Lycopene is an antioxidant that is present in red- and pink-coloured fruits and vegetables. As well as being used as a food colouring, it is also used in supplements. The role of lycopene in heart health and in reducing the risk of certain cancers is supported by a body of research.
Red tomatoes typically contain about 95 per cent of their lycopene as the all-trans-isomer, reported to be the most stable form. In tangerine tomatoes, on the other hand, the lycopene is also present as tetra-cis-lycopene, a geometric isomer of all-trans-lycopene.
Geometric isomers refer to two or more substances that have the same chemical make-up but the arrangement of the constituent elements is different, giving the substances different properties.
But evidence is mounting that the tetra-cis-lycopene form is more bioavailable to humans. But the researchers report that there are 72 different types of cis-lycopene, with the so-called 5Z-, 9Z- and 13Z-lycopene usually predominating. (The Z nomenclature is another, more complicated way of naming isomers. Roughly, the Z form refers to cis, and E refers to trans).
New data
According to data from scientists at the Nestlé Research Center in Lausanne and four French research centers, the majority of the lycopene consumed in the diet is in the all-E form. The body then converts this into various (Z)-isomers.
“Because these isomers offer potentially better health benefits than the (all-E) isomer, the aim of the present study was to investigate if the profile of lycopene isomers in intestinal lipoproteins is affected by the profile of lycopene isomers in the meal and by the tomato preparation,” explained the researchers in the British Journal of Nutrition.
To test this, the team fed six different meals to a group of 30 healthy men in a cross-over study. Three of the meals provided 70% of the lycopene as (Z)-isomers: 5-(Z); or 13-(Z), or 9-(Z) plus 13-(Z) lycopene. The other three provided tomato preparations with lycopene mainly in the (all-E) isomer form.
The highest absorption was observed when lycopene was consumed as 5-(Z), said the researchers, a result that indicated “good absorption and/or a low intestinal conversion of this isomer”.
On the other hand, the 9-(Z) and 13-(Z) meals resulted in low levels of both these forms, they added, but high levels of 5-(Z) and (all-E).
“This indicates that the 9-(Z) and 13-(Z) isomers were less absorbed or were converted into 5-(Z) and (all-E) isomers,” explained the scientists.
“These results show that although the human intestine is able to modify the profile of dietary lycopene isomers which is finally found in the body, the resulting profile is not the same for all isomer sources supplied but is dependent on the initial relative proportions of these isomers existing in the meal.
“This suggests that the mechanism of (E)-to-(Z) conversion can be overwhelmed by offering high amounts of dietary lycopene (Z)-isomers, e.g. 5-(Z).
“It is, therefore, possible to modulate the profile of (Z)-isomers which enter the human body via the intestinal lipoproteins by a lycopene isomer-rich diet,” they concluded.
Nestlé research into lycopene
Nestlé is not new to lycopene research, and has produced a form of lacto-lycopene with high bioavailability, giving the company a patentable form of an existing nutrient. This resulted is Nestlé's innéov lycopene supplement for skin health and beauty - the company's first and only move into dietary supplements, produced in collaboration with L'Oreal.
Nestlé scientists have also worked with Italian ingredient supplier Indena to improve the isomer profile, with the quantity of trans-isomers significantly increased. This research was published in 2009 in Food Chemistry.
The researchers were affiliated with Nestlé Research Center, Avantage Nutrition, INSERM, INRA, and the University Aix-Marseille.
Source: British Journal of Nutrition
Published online ahead of print, FirstView Articles, doi:10.1017/S0007114511004569
“The proportion of lycopene isomers in human plasma is modulated by lycopene isomer profile in the meal but not by lycopene preparation”
Authors: M. Richelle, P. Lambelet, A. Rytz, I. Tavazzi, A-F. Mermoud, C. Juhel, P. Borel, K. Bortlik