Your Sense of Smell May be the Key to a Balanced Diet

Lila Reynolds wrote . . . . . . . . .

Walking past a corner bakery, you may find yourself drawn in by the fresh smell of sweets wafting from the front door. You’re not alone: The knowledge that humans make decisions based on their nose has led major brands like Cinnabon and Panera Bread to pump the scents of baked goods into their restaurants, leading to big spikes in sales.

But according to a new study, the food you ate just before your walk past the bakery may impact your likelihood of stopping in for a sweet treat – and not just because you’re full.

Scientists at Northwestern University found that people became less sensitive to food odors based on the meal they had eaten just before. So, if you were snacking on baked goods from a coworker before your walk, for example, you may be less likely to stop into that sweet-smelling bakery.

The study, “Olfactory perceptual decision-making is biased by motivational state,” was published in the journal PLOS Biology.

Smell regulates what we eat, and vice versa

The study found that participants who had just eaten a meal of either cinnamon buns or pizza were less likely to perceive “meal-matched” odors, but not non-matched odors. The findings were then corroborated with brain scans that showed brain activity in parts of the brain that process odors was altered in a similar way.

These findings show that just as smell regulates what we eat, what we eat, in turn, regulates our sense of smell.

Feedback between food intake and the olfactory system may have an evolutionary benefit, said senior and corresponding study author Thorsten Kahnt, an assistant professor of neurology and psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine.

“If you think about our ancestors roaming the forest trying to find food, they find and eat berries and then aren’t as sensitive to the smell of berries anymore,” Kahnt said. “But maybe they’re still sensitive to the smell of mushrooms, so it could theoretically help facilitate diversity in food and nutrient intake.”

Kahnt said while we don’t see the hunter-gatherer adaptation come out in day-to-day decision-making, the connection between our nose, what we seek out and what we can detect with our nose may still be very important. If the nose isn’t working right, for example, the feedback loop may be disrupted, leading to problems with disordered eating and obesity. There may even be links to disrupted sleep, another tie to the olfactory system the Kahnt lab is researching.

Using brain imaging, behavioral testing and non-invasive brain stimulation, the Kahnt lab studies how the sense of smell guides learning and appetite behavior, particularly as it pertains to psychiatric conditions like obesity, addiction and dementia. In a past study, the team found the brain’s response to smell is altered in sleep-deprived participants, and next wanted to know whether and how food intake changes our ability to perceive food smells.

According to Laura Shanahan, a postdoctoral fellow in the Kahnt lab and the first and co-corresponding author of the study, there’s very little work on how odor perception changes due to different factors. “There’s some research on odor pleasantness”, Shanahan said, “but our work focuses in on how sensitive you are to these odors in different states.”

Pizza and pine; cinnamon and cedar

To conduct the study, the team developed a novel task in which participants were presented with a smell that was a mixture between a food and a non-food odor (either “pizza and pine” or “cinnamon bun and cedar” – odors that “pair well” and are distinct from each other). The ratio of food and non-food odor varied in each mixture, from pure food to pure non-food. After a mixture was presented, participants were asked whether the food or the non-food odor was dominant.

Participants completed the task twice inside an MRI scanner: First, when they were hungry, then, after they’d eaten a meal that matched one of the two odors.

“In parallel with the first part of the experiment running in the MRI scanner, I was preparing the meal in another room,” Shanahan said. “We wanted everything fresh and ready and warm because we wanted the participant to eat as much as they could until they were very full.”

The team took a scientific approach to baking, using a scale to measure the exact amount of icing to place on each cinnamon roll
The team then computed how much food odor was required in the mixture in each session for the participant to perceive the food odor as dominant. The team found when participants were hungry, they needed a lower percentage of food odor in a mixture to perceive it as dominant – for example, a hungry participant may require a 50% cinnamon bun to cedar mixture when hungry, but 80% when full of cinnamon buns.

Through brain imaging, the team provided further evidence for the hypothesis. Brain scans from the MRI demonstrated a parallel change occurring in the part of the brain that processes odors after a meal. The brain’s response to a meal-matched odor was less “food-like” than responses to a non-matched meal odor.

Applying findings to future sleep deprivation research

Findings from this study will allow the Kahnt lab to take on more complex projects. Kahnt said with a better understanding of the feedback loop between smell and food intake, he’s hoping to take the project full circle back to sleep deprivation to see if lack of sleep may impair the loop in some way. He added that with brain imaging, there are more questions about how the adaptation may impact sensory and decision-making circuits in the brain.

“After the meal, the olfactory cortex didn’t represent meal-matched food odors as much as food anymore, so the adaptation seems to be happening relatively early on in processing,” Kahnt said. “We’re following up on how that information is changed and how the altered information is used by the rest of the brain to make decisions about food intake.”

Source: Northwestern University

In Pictures: Food of Roganic in Causeway Bay, Hong Kong

Contemporary British and European Cuisine

The Michelin 1-star Restaurant

Eating Walnuts Daily Lowered Bad Cholesterol and May Reduce Cardiovascular Disease Risk

Eating about ½ cup of walnuts every day for two years modestly lowered levels of low-density lipoprotein (LDL) cholesterol, known as “bad cholesterol,” and reduced the number of total LDL particles and small LDL particles in healthy, older adults, according to new research published today in the American Heart Association’s flagship journal Circulation.

Walnuts are a rich source of omega-3 fatty acids (alpha-linolenic acid), which have been shown to have a beneficial effect on cardiovascular health.

“Prior studies have shown that nuts in general, and walnuts in particular, are associated with lower rates of heart disease and stroke. One of the reasons is that they lower LDL-cholesterol levels, and now we have another reason: they improve the quality of LDL particles,” said study co-author Emilio Ros, M.D., Ph.D., director of the Lipid Clinic at the Endocrinology and Nutrition Service of the Hospital Clínic of Barcelona in Spain. “LDL particles come in various sizes. Research has shown that small, dense LDL particles are more often associated with atherosclerosis, the plaque or fatty deposits that build up in the arteries. Our study goes beyond LDL cholesterol levels to get a complete picture of all of the lipoproteins and the impact of eating walnuts daily on their potential to improve cardiovascular risk.”

In a sub-study of the Walnuts and Healthy Aging study, a large, two-year randomized controlled trial examining whether walnuts contribute to healthy aging, researchers evaluated if regular walnut consumption, regardless of a person’s diet or where they live, has beneficial effects on lipoproteins.

This study was conducted from May 2012 to May 2016 and involved 708 participants between the ages of 63 and 79 (68% women) who were healthy, independent-living adults residing in Barcelona, Spain, and Loma Linda, California.

Participants were randomly divided into two groups: active intervention and control. Those allocated to the intervention group added about a half cup of walnuts to their usual daily diet, while participants in the control group abstained from eating any walnuts. After two years, participants’ cholesterol levels were tested, and the concentration and size of lipoproteins were analyzed by nuclear magnetic resonance spectroscopy. This advanced test enables physicians to more accurately identify lipoprotein features known to relate to the risk of cardiovascular disease.

The two-year study had a 90% retention rate (632 participants completed the study). Complete lipoprotein analyses were available in 628.

Among key findings of all study participants:

  • At 2 years, participants in the walnut group had lower LDL cholesterol levels – by an average of 4.3 mg/dL, and total cholesterol was lowered by an average of 8.5 mg/dL.
  • Daily consumption of walnuts reduced the number of total LDL particles by 4.3% and small LDL particles by 6.1%. These changes in LDL particle concentration and composition are associated with a lower risk of cardiovascular disease.
  • Intermediate Density Lipoprotein (IDL) cholesterol also decreased. It is known that IDL cholesterol is a precursor to LDL and refers to a density between that of low-density and very-low-density lipoproteins. In the last decade, IDL cholesterol has emerged as a relevant lipid cardiovascular risk factor independent of LDL cholesterol.
  • LDL cholesterol changes among the walnut group differed by sex; in men, LDL cholesterol fell by 7.9% and in women by 2.6%.

“While this is not a tremendous decrease in LDL cholesterol, it’s important to note that at the start of the study all our participants were quite healthy, free of major non-communicable diseases. However, as expected in an elderly population, close to 50% of participants were being treated for both high blood pressure and hypercholesterolemia. Thanks in part to statin treatment in 32%, the average cholesterol levels of all the people in our study were normal,” Ros said. “For individuals with high blood cholesterol levels, the LDL cholesterol reduction after a nut-enriched diet may be much greater.”

“Eating a handful of walnuts every day is a simple way to promote cardiovascular health. Many people are worried about unwanted weight gain when they include nuts in their diet,” Ros said. “Our study found that the healthy fats in walnuts did not cause participants to gain weight.”

The major limitation of this investigation is that both participants and researchers knew who was and was not eating walnuts. However, the study did involve two very different populations with distinct diets. “The outcomes were similar in both groups, so we can safely apply the results of this study to other populations,” Ros said. More research is also needed to clarify the different LDL results in men and women.

According to the American Heart Association, walnuts are especially high in omega-3 fatty acids, the same heart-healthy fat found in oily fish. A serving size is a small handful or 1.5 ounces of whole nuts or 2 tablespoons of nut butter.

Source: American Heart Association

Corned Beef and Cabbage with Horseradish Mustard Sauce

Ingredients

1 large onion, cut into chunks
1-1/2 cups baby carrots
16 small (1-inch) red potatoes (about l-1/4 pounds)
1 corned beef brisket (2 to 2-1/2 pounds)
1/2 large head cabbage (1 pound), cut into 8 thin wedges

Horseradish Mustard Sauce

1/3 cup sour cream
1/3 cup mayonnaise
2 tablespoons Dijon mustard
2 tablespoons prepared horseradish

Method

  1. Place onion, carrots and potatoes in a slow cooker.
  2. Drain corned beef, reserving spice packet and juices from package.
  3. Place corned beef on vegetables. Pour juices over beef and top with contents of spice packet. Add enough water to barely cover beef and vegetables (about 4 cups). Cover and cook on LOW 8 to 9 hours or on HIGH 5 to 6 hours or until corned beef is fork-tender.
  4. Transfer corned beef to large sheet of heavy-duty foil. Wrap tightly and set aside.
  5. Add cabbage to vegetables, pushing down into liquid. Increase heat to HIGH. Cover and cook on HIGH 30 to 40 minutes or until vegetables are tender.
  6. combine sour cream, mayonnaise, mustard and horseradish in small bowl. Mix well.
  7. Reserve 1/2 cup of juices in slow cooker. Drain vegetables and transfer to serving platter.
  8. Thinly slice corned beef. Arrange on platter and drizzle with reserved juices.
  9. Serve with horseradish mustard sauce.

Makes 6 to 8 servings.

Source: Irish Cooking Bible


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