L7 & L8 | Food Choice I

Food Choice I

• The broader problem of food choice and innate factors are based on Logue Ch.5
• Appetite: The psychology of eating and drinking
• What dictates human food choice?
  • Factors dictating what foods we choose to eat will be examined
  • Definitions: liking and preference
    • Preference is relative (e.g., stale bread vs deep-fried spider)
    • Liking is absolute (e.g., neither would probably be liked)
• Study of food choice is important for health reasons
  • Dietary choices have a major effect on health
  • Obesity/overweight is increasing at 1% per year
  • Avoidance of dietary-related cancer and heart disease (e.g., processed meats and colon cancer; saturated fat and heart disease)
  • Cost savings from avoiding diet-related diseases
  • Improving diet is cheaper than psychotherapy and helps with recovery from depression
• Study of food choice is important for business reasons
  • Processed food manufacture in Australia has a large turnover (74 Billion dollars in 10 years)
  • Fast food sales alone in 2015 were worth 17 Billion dollars
  • Food and liquor sales account for nearly half of all retail spending
  • Australian food exports are worth 30 Billion dollars, accounting for 11% of exports, and processed food is the most profitable sector
• Innate preferences
  • Genetic and environmental influences on food preferences interact
  • Focus on food preferences influenced by genes, examining five cases (sweet, salty, milk, personality, and other factors)

Innate Preferences

• Although it's simpler to split the discussion into genetic vs environmental influences, they generally interact
• Bitter sensitivity is moderated by parental influence
• Focus on food preferences that are primarily influenced by genes
• Five cases: sweet, milk, salty, bitter, personality factors (neophobia)
• Emphasize that the most important genetic disposition is capacity to learn about food

Sweet

• In almost every animal studied, a sweetened food is preferred over a non-sweetened one.
• Sweet foods typically signal calories, energy, and are relatively rare (e.g., honey, honey ants, fruits).
• Liking for sweet foods has several effects, including a role in African slavery and current high rates of sugar consumption in the US
• It's a significant factor in obesity: liquid form of sugar causes minimal fullness and compensation

Is liking or preference for sucrose in our genes?

• Newborns even prefer sucking a sucrose-impregnated nipple to a plain one

Physiology

• The tongue has one type of sweetness receptor, which passes signals to the chorda tympani nerve (more fibers dedicated to 'sweet' than other tastes)
• This nerve sends signals to areas in the brain that drive liking for sweetness (periaqueductal gray and nucleus accumbens shell)

Genetic Evidence I

• Table sugar breaks down into fructose in the gut; intolerance is caused by an inability to move fructose across the gut wall or (making a person quite unwell)
• The failure to find difference in sucrose consumption/liking between MZ and DZ twins for sweet things also suggests, it's probably similar in many people

Genetic Evidence II

• Preference to like sucrose can be bred into rats
• Concentration of peak liking to sucrose can be shifted upward, selectively breeding rats who like the sweetest things
• Reduction of sucrose liking in 'supertasters'due to more sweetness receptors

Salt

• Many animals and people will go to great lengths to obtain salt, which is often not readily available
• Salt is essential for many functions, including maintaining blood pressure and hydration
• During times of limited access to salt, people often go to great lengths to find it.
• Salt is an essential part of our diet and lack of salt is fatal
• Reflects in the Roman word for salary as it came from the Roman word for a salt ration

Salt Craving in Humans I

• Babies may not be initially sensitive to salt, but they readily consume salt-formulas, after mixing errors, showing they can't taste high levels of it, but have readily consumed and react to it
• Mothers exposed to dehydration during pregnancy may have children who prefer higher salt concentrations

Salt Craving in Humans II

• What evidence do we have in humans that salt cravings are directly under physiological control?
• Demonstrating that salt preferences peak in adolescence suggests a role for hormones
• Exercise and salt preferences (increased salt cravings after intense exercise)
• Evidence in mice that experience of high saline diet produces less frostbite when compared to a low salt diet

Salt in Food

• Salt is added as a bulking agent, preservative, and flavor enhancer in processed foods; this is a major reason for excess salt consumption

Evolution and Salt Craving

• Cystic fibrosis is a genetic disorder that affects the intestines and airways
• Carriers of the cystic fibrosis gene excrete far less salt, which may be beneficial in certain environments

Bitter

• Things that are bitter are almost always poisonous, hence the facial expression for bitter foods
• Exposure does appear to affect preference for bitter foods: If people are exposed to bitter tastes, their preference for bitter foods can be reduced
• The Aymara people in Latin America reject bitter tastes

Milk

• Being a mammal is synonymous with consumption of milk in infancy, specifically milk is slightly sweet (7% lactose), and it comes as no surprise that infants readily consume it.
• No animal consumes milk into adulthood, the puzzle of why Norther Europeans can/do consume milk into adulthood
• A key question is why can people tolerate milk (e.g., Northern Europeans) longer into adulthood when other mammals don't.

Lactase

• Loss of lactase production after 2-3 years of age in humans makes the ability to tolerate milk, in Northern Europeans, a consequence of exposure (continued consumption) rather than genetic ability to produce lactase.

Genetic Control of Lactase I

• The ability to produce lactase into adulthood is likely determined by genetics
• Two evolutionary arguments for genetic traits tied to lactase tolerance (famine means death and vitamin D/calcium absorption)

Genetic Control of Lactase II

• The pastoralist account of lactase tolerance is supported by its presence in North-South gradient in Europe (c.f. cloud cover), correlating with average cloud cover
• Also evident in all pastoralist societies, such as Tuaregs in Africa
• Presence of lactose tolerance is a dominant genetic trait, enabling for rapid spread in populations

Personality

• Personality traits are heritable, influencing food preferences (e.g., conscientiousness is linked to fruit and veg intake)
• Impulsivity is linked to higher consumption of risky foods, like fast foods, processed foods, and soft drinks

Genes - Conclusion

• Strong genetic influences on preferences for sweet, salty, bitter foods, and milk tolerance.
• Capacity to learn about food as the most important genetic influence on food choices.
• Learning about what and how to eat is a major focus for a later lecture.

Food Choice II

• Biological, Experience, and Development aspects of food preferences.

A Biological Needs Model of Food Choice

• Many believe food likes and dislikes are dictated by biological needs for specific micro/macronutrients
• If the body is deficient in a particular nutrient (e.g., iron, vitamin B) it will try to seek that particular food for its needs
• Wisdom of the body" theory: suggests that if people could freely choose any food and eat for their nutritional needs, their body will choose a diet that perfectly meets those needs- but is that accurate

Wisdom of the Body I

• Idea that bodies can naturally select a nutritionally complete diet developed between 1900 and 1960
• Clara Davies's study in 1935 and similar work in animals is a critical finding in the human domain

Wisdom of the Body II

• Concerns about how social interaction and circumstances might affect food preference choices, and potentially influence observations on the ability of people/animals to choose healthy diets

Wisdom of the Body III - Animals

• Strongest claims for the wisdom-of-the-body theory is in animal studies examining thiamine deficiency in rats (rats can select diets rich in thiamine if they've been deprived of it, but it might be due to an aversion to previous deficient diet)

Wisdom of the Body IV - Animals

• Broader look at animal data doesn't strongly support the wisdom-of-the-body theory
• Early studies often lacked statistical analysis
• When more palatable alternatives are available, animals will choose them (over healthier, less desirable foods).

Wisdom of the Body V - Scurvy

• Individuals with scurvy (lack of Vitamin C) show a similar lack of self-selection when deciding what to eat
• It took 200 years for the world to determine the link between diet and scurvy, showcasing how biological choices aren't necessarily indicative of what's needed

Advertising I

• Advertising of food, especially to children in the United States is very powerful
• The amount of money spent on advertising food (e.g., fast food) is extremely high
• Children, exposed to food advertisements, often request those advertisements (to their parents) leading to greater likelihood of purchase

Advertising II

• Child-oriented ads are most effective when foods or drinks are associated with particular TV characters
• Research shows that exposure to TV ads and subsequently asking for purchase is overwhelmingly correlated with higher consumption and purchases among children.

Getting from Milk to Adult-Like Food Preferences

• The cumulative effect of various childhood experiences in shaping adult food preferences
• Exposure to foods and learning about nutritional value and preferences

Conclusion

• Both innate and experiential factors are important in shaping food choices.
• The most important determinant of what people eat is their culture: Cultural norms about food dictate what is safe and permissible to eat and not to eat. The main focus of the next lecture.

Explore the psychology behind human food choices based on Logue Chapter 5. This quiz delves into factors influencing our preferences and likings, along with implications for health and business. Learn how understanding food choice can impact obesity, dietary-related diseases, and economic factors.