While the cholesterol-lowering properties of soy proteins are well-documented, and more research is being conducted on pea protein, lupin has been hiding its light under a bushel, say the authors of ‘Cholesterol-lowering effect of whole lupin (Lupinus albus) seed and its protein isolate’.
The protein content of lupin is in the 28-42% range compared with about 30-40% for soy. Yet “no study has been undertaken to demonstrate the cholesterol-lowering effect of the whole lupin and/or its protein isolate using hamsters, the best type of animal for use in experiments involving lipoid metabolism”, note the authors.
Whole lupin and its protein isolate ‘have the potential to be used as functional foods’
In the study,published online ahead of print in the journal Food Chemistry, they write: “It can be concluded that whole lupin and its protein isolate have the potential to be used as functional foods and are efficient in the reduction of total cholesterol and plasma non-HDL cholesterol.”
The results also suggested that lupin could have protective effects on the liver, they added:“[Lupin] showed a hepatoprotective effect, reducing the accumulation of fat in the hepatocytes, even in the presence of hypercholesterolaemic diets, containing high levels of fats and cholesterol.”
While theprotein was probably chiefly responsible for the cholesterol-lowering effects, there appeared to be a “synergy between other components of the whole grain such as fibres, saponins and phytosterols”, they added.
Three groups: Protein isolate, whole lupin seed, control group
In the study, four-week-old male Golden Syrian hamsters were fed a diet rich in saturated fat and cholesterol for three weeks in order to induce hypercholesterolaemia.
They were then randomized and assigned to one of three groups for the next four weeks:
- HC– The casein group, kept on a hypercholesterolaemic casein diet (the control group).
- HWS – The hypercholesterolaemic whole seed group, fed a diet rich in saturated fatty acids and cholesterol but containing whole lupin seed from a sweet variety of white lupin.
- HPI - The hypercholesterolaemic protein isolate group, fed a diet rich in saturated fatty acids and cholesterol but containing lupin protein isolate (92% purity).
Blood, liver and fecal samples were then taken.
Protective effects on the liver?
The whole seed and protein isolate diet both promoted a significant reduction of total cholesterol and non-HDL cholesterol compared with the control.
Histological analysis of the liver revealed that animals fed on the whole seed and protein isolate diet also presented a low level of steatosis (level 1) compared with hamsters in the control group (level 4), revealed the authors.
“Our findings demonstrate that protein isolate from Lupinus albus from Brazil has a metabolic effect on endogenous cholesterol metabolism and a protector effect on development of hepatic steatosis.”
“The mechanism through which the lupin protein isolate provided a hepatoprotective and hypocholesterolaemic effect seems to be related to bioactive peptides which are bio-available in the protein isolate that act on enzymes related to the metabolism and not on the excretion of total sterols.”
Studies are now being conducted to show which peptides in this protein isolate are the bio-available bioactive and to better understand the mechanism of the action of the protein isolate in the hypocholesterolaemic effect, said the authors.
Click here to read about potential anti-diabetic effects of lupin.
Click here to read about lupin flour and blood pressure.
Source: Food Chemistry, 2012, published online ahead of print
‘Cholesterol-lowering effect of whole lupin (Lupinus albus) seed and its protein isolate.’
Authors: Gustavo Guadagnucci Fontanari, José Paschoal Batistuti, Robison José da Cruz,
Paulo Hilário Nascimento Saldiva, and José Alfredo Gomes Arêas .