Slim Down, Speed Up

The lat­est re­search shows that boost­ing your GUT BAC­TE­RIA could be the key to your next PB, while RUN­NING CAN, IN TURN, IM­PROVE YOUR DI­GES­TIVE HEALTH. Han­nah Ebelthite, co-au­thor of The g plan Diet, ex­plains how to get the most from this vi­tal re­la­tion­shi

Runner's World (UK) - - IN THS ISSUE -

The new se­cret to get­ting lean and fast. It’s all about look­ing after what's on the in­side

You are a walk­ing – or run­ning – bac­te­ria colony. There are around 100 tril­lion mi­crobes, mostly bac­te­ria, liv­ing in and on your body, the ma­jor­ity in your large in­tes­tine. Bac­te­ria out­num­ber your own body cells by about 10:1. And their genes out­num­ber your genes by over 100:1. Col­lec­tively, they form your mi­cro­biome. But what, ex­actly, have they got to do with run­ning?

Quite a lot, sur­pris­ingly, be­cause these mi­crobes in your gut are not only es­sen­tial to your abil­ity to di­gest food, but they also pro­vide vi­tal nu­tri­ents and en­zymes, and are in­volved in me­tab­o­lism. They can al­ter the way you store fat, how you bal­ance your blood glu­cose lev­els and how you re­spond to hor­mones sig­nalling hunger and sati­ety. Your mi­cro­biome also pro­tects you against pathogens (agents of dis­ease), con­trols hor­mones and trains your im­mune sys­tem. (In fact, your gut has the largest num­ber of im­mune cells and the largest num­ber of hor­mone cells in the body). And, cru­cially, you can in­flu­ence how well it does these things.

Ev­ery­one’s mi­cro­biome is unique, like a fin­ger­print. We pick up our mother’s mi­cro­biome dur­ing birth. Then, as we go through life, it’s in flux, mod­er­ated by diet, life­style, stress, med­i­ca­tion, ex­er­cise and even fac­tors such as ex­po­sure to an­i­mals and dirt.

Only in the past decade have we had the knowl­edge and tech­nol­ogy – rapid gene-se­quenc­ing tech­niques – to iden­tify dif­fer­ent strains of bac­te­ria and what their func­tion might be. We know if your mi­cro­biome is out of bal­ance then di­ges­tive and weight is­sues, low mood and low im­mu­nity can re­sult. While it’s un­likely to be a straight­for­ward cause-and-ef­fect sit­u­a­tion, re­search has also found links be­tween poor gut flora and ir­ri­ta­ble bowel syn­drome (IBS), in­flam­ma­tory bowel dis­ease (IBD), obe­sity, type 2 di­a­betes, Parkin­son’s dis­ease, Alzheimer’s dis­ease, arthri­tis, car­dio­vas­cu­lar dis­ease, colon can­cer, de­pres­sion, anx­i­ety, autism, asthma, al­ler­gies and re­s­pi­ra­tory tract in­fec­tions (RTIS).

‘The real se­cret to how our bod­ies re­spond to dif­fer­ent foods lies in our mi­crobes, not our genes, as was al­ways thought,’ says Tim Spec­tor, pro­fes­sor of ge­netic epi­demi­ol­ogy at King’s Col­lege Lon­don and au­thor of The diet

Myth (W&N). ‘It’s why some peo­ple store carbs as fat more eas­ily than oth­ers, why some run­ners do bet­ter on a high-pro­tein diet or why some are pre­dis­posed to obe­sity. As we come to un­der­stand the com­plex­i­ties of this, we can do a lot more to tai­lor our di­ets and im­prove all as­pects of our health.’

Can bac­te­ria boost my run­ning?

‘A lot of run­ners come to see me be­cause they’re not get­ting the re­sults they want but can’t work out why,’ says Sarah Dana­her, a clin­i­cal and sports di­eti­tian based in North­ern Ire­land. ‘And one of the first things we’ll do is work on boost­ing their mi­cro­biome.’ Dana­her is not alone in tak­ing this ap­proach; the ex­pert con­sen­sus is that the right bal­ance of gut flora can im­prove run­ning per­for­mance. The ex­act mech­a­nisms are yet to be fully un­der­stood, but it’s likely we’re look­ing at a host of in­di­rect ef­fects that equal a per­for­mance ben­e­fit.

Re­search at Na­tional Tai­wan Sport Univer­sity, pub­lished in the Jour­nal of Strength and con­di­tion­ing re­search, looked at the ef­fect of gut mi­crobes on ex­er­cise per­for­mance in mice. The study found those with nor­mal gut bac­te­ria fared bet­ter in a time-to-ex­haus­tion swim­ming test, while those ster­ilised to have no gut bac­te­ria per­formed the worst. The re­searchers sug­gest me­tab­o­lism and an­tiox­i­dant re­sponse may be key.

Last year, a large re­view by sci­en­tists at Shang­hai Univer­sity of Sport, pub­lished in the Jour­nal of sport and health sci­ence, looked to iden­tify more closely the re­la­tion­ship be­tween en­durance ex­er­cise and the mi­cro­biome, par­tic­u­larly at what role a healthy mi­cro­biome might play in adap­ta­tions to ex­er­cise. The re­view looked at 33 pa­pers pub­lished since 2007 and con­cluded that the mi­cro­biome may play a key role in con­trol­ling ox­ida­tive stress and in­flam­ma­tory re­sponses, as well as im­prov­ing en­ergy ex­pen­di­ture, hy­dra­tion and me­tab­o­lism dur­ing in­tense ex­er­cise.

‘ We know a healthy mi­cro­biome has a pos­i­tive ef­fect on im­mu­nity and in­flam­ma­tion, as well as en­ergy re­lease,’ says Spec­tor. ‘This will ben­e­fit the run­ner in both the short and long term, con­tribut­ing to a bet­ter run as well as im­proved re­cov­ery and faster fit­ness gains.’


With bet­ter im­mu­nity, run­ners are also less likely to suf­fer from re­s­pi­ra­tory tract in­fec­tions, as well as tummy bugs and other GI prob­lems that can trash our train­ing.

What about the other ‘runs’?

While we run­ners spend plenty of time think­ing about the di­ges­tive per­ils of our sport, like those dreaded midrun bowel re­bel­lions, re­search sug­gests that in the longer term ex­er­cise can pro­duce a health­ier, more di­verse mi­cro­biome and, with this, all the knock-on ef­fects on not just di­ges­tion but also mood, im­mu­nity, chronic dis­ease risk and more.

A re­cent study pub­lished in the jour­nal Gut, which com­pared 40 pro­fes­sional ath­letes with or­di­nary, healthy men, found that the ath­letes had a sig­nif­i­cantly higher di­ver­sity of gut mi­crobes, in­clud­ing bac­te­ria as­so­ci­ated with lower rates of obe­sity and obe­sity-re­lated dis­or­ders. This pro­vides ev­i­dence for the ef­fect of ex­er­cise on the mi­cro­biome – al­though, as Spec­tor points out, the re­la­tion­ship was likely to be com­plex and in­flu­enced by the healthy di­ets fol­lowed by elite sports­peo­ple.

Other stud­ies in Spain and at the Univer­sity of Colorado in the US have found in­creas­ing mod­er­ate-ex­er­cise fre­quency in hu­mans has a ben­e­fi­cial ef­fect on gut bac­te­ria, in­creas­ing di­ver­sity of ben­e­fi­cial strains. Sim­i­lar re­sults have been found in rat and mice stud­ies.

‘ We don’t know enough yet to pre­scribe cer­tain types of ex­er­cise; suf­fice to say that there’s an all-round ben­e­fit to be­ing ac­tive,’

says Spec­tor. And it’s a two-way street: run to boost your mi­cro­biome, boost your mi­cro­biome to im­prove your adap­ta­tion to run­ning.

That may not sit com­fort­ably with run­ners who find them­selves dou­bled up with cramps dur­ing or after a run, or who spend the hours be­fore a race in the queue for the por­ta­ble toi­lets. But build­ing a bet­ter mi­cro­biome is the best ap­proach to these gut gripes, too – what­ever their cause. ‘Run­ners are known for gas­troin­testi­nal is­sues, par­tic­u­larly those that push them­selves harder for dis­tance or times,’ says Pro­fes­sor Peter Whor­well, con­sul­tant gas­tro en­terol­o­gist and au­thor of Take con­trol of you ribs( Ver­mil­ion ). ‘Marathon­ers of­ten com­plain of loose bow­els, not just when run­ning, but all the time. It’s of­ten the case that they have ir­ri­ta­ble bowel syn­drome (IBS), per­haps with­out know­ing, and vig­or­ous ex­er­cise makes it worse.’

IBS is a tricky con­di­tion for run­ners, as stress is also a com­mon trig­ger. ‘So if go­ing for a run de-stresses you, then it can be a help­ful part of treat­ment,’ says Whor­well. ‘But if you’re stressed out be­fore a race or a hard train­ing ses­sion, that can ag­gra­vate IBS. Mod­er­ate run­ning is usu­ally fine for IBS and may even help it. If you have con­sti­pa­tion, more vig­or­ous ex­er­cise (faster or longer run­ning) can be use­ful. If you have loose IBS it’s best avoided.’

As a run­ner, your di­ges­tive sys­tem may be par­tic­u­larly sen­si­tive to the phys­i­cal jolt­ing of run­ning, or you may be sen­si­tive to the spe­cial­ist drinks or food you’re tak­ing on board to fuel your ef­forts. ‘Avoid prod­ucts con­tain­ing fruc­tose or ar­ti­fi­cial sweet­en­ers, known to cause up­set,’ says Whor­well. ‘Ad­just your meal tim­ings and try self-hyp­no­sis and med­i­ta­tion to calm nerves.’

Run­ning has also been linked to ‘leaky gut syn­drome’. ‘This is a con­tro­ver­sial area but the con­di­tion does ex­ist,’ says Whor­well. ‘The gut can be­come more per­me­able after an in­fec­tion and let po­ten­tially harm­ful food anti­gens and bac­te­ria into the blood­stream. This can also hap­pen due to stress and, it’s thought, ex­er­cise – al­though only in the short term.’

Could pro­bi­otics be the an­swer?

Re­search pub­lished in the Euro­pean­jour­nal

ofap­plied­phys­i­ol­ogy sug­gested tak­ing pro­bi­otics – sup­ple­ments con­tain­ing live bac­te­ria – not only re­duced gut per­me­abil­ity but in­creased the time it took run­ners to fa­tigue when train­ing in hot tem­per­a­tures. An­other, pub­lished in the Bri­tishjour­nalof

Sportsmedicine, found dis­tance run­ners given a pro­bi­otic sup­ple­ment for a month re­ported less than half the num­ber of days of re­s­pi­ra­tory symp­toms than a con­trol group. Other re­search has sug­gested that pro­bi­otics may help re­duce in­flam­ma­tion, ox­ida­tive stress and gas­troin­testi­nal ill­ness in ac­tive peo­ple. So they have an in­di­rect rather than er­gogenic ef­fect.

How­ever, many ex­perts ques­tion whether pro­bi­otic supps can re­ally of­fer a magic bul­let to the guts – at least for now. The dif­fi­culty is know­ing which strains of bac­te­ria a pill or pow­der con­tains, and which your mi­cro­biome lacks, in what amounts, and if they can sur­vive the jour­ney to your gut.

‘Be­cause ev­ery­one’s mi­cro­biome is unique, there’s no one-size-fits-all ap­proach to sup­ple­ment­ing,’ ex­plains Spec­tor. ‘In the fu­ture, we can ex­pect be­spoke pro­bi­otic med­i­ca­tion and my goal is for­mu­la­tions to fight obe­sity or other dis­eases.’


For now, though? Save your money and con­cen­trate on your diet first (See The top 10 foods to eat if you want a healthy gut, p 60).

How can I boost my mi­cro­biome?

‘ Whether you want to deal with di­ges­tive is­sues or low im­mu­nity, or sim­ply get your­self in the best pos­si­ble shape to run bet­ter, show your mi­crobes some TLC – and the ben­e­fits will cas­cade from that,’ says Dana­her. But how, pre­cisely can you ap­ply that TLC? I wrote The g plan diet with nu­tri­tion­ist Amanda Hamil­ton to give peo­ple a prac­ti­cal guide to reap­ing the ben­e­fits of all the lat­est gut-health re­search. We know a healthy mi­cro­biome is plen­ti­ful and var­ied, so how do we in­crease our own di­ver­sity? We de­vised a 21-day plan de­signed to boost your di­ges­tive sys­tem, in­crease the num­ber and di­ver­sity of your gut mi­crobes and guide you into bet­ter eat­ing habits for life. Here are some guid­ing prin­ci­ples you can take from it:

GO FOR VA­RI­ETY. Our bod­ies thrive on real food and di­ver­sity. Yet the West­ern diet, based around pro­cessed con­ve­nience food and drinks, is very lim­ited. Many of us eat as few as six or seven meals on ro­ta­tion and fail to get our five – or should that be 10? – a day of fruit and veg­eta­bles. Dana­her says a com­mon prob­lem is run­ners fol­low­ing faddy di­ets and there­fore cut­ting out foods their mi­cro­biome needs.

‘The surest route to an abun­dant and di­verse mi­cro­biome is a di­verse diet,’ Spec­tor agrees: ‘Run­ners can be guilty of get­ting into cer­tain, lim­ited di­etary habits they think work for them. Branch­ing out and en­joy­ing a much wider range of foods is a very good start.’

From a weight-loss/management per­spec­tive, re­search shows that di­eters who eat a greater va­ri­ety of healthy foods are more likely to lose weight and fat long term and less likely to de­velop meta­bolic syn­drome (as­so­ci­ated with type 2 di­a­betes and heart dis­ease). So, choose a rain­bow of fruit and veg, try new foods and flavours, and eat sea­son­ally. Each time you pre­pare a meal, think, ‘What else could I add?’ Then up the di­ver­sity with some sprouted seeds, some ex­tra veg, a side of pick­les.

CHOOSE UN­PRO­CESSED. Va­ri­ety doesn’t mean ex­tra wings with your de­liv­ery pizza. Pro­cessed foods, take­aways and ready meals do our guts no favours. Very of­ten high in sugar, salt, trans or sat­u­rated fats, ad­di­tives and preser­va­tives, they’re also much lower on the nu­tri­tional scale than real foods. Re­fined, white starchy carbs such as white flour, bread, pasta and rice of­fer much less for the mi­cro­biome than their whole­grain al­ter­na­tives. Avoid them and you au­to­mat­i­cally avoid foods such as pas­tries, cakes and bis­cuits. Sugar sup­presses ben­e­fi­cial bac­te­ria and can al­low un­healthy mi­crobes to take over. Ar­ti­fi­cial sweet­en­ers are equally un­help­ful to gut health.

‘I can see why run­ners go for the in­stant fix of glu­cose-based drinks, gels and bars,’ says Spec­tor. ‘But try­ing to wean your­self off pro­cessed en­ergy foods and drinks and onto real food for fuel will ben­e­fit your di­ges­tion, over­all health and per­for­mance.’

FEED YOUR GUT. What you eat doesn’t just feed you, it feeds your mi­crobes, too. Make sure your diet in­cludes plenty of pre­bi­otics. These are foods made up of a form of in­di­gestible fi­bre. They end up in the large in­tes­tine, where they pro­vide a feast for wait­ing mi­crobes. Think of them as fer­tiliser that helps your friendly bac­te­ria to grow. Fi­brous fruit and veg­eta­bles are top sources, as are whole­grains, pulses, nuts and seeds. Whor­well does cau­tion that some peo­ple with IBS need to fol­low a lower fi­bre diet with­out fer­mentable carbs. If you re­act to these sorts of foods, ask a di­eti­tian about the FODMAPS diet, which avoids them.)

GET FER­MENT­ING. Fer­mented food and drinks con­tain live bac­te­ria and yeasts – pro­bi­otics that sur­vive the di­ges­tive tract and help to in­crease the pop­u­la­tion and ac­tiv­ity of the mi­cro­biome. There are many ways to en­joy fer­mented prod­ucts and they’re be­com­ing fash­ion­able as the health ben­e­fits are more widely re­ported. Get your fill of nat­u­ral yo­ghurt, ke­fir, fer­mented veg­eta­bles or pick­les and kom­bucha. Even aged, un­pastuerised cheese and red wine have their ben­e­fits.

The g plan diet by Amanda Hamil­ton and Han­nah Ebelthite is out now ( Aster, £ 8.99), along with The G Plan app (£ 2.99, itunes/ Google Play). For £ 85 you can par­tic­i­pate in Pro­fes­sor Spec­tor’s Bri­tish Gut Pro­ject, which gives you a ba­sic over­view of your mi­cro­biome ( via a stool test). Visit

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