Feel bet­ter go­ing gluten-free? Fruc­tans may be the is­sue

The Idaho Statesman (Sunday) - - EXPLORE - BY CAR­RIE DEN­NETT Wash­ing­ton Post

Amer­i­cans love to des­ig­nate di­etary devils. MSG. Fat. Carbs. Gluten. The lat­est food to be nom­i­nated for dev­il­hood is fruc­tans. And the fo­cus on them came about, in part, be­cause of our ob­ses­sion with gluten.

Here’s how: We know that many peo­ple who fol­low a gluten-free diet don’t need to for med­i­cal rea­sons, such as hav­ing celiac dis­ease. Yet some in­sist they aren’t go­ing gluten-free be­cause it’s trendy – they’re go­ing gluten-free be­cause it makes them feel bet­ter. Many re­searchers be­lieve th­ese peo­ple who think they can’t tol­er­ate gluten are ac­tu­ally sen­si­tive to fruc­tans.

Fruc­tans are a type of car­bo­hy­drate com­posed of chains of fruc­tose, the sim­ple sugar found in honey and fruit. Amer­i­cans en­counter fruc­tans most com­monly in wheat and onions, but they are also found in rye, oats, bar­ley, ar­ti­chokes, as­para­gus, leeks, gar­lic and let­tuce.

Hu­mans have lim­ited abil­ity to di­gest fruc­tans in the small in­tes­tine. That means they’re still in­tact when they reach the large in­tes­tine (colon), where gut bac­te­ria break them down. In some peo­ple, this fer­men­ta­tion cre­ates excessive gas and bloat­ing, and some­times di­ar­rhea. Avoid­ing th­ese symp­toms means lim­it­ing daily in­take of fruc­tans, al­though the an­swer to “how much is too much” varies from per­son to per­son.

Just as we don’t all need to avoid gluten, we don’t all need to avoid fruc­tans. Still, some peo­ple try to do just that, rea­son­ing that if some peo­ple re­act badly to fruc­tans, per­haps ev­ery­one should avoid them. And then there are those who con­fuse fruc­tose, a dif­fer­ent car­bo­hy­drate, with fruc­tans. (Fear of fruc­tose also has prompted peo­ple to not only es­chew corn syrup, but to also shun fruit, de­spite the fact that it’s a whole, nu­tri­ent-rich food.)

For most peo­ple, fruc­tans have ben­e­fits for gut health and gen­eral health. Three ma­jor types of fruc­tans –

in­ulin, oligofruc­tose and fructo-oligosac­cha­rides – are pre­bi­otics, food com­po­nents that nour­ish the ben­e­fi­cial bac­te­ria in our gut mi­cro­biota. Re­searchers are also find­ing that fruc­tans may have an­tiox­i­dant ben­e­fits, and con­trib­ute to healthy blood-sugar lev­els and im­mune sys­tem func­tion. No won­der in­ulin is added to so many foods as a “func­tional fiber.”

When you con­sider that wheat is a ma­jor source of gluten (a pro­tein that helps make dough elas­tic), and also con­trib­utes about 70 per­cent of the fruc­tans in the Amer­i­can diet, it’s easy to un­der­stand why some­one who feels bet­ter af­ter elim­i­nat­ing wheat might con­clude that they’ve iden­ti­fied a gluten in­tol­er­ance. How­ever, avoid­ing wheat and other gluten sources when fruc­tans are the culprit is an in­com­plete so­lu­tion, be­cause symp­toms will prob­a­bly oc­cur when other fruc­tan-rich foods are eaten.

One difficulty with di­ag­nos­ing food sen­si­tiv­i­ties is that the food com­po­nents that pro­voke them don’t ex­ist in iso­la­tion. They are part of a com­plex ma­trix with nu­mer­ous other food com­po­nents that could po­ten­tially cause an ad­verse re­ac­tion in some in­di­vid­u­als. For most peo­ple, wheat is a nu­tri­tious food. But for the mi­nor­ity who re­act to wheat, any one or more of the grain’s many com­po­nents – not just fruc­tans and gluten, for ex­am­ple, but non-gluten pro­teins – could be the culprit. A sec­ond difficulty is that, un­like with celiac dis­ease and wheat al­ler­gies, there is no sci­en­tif­i­cally valid way to test for most food sen­si­tiv­i­ties.

Peo­ple with celiac dis­ease need to avoid gluten, which is also found in rye and bar­ley, and peo­ple with wheat al­ler­gies need to avoid wheat, but peo­ple with what is termed as non-celiac gluten/wheat sen­si­tiv­ity are in a di­etary gray area. A group of re­searchers from Nor­way ran­domly as­signed 59 peo­ple, who did not have celiac dis­ease but were avoid­ing gluten be­cause they thought they had a gluten sen­si­tiv­ity, to eat baked muesli bars con­tain­ing gluten, fruc­tans or nei­ther – the placebo bar – for seven days. The study was dou­ble-blind, so nei­ther the par­tic­i­pants nor the re­searchers knew which bars were which dur­ing the ac­tive por­tion of the study. The results, pub­lished in Fe­bru­ary in the jour­nal Gas­troen­terol­ogy, showed fruc­tans were ac­tu­ally more likely to pro­duce symp­toms than gluten: Thir­teen par­tic­i­pants ex­pe­ri­enced the worst symp­toms af­ter eat­ing the bars with gluten, while 24 re­ported feel­ing worse af­ter eat­ing the fruc­tan-rich bars. In­ter­est­ingly, 22 said the placebo bars both­ered them most.

So how can some­one find out whether they’re fruc­tan in­tol­er­ant? Breath test­ing is one pos­si­ble op­tion, but its re­li­a­bil­ity is un­cer­tain. Some peo­ple have luck with elim­i­nat­ing all di­etary fruc­tans for a few weeks, then, if symp­toms go away, adding back non-wheat sources of fruc­tans. If symp­toms re­turn, it’s likely the fruc­tans, not wheat.

This is where seek­ing the guid­ance of a di­eti­tian who is ex­pe­ri­enced with food in­tol­er­ances is help­ful, es­pe­cially be­cause fruc­tans are one of many types of di­etary car­bo­hy­drates that may cause symp­toms in peo­ple with ir­ri­ta­ble bowel syn­drome (IBS). Like fruc­tans, fruc­tose, lac­tose and sugar al­co­hols such as sor­bitol and xyl­i­tol, are highly fer­mentable in the large in­tes­tine, lead­ing to gas, painful bloat­ing and di­ar­rhea, con­sti­pa­tion or both. Th­ese carbs are col­lec­tively known un­der the acro­nym FODMAPS – fer­mentable oligo-, diand monosac­cha­rides and poly­ols (fruc­tans fall into the oligosac­cha­ride camp).

Rather than avoid­ing a whole class of food, it’s bet­ter to de­ter­mine ex­actly which food com­po­nents – and their hid­den sources – you need to elim­i­nate to stay symp­tom-free. The ul­ti­mate goal is to en­joy as var­ied a diet as pos­si­ble.

Den­nett is a reg­is­tered di­eti­tian nu­tri­tion­ist.

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