Fruktose og sukker kan stimulere fettlagring



Her så man på den akutte effekten av å innta 100g karbohydrater enten i form av ren glukose/druesukker, i form av en 50:50 blanding mellom fruktose og glukose (det samme som man finner i vanlig sukker), og til slutt i en sammensetning med 75% fruktose og 25% glukose. På akutt basis så man at lipogenesis, eller omdanning til fett ble fordoblet når man inntok 50-75g fruktose (tilsvarende minst 100g sukker), og at det var 11-29% høyere nivåer av fettsyrer i blodet. Jeg har jo tidligere nevnt at fruktose primært lagres i leveren og derfor har lav GI – det vil ikke gi økninger i blodsukkernivåer i nevneverdig grad. Dette er imidlertid ikke spesielt gunstig da leveren bare kan lagre omtrent 50g fruktose, og det overskytende vil omdannes til fett. Dette gjelder på vedlikeholdsnivå og overskudd, på en diett vil man gradvis tømme leveren for glykogen og da spiller dette neppe så stor rolle.

Frukt inneholder som regel maks 5g fruktose pr stk (banan, appelsin, eple, nektarin osv) så det er ingen grunn til å unngå å spise frukt. Det er når man inntar store mengder ren fruktose eller sukker at man kan øke sjansen for omdanning til fett i leveren, samt at fettet man spiser lettere lagres.

J Nutr. 2008 Jun;138(6):1039-46.

Dietary sugars stimulate fatty acid synthesis in adults.

Parks EJ, Skokan LE, Timlin MT, Dingfelder CS.

Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9052, USA. elizabeth.parks@utsouthwestern.edu

The goal of this study was to determine the magnitude by which acute consumption of fructose in a morning bolus would stimulate lipogenesis (measured by infusion of 13C1-acetate and analysis by GC-MS) immediately and after a subsequent meal. Six healthy subjects [4 men and 2 women; aged (mean +/- SD) 28 +/- 8 y; BMI, 24.3 +/- 2.8 kg/m(2); and serum triacylglycerols (TG), 1.03 +/- 0.32 mmol/L] consumed carbohydrate boluses of sugars (85 g each) in a random and blinded order, followed by a standardized lunch 4 h later. Subjects completed a control test of glucose (100:0) and a mixture of 50:50 glucose:fructose and one of 25:75 (wt:wt). Following the morning boluses, serum glucose and insulin after 100:0 were greater than both other treatments (P < 0.05) and this pattern occurred again after lunch. In the morning, fractional lipogenesis was stimulated when subjects ingested fructose and peaked at 15.9 +/- 5.4% after the 50:50 treatment and at 16.9 +/- 5.2% after the 25:75 treatment, values that were greater than after the 100:0 treatment (7.8 +/- 5.7%; P < 0.02). When fructose was consumed, absolute lipogenesis was 2-fold greater than when it was absent (100:0). Postlunch, serum TG were 11-29% greater than 100:0 and TG-rich lipoprotein-TG concentrations were 76-200% greater after 50:50 and 25:75 were consumed (P < 0.05). The data demonstrate that an early stimulation of lipogenesis after fructose, consumed in a mixture of sugars, augments subsequent postprandial lipemia. The postlunch blood TG elevation was only partially due to carry-over from the morning. Acute intake of fructose stimulates lipogenesis and may create a metabolic milieu that enhances subsequent esterification of fatty acids flowing to the liver to elevate TG synthesis postprandially.

__________________

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s