As science dis­cov­ers that a diet clin­i­cally proven to con­trol high blood pres­sure could also fu­ture-proof your men­tal health, wh asks...

Women's Health Australia - - FRONT PAGE - By Vicky Spratt

Your at­ten­tion was prob­a­bly else­where in the late ’90s. Watch­ing the Wannabe mu­sic video on re­peat to de­cide which Spice Girl you were, or try­ing to work out if Leo and Kate could both have fit­ted on that float­ing door. Ei­ther way, you may have been too pre­oc­cu­pied to spot a study pub­lished in The New Eng­land Jour­nal of Medicine in 1997 about how a spe­cific way of eat­ing can sig­nif­i­cantly in­flu­ence blood pres­sure. The di­etary ap­proaches to stop hy­per­ten­sion (DASH, to its mates) diet was found to sub­stan­tially re­duce hy­per­ten­sion (hence the name), thanks to the re­duced fat con­sump­tion that came with an ap­proach rich in whole grains, fruit, veg and low-fat dairy. Cool story for any­one look­ing to re­duce their blood pres­sure stats. But also rel­e­vant for pretty much ev­ery­one else, be­cause – so says a grow­ing body of re­search – this niche ’90s diet could be the key to fu­ture­proof­ing your mind. Bet we’ve got your at­ten­tion now.

So why all the buzz? In April

2018, more than two decades af­ter DASH was first con­ceived, a study pre­sented to the Amer­i­can Academy of Neu­rol­ogy found that those who fol­lowed the ap­proach, or some­thing sim­i­lar, were less likely to de­velop de­pres­sion than those who didn’t. Con­versely, those same re­searchers from Rush Univer­sity Med­i­cal Cen­ter in Chicago found that the more closely par­tic­i­pants fol­lowed a typ­i­cal Western diet (high in sat­u­rated fat and red meat, low in fruit and ve­g­ies), the more likely they were to de­velop de­pres­sion. “This is a rel­a­tively small study that was ob­ser­va­tional in na­ture, so we can’t claim a cause­and-ef­fect re­la­tion­ship,” says Dr Lau­rel Che­rian, as­sis­tant pro­fes­sor in the Depart­ment of Neu­ro­log­i­cal Sciences at Rush and lead au­thor of the study. “I think the re­sults are one more piece in a larger puz­zle that is com­ing to­gether to show us that diet is a valu­able weapon in our arse­nal against de­pres­sion.”

Eat­ing your feel­ings

Che­rian’s not wrong. Other ma­jor pieces of the puz­zle in­clude a 2017 study in which sci­en­tists from

Spain’s Univer­sity of Navarra found that peo­ple who fol­lowed the DASH diet, even mod­er­ately, had a lower risk of de­vel­op­ing de­pres­sion. A Deakin Univer­sity team also found that a diet cen­tred on fruit, veg­eta­bles, fish and whole grains – DASH, es­sen­tially – was as­so­ci­ated with lower odds of de­vel­op­ing ma­jor de­pres­sion and anx­i­ety dis­or­ders, while a Western diet was linked with higher odds. Par­tic­u­larly sig­nif­i­cant was the fact that this re­search didn’t just fo­cus on older peo­ple (as in the Rush study) but in­cluded women as young as 20.

Sure, the no­tion that what you eat af­fects your men­tal health isn’t new. But while you might have long sus­pected that this re­la­tion­ship ex­ists, it’s only rel­a­tively re­cently that ex­perts have be­gun work­ing out why it does. How­ever – as with Me­la­nia and Don­ald – un­der­stand­ing the con­nec­tion is tricky. “Prov­ing a di­rect causal re­la­tion­ship be­tween health and food is enor­mously com­pli­cated be­cause there are so many vari­ables that can af­fect out­comes,” says Kim­ber­ley Wil­son, whose prac­tice, Mon­u­men­tal

Health, com­bines the lat­est re­search into nutri­tion neu­ro­science with psy­cho­log­i­cal ther­apy. “Add men­tal health into the mix and you’re in­tro­duc­ing an­other layer of

com­plex­ity given that, his­tor­i­cally, men­tal health re­search hasn’t had the same fund­ing as, say, heart dis­ease or can­cer.” But, she ex­plains, there are two key strands that re­searchers are ex­plor­ing: the ways in which fol­low­ing a good diet can help safe­guard your men­tal health, and how and why a bad diet can neg­a­tively af­fect your mind.

In­flam­ma­tory re­sponse

What’s re­ally fas­ci­nat­ing? Re­cent re­search in­di­cates it’s what you

don’t eat on the DASH diet that could be key to un­der­stand­ing this pro­tec­tive ef­fect. It can be ex­plained in a word that’s cap­tured the imag­i­na­tion of the sci­en­tific com­mu­nity the way in­flat­able pool toys have cap­tured that of In­sta­gram­mers: in­flam­ma­tion. In the past decade, ex­perts have started look­ing into the po­ten­tial links be­tween in­flam­ma­tion and de­pres­sion – specif­i­cally, the idea that re­duc­ing the for­mer could pro­tect against the lat­ter.

In a 2016 study pub­lished in Cur­rent Neu­rophar­ma­col­ogy, re­searchers con­cluded that a bet­ter un­der­stand­ing of in­flam­ma­tion in the brain could help treat de­pres­sion more ef­fec­tively. This is some­thing Pro­fes­sor Ed­ward Bull­more, head of psy­chi­a­try at Cam­bridge Univer­sity, in­ves­ti­gates in his book The In­flamed Mind – the grow­ing body of ev­i­dence that links eat­ing high-fat foods with in­flam­ma­tion, which, in turn, can con­trib­ute to de­pres­sion. “There are many in­flam­ma­tory cells embed­ded in fatty adi­pose tis­sue, which is why obe­sity is as­so­ci­ated with an in­crease in blood lev­els of in­flam­ma­tory pro­teins, such as cy­tokines,” he ex­plains. Cy­tokines are pro­teins that play a vi­tal role in the way our cells talk to each other. “The ev­i­dence shows that in­creased cy­tokine lev­els can cause in­flam­ma­tion in the brain, lead­ing to with­drawal from so­cial con­tact, loss of plea­sure and other de­pres­sive symp­toms,” he adds.

The fact that an as­so­ci­a­tion has been found be­tween obe­sity and in­flam­ma­tion, Bull­more says, could help to ex­plain why there is also a link be­tween obe­sity and de­pres­sion. But as to the ques­tion of whether an anti-in­flam­ma­tory diet can pro­tect against de­pres­sion, he is clear: we need a great deal more ev­i­dence be­fore we can make any con­clu­sions. “I think it’s con­ceiv­able, based on my work, that chang­ing your diet could have an anti-in­flam­ma­tory ef­fect – and there­fore could of­fer men­tal health ben­e­fits – but we need much more data to be sure,” he says. .

Gut in­stinct

The ab­sence of high-fat foods only goes some way to­wards ex­plain­ing why DASH could be so pow­er­ful. Fac­tor in the pro­tec­tive ef­fect of many of the foods on its menu and the case for keep­ing your mind healthy via your plate stacks up. This is where the mind-gut con­nec­tion comes in. Pre­bi­otic plants – the likes of as­para­gus, leeks and Jerusalem ar­ti­chokes – feed your gut mi­cro­biome as ef­fec­tively as a Mc­muf­fin feeds a hang­over. “Pre­bi­otics are di­etary fi­bres found in plants that the good bac­te­ria in your gut feed on

to mul­ti­ply,” ex­plains psy­chi­a­try pro­fes­sor Dr Philip Bur­net. “Gut bac­te­ria con­tain an amino acid that af­fects a cer­tain type of mol­e­cule in the brain. I wanted to see if in­creas­ing ben­e­fi­cial gut bac­te­ria with a pre­bi­otic sup­ple­ment – and in turn pro­duc­ing more of this amino acid – could im­prove mood and cog­ni­tive pro­cess­ing. It turns out it does in an­i­mals, and to some ex­tent in hu­mans, but this isn’t hap­pen­ing via the amino acid that we thought. We now think it hap­pens via the im­mune sys­tem, and the mol­e­cules pro­duced from the bac­te­rial di­ges­tion of the pre­bi­otic.” Once again, more hu­man stud­ies are needed, but Bur­net be­lieves pre­bi­otic sup­ple­ments could work via the same mech­a­nism as an­tide­pres­sants, by re­duc­ing lev­els of stress hor­mones in the brain.

So what about pre­bi­otic plants – the kind you’ll find on your av­er­age DASH plate? “Plants con­tain car­bo­hy­drates, which have pre­bi­otic prop­er­ties, mean­ing they should pro­vide the same health ben­e­fits via the gut bac­te­ria,” adds Bur­net. “But all nat­u­ral pre­bi­otics and sup­ple­ment for­ma­tions still need to go through clin­i­cal tri­als to test if they re­ally do have ther­a­peu­tic ef­fects on men­tal ill­nesses. So far, we have only shown that a pre­bi­otic sup­ple­ment in­flu­enced one psy­cho­log­i­cal path­way that un­der­lies mood – we didn’t see a change in mood per se, and we won’t know more un­til more work is done.” Still, no harm in chuck­ing some leeks in that salad.

The anti-diet

If you’re feel­ing the urge to take up a fresh-veg box sub­scrip­tion right now, con­sider the big­ger im­pli­ca­tions for peo­ple ex­pe­ri­enc­ing an on­go­ing men­tal health bat­tle. We need to con­sider the ev­i­dence in con­text, adds Che­rian. “When we talk about the role that diet plays in men­tal health, it isn’t a case of telling peo­ple [a strict for­mula] be­cause it cer­tainly isn’t that sim­ple,” she says. “But chang­ing your diet in a way that re­duces your con­sump­tion of high-fat food and in­creases your in­take of pre­bi­otic plants could play a cru­cial part of a com­pre­hen­sive plan for pre­vent­ing, and also treat­ing, de­pres­sion – com­pre­hen­sive be­ing the im­por­tant word.” Che­rian em­pha­sises med­i­ca­tion, ther­apy and ex­er­cise all play key roles and peo­ple who com­bine them with good nutri­tion may see the great­est ben­e­fit to their men­tal health.

Where this diet has real prom­ise is that there’s no num­ber-count­ing or a for­ever-off-lim­its list of foods. “DASH en­cour­ages peo­ple to eat well with­out lim­it­ing what they al­low them­selves,” Wil­son ex­plains. “Like the Mediter­ranean way of eat­ing, DASH is nei­ther re­stric­tive nor pre­scrip­tive. Be­cause it pro­vides guide­lines for peo­ple to work within and ad­just to suit their lifestyle, there’s no fall­ing off the wagon.”

In short, it’s a diet in the truest sense of the word. One that ac­tu­ally recog­nises you’re hu­man. Now, that’s what we call se­ri­ously smart.

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