Lymphatic absorption of a -linolenic acid in rats fed flaxseed oil -based emulsion

January 1, 2010 Human Health and Nutrition Data 0 Comments

Lymphatic absorption of a -linolenic acid in rats fed flaxseed oil -based emulsion

Year: 2010
Authors: Couedelo, L. Bou-Vaysse, C. Fonseca, L. Montesinos, E. Djoukitch, S. Combe, N. Cansell, M.
Publication Name: British Journal of Nutrition
Publication Details: doi:10.1017/S000711451000454X


The bioavailability of alpha-linolenic acid (ALA) from flaxseed oil in an emulsified form vs. a non-emulsified form was investigated by using two complementary approaches: the first one dealt with the characterisation of the flaxseed oil emulsion in in vitro gastrointestinal-like conditions; the second one compared the intestinal absorption of ALA in rats fed the two forms of the oil. The in vitro study on emulsified flaxseed oil showed that decreasing the pH from 7.3 to 1.5 at the physiological temperature (37oC) induced instantaneous oil globule coalescence. Some phase separation was observed under acidic conditions that vanished after further neutralisation. The lecithin used to stabilise the emulsions inhibited TAG hydrolysis by pancreatic lipase. In contrast, lipid solubilisation by bile salts (after lipase and phospholipase hydrolysis) was favoured by preliminary oil emulsification. The in vivo absorption of ALA in thoracic lymph duct-cannulated rats fed flaxseed oil, emulsified or non-emulsified, was quantified. Oil emulsification significantly favoured the rate and extent of ALA recovery as measured by the maximum ALA concentration in the lymph (Cmax= 14mg/ml at 3h in the emulsion group v. 9 mg/ml at 5h in the oil group; P<0.05). Likewise, the area under the curve of the kinetics was significantly higher in the emulsion group (48mg x h/ml for rats fed emulsion v. 26mg x h/ml for rats fed oil; P<0.05). On the whole, ALA bioavailability was improved with flaxseed oil ingested in an emulsified state. Data obtained from the in vitro studies helped to partly interpret the physiological results. (Author's abstract)
The bioavailability of a lipid nutrient present in food is affected by nature of the lipid nature and pancreatic lipase activity due to the TAG structure, the inherent resistance of very long PUFA to hydrolysis and the more efficient hydrolysis of short and medium-chain TAG. The objective of the present study was to measure the intestinal absorption of alpha-linolenic acid (ALA) in rats after the administration of flaxseed oil in both emulsified and non-emulsified states. With the aim of probing how lipid bioavailability depends on its dispersion state, rats were fed flaxseed oil either in a bulk phase or an oil-in-water (O/W) emulsion. Soya lecithin was used to stabilise the oil interface. The present study was carried out to determine whether the emulsified state of the lipids influenced ALA lymphatic absorption and, more generally, its bioavailability. In addition, the emulsion stability was characterised under conditions that mimicked those of the gastrointestinal tract in terms of pH variation, enzyme lipolysis and bile salt (BS) solubilisation. 
The present demonstrated that TAG were more efficiently absorbed when provided as an emulsion rather than as a bulk phase. As a result, fatty acid and ALA enrichment in chylomicrons was greater (Cmax) and faster (Tmax) in rats fed emulsified oil than in rats fed bulk oil. Results showed that the emulsified state was maintained even with large variations in pH, suggesting that in vivo, the lipid water interface may be preserved up to the intestine level.  The present in vivo results suggested that the emulsification of flaxseed oil enhances its digestibility, due to the faster hydrolysis of TAG because of the pre-existing oil water interface and a better solubilisation of hydrolysis products in mixed micelles. ALA enrichment in chylomicrons was observed irrespective of the dietary form of flaxseed oil. The percentage of ALA esterified at the sn-2 position of chylomicron TAG was slightly lower (18 and 23% for oil and emulsion, respectively) compared with that in dietary flaxseed oil (28%). This may be attributed to a degradation of some 2-monolinolenate glycerols. The authors suggest that basic information on ALA bioavailability from flaxseed oil is still necessary to understand its biological efficiency. In particular, because the intramolecular fatty acid distribution in chylomicron TAG did not exactly reflect that of the dietary oil, the metabolic pathway of ALA during the digestion process remains to be further explored. (Editor's comments)

Back to Databases

Affiliated Organizations

Flax Focus Newsletter

Stay up-to-date with important flax news and announcements with our FLAX FOCUS newsletter.