For the first time, scientists have linked the love of chocolate to a specific, chemical signature programmed into a person's metabolism, the chemical processes that take place in body, as measured by tests on blood and urine.
Tests by Sunil Kochhar of the Nestlé Research Centre in Lausanne, Switzerland and Prof Jeremy Nicholson at Imperial College London show that this signature reads 'chocolate lover' in some people and indifference to the popular sweet in others, the researchers say today in the Journal of Proteome Research.
Prof Nicholson is the founder of "metabonomics", where scientists hunt for subtle changes in metabolism - the complex web of thousands of chemical reactions that runs a body - caused by toxins, drugs or illness, such as heart disease. Many of these are influenced by gut bacteria, which play a central role in breaking down a food such as chocolate.
In this case, the team studied 11 volunteers who classified themselves on a questionnaire as 'chocolate desiring' and 11 volunteers who were 'chocolate indifferent.' In a controlled clinical study, each subject - all men of normal weight - ate chocolate or placebo over a five day period while the make-up of chemicals in their blood and urine samples was analysed.
The 'chocolate lovers' had a hallmark metabolic profile that involved low levels of LDL-cholesterol (so-called 'bad' cholesterol) and marginally elevated levels of albumin, a beneficial protein, the scientists say.
The chocolate lovers showed this tell-tale chemical profile, a quite different pattern of fats, even when they ate no chocolate, the researchers note. The activity of the gut microbes in the chocolate lovers was also distinctively different from the other subjects, they add. "We found that we could easily distinguish the groups metabolically," said Prof Nicholson.
"This is the first demonstration that a dietary preference has an imprinted effect on your metabolism and that might link to all sorts of long term health implications- interestingly the chocolate preferring people had a better gut microbial metabolite profile than the people that don't like chocs," said Prof Nicholson.
"Chocolates are rich in antioxidant polyphenolics which are good for you (which themselves are microbially metabolised) and this could be part of the connection."
An essential ingredient in chocolate is cocoa which is rich in flavonoids, the most active polyphenols, in particular, three members of the flavanol family, catechin, epicatechin and procyanidins. Cocoa beans and chocolate generally contain more of the active polyphenols than any other food.
"It is known that by eating chocolate, catechin and epicatechin can reach the bloodstream where they can be transported around the body, helping to prevent oxidation so the body can stay healthier," said Kochhar.
"Our study shows that food preferences, including chocolate, might be programmed or imprinted into our metabolic system in such a way that the body becomes attuned to a particular diet," says Kochhar.
"We know that some people can eat a diet that is high in steak and carbs and generally remain healthy, while the same food in others is unhealthy," he explains.
"Knowing one's metabolic profile could open-the-door to dietary or nutritional interventions that are customised to your type so that your metabolism can be nudged to a healthier status."
Researchers have known for some time that the metabolic makeup and and food preferences can vary from person to person and even between different cultures.
"There's a lot of information in metabolism that can be used to improve health and this information is just now being explored and tapped," the researcher says.
Women were not included in the current study in order to avoid any metabolic variations linked to the menstrual cycle, which has been shown in studies by others to influence metabolic differences, Kochhar says. But the researchers plan to include women in future clinical trials on women who love the treat.
In addition to providing a better understanding of individual metabolic types, the current study could also lead to the discovery of additional biomarkers that can identify new health benefits linked to chocolate and other foods, says Kochhar, whose research was funded by Nestlé.
By Roger Highfield, Science Editor