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Effects of Peeling or Cooking on FODMAPs in Fruits and Vegetables?

Does peeling, cooking or pureeing fruits and vegetables change the FODMAP content? Short version: this common questions does not have a good answer at this time.

Traditional nutrient database show little difference between cooked and raw fruits and vegetables. Published data from more complete FODMAP analysis has not yet explored many of these subtler variations in fruit and vegetable preparation.

It makes sense that peeling and cooking would affect certain FODMAPs in food, but there isn't enough info to be specific except in a couple of cases. We know that fructans in vegetables are water soluble and leach out into the cooking water, which is why onions and garlic in a soup or stew are potential problems even if you pick them out. We don't know specifically how many grams change, though. This effect could be useful for vegetables like broccoli and cabbage, I would think, suggesting that boiled and drained vegetables would have less fructans than raw or sauteed, but there is no data to prove it.

Peeled v. unpeeled apples and pears were analyzed in two studies by researchers at Monash University, Australia. Overall, peeled apples and pears by % weight actually had slightly more fructose than unpeeled (we might conclude fructose must be in the flesh of the fruit rather than the peel). Two varieties of apples were analyzed for polyols, peeled v. unpeeled . Peeled Granny Smith's had slightly more sorbitol than unpeeled. Peeled Pink Lady's had slightly less sorbitol than unpeeled. No generalization can be drawn, apparently. I have not seen any FODMAP data on cooked v. uncooked fruits.

It is hard to imagine any way that pureeing would change the fructose or polyol composition of fruits or vegetables. I am not aware of any specific data about whether pureeing can break down fructans in vegetables. My guess is that it can't break the molecular bonds of fructose links in fructans. Even if it could, would that be an advantage? Breaking down fructans, for example, would just mean the puree would be higher in fructose, which is also a FODMAP! (Might be helpful for someone without fructose malabsortion.)

What about food preparation methods that involve fermentation? Theoretically, the bacteria and/or yeast in fermented food could reduce the FODMAP content of the food before you eat it (instead of after you eat it, in your gut!). So far, we know that sourdough breads have less fructans than breads leavened with baker's yeast. The traditional two-day sourdough fermentation is what counts, not the word "sourdough" in the name or the flavor of the bread. These will usually be artisan breads from specialty bakeries. One clue to identifying a bread made by the sourdough process: there will be no baker's yeast in the list of ingredients.

Those are my thoughts on the subject, what about yours?

Updated 12/17/2012

We're Jammin'

When you need a little something sweet, what jams or jellies are FODMAPS-friendly? There are three things to consider: the fruit, the sweetener, and the total grams of sugar. Check the ingredients.

The fruit should be tart: blueberries, raspberries, strawberries, lemon.

The sweetener should be sugar or regular corn syrup (not high-fructose corn syrup).

The total grams of sugar per serving should not exceed 40 grams.

Make your own, or look for upscale or imported brands such as Stonewall Kitchen, Hero or Bonne Maman; there are many varieties that might work for you! Cheaper brands tend to be sweetened with high-fructose corn syrup. As usual, read the ingredients on the label before you buy, in case the manufacturer has made last minute changes.

For more information about the FODMAPS elimination diet, see IBS--Free at Last!, by Patsy Catsos, MS, RD, LD.

FODMAPS--Inconsistent Facts?

If you've done much searching about on the internet or in the medical literature to learn about FODMAPS, you may have noticed some inconsistencies regarding whether certain fruits and vegetables are "allowed" or "not allowed" on a FODMAPS elimination diet.

Remember having more fructose than glucose in a food can contribute to fructose malabsorption. Some fruits and vegetables contain sugar alchohols (polyols) such as mannitol or sorbitol. These foods are "not allowed" or considered "unfavorable" during the elimination phase of the diet. Why the confusion about some fruits and vegetables?

• Sugar and polyol content of produce can vary depending on ripeness--think about your last over or under-ripe banana, and you can easily picture this.
• Sugar and polyol content of produce can vary depending on the variety--think of all the different varietals of grapes grown for wine-making or the many varieties of apples for sale in your local grocery store; other fruits and vegetables have many varieties as well.
• Growing conditions during a season vary from one to the next.
• Methodology for measuring sugars and sugar alcohols has changed over the years.

Information sources might differ for any of the above reasons. Don't drive yourself mad trying to sort this type of discrepancy--any fruits that are that close to the line aren't likely to be the worst offenders when it comes to provoking symptoms due to FODMAPS, anyway. Just remember to keep the portion sizes of fruit small, even the allowed fruits--when in doubt, less than 1/2 cup.

Polyols 101

Many of my clients tell me that even a few small pieces of sugar-free candy or gum cause diarrhea. Ditto for the well-know effect of prunes or cherries. What do these foods have in common? They contain polyols, also known as "sugar alcohols".

Technically, they are FODMAPS carbohydrates, and they are sweet! Most polyols are poorly absorbed, and wind up in the large intestine when they are consumed. In the large intestine, polyols are fermented by gut bacteria. They are also capable of drawing water into the large intestine. Together, the excess gas and excess fluid can cause distension of the colon, which cause bloating, flatulence and looser stools for the IBS sufferer. In a double whammy, eating or drinking sugar alcohols worsens fructose intolerance!

Some sugar alcohols, such as sorbitol, occur naturally in fruits such as apples, pears, and the "stone fruits," which include plums, prunes, apricots, peaches, cherries and so on. Sugar alcohols are often used to sweeten "sugar-free" foods (such as candy, gum, low-carb items, and bubbly water) and liquid medications. They can be recognized on the food label's list of ingredients by the ending "-ol". Examples are xylitol and maltitol.

Note that erythritol seems to be an exception. Studies have shown it is well absorbed and unlikely to cause GI symptoms.

Which Tomato Products are FODMAPS-Friendly?

Fresh tomatoes contain fructose in very small amounts. They are FODMAPS-friendly. However, when tomatoes are processed into tomato paste, the fructose is concentrated a great deal. According to one of my favorite references, Cook's Thesaurus, just 1tablespoon of tomato paste is equivalent to 1 medium tomato! So tomato paste is NOT allowed during the elimination phase of a FODMAPS-elimination diet. Depending where you are in the world, tomato paste may be called tomato puree or tomato concentrate, so check food labels for all these terms.

Check the nutrition facts on the label to see how the product compares to fresh tomatoes (2 grams sugar per 1/2 cup) versus tomato paste (16 grams sugar per 1/2 cup). This tip assumes the product has no sugar added as an ingredient, and that the sugar listed on the nutrition facts panel is all coming from the natural sugars in the tomato.

After reading the label, if you're still not sure whether the tomato product you have is OK to eat during the elimination phase, you may have to open the can and look inside. Whole canned tomatoes or diced canned tomatoes with watery-looking juice in the can are OK to eat during the elimination phase of the diet. If the juice in the can is thicker than water, transfer the contents to a a freezer-safe container, stash in the freezer, and wait until the fructose challenge phase to eat this tomato product.

Fructose 101

Fructose is known as "fruit sugar". It is present in fruits, some vegetables, honey, granulated sugar, agave syrup and high-fructose corn syrup. In the past, the human diet was lower in fructose than it is today--think of how hard it was to get honey in the wild, for example, or what a treat it would have been in the past to have fruit out of season, much less a never-ending supply of ketchup, cookies, candy and other sweets. Now it seems as though fructose is everywhere in our food supply.

Our capacity to absorb fructose is easily overwhelmed; it is almost considered normal to experience abdominal pain, flatulence, bloating or diarrhea when we overdo the amount of fruit or fruit juice we consume--many people have experienced this phenomenon. But some of us experience symptoms with much smaller intakes of fructose. And most of us overlook the impact that large portions of sugary sweets, baked goods and soft drinks can have. And what about those honey or fruit juice concentrate-sweetened energy bars? Interestingly, apples are part of the traditional BRAT diet sometimes recommended to fight diarrhea. Umm...maybe apples and apple juice aren't such a good idea for some people with diarrhea.

Diagnostic dietary fructose intolerance tests are available, but are not ordered as frequently in the US as they are elsewhere. If you suspect you don't tolerate fructose very well, try cutting back on soft drink and other sweets. Limit tomato paste. Choose small portions of fruits that are lower in fructose, such as kiwi, berries, citrus fruits, and bananas. Read labels, and avoid or limit portion sizes of foods sweetened with honey, fructose, high-fructose corn syrup, agave syrup and fruit juice concentrates.  See if you feel better!

Fructose malabsorption can occur on its own, or it can be part of the larger IBS picture.The FODMAPS elimination diet in IBS--Free at Last! can help you figure out how fructose fits into your IBS scenario.

It is important to distinguish dietary fructose intolerance, described in this posting, from hereditary fructose intolerance, which is a serious, hereditary disorder requiring a truly fructose-free diet.

Click here for more details about dietary fructose intolerance and how it causes GI symptoms.

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Fructose Malabsorption and Fructose:Glucose Ratio

What's up with the fructose:glucose ratio? If I experience dietary fructose intolerance, why can I tolerate fructose better if there is an equal amount of fructose in the meal?

First, let's recall the context here: the goal is to manage gastrointestinal symptoms, not to eliminate fructose, per se, from the diet. That's just not necessary (unless one has hereditary fructose intolerance, another subject entirely). Next, recall that high fructose foods include many fruits, honey, and sweetening ingredients such as high fructose corn syrup, crystalline fructose, and fruit juice concentrates.

The ability of the small intestine to absorb fructose is limited, at best. This was less of a problem years ago, when our intake of fructose was also limited! As recently as 30 years ago, the average U.S. intake of fructose was only 2/3 of what is is today, due to changes in the food supply. Imagine the distant past, when honey would have been a rare sweet treat, requiring feats of courage and strength to obtain. Cane or beet sugar and a wide variety of fruits would not have been available to most people in the world, except on rare occasions. Now, our diets contain lots of fructose, although over half of us can't fully absorb a 50 gram serving of fructose. Any time you are eating fructose faster than your personal ability to absorb it, the unabsorbed fructose will be carried on into the large intestine, where it is fermented by the resident bacteria, causing gas, bloating and altered bowel habits.

It appears there are probably two way fructose is absorbed through the cell walls of the small intestine. The first way is a low-capacity type of diffusion, in which a fructose molecule can pass through the cell wall on its own. The second mechanism is transport system that only works when there is one glucose molecule available for every fructose molecule. If there is no glucose-fructose pair, there is no absorption.

This explains why granulated sugar, which contains an equal amount of glucose and fructose is well tolerated in moderation, even by fructose intolerant individuals. Also, fruits such as berries, certain melons, and citrus fruits, which do not have an excess of fructose compared to glucose, can be tolerated in small servings. The fructose intolerant individual could still experience symptoms if very large portions of these "allowed" foods or beverages are consumed.

If you learn that you have dietary fructose intolerance, but would still like to consume high fructose foods, you might be able to do so if  you take a glucose/dextrose tablet along with the food, to improve the fructose:glucose ratio. These inexpensive tablets are sold at your local pharmacy along with diabetic supplies.

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