Eat­ing more fruit, par­tic­u­lar­ly blue­ber­ries, ap­ples and grapes, is linked to a re­duced risk of de­vel­op­ing type-2 di­a­betes, sug­gests a study in the British Med­ical Jour­nal.

Blue­ber­ries cut the risk by 26 per cent com­pared with two per cent for three serv­ings of any whole fruit, but fruit juice did not ap­pear to have the same ef­fect.

The re­search looked at the di­ets of more than 187,000 peo­ple in the US.

But Di­a­betes UK said the re­sults of the study should be treat­ed with cau­tion.

Re­searchers from the UK, US and Sin­ga­pore used da­ta from three large stud­ies of nurs­es and health pro­fes­sion­als in the US to ex­am­ine the link be­tween fruit con­sump­tion and the risk of con­tract­ing type-2 di­a­betes.

In these stud­ies, 6.5 per cent of par­tic­i­pants (12,198 out of 187,382) de­vel­oped type-2 di­a­betes.

The stud­ies used food fre­quen­cy ques­tion­naires to fol­low up the par­tic­i­pants every four years, ask­ing how of­ten, on av­er­age, they ate a stan­dard por­tion of each fruit.

The fruits used in the study were grapes or raisins, peach­es, plums or apri­cots, prunes, ba­nanas, can­taloupe, ap­ples or pears, or­anges, grape­fruit, straw­ber­ries and blue­ber­ries.

The re­searchers' analy­sis of the da­ta showed that three serv­ings per week of blue­ber­ries, grapes and raisins, and ap­ples and pears sig­nif­i­cant­ly re­duced the risk of type-2 di­a­betes.

While all fruit was shown to re­duce the risk, these fruits ap­peared to be par­tic­u­lar­ly ef­fec­tive.

The re­searchers said this could be due to the fact these fruits con­tain high lev­els of an­tho­cyanins, which have been shown to en­hance glu­cose up­take in mice. The same fruits con­tain nat­u­ral­ly-oc­cur­ring polyphe­nols which are known to have ben­e­fi­cial ef­fects.

In the study pa­per, they wrote: "Fruits have high­ly vari­able con­tents of fi­bre, an­tiox­i­dants, oth­er nu­tri­ents, and phy­to­chem­i­cals that joint­ly may in­flu­ence the risk."

But the gly­caemic load of dif­fer­ent types of fruit, the qual­i­ty and quan­ti­ty of car­bo­hy­drate they con­tain, did not ful­ly ex­plain the re­sults, the study said.

When they looked at the ef­fects of fruit juice con­sump­tion, the re­searchers found a slight­ly in­creased risk of type-2 di­a­betes.

The study cal­cu­lat­ed that re­plac­ing week­ly fruit juice con­sump­tion with whole fruits could bring health ben­e­fits.

For ex­am­ple, re­plac­ing fruit juice with blue­ber­ries could re­duce the risk of con­tract­ing type-2 di­a­betes by 33 per cent, with grapes and raisins by 19 per cent, ap­ples and pears by 13 per cent, and with any com­bi­na­tion of whole fruit by sev­en per cent.

Re­plac­ing fruit juice with or­anges, peach­es, plums and apri­cots had a sim­i­lar ef­fect.

Qi Sun, study au­thor and as­sis­tant pro­fes­sor at Har­vard School of Pub­lic Health, said, in gen­er­al, fruit juices con­tained less of the ben­e­fi­cial com­pounds found in whole fruits.

"The juic­ing process gets rid of the fruit, just leav­ing flu­ids which are ab­sorbed more quick­ly, caus­ing blood sug­ars and in­sulin lev­els to rise if they con­tain sug­ars.

"To try to min­imise the risk of type-2 di­a­betes as much as pos­si­ble it is rea­son­able to re­duce fruit juice con­sump­tion and in­crease con­sump­tion of whole fruits."

Ex­perts say the best way to re­duce your risk of de­vel­op­ing type-2 di­a­betes is to eat a bal­anced, healthy di­et that in­cludes a va­ri­ety of fruits and veg­eta­bles and to be as phys­i­cal­ly ac­tive as pos­si­ble.

Dr Matthew Hobbs, head of re­search for Di­a­betes UK, said the study pro­vid­ed fur­ther ev­i­dence that eat­ing plen­ty of whole fruit was a key part of the bal­anced di­et that will min­imise the risk of de­vel­op­ing type-2 di­a­betes.

How­ev­er, he said the links be­tween type-2 di­a­betes and spe­cif­ic types of fruit or fruit drinks should be treat­ed with cau­tion.

"Some of the find­ings are based on a num­ber of as­sump­tions and mod­els which may have dis­tort­ed the re­sults sig­nif­i­cant­ly.

"For ex­am­ple, the re­searchers used sur­veys to ask par­tic­i­pants how of­ten they ate cer­tain foods. This type of sur­vey can of­ten be un­re­li­able as peo­ple are more like­ly to re­mem­ber cer­tain types of food."

Kam­lesh Khunti, pro­fes­sor of pri­ma­ry care di­a­betes and vas­cu­lar med­i­cine at the Uni­ver­si­ty of Leices­ter, said the large study showed that eat­ing any fruit is good.

"Eat­ing all kinds of fruit works and there is still a re­duc­tion in risk.

"The gov­ern­ment rec­om­mends eat­ing five por­tions of fruit and veg­eta­bles every day." (BBC)

About type-2 di­a­betes

Di­a­betes is an in­cur­able con­di­tion in which the body can­not con­trol blood sug­ar lev­els, be­cause of prob­lems with the hor­mone in­sulin.

In type-2 di­a­betes, ei­ther the pan­creas cells do not make enough in­sulin, or the body's cells do not re­act prop­er­ly to it.

This is known as in­sulin re­sis­tance.

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