolerance and greater decrease in waist size. Have the cavemen knocked the shepherds off the hill? Not yet. 

Studies are one thing; real life is another

For one thing, I wonder about the long-term practicality of the Paleo diet. Diets which depart dramatically from the cultural norm often lead to dramatic weight loss. This may be partly due to the metabolic "magic" put forth by proponents. But I think it's also at least in part behavioral and practical: when whole categories of food are off limits, you tend to eat less and weight loss ensues.

Paleo and other dietary theorists have compelling stories to tell, but what are the realities on the ground?  What are the subjects in the study going to eat when the study is over? History has shown that, while purists and zealots may succeed in renouncing grains, carbs, dairy, etc. for life, mere mortals eventually find these diets too difficult to maintain and lapse back into prior eating habits. 

And while cutting fat and calories and getting more exercise may seem hopelessly old-fashioned in an era of "good calories, bad calories," let's not ignore the fact that millions of people continue to lose weight and keep it off doing nothing more exotic than that.

Do what works

A change in diet only really improves health outcomes if it's sustainable. And sustainability involves practicality, logistics, economics, personal preferences and beliefs, as well as social conditioning and cultural norms. By all means, let's use what we're learning in the research lab to to nudge our social and cultural norms and public health and food policies in the right direction.

But changing cultural norms takes time. Right now, I think the Mediterranean diet may have a practical advantage over the more extreme Paleo approach.  Fortunately, we don't all need to agree on the same solution. If what you're doing isn't producing results, try a different approach. If you've found what works for you, keep doing it. But don't assume that what works for you is the (only) solution for everyone.

What's so magical about the Mediterranean diet?

Forget the mouse studies. After a couple weeks of controversial and much-contested rat studies on the effects of carbohydrates on various aspects of metabolism and disease, here's a study involving 200 newly-diagnosed, diabetic humans.  Half were told to follow a Mediterranean-style diet, rich in vegetables, whole grains, and monounsaturated fats from poultry, fish, and olive oil and limiting carbohydrates to 50% or less of total calories.

The other half were assigned to a "low-fat" diet, which also emphasized whole grains and discouraged sweets and high fat snacks. Fat was limited to 30% or less of calories and saturated fat to 10% or less of calories.

After four years, the Mediterranean group had lost more weight and was only half as likely to need anti-diabetic medications.

What's the real difference here?

Notice that the macronutrient distributions between the two diets are not all that different. The Mediterranean diet was not terribly low in carbohydrates (although it's being described in media reports as a "low-carb" diet). The low-fat diet isn't really all that low in fat. The two percentages certainly aren't mutually exclusive. In fact, it's entirely possible that the distribution of fats, proteins, and carbohydrates between the two groups was very similar.  Nor can we necessarily chalk it up to refined versus complex carbohydrates.  Both groups were instructed to favor whole grains.

Perhaps it was just a matter of what the dieters were told to focus on.  The Mediterranean group was told what to eat: vegetables, fish, grains, olive oil. The low-fat group were told what to avoid: sugary snacks and high-fat foods.  Could it be as simple as casting dietary recommendations in terms of positives instead of negatives?

High fat diet increases insulin resistance?

I was just re-reading Tara Parker Pope's article in the NY Times on the now-famous rat study which found that high-fat meals impaired cognitive and athletic performance. Predictably, the study was dissed and dismissed by the low-carb and pro-fat bloggerati.

(By the way, for those who dismissed the study because it involved rodents, data from a parallel human study are still being analyzed but appear to line up with the original findings.)

Whatever the merits and implications of this particular study, I was struck by the following quote from Pope's article:

It’s not clear why fatty foods would cause a short-term decline in cognitive function. One theory is that a high-fat diet can trigger insulin resistance, which means the body becomes less efficient at using the glucose, or blood sugar, so important to brain function.

This, of course, is exactly the opposite of what low-carb/high-fat advocates are always telling us The story is that a high carbohydrate diet is the culprit (and a low-carb diet is the cure) for insulin resistance.

Specifically, ingestion of carbohydrates (especially high glycemic carbs) sends blood sugar soaring, which triggers insulin secretion. Over time, cells become less sensitive to the effects of all that insulin and blood sugar levels creep dangerously higher.  Next stop: obesity, Type 2 Diabetes, and heart disease. Cutting down on carbs reverses the whole cycle.

So what's all this about a high-fat diet triggering insulin resistance? 

In a long discussion, Mark Jenkins, MD, suggests that while carbohydrates may raise insulin levels, high insulin levels do not cause cells to become insulin resistant. Further, he suggests that obesity leads to insulin resistance and not the other way around.

Here are a few of his observations, which some may find surprising:

• High fat stores [in obese individuals] down-regulate insulin receptors and cause a resistance to circulating insulin.
• It has been repeatedly shown in the medical literature that...insulin sensitization is accomplished by aerobic exercise, low-fat / high-carbohydrate diet, and reduction of excessive body fat. Conversely, obesity and high fat diets have been shown to induce insulin resistance. 
• It is important that the high carbohydrate diet have predominantly complex carbohydrates and also have a high fiber content.  Overly refined, simple sugars do not appear to have the same effect as complex carbos. 

Please see Jenkins' entire discussion here and selected references here.

Maybe the problem is not the fat in our foods but the fat in our bodies

Jenkins' arguments don't separate the effects of diet composition from the effects of body weight or weight loss. In the studies he cites, those with insulin resistance aren't just eating a high fat diet; they're also obese. Those who see increased insulin sensitivity aren't just eating a low-fat diet, they're also exercising and losing weight. One wonders: Does a high fat diet lead to insulin resistance in normal weight people? Does a low-fat diet improve insulin resistance if the subjects don't lose weight? What if they lose weight on a high fat diet?

The epidemiological argument?

I find it interesting that both sides of this debate invoke epidemiological evidence. The pro-fat folks (the Weston Price gang, for example) claim that atherosclerosis and diabetes were "unheard of" in traditional cultures which had high fat, grain-free diets.  Jenkins, on the other hand, says:

If one looks at epidemiological data, the traditional diet of many third world countries consists of high complex carbohydrate content, very low fat, and high fiber. Atherosclerotic disease was virtually unheard of until the introduction of the high fat Western diet. 

Obviously the ratio of fats to carbohydrates does not tell the whole story.  Jenkin's observation about the difference between complex and simple carbohydrates is one key.

Maybe we can't blame the modern epidemic of obesity, heart disease, and diabetes on fat OR carbohydrates--but on a toxic combination of fat AND refined carbohydrates (with over-consumption and sedentary lifestyles playing significant supporting roles).

Your thoughts?

Can very active people tolerate a higher glycemic diet?

Q. How important do you think the glycemic load is for someone who is very active? I eat a lot of fruit and vegetables and therefore have a very high glycemic load by the end of the day (about 170). The website says to try and keep it below 100, but in order for me to do that, I would have to restrict fruit intake to the point where my diet would be deficient in many vitamins and minerals, not to mention the fact that I wouldn't have enough energy to do many of the things I love to do.

A. In order to help orient people who aren't familiar with the concept of glycemic load, we include a note next to the eGL display saying that "Typical target is 100/day or less."  But if you click on the "what's this?" icon, you'll get a slightly more expansive comment:

"Experts vary on their recommendations for what your total glycemic load should be each day. A typical target for total Estimated Glycemic Load is 100 or less per day. If you have diabetes or metabolic syndrome, you might want to aim a little lower. If you are not overweight and are physically active, a little higher is acceptable."

In other words, this is yet another illustration that, when it comes to dietary recommendations, one size does not fit all.

Who needs to worry about glycemic load?

The main reason to be concerned with glycemic load is that a high glycemic diet can promote insulin resistance (sometimes called "pre-diabetes") and obesity.  But people who are very active are much less likely to suffer from insulin resistance, in part because vigorous exercise is a great way to improve insulin sensitivity.  Athletes have far less to fear from carbohydrates than sedentary people.

A glycemic load of 170 is fairly high.  But a lot depends on the context.  If you are quite physically active, maintaining a healthy weight and body composition, have normal blood sugar levels, meeting your nutritional requirements, and the lion's share of your glycemic load is coming from whole fruits and vegetables, a daily glycemic load of 170 may be okay.

That's an awful lot of "If's."  

You say that in order to reduce your glycemic load, you'd have to restrict your fruit intake to the point where you'd be deficient in many vitamins and minerals. But couldn't you be getting those nutrients from vegetables, instead? A yellow or red bell pepper, for example, has as much as much vitamin C as an orange (plus lots more vitamin A) with a much lower glycemic load.

In terms of having enough energy, you can get energy (i.e., calories) from any number of foods with a lower glycemic load. A hard-boiled egg or small serving of edamame provide as many calories as an apple but half the glycemic load.

Thoughts? Comments?

More evidence that saturated fat has been falsely accused?

What if cancer, heart disease, and diabetes are really all the same disease?

An excellent commentary in this month's issue of the Journal of the American Dietetic Association lays out a compelling and detailed map showing how obesity and insulin resistance interact to promote the growth of cancerous tumors. The authors argue that weight loss (if appropriate) should be a central feature of cancer prevention and treatment. Going a step further, the journal's editors suggest that obesity (and insulin resistance) is the common culprit in all of the Dreaded Three: cancer, diabetes and heart disease. 

Now, if you ask the dietary establishment how to prevent obesity, cancer, and heart disease, they will most likely advise you to reduce your intake of total fat, saturated fat, and red meat. (See, for example, the American Cancer Society, the American Institute for Cancer Research, and the American Heart Association.)

Yet another study in the same issue of JADA tells a different story:

Saturated fat and red meat seem to prevent expanding waistlines

Danish researchers studied the links between consumption of various food groups and change in waist size.  Why are they worried about waist size? An increase in waist size signals an increase in visceral, or abdominal, fat. This is considered the most dangerous pattern of weight gain because abdominal fat is strongly linked to increased risk of heart disease, cancer, insulin resistance, and diabetes.  In fact, the association is so strong that a waist measurement of more than 35"  (for women) or 40" (for men) is an independent risk factor for heart disease.

Surprisingly (to some), they found that women who ate more butter and high fat dairy products gained less weight around the waist than those whose diets are lower in saturated fat. A similar association was observed with red meat--that is, those who ate more red meat had smaller waistlines. The researchers seem to be at a loss to explain these findings.

Some would argue that a diet higher in fat and protein may be lower in carbohydrates and that carbohydrates drive insulin resistance and obesity.

No consistent link found between animal fat and breast cancer

Then there was this study in the American Journal of Clinical Nutrition: Researchers from several European countries collected and analyzed dietary records for 319,000 women and found "no consistent association" between the consumption of eggs, meat, or dairy products with breast cancer. This, of course, contradicts previous observations.

I'm reminded of our extended debate over whether or not eating red meat increases your risk of cancer. And many of the same observations apply here: trying to draw definitive conclusions about the impact of diet on disease using diet records is a very tricky proposition. It's possible that red meat may be a red herring. For one thing, any category that lumps a char-grilled fast food hamburger (and the fries likely to accompany it) together with a grass-fed bison filet is completely meaningless.

Should you start eating more meat?

I'm not making any blanket recommendations one way or another.  Some thoughts:

The prevailing wisdom that meat and saturated fat are unhealthy is based on the same sort of inconclusive, circumstantial evidence as the studies I've noted here.  But if we really want to get to the truth, we're going to need to consider ALL the (flawed) evidence, not just that which supports our point of view.

As many of you know, I'm not a big meat eater myself--although this is more for environmental, ecological, and ethical reasons than nutritional concerns.  But I'm pretty sure that no one food or group of foods causes disease. In fact, to circle back to the beginning of this post (and a recurring theme around here), it seems that plain overconsumption of food in general is a bigger problem.  The fact that so much of that food is over-processed and nutrient-poor sure doesn't help.

If you're eating a calorically-appropriate diet made up mostly of whole foods, I'm prepared to be pretty darned flexible about the details.

Are grains necessary to a healthy diet?

Q. What is the purpose of eating grains?  If you are tracking your nutrition and getting all of the necessary nutrients, is there any reason that you couldn't eliminate grains from your diet?

A. What?! You want to eliminate one of the five basic food groups? Grains are the foundation of the Healthy Food Pyramid.  They must be essential to a healthy diet.

I'm kidding, of course. As far as I'm concerned, grains (such as wheat, corn, oats, rye, etc.) are not essential to a healthy diet.  I think the main reason that grains have long been counted as a basic food group is that dietary policy-makers have viewed them as an innocuous way to cover one's calorie needs (plus maybe some pressure from agricultural lobbies and interests).

You see, the powers-that-be don't want you filling your calorie needs with fat--especially saturated fat from animal products--because fat has long been seen as the villain in heart disease and obesity.  And it would be challenging to meet your calorie needs eating nothing but fruits and vegetables because, while they're packed with nutrients, vegetables are notoriously low-calorie.

Grains would seem to fill the void nicely. They're plentiful, filling, fat-free, shelf-stable, and relatively inexpensive--thanks in part to a government-subsidized agricultural industry.

They don't, however, provide any nutrients that can't be gotten from other foods. More to the point, many argue (ferociously) that the saturated-fat/heart-disease theory has been completely discredited and that carbohydrates--especially the refined, processed type) are the true culprits--in heart disease, obesity, and diabetes.  See for example Steve Parker's post "Are Saturated Fats All that Bad?" on the NutritionData Heart Health blog.

Although the carb-bashers can get a little strident, I'm on board with the basic concept.  I suspect that refined carbohydrates do a lot more damage than saturated fats, per se, do. I also think that being overweight, in and of itself, is more harmful than the foods you overeat to get that way. 

To get back to your question: Anyone who chooses to eliminate grains from their diets does so with my blessing, providing, of course, that they're covering their nutritional needs. But I'm not dogmatic about it.  Although grains are not essential to a complete diet, I think a healthy diet can include grains, ideally, whole and minimally processed. 

More importantly, the total number of calories you consume needs to be in line with what you need to maintain (or achieve) a healthy body weight. To repeat an opinion I expressed in a recent post, I think maintaining a healthy body weight is ultimately more important than what percentage of the diet is protein, fat, or carbohydrate.

I'm sure you've got some opinions: Let's hear 'em!

Four steps to a longer healthier life?

A giant study (involving over 20,000 subjects over 8 years) looked at how four "healthy lifestyle habits" affected the risk of common diseases like heart disease and cancer. The four habits they chose to track?

1. Never smoking

2. Maintaining a BMI of 30 or lower (Calculate your BMI here.)

3. Engaging in at least 3 1/2 hours of physical activity per week

4. Eating a healthy diet, which was defined as one high in fruits, vegetables, and whole grains and low in meat. (Don't shoot the messenger!)

Less than 4% of the subjects had zero healthy behaviors. About twice as many (9%) could take credit for all four.  Here's what's making headlines: The Four-Behavior Group had:

• 93% lower risk of diabetes
• 81% lower risk of heart attack
• 50% lower risk of stroke
• 36% lower risk of cancer

Of course, this study was purely observational, and there may be (and probably ARE) other unmeasured variables that came into play. 

But, for what it's worth, the correlation between these four behaviors (especially in combination) and the risk of the four most common diseases is notable.  Note that diabetes appears to be almost three times more "responsive" to lifestyle than cancer.

It's also interesting that of the four factors, diet had the weakest effect on risk.  Avoiding obesity was the strongest factor, followed by never smoking, exercise, and (in last place) diet. Of course, that could have something to do with the way they defined "healthy" diet.

But it does underline something I've been saying a lot lately in comments and discussion on the blog.  I suspect that obesity has a stronger impact on health than the details of dietary composition. In other words, it's an oversimplification to say that a certain diet (low-fat, low-carb, whatever) is healthier than another.  Whatever diet (within reason) helps you achieve and maintain a healthy body weight has my vote. And, obviously, we're not all the same.

Just for kicks, how do Nutrition Data readers stack up against the German subjects in this study?

Online Surveys & Market Research

Online Surveys & Market Research

Online Surveys & Market Research

Source: Archives of Internal Medicine