Previous research has found associations between a general liking for salty and fatty foods with uncontrolled eating, overweight and higher energy intakes to a greater extent than a liking for sweet and fatty foods. But the findings of this study suggest that the addition of salt can increase energy intake in just one meal – even among those who are highly fat taste sensitive and who tend to have a reduced preference for fatty foods.
The Australian team of researchers gave participants in the study four variations of the same meal – low fat (0.02%) and low salt (0.06%); low-fat and high-salt (0.5%); high fat (34%) and low-salt; or high-fat and high-salt.
Participants were told they could eat as much as they liked until comfortably full while the researchers recorded the amount eaten as well as eating rate, pleasantness and subjective ratings of hunger and fullness.
They found that salt increased food and energy intakes by 11% - independent of fat concentration.
“The addition of salt, but not fat, increased pleasantness, which probably explains the higher food intake due to salt. The higher intake of the high salt meals was accompanied by stronger decreases in ratings of prospective consumption and hunger, whereas this was not influenced by fat,” they wrote.
Participants with the lowest fat taste thresholds ate less of the high fat meal but only when in the low salt condition. When given a meal that was both high fat and high salt, their consumption increased. “In addition to the overall effect of salt in driving passive overconsumption of fat, these results suggest that salt overrides fat-mediated satiation in fat taste–sensitive individuals,” wrote lead researcher Russell Keast and his team.
In today’s food environment where snacks are widely available, the potential impact of this is significant.
“Fat does not necessarily need salt for the consumption of excess energy. However, in real-life situations, foods high in dietary fat are most likely accompanied by a salty, savoury, or sweet taste and are not just a fatty-tasting food. In this perspective, salt does promote overconsumption of dietary fat, simply because fatty foods without another dominant taste are not common and are unlikely to be consumed,” they write.
The effect of fat on food palatability is complex, write Keast et al., and increases in fat content do not always lead to increases in food intake or increased pleasantness, unless accompanied by varying combinations of salt and sugar.
A total of 48 individuals aged between 18 and 54 years with a body mass index (BMI) of between 17.8 and 34.4 took part of the study. Fat taste sensitivity was determined by measuring the detection threshold of oleic acid.
After eating the same breakfast, participants attended four lunchtime sessions consisting of 56% macaroni pasta and 44% sauce. The sauces were either: low fat (0.02%) and low salt (0.06%); low-fat and high-salt (0.5%); high fat (34%) and low-salt; or high-fat and high-salt, and participants were told they could eat as much as they liked until comfortably full. The researchers measured the amount eaten as well as eating rate, pleasantness, and subjective ratings of hunger and fullness.
The low fat pasta sauce provided 0.6 g of fat per 100 g compared with 15.5 g for the high fat version, which led to a 60% increase in energy intake.
Salt content had a main effect on pleasantness unlike fat, and participants reported greater desire to eat the high salt food than the low salt meal. However, no effect was observed for high fat versus low fat.
Source: The Journal of Nutrition
First published ahead of print, 2 March 2016, doi: 10.3945/jn.115.226365
Salt Promotes Passive Overconsumption of Dietary Fat in Humans
Authors: Dieuwerke P. Bolhuis, Andrew Costanzo, Lisa P. Newman, Russell S.J. Keast