New science shows a cooking trick used to get children to eat vegetables can also help adults hoping to cut their calorie intake, discovers Emily Shardlow
For parents who worry about ensuring that their young children eat a nutritious, balanced diet, the idea of the covert vegetable is nothing new. Slipping a few possibly maligned ingredients into a child's favourite dinner without openly acknowledging it may be the only way to ensure he or she eats those veggies: chopped carrots added to a favourite pasta sauce, sweetcorn or tomatoes served under a blanket of cheese as a pizza topping, a couple of less-loved pieces of fruit added to a strawberry smoothie.
Deceptively Delicious by Jessica Seinfeld (2008) and The Sneaky Chef: Simple Strategies for Hiding Healthy Foods in Kids' Favorite Meals (2007) by Missy Chase Lepine were both bestselling books that provided a variety of recipes all with a single premise: finding a way to hide vegetables in a meal by using vegetable purées, so that children eat more healthily.
Seinfeld's latest book, Double Delicious! Good, Simple Food for Busy, Complicated Lives was released late last year as the follow-up to Deceptively Delicious. Again, hidden vegetable purées are used as alternatives to processed sugars and flours.
Except that this time, the parents are the targets. And there is science to back it up.
A study by researchers at Pennsylvania State University in the US, published in the April 2011 issue of the American Journal of Clinical Nutrition, found that adding puréed vegetables to main meals in place of traditional, more energy-rich ingredients, increased overall vegetable consumption while reducing energy - or calorie - intake.
Alexandria D Blatt, one of the lead authors of the study and a recent PhD recipient in nutritional sciences, explains: "We had previously conducted a study to determine if increasing the portion size of vegetables served as a side dish would increase vegetable intake and reduce energy intake. This was a version of a follow-up study to determine whether increasing the vegetables within the dish would have a similar effect. However, with this study, we wanted to make the vegetable manipulations covert - so we puréed the vegetables."
Candidates who took part in the study visited a laboratory one day a week for three weeks and were served the same meals each time: carrot bread for breakfast, macaroni and cheese for lunch, chicken and rice casserole for dinner. They were allowed to control portion sizes themselves and were offered a choice of side dishes. Unknown to the diners, puréed carrots, squash and cauliflower were being added to some of the dishes.
"We formulated the entrees so that they were as similar as possible across all the conditions in taste, texture and appearance," says Blatt.
While the majority of people who took part in the study noted that they could taste something different about the dishes, only two worked out that vegetables had been added. The test candidates ate the same weight of food, regardless of whether it contained vegetable purée or not. Because the vegetables contained fewer calories per gram than the ingredients that they had replaced, the researchers found that overall calorie consumption decreased by as much as 360 calories a day when the meals consisted of 25 per cent purée, and vegetable consumption increased.
As Blatt notes: "The study reinforces that you can put lots of additional vegetables in your meals with minimal changes in the foods' characteristics."
When I ask her if she thinks that the participants' positive reactions hinged on their being oblivious to the vegetable aspect, she says that this would make for an interesting follow-up study. "For some people, nothing would change. For people who really dislike vegetables, they may be more opposed to the food, even if they did actually like it."
Sarah Queen, consultant director of Nutrition Matters Arabia - an Abu Dhabi-based company offering private consultations and corporate healthy eating workshops - has her reservations. "If an adult does not like a particular vegetable, psychologically I think it would be difficult for them to eat the dish knowing this vegetable is in it.
Attitudes towards food, be they positive or negative, are often formulated when we are young. Queen says that because of this it is important for children knowingly to sample a wide variety of vegetables. She suggests allowing them to help with food shopping and preparation, serving small portions of new ingredients one at a time, encouraging children to smell as well as taste them and offering plenty of praise when they do so.
Puréeing vegetables to hide them in dishes "can also add on extra preparation time, which people don't always have the inclination nor time for in the evenings", says Queen. "I would suggest that instead, a person concentrates on the vegetables that they like and then think about others that they may want to introduce."
While this is sound advice, Blatt's counter-argument that "this study should encourage adults who don't like vegetables to purée them and incorporate them into foods, because you can't taste them" also makes sense.