The Multivitamin Paradox: taking a supplement gives a license to indulge, relax and smoke

Recent research has suggested that taking multi-vitamins can shorten your life. And this suggestion is not based on a single study, but on a review of 68 studies with more than 232.000 participants.The authors of this review state that there could be several explanations for this increase in the risk of early death. One of them is that multivitamins may interfere with the natural defense system of the body.

This could indeed be the underlying physiological mechanism. However, a recent paper of Chiou and colleagues in Psychological science an interesting psychological mechanism of consumers taking multivitamins. In two studies, they show that taking a simple pill (which participants believed was a multivitamin) generated a psychological license to exercise less and indulge in unhealthy food choices. Taking vitamins gives you 'permission' to do something bad, while still feeling good about yourself.

Vitamins; a license to indulge in Dutch Spice Nuts (pepernoten) 

To make it worse, another recent study in Addiction showed that taking dietary vitamins decreased the motivation to smoke less, giving smokers an 'illusion of invulnerability'.

Maybe this explains why the huge popularity of dietary supplements has not translated in healthier people.

Do increased serving bowl sizes influence how much we eat?

It is often stated that that the increasing size of food portions is a strong factor contributing to the incidence of overweight and obesity. Numerous studies have shown it again and again: larger portion sizes, serving devices and packages lead people to eat more, often without them realizing it. In particular, individual serving devices such as plates, spoons and bowl have been shown to influence food intake. However, what has not been shown is whether the most central focus of the dinner table, the main serving bowl, has a similar magnifying effect. When one is eating at home and eating out in buffet restaurants, food is often available in serving bowls from which individual portions are distributed.

This month, the paper 'Serving bowl biases the amount of food served' I wrote together with Mitsuru Shimizu and Brian Wansink came out in the Journal of Nutrition Education and Behavior. This paper reports our study in which we wanted to determine how serving bowls filled with food for many persons influence serving behaviour and consumption. We expected that the larger the size of a multiple-serving bowl, the more people will serve and consume. In the study, 68 participants were randomly assigned to a group serving pasta from a large-sized bowl (almost 7 litre capacity) or a medium-sized bowl (almost 4 litre capacity). When given a large bowl, diners served 77% more pasta compared with the diners serving from the medium-sized bowl. They ate more, even though the food was not rated tastier or otherwise notable different.


Bowl size matters, so fill your largest bowl with salad



We wondered about the reasons for our findings. It could be that more 'social' reasons inhibit an individual from taking too much food from a smaller common bowl. Perhaps people use the size of serving bowl filled with food for multiple persons as an indication of how much they can best serve themselves. It could even seem greedy to take more food from a smaller bowl.

In any case, small increases in food intake may lead to substantial additional caloric intake over a longer time period and even weight gain. Just like larger package sizes, large serving devices seem to suggest to people that large portions are appropriate to consume.

These findings again highlight the role that external cues play in food consumption and show the importance of considering serving bowl size in nutrition education. Maybe our findings can be used to turn bad habits around; just put your salad in bigger bowls.