Nov 9, 2014 - Research Digest. Exclusive Sneak Peek. Issue 1 â. November 2014. Click here to purchase ERD - introducto
Research Digest Exclusive Sneak Peek
Issue 1 ◆ November 2014
Click here to purchase ERD - introductory 20% off sale until November 9 2014
Umami appetizers backed by science
Umami flavor enhances appetite but also increases satiety
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Introduction
A recent study evaluated the effects of monosodium glutamate (MSG) in combination with inosine 5’-monophosphate (IMP) on satiety. The goal of the study was to determine whether these compounds help induce satiety and thus may help us eat less. First, let’s define some important terms: Umami: Savory flavor. Foods that naturally have umami flavor include meats, seafood, mushrooms (especially shiitake mushrooms), aged cheeses like parmesan, soy sauce, and nutritional yeast. These foods are umami because they are rich in free glutamic acid, a naturally occurring amino acid, or other nucleotides such as inosine 5’-monophosphate (IMP). Monosodium glutamate (MSG): This compound is often added to chips, sausages, and Chinese food as a flavor enhancer. MSG enhances the umami flavor of the food. In this study, MSG was used as a substitute for the free glutamic acid found in natural foods. Inosine 5’-monophosphate (IMP): This compound occurs naturally in meats exhibiting a strong umami flavor as well as other umami foods. When MSG and IMP are present together, they may act synergistically to increase the umami flavor.
The nitty-gritty
This study included twenty-seven participants (11 men and 16 women) with a mean age of about 22 years. The average BMI of the participants was approximately 23, with a range of 19-29, so all of the subjects were either normal weight or overweight, but not obese. Subjects who scored as “restrained eaters” on the Three-Factor Eating Questionnaire, indicating they have a greater ability than the general population to resist tempting foods, were excluded. Study participants were told that the study was meant to “determine the effect of food on motor skills.” This
A bit more about umami Umami is the fifth basic taste sensation, but gets much less attention than the others. Researchers believe that all basic tastes stem from humans evolving to eat nourishing and safe foods. For example, most people don’t enjoy extremely bitter tastes, which makes sense because many toxins are bitter. Very sour food may be spoiled. Sweet foods like carbohydrates provide quick energy, while salty foods help us balance electrolytes. Umami is unique. It helps tie the rest of the tastes together, with a full and savory feeling that lingers on the tongue. Since umami is present in many meat products, it indicates to our mouths that protein is on the way. Millenia ago, in a time before nutrition labels, these rough approximators came in handy. Currently, popular dishes from a variety of global cuisines utilize combinations of umami flavors, such as western beef stew or Japanese dashi. Food chemists have taken advantage of umami enhancers and heightened palatability to produce foods that aren’t nourishing, but are hard to stop eating. Think instant ramen or potato chips. The link between a food’s taste and nutrition value is much harder to detect today, which is likely a factor in rising obesity rates.
deception was necessary because if the subjects knew the intent of the study, it could potentially influence their eating behaviors. Several times during the study, subjects were asked to complete a motor skills task, though no actual data was collected.
Intervention
The study was conducted over four non-consecutive days, with each participant participating in each intervention. Study participants were required to fast from 11 p.m. the night before each study day. In the morning, everyone ate a standard breakfast of cereal, semi-skim milk and orange juice, providing 504 calories for men and 404 calories for women. No food or drink, other than water, was allowed for the next three hours. Three hours after breakfast, subjects completed appetite and mood ratings, rating themselves on the following feelings: alert, clear-headed, energetic, full, hungry, nauseous, thirsty. Everyone ate a 450 gram portion of spiced carrot soup before lunch. There were actually four different soups: 1. Control soup (carrot spice) with MSG/IMP: 126 calories 2. Control soup (carrot spice) without MSG/IMP: 126 calories 3. High calorie/carb/protein soup (carrot spice with whey protein/ maltodextrin) with MSG/IMP: 311 calories 4. High calorie/carb/protein soup (carrot spice with whey protein/ maltodextrin) without MSG/IMP: 311 calories The researchers wanted to get a grasp of how much soup it took to produce effects. After every 50 grams of soup, the participants of the study provided appetite ratings (full, hungry, thirsty) and were asked to describe how filling, pleasant, salty, savory, strong, or sweet the soup tasted. The period between the soup meal and lunch was controlled to ensure that participant experiences were comparable. After eating the soup, the participants were allowed no food or drink, other than water, for 45 minutes. After 45 minutes, mood appetite ratings were taken again and participants were given a taste of what they would be having for lunch. Lunch was a 450 gram portion of pasta with tomato sauce. Study participants were given the following instructions: “Please eat as much pasta
as you like until you feel comfortably full.” Refills were provided upon request. The lunch meal was the same on all four days of the study. The study took place on four non-consecutive days. After a fast, study participants were provided breakfast, a pre-lunch soup, a taste of lunch, and finally, lunch itself. Researchers measured the hunger and satiety levels of the participants. Some soup contained added MSG/IMP.
Results Calories consumed at lunch Study participants that ate the pre-lunch soup with MSG/IMP consumed significantly fewer calories at lunch, compared to the soup without MSG/IMP (408 calories versus 446 calories). This applies to both the high calorie and low calorie control soups. People who ate the high calorie soups also ate less at lunch than people who ate the control soup (381 calories versus 472 calories). These results are summarized below.
Energy Compensation Energy compensation increased when the soup contained MSG/IMP, compared to soup without the compounds (70% versus 44%). Energy compensation refers to how much a subject adjusts calorie intake in response to the calories they at previously. A higher percentage means they compensated better; in others they appropriately reduced calorie intake in response to their prior calorie ingestion. It would take an energy compensation of 100% for a subject to completely compensate for the extra calories in the high calorie soup. In other words, to not end up eating more total calories at the end of the day. Because the high calorie soup contains 187 more calories than the control soup, 100% compensation would mean that a subject has to eat 187 fewer calories at lunch. This was not the case, since study participants eating soup with MSG/IMP had an average energy compensation of 70%, compared to 44% for people that ate the soup without MSG/IMP. Hunger and Fullness Hunger and fullness were assessed several times throughout the study, including after every 50 grams
Low calorie 126 kcal
High calorie 311 kcal
Had MSG/IMP
Didn’t have MSG/IMP
472g
381g
408g
446g
of soup eaten. The subjects eating the soup containing MSG/ IMP experienced a significant increase in hunger after tasting the soup, compared to the soup without MSG/IMP. This increase in hunger is likely related to the flavor-enhancing and umami characteristic of MSG/IMP. There was no difference in perceived hunger or fullness when measurements were taken after all the soup had been eaten. This means the increase in hunger after tasting the MSG/IMP soup was temporary. It’s possible that if study participants were allowed to eat as much soup as they wanted, people eating the MSG/IMP soup would have eaten more soup than the control group. After tasting lunch (pasta with tomato sauce), the subjects who ate the high calorie soup with MSG/IMP rated their hunger as significantly lower and fullness as significantly higher than any of the other three soup groups (high calorie soup without MSG/ IMP and both control soups +/- MSG/IMP). This indicates that MSG/IMP was most effective in inducing satiety when it was added to the high calorie soup.
Umami from East to West C
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Chinese Cabbage
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Chicken Leeks
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Carrots
Beef
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Study participants that ate a soup with added MSG/IMP ate fewer calories at lunch, compared to people that ate soup with no additives.
What does this study tell us?
This study tells us that the combination of MSG and IMP makes people hungrier when they first taste the food, but that effect wanes over time. Hence, eating these compounds tends to result in higher energy compensation at the next meal. Total caloric intake from the soup and lunch was higher when subjects ate the higher calorie soup than when they ate the lower calorie soup control, whether or not there was MSG/IMP added. Eating a high calorie soup with MSG/IMP did not result in 100% energy compensation at lunch, but people that ate the high calorie soup containing MSG/IMP had a higher energy compensation than people that ate the high calorie soup without additives.
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Hoshi Shiitake (dried shiitake)
Katsuobushi
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Kombu (dried kelp)
( dried bonito flakes)
Iriko
(dried anchovies)
Based on these study results, it’s reasonable to think that umami foods naturally rich in free glutamic acid and IMP could help reduce daily calorie intake when eaten 45 minutes before a meal. In other words, an umami appetizer could help you eat less at lunch. That is, if it replaces a food low in umami rather than being added as an extra snack. It isn’t clear if this effect persists over a four hour time period - from breakfast to lunch, for example. The study was conducted on young people, with an average age of 22. While it’s reasonable to expect these results to apply to older adults as well, this has not been tested. Appetite regulation and taste sensation may change with age. In a study comparing older and younger rats, younger rats had a stronger preference for the umami flavor than older rats. Furthermore, all of the study participants were either a healthy weight or overweight. There were no obese participants. It’s possible that appetite regulation and energy compensation behave differently in people who are obese, have certain medical conditions, like diabetes, and who take certain medications. For example, obese people tend to have higher levels of leptin, a hormone involved in inducing satiety. While this may seem counterintuitive, people who are obese can have leptin resistance, which means leptin is less effective at causing satiety. It is unclear how MSG/IMP may affect appetite and subsequent food consumption in obese people. This study was funded by Ajinomoto, a company that manufactures MSG. The authors report that Ajinomoto had no role in the design of the study, analysis, or writing of the manuscript. Ajinomoto was the first company to manufacture MSG after a chemist invented it. It’s interesting to note that the inventor of MSG coined the term “umami.” Umami appetizers may result in fewer calories consumed afterwards at lunch compared to non-umami appetizers, but that doesn’t necessarily mean that umami is a weight loss aid. A high-calorie umami appetizer is still likely to increase overall calories, as is a standalone umami snack. But replacing a non-umami appetizer with an umami one may help lower calorie intake.
The big picture
Protein-rich foods are known to be satiating, and it had previously been hypothesized that protein itself was the component causing the satiating effect. However, MSG and IMP are also a component of many protein-rich foods. This study went beyond previous studies in examining the satiety effect of these compounds by controlling for protein in the soup. It is also the first study to clearly show a biphasic effect of MSG/IMP, in that this combination causes an immediate increase in appetite but a later decrease in appetite. Since the researchers tested both high protein soups and low protein soups, the authors were less likely to have the satiety effects of MSG/IMP washed out by the satiety effects of high protein content. From this study, it’s safe to conclude that there is likely an additive satiety effect from both protein and IMP in protein-containing foods. Future research could compare the effects of MSG/IMP against MSG combined with guanosine monophosphate (GMP), which is an umami-promoting compound typically found in lower-protein foods.
Frequently Asked Questions
Should I expect that a pre-lunch soup with MSG/IMP in it will affect lunch intake? That is unclear based on these study results. The lunch meal after the pre-lunch soup was 75% carbohydrate, as it consisted of only pasta with tomato sauce. This may not mirror the macronutrient balance of your lunch. The controlled breakfast was also very high in carbohydrates, so this also may affect how the MSG/IMP influenced appetite. In addition, it is unknown who specifically is most and least impacted by MSG/IMP. Is MSG harmful, and does it occur naturally in food? There is no concrete evidence that MSG is harmful in small doses. It is likely relatively safe, as long as you don’t experience any side effects from it or consume massive amounts. You can
read more about the safety of MSG here. MSG does not occur naturally in food. Free glutamate, however, does occur naturally in aged cheeses, soy sauce, walnuts, and nutritional yeast. MSG is often associated with headaches in those who believe that they are sensitive. “MSG symptom complex” is a condition that has not been verified as a diagnosable, but research is not conclusive. Are umami foods a weight loss aid? Since umami flavor does not result in 100% calorie compensation, eating more calories in the presence of umami is not beneficial for weight loss. For example, eating a high calorie soup with added MSG/ IMP results in higher total caloric intake than eating a lower calorie soup. Incorporating both strategies, eating a lower calorie soup that is also umami, would be the most helpful way to reduce total calorie intake to promote weight loss. I’ve read that there is some concern that MSG might actually increase obesity risk. Is this true? Injecting MSG into the brains of rats and mice induces obesity. Since animals are used as a model to study obesity, this effect has been argued as evidence that MSG causes obesity. However, it has been demonstrated that very little ingested MSG actually reaches the brain. Human studies have produced mixed results, with some studies noting increased food intake, while others show the opposite. There is currently insufficient evidence to suggest that MSG contributes to weight gain, and effects beyond those expected from added MSG in junk foods are unlikely.
What should I know?
The results of this study suggest that the combination of MSG and IMP added to soup consumed 45 minutes before a meal decreases caloric consumption at that subsequent meal by about 20-50 calories, when the calorie content of the soup is held constant. This indicates that MSG/IMP, used as a substitute for the savory flavor that comes from naturally-occurring IMP and free glutamate in foods, may increase satiety and thus decrease subsequent food intake, but only by a small amount. There is an applicability issue with the results of this study. In this particular study, the pre-lunch soup was a 450 gram portion. More soup was not provided. In the real world, we’re free to choose to eat more of a food if it’s pleasing and has a strong umami flavor due to MSG or free glutamate and IMP. This could lead to more food consumed, which could theoretically increase the total number of calories consumed in a day. Based on this study and available research, eating a controlled quantity of a low calorie umami dish before a main meal may slightly decrease caloric intake at that subsequent meal. Still, eating more food just because it’s umami flavor will not aid weight loss, due to the increased caloric intake. More research is needed in this interesting area of appetite and intake regulation. ◆
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