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.

Eye tracking studies done by our research group on Dutch television

Last Tuesday, the Dutch television show 'Altijd Wat' paid attention to the debate on how to best inform consumers about making a healthy choice in the supermarket. Increasingly, information about the healthiness of a food is put front of pack in the form of a logo or health stamp. These logos are supposed to make your healthy choice more intuitive and easy.

But do consumer see these logos and labels in the midst of other information on the package? And to they use them to make a healthier food choice?

To get insights into which elements at a food package really attract consumer attention, Erica van Herpen and Hans van Trijp use eye tracking techniques. An eye tracker is a tool for measuring how the eyes move over an object (such as a food package) and at which point they stop to focus. Their latest paper on this topic examined which type of nutrition label attracts most attention, even when consumers are under time pressure (as we often are in the supermarket).

Watch Hans and Erica in action while demonstrating the eye tracker (item starts after about 10 minutes).

Are you thinking too much or too little about food?

I came across a really good paper of Dan Ariely and Michael Norton about the fascinating research being done in human decision making: 'From thinking too little to thinking too much: a continuum of decision making'.

Basically, there are two approaches to thinking; on the one end of the extreme someone is thinking too much and too carefully. On the other end of the extreme someone is thinking too little; a thinking style based on intuition, heuristics and quick short cuts. Both thinking too little and too much can have negative consequences and lead to mistakes, they argue.


More ice-cream options is definitely better... 

Thinking too much makes decisions harder or leads to postponing them. They refer to the famous study of Iyengar and Lepper who showed that grocery shoppers who were offered free samples of 24 jam flavors were less likely to buy any jam at all than those shoppers who sampled only 6 flavors. This clearly shows that considering too many options made it too hard to choose one. Barry Schwartz calls this 'the paradox of choice. Why more is less' and argues that we are faced with far too many choices on a daily basis. Nevertheless, Iyengar and Lepper's study also showed that people given more options enjoy the process of choosing. That is what I recognize when looking at my daughters in an Italian gelateria. They love to take their time to make a decision, although they typically end up with the same familiar strawberry flavour.

Dieters tend to think a lot about eating, particular negative self-thoughts. Their long history of going on and off on diets and guilty thinking patterns makes them more likely to overeat when confronted with tempting foods. Clearly an example of thinking too much, with harmful consequences. That is because their thinking is too 'concretely' and too much about the struggles of the moment ('shall I take the apple or the chocolate cake?). This uses up a lot of self-control in contrast to thinking about long-term goals (such as being fit and healthy) which can enhance your self-control. This finding came out of a study of Fujita and Han in Psychological Science.

Relying on habits ('I have always done it in this way') can be harmful as well. For example, out of habit, people tend to eat the entire portion that is served to them, even when it is stale popcorn. A little bit more thought could be good in that case. In other words, you may miss out opportunities to eat healthier when you often make quick decisions out of habit.

In an interview, Norton concludes by saying: 'What we know now is that people sometimes think too much, and sometimes they think too little. But we still don't know the right amount to think for any given decision, which is a fascinating decision yet to be solved.'