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.

Can better nutrition help small kids grow faster?

Q.  I have a 10 year old daughter who is small for her age and wants to grow and gain some weight. She eats well when she likes what is on the table, however she is kind of picky. She does not care for meat and doesn't eat many vegetables. She loves fruit and would live on pizza if we let her. She takes a multi-vitamin every day. I don't know what to do that would be healthy for her and help her grow. Should I give her a nutrition drink supplement?

A.  First, don't worry too much about your daughter's picky eating habits. It's very common for kids to shun vegetables in favor of pizza and still grow up strong and healthy.  Keep on doing what you can to encourage healthy eating habits without turning the family dinner table into a battle zone.

The truth is that your daughter's height is probably not a nutritional issue. Severe malnutrition can result in poor growth, but I'm fairly certain that this is not the case with your daughter.  Short of growth hormone injections (highly controversial) there's not too much you can do to affect her height, which is genetically programmed.

If, on the other hand, your daughter is underweight, getting more calories into her will help her gain weight.  Foods that are calorie-dense as well as nutrient dense can help. Whole milk, full fat yogurt and cottage cheese, cheese, peanut butter, dried fruit, and nuts are all nutritious, calorie-dense foods that she might enjoy.

I'm not a big fan of nutritional supplement drinks. They're usually very high in sugar (high-fructose corn syrup) and the vitamins and minerals they provide are all found in a multi-vitamin, which she's already taking. I think she'd be better off getting her calories from real food!  You could experiment to see if you can come up with a healthy "milkshake" to supplement her calorie intake. Try some whole milk, frozen bananas, cocoa powder, peanut butter, and a little honey.

Here are some more resources for you to explore.

Growth calculators. Here are a series of calculators that show you how your child's height, weight, and body mass compare to the norms. And here is a calculator that shows you a healthy weight for a child of a certain age and height.

Nutrition for Kids. Here are some previous posts on getting kids to eat healthy, getting kids to eat more vegetables, a recent episode of my weekly podcast focusing on kid's nutrition, and a n interview I did on the Ben Greenfield Fitness Podcast on the subject of kids, nutrition, and obesity

Calorie-dense foods. When you look up foods on ND, you'll see our Nutritional Target Map, which shows you how nutrient dense and how calorie-dense every food is.  Foods for healthy weight gain are those that are both, and they'll map in the lower right hand corner of the map.

People looking to lose weight usually want to select foods that fall in the upper right hand corner of the Nutritional Target Map. These are foods that are nutrient dense but not calorie dense.

For more on how to use the Nutritional Target Map, see our help page. Here is our Nutritional Map Search Tool.

Where do I find the potassium content of foods?

Q. My husband needs to reduce potassium/sodium levels in what he eats. I find the sodium levels but potassium is rarely listed. How do I find this?

A. Information about sodium is required on the nutrition facts label but information about potassium is optional--and many manufacturers don't include it.  The ingredient list won't contain many clues, either.  Products that are marketed as "heart-healthy" are more likely to list potassium content, by the way. Usually, these are foods that are relatively high in potassium and low in sodium.

You can look up the potassium content of foods here on ND, of course. Simply scroll down to the Nutrient Information box on any food detail page to see the amount of potassium that food contains. (Remember to select the appropriate serving size at the top of the page.) You can also use our nutrient search tool to research which foods are highest and lowest in potassium and sodium. 

In general, fruits and vegetables are the richest sources of dietary potassium. The average person eats about 3,000 mg of potassium a day. People with the highest intake of fruits and vegetables take in 4 or 5 times as much.

Fruits and vegetables that are particularly high in potassium include beet greens and spinach, potatoes, lima beans, green soybeans (edamame), bananas, prunes and prune juice, acorn squash, tomato juice, and raisins.  

Fruits and veggies for a low potassium diet

Of course, fruits and vegetables are among the healthiest foods that you can eat--which creates a bit of a dilemma for those who need to restrict potassium.  Fruits and vegetables that are relatively low in potassium include turnips and turnip greens, Napa cabbage, bean sprouts, leeks, pears, blueberries, cranberries, and apples. Cooking (and draining) vegetables and fruits can also remove up to 70% of the potassium--although other nutrients are lost as well. 

Hope that helps!

Phytoestrogens: Helpful or harmful?

Q. I consume about 1-2.5 tbsp of ground flaxseeds per day. I know from my symptoms (breast tenderness etc) that I have a bit of estrogen dominance. Could the phytoestrogens be negatively impacting my estrogen balance?

A. Does flax contain phytoestrogens? Yes.  In fact, flax seeds are a more potent source of phytoestrogens than soybeans. Is the ground flax causing your symptoms? Hard to say.

The whole issue of phytoestrogens (estrogen-like compounds found in plant sources including soy and flax) continues to bedevil researchers. Do they block the effects of estrogen, thereby protecting against things like breast cancer? Or, do they exert weak estrogenic effects, thereby protecting against things like heart disease and osteoporosis? Both? Sometimes one and sometimes the other?

Despite copious research, we still don't have a definitive answer on how phytoestrogens behave in the human body and why.  

Searching for clues in a sea of conflicting and confounding information, it appears that phytoestrogens probably don't do much for hot flashes but may help preserve bone density and reduce risk of heart disease.  The findings on cancer are even less conclusive. Phytoestrogens may protect some people against cancer,  but those with hormone-sensitive cancers are usually advised to avoid them. 

I have fewer concerns about whole foods like flaxseed and soybeans than I do about supplements which extract, isolate, and concentrate the bioactive compounds.

Returning to your question: I don't know if your symptoms are due to "estrogen dominance" or not. But the easiest way to find out whether flaxseed is contributing to them might be to stop eating flax for several weeks (try to keep everything else about your diet the same) and see if you notice any improvement.

Health benefits of sourdough?

Q. I use homemade whole-grain sourdough daily. I am totally convinced it has exceptional health benefits. But I can't find nutritional info on it. It seems to me that it has to have probiotics, for instance.

A.   Sourdough starter does contain lactobacillus bacteria, often referred to as probiotics. It's the lactobacillus that give sourdough its characteristic sour flavor. But it's hard to say for sure which strains are present in a sourdough without laboratory analysis. The sourdough in my kitchen probably has different strains than the one in yours, for example. And different strains of lactobacillus offer varying health benefits, as discussed in this recent post on probiotics.

But whatever beneficial bacteria may be present in your sourdough starter, they will probably be destroyed by cooking. Most lactobacillus bacteria are only viable to about 112 degrees F.  So while sourdough starter could be considered a probiotic food, sourdough bread would not.

Another potential health benefit of sourdough is that the bacteria partially "digest" some of the starches and sugars in the grains.  As a result, sourdough bread appears to cause less of an increase in blood sugar than yeast breads. (Here's a link to the study.)

In terms of the relative nutritional value of sourdough, the biggest factor is probably whether it's made with refined or whole-grain flour. And, although whole-grain sourdough may be healthier than regular white bread, it is still basically bread. I wouldn't eat it in unlimited quantities!

For more on the science of sourdough, see this article.

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Can you absorb fat-soluble vitamin D from skim milk?

Q. I recently read that Vitamins A, D, E, and K are fat soluble, meaning that they dissolve in fat instead of water. Does this mean that these vitamins need to be eaten with some type of fat source for the body to absorb them? For instance, if somebody ingested just a cup of skim milk would any of the Vitamin D not be absorbed because of the lack of fat?

A. It's not so much that fat-soluble vitamins dissolve in fat, but that they are carried across the intestinal cell barrier by lipid (fat) molecules.  So, while it is true that fats are necessary for transport and absorption of fat-soluble vitamins, it doesn't take much!

A couple of years ago, there was a study that found that eating avocado with vegetables increased the absorption of fat-soluble beta-carotene from the vegetables. However, a study that looked specifically at vitamin D found that vitamin D was absorbed just as well from both skim milk and orange juice as it was from whole milk. (Maybe the fiber in the vegetables plays a role somehow?)

The most likely causes of fat-soluble vitamin deficiency includea missing or malfunctioning gall bladder, bariatric (weight loss surgery), intestinal resection, or other serious digestive diseases that interfere with absorption of fats.

High cholesterol no cause for worry?

Q. I am a 24-year-old female. I'm a normal weight (5'7", 133 lbs). I work out at least 5 days per week. I  avoid all processed food and generally try to fill my days with whole grains, veggies, fruits and non-fat dairy sources. I usually have a small amount of caffeine in the mornings, I don't smoke, and I drink two or three times per month. All in all, I think I lead a pretty healthy lifestyle. However, I went to my doctor last week and was surprised to find that my cholesterol is slightly high (more than 200 mg/dL). I don't have a family history of high cholesterol or heart disease.  Is this a common problem in people who lead otherwise healthy lifestyles? I'm hoping to avoid taking prescription meds for the rest of my life.

A. I think it's a little soon to be thinking about prescription meds for life!!  Given all you've reported here, you may not have anything to worry about.  For one thing, high cholesterol does not mean you have (or will develop) heart disease.  Although elevated cholesterol is statistically linked to a higher incidence of heart disease, many people who die of heart disease have normal cholesterol...and many people with elevated cholesterol never get heart disease.  Cholesterol tests are screening tools, not diagnostic ones.

Cholesterol is only one piece in a larger picture. Given the rest of the details you've given (normal weight, not sedentary, no family history of heart disease or high cholesterol, normal blood pressure), your statistical risk of developing heart disease in the next ten years is extremely small. 

I'm also wondering about the details of your cholesterol--specifically about the break-down of HDL ("good") and LDL ("bad") cholesterol.  Your total cholesterol may be high because your HDL is high, thanks to all your healthy habits.   I would think before prescribing medication, your doctor would follow up with a more comprehensive lipid panel. I'd give even odds that a retest would show normal cholesterol, anyway. The slightly high reading may well have been an anomaly.

Finally, it sounds as if your diet is very low in fat and fairly high in carbohydrates.  If you wanted to see if dietary modifications might nudge your cholesterol numbers in the right direction (although, again, I'm not sure you really have that much to worry about), you might try adjusting the balance of your diet to be a little higher in fat and lower in carbs, particularly grains. Olives, olive oil, almonds, and avocados (all rich in monounsaturated fats) would be good choices.

Let us know what happens next.

 

How much omega-3 is too much?

Q. Is there any upper limit as far as how many grams of omega 3 you can take? I'm aiming for an omega-6 to omega-3 ratio of 4:1.  As an example, if I ate 10g of omega 3 and 40g of omega 6, that's still in the 4:1 ratio but is 10g of omega-3 too much? What would be the upper limit?

A. There is no UL (tolerable upper limit) for omega-3 or omega-6 fatty acids (PUFAs).  The USDA feels it has "insufficient evidence" to set one. Instead, you might want to consider how much total fat you're going to eat and how you want to divide that up. For example, consuming large amounts of PUFAs might either cause you to miss out on the benefits of other fats, such as monounsaturated fats, or lead you to eat too much total fat.

Many experts recommend that PUFAs should make up 5-10% of your dietary calories and that seems reasonable to me.  The rest of your fat calories would come from monounsaturated fats like those found in olives and avocados and/or saturated fats from meat, dairy, and tropical oils.  Trans fats from hydrogenated oils and fried foods should ideally be kept to an absolute minimum.

In your example, you'd be eating 50g of PUFAs, for a total of 450 calories. Unless you're eating 4500 calories a day, that might be a little out of balance.  Without knowing the particulars of your situation, sounds as if you might want to think about ratcheting your intake of BOTH kinds of PUFAs back a bit.

Building your dietary fat "profile"

Here's how a healthy distribution of fats might look for a typical person eating 2500 calories a day:

30% of calories as fat = 83 g 

Of that:

    15% of calories from monounsaturated fat = 40g

    7% of calories from saturated fat = 20g

    7% of calories from polyunsaturated fats = 20g

To maintain a 4:1 ratio of omega-6 to omega-3, that would be 16g omega of omega 6 and 4g of omega 3.

Fish or flax?

As far as the dangers of taking too much omega-3, it depends whether you're talking about 10g of flax oil, which provides alpha-linolenic acid (ALA), or 10g of fish oil, which contains the much more biologically active forms of omega 3 (EPA and DHA). 

Ten grams of fish oil could potentially create some issues, such as interfering with blood-coagulation and immune function (not to mention digestive distress). Whether or not these might be concerns for you is a question for a licensed nutrition professional who knows the details of your situation.

       

   

Did the Dairy Council set the RDA for calcium?

Q. The RDA for calcium seems impossible to achieve unless someone eats dairy (or takes supplements), but considering that dairy has been part of the human diet for only a short period of time (and most people are lactose intolerant), how can our requirements really be that high? Is there scientific evidence that we need that much calcium or has the Dairy Council had a hand in the government's guidelines?

A. You mean, was there a conspiracy to get Americans to consume more dairy products by setting the recommendations for calcium intake higher than necessary? I wouldn't go that far (although I'm sure some would!).

The RDA for calcium reflects the realities of the typical Western diet

The RDA for calcium represents the amount that will meet the needs of most (97%) healthy individuals. They're taking into account not only the amount needed to prevent acute calcium deficiency but also to prevent long-term consequences like osteoporosis.

This is based on scientific research, of course. But most of that research is done on people who eat a typical Western diet--which is relatively high in both protein and sodium. Coffee and soft drinks (containing caffeine and phosphates) are frequently consumed.  All of these things can increase the body's calcium requirements.

The RDA for calcium reflects how much calcium it takes for someone with a typical Western diet to maintain adequate calcium stores.  Those on a lower protein or lower sodium diet might require less.

Non-dairy sources of calcium

Not only are dairy products some of the richest sources of dietary calcium, but the calcium in dairy is well absorbed by the body. But if you're not into dairy, canned salmon and sardines are great non-dairy sources. Tiny bones in the fish--so soft that they're simply consumed with the flesh--are what makes these fish good calcium sources.  Kale and collard greens are also good sources. A cup of collards has as much calcium as a cup of milk.

Probiotic confusion

Last week, I answered a question from a reader who had seen a study showing that probiotic supplements reduced cold and flu symptoms in children. He reasoned that eating yogurt every day might be a good step and wondered how much he'd have to eat to get a similar "dose" of probiotics.   To answer his question, I compared the number of active cultures in a typical probiotic supplement to the number of active cultures in a typical yogurt.

But I missed an opportunity to clarify what I think is a widespread misunderstanding about probiotics. Many people think of all probiotic supplements and foods as being somewhat interchangeable. They're not.

Probiotics: an umbrella term for thousands of different bacteria

In terms of labeling foods and supplements, the FAO/WHO defines probiotics as "Live microorganisms which when administered in adequate amounts confer a health benefit on the host."  That's any health benefit.

There are hundreds of different strains of lactobacillus bacteria and they offer a variety of potential health benefits to humans. Some colonize the large intestine, others live in the lining of the stomach, still others have an affinity for the mucus membranes in the nose.  Of the many strains likely to colonize the large intestine, for example, some may improve gut immune function, others digest complex sugars, others may benefit the host by producing vitamin K.

There are also lactobacillus bacteria that don't do much of anything to improve or defend your health. These, while harmless, would technically not be classified as probiotics--although they might still be considered "live and active cultures.". 

Foods versus supplements

Most probiotic foods contain a variety of bacterial strains--your average supermarket yogurt might contain six different bacterial strains. And the lactobacillus bacteria found in yogurt are not necessarily the same as those found in other fermented foods like kefir or kim-chi.

Many of the studies you read about use "boutique" strains that are not likely to be found in any traditionally-fermented foods. In the case of the study I mentioned above, for example, they used two trademarked strains called Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi-07.

Is there any point to consuming probiotic foods?

I still think there are general health benefits to eating traditionally-fermented foods like yogurt, kefir, kim-chi, kombucha, sauerkraut, and miso. Eating a variety of fermented foods, which provides a wider variety of bacterial strains, might offer a wider range of benefits.

But we need to be careful about assuming that the findings on a particular strain apply to all probiotics and probiotic foods.  If you're going for a specific therapeutic benefit, such as protecting against side effects while taking antibiotics or improving flu resistance, there's no guarantee that yogurt or any other fermented food will contain the same bacteria as were used in a particular study.

Similarly, when shopping for probiotic supplements, pay attention to the individual strains in that supplement and how they compare with the strains used in various studies you might be responding to.