Consumption of raw brown onions variably modulate plasma lipid profile and lipoprotein oxidation in pigs fed a high‐fat diet

Abstract

This study was undertaken to determine the effects of two commercially available brown onion varieties, 'Cavalier' and 'Destiny', supplemented at two different levels, on blood lipid and oxidative status using the pig as a model. Twenty-five female cross-bred pigs were allocated to one of five dietary treatments that consisted of a high-fat control diet with no onion added, a low onion dose of 10 g onion MJ −1 DE and a high dose of 25 g onion MJ −1 DE for each variety of onion. Supplementation with 'Destiny' onion resulted in a 21% (p < 0.05) reduction in the averaged fasted and postprandial plasma triacylglyceride (TG) measurements taken over the six-week period in comparison with the control pigs. The average fasting and postprandial plasma cholesterol concentrations were significantly reduced by 5.5 and 12.4% in pigs that consumed the low and high dose of 'Destiny' onion, respectively (p < 0.010), while 'Cavalier' was only effective at lowering cholesterol levels by 10% at the lower dose of supplementation. Inhibition in the rate of serum lipoprotein oxidation, measured as lag time, was increased by 23% (p < 0.05) in plasma obtained from pigs that consumed 'Cavalier' compared with the control and 'Destiny' onion diets. These data indicate that onion consumption level may provide a dietary means of manipulating some of the risk indices associated with coronary heart disease, but the responses varied with type and dose of onion.

Welsh Onion Attenuates Hyperlipidemia in Rats Fed on High-Fat High-Sucrose Diet

“…The reason for such a difference in these results is not clear at the moment, but Gabler et al have suggested that the lipid-lowering effect of onion varies with the type and dose of the onion used. 13) Few studies on the hypolipidemic activity of the Welsh onion have been reported, and this present study would be the first to propose the lipid-lowering effects of green Welsh onion in the plasma and liver of an animal model.…”

Dietary Onion Intake as Part of a Typical High Fat Diet Improves Indices of Cardiovascular Health Using The Mixed Sex Pig Model

“…However, the overall fasting and postprandial plasma TG levels increased over the duration of the experiment, highlighting a period of adaptation to a high fat diet, and the greatest reductions in postprandial lipidaemia were observed in the final two weeks of the onion supplementation [3]. Since fasting concentration of plasma TG has been shown to be an important determinant of the magnitude and duration of the postprandial TG response [9], the effect of onion supplementation on fat metabolism may be more pronounced in individuals with high fasting TG levels.…”

“…The degree of oxidation of lipoproteins in diluted serum was measured according to Kontush and Beisiegel [13] as modified by Gabler et al [3]. Oxidation kinetics were determined by measuring the lipoprotein diene formation of serum exposed to Cu 2+ over a 30 h period.…”

“…The main groups of compounds that have been linked to health benefits in onions are flavonoids and the alk(en)yl cysteine sulfoxides (CSO) [1,2]. Our previous studies showed that dietary raw onions have hypolipogenic, haematocritic, immunological, antioxidant and blood clotting modulating effects in female pigs fed a 10% fat diet [3,4] and consequently, potentially reduce risk indices of cardiovascular disease and obesity. However, "western" diets contain on average 25% fat of which approximately 15 and 8% are saturated and polyunsaturated fats, respectively [5].…”

“…In our previous studies [3,4], female pigs consuming a &Destiny' brown onion variety had reduced plasma triglyceride (TG) levels in both fasting and postprandial states. However, the overall fasting and postprandial plasma TG levels increased over the duration of the experiment, highlighting a period of adaptation to a high fat diet, and the greatest reductions in postprandial lipidaemia were observed in the final two weeks of the onion supplementation [3].…”