Hrana s cjelovitim žitaricama za sprječavanje dijabetesa tipa 2

Prehrambeni proizvodi koji se dobivaju iz cjelovitih žitarica, kao što su pšenica, riža, kukuruz, raž, zob i ječam čine glavni udio u prehrani ljudi iz brojnih zemalja. U proizvodima od rafiniranih žitarica uklanjaju se mekinje i klice žitarice, koje sadrže glavninu hranjivih tvari i prehrambenih vlakana te se ostavlja samo škrobni unutarnji dio žitarice (oko 80% čitavoga zrna). Hrana s cjelovitim žitaricama sadrži netaknute žitarice, ili žitarice koje su u dijelovima, grubo usitnjene ili se radi o brašnu napravljenom od cjelovitih žitarica. U ovom Cochrane sustavnom pregledu ispitan je učinak cjelovitih žitarica i vlakana iz žitarica (kao mjera unosa cjelovitih žitarica) na sprječavanje dijabetesa tipa 2. U sustavni pregled uključene su sve kohortne studije koje su pratile ispitanike određeno vrijeme, kao i klinička ispitivanja sa slučajnim uzorkom ispitanika. Pronađeno je samo jedno kliničko ispitivanje sa slučajnim uzorkom ispitanika, a i to jedno je bilo loše metodološke kvalitete. U toj je studiji na 12 pretilih osoba tijekom šest tjedana uspoređen utjecaj konzumiranja hrane s rafiniranim žitaricama i hrane s cjelovitim žitaricama na osjetljivost na inzulin (čimbenik rizika za razvoj dijabetesa tipa 2). Unos cjelovitih žitarica donekle je poboljšao osjetljivost na inzulin, povećao aktivnost crijeva i nisu uočene nuspojave. Nisu navedene nikakve informacije o zadovoljstvu pacijenata, kvaliteti života povezanoj sa zdravljem, ukupnoj smrtnosti i pobolu. Osim ove studije, pronađeno je i 11 prospektivnih kohortnih studija. Jedna je provedena u Finskoj, a ostale u SAD-u, od kojih je sedam provedeno među zdravstvenim djelatnicima. Neke od ovih studija bile su ograničene kvalitete. Studije su konzistentno pokazale da je veći unos cjelovitih žitarica ili vlakana iz žitarica povezan s manjim rizikom od razvoja dijabetesa tipa 2. Međutim, dokazi za zaštitni učinak koji se dobiju prospektivnim kohortnim studijama trebaju se smatrati slabim dokazima jer u ovakvoj vrsti istraživanja nije moguće povezati uzrok i posljedicu. Nužna su nam dobro osmišljena kontrolirana ispitivanja na slučajnom uzorku ispitanika kako bi se mogli donijeti definitivni zaključci o preventivnom učinku konzumiranja cjelovitih žitarica na razvoj dijabetesa tipa 2.

Conclusions des auteurs: 

The evidence from only prospective cohort trials is considered to be too weak to be able to draw a definite conclusion about the preventive effect of whole grain foods on the development of T2DM. Properly designed long-term randomised controlled trials are needed. To facilitate this, further mechanistic research should focus on finding a set of relevant intermediate endpoints for T2DM and on identifying genetic subgroups of the population at risk that are most susceptible to dietary intervention.

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Contexte: 

Diet as one aspect of lifestyle is thought to be one of the modifiable risk factors for the development of type 2 diabetes mellitus (T2DM). Information is needed as to which components of the diet could be protective for this disease.

Objectifs: 

To asses the effects of whole-grain foods for the prevention of T2DM.

La stratégie de recherche documentaire: 

We searched CENTRAL, MEDLINE, EMBASE, CINAHL and AMED.

Critères de sélection: 

We selected cohort studies with a minimum duration of five years that assessed the association between intake of whole-grain foods or cereal fibre and incidence of T2DM. Randomised controlled trials lasting at least six weeks were selected that assessed the effect of a diet rich in whole-grain foods compared to a diet rich in refined grain foods on T2DM and its major risk factors.

Recueil et analyse des données: 

Two authors independently selected the studies, assessed study quality and extracted data. Data of studies were not pooled because of methodological diversity.

Résultats principaux: 

One randomised controlled trial and eleven prospective cohort studies were identified. The randomised controlled trial, which was of low methodological quality, reported the change in insulin sensitivity in 12 obese hyperinsulinemic participants after six-week long interventions. Intake of whole grain foods resulted in a slight improvement of insulin sensitivity and no adverse effects. Patient satisfaction, health related quality of life, total mortality and morbidity was not reported.
Four of the eleven cohort studies measured cereal fibre intake, three studies whole grain intake and two studies both. Two studies measured the change in whole grain food intake and one of them also change in cereal fibre intake. The incidence of T2DM was assessed in nine studies and changes in weight gain in two studies. The prospective studies consistently showed a reduced risk for high intake of whole grain foods (27% to 30%) or cereal fibre (28% to 37%) on the development of T2DM.

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