The role of learning. Babies are born with taste receptors for sweet, sour, salt, bitter and umami taste qualities. They like sweet tastes, and in fact sweet foods are effective in reducing distress in babies (Benton, 2002) This leads us to ask whether we have innate (genetic) food preferences. Food neophobia is widespread in the animal kingdom as a basic survival mechanism. Neophobia was also found in babies and children although it decreases with age. Birch and Marlin found that exposure of two year olds to a new food over 6 weeks increased preference for that food, a minimum of 8-10 exposures was necessary for the dislike to change to a preference. The children learn the food is safe. Birch (1999) proposes that we are not born with innate (genetic) food preferences, but with an innate ability to associate food tastes and smells with the consequences of eating that food. In this way we learn from experience the foods that are good for us and those which are not. Birch’s proposal that we inherit an ability to make such associations suggest an interaction between nature and nurture. We learn through experience what is good for us (nurture) but that learning depends upon brain circuits that are innate (nature)

Parents attitudes and food preference. Parents, usually the mother, provide food for the child. Therefore the mothers attitude will affect the child’s preferences. As expected, there is a significant correlation between the diets of mothers and children (Ogden, 2007). Once the child starts school, peers become more important. Studies have shown that modelling using admired peers can increase consumption of fruit and vegetables (lowe, Dowey and Horne, 1998) Children are also exposed to widespread food advertisement on television to make the food more attractive. This can be effective in developing preferences, but unfortunately advertised food tends to be high in carbohydrates and fat contributing to childhood obesity. Nicklaus et al: Investigated the correlations between food preferences at 2 and 22 in a longitudinal study of French children. Although there were only low correlations between overall diet at age 2 and adult diet, for about 50% of dietary items there was a clear association between childhood and adult preferences especially for cheese and vegetables. Preference for meat decreases in females as they got older, possibly due to ethical and health concerns. There was clear links between childhood food preferences and adult diet but there were also changes suggesting other factors are involved. Adult preferences were assessed by questionnaires and interviews which raises the problem of social desirability bias as participants may have given ‘healthier answers’

Mood. Studies which investigate the effect of mood and distress on eating often look for evidence of either hypophagia (excessive under eating) or hyperphagia (excessive over eating) as well as changes in patterns of consumption and food preferences. Ogden suggests that dieters who overeat in response to low mood may be seeking to mask their negative mood with a temporary heightened mood induced by eating. The serotonin Hypothesis: Carbohydrates such as chocolate contain the amino acid- Tryptophan. This is usually used by the brain in the manufacture of the neurotransmitter serotonin. Low levels of serotonin are associated with depression. It has been proposed that people with stress or depression take in carbohydrates because it leads to increased levels of serotonin in the brain which reduced their depression. The opiate hypothesis : opiate neurotransmitters such as enkaphlin and beta-endorphin are released from neurons and act at synapses with opiate receptors. Opiates produce pleasurable feelings and euphoria. It seems likely the brains opiate pathways are part of our reward system, a network of pathways that control our feelings of pleasure and reward. This reward system is activated by natural rewards such as food and drink. Unfortunately this increase in serotonin levels only occurs when we take in pure carbohydrates, which is extremely rare. The presence of even a small amount of protein as in chocolate prevents the tryptophan entering the brain and so serotonin levels will not change. The serotonin hypothesis is unlikely to explain the antidepressant effects of high carbohydrate diets.

Mood. Grigson: found that opiate drugs (e.g. Heroin) increase food intake and increase the perceived tastiness of food. Blocking the endorphin system with the drug naloxone reduces food intake, especially sweet foods and supresses thoughts about food. This shows the system is involved in feeding regulation. Glucose reliably improves performance on cognitive tasks. However if people are given a glucose drink but told it’s a placebo then the effect disappears. Expectations override the actual intake of glucose. The sweet taste of a glucose solution immediately produce a release of insulin from the pancreas gland, anticipating a rise in blood glucose levels. This happens even with drinks sweetened with saccharine, a compound that is not processes by the body. However we have learnt that sweet tastes usually mean glucose, so our body prepares itself. Anticipation and expectation on the basis of learning and experience affect out response to it. Because food is so vital we are very efficient at learning associations between taste and consequences (taste aversion) this applies to positive effects as well- we learn to associate the mood-improving effects of carbohydrates with the sweet taste so when we taste the food, we have expectations about the consequences.

Culture. Significant differences in diets across cultures. This is often due to availability of certain foods. Globalisation of the food market means that even remote communities food choice is increasing. Leshem: compared Bedouin Arab women living in a desert encampments with those now living in urban environments, and also with a group of urban Jewish women. The diet of urban Bedouins was similar to that of the desert living Bedouins (despite the access to a far greater range of food in the urban settings) a much high intake of carbohydrates, proteins and salts that the Jewish group. In a later study Leshem found that the diet of a Muslim community living in the same urban setting as a Christian group was much higher in carbohydrates, protein and salt that the Christian community, although body mass was the same. Wardle et al, surveyed the diets of 16,000 young adults across 21 European countries and found that in general the number eating a basic and healthy diet was low ( females doing better than males) People in the Mediterranean countries eat more fruit and vegetables that England and Scotland. People in Scandinavian counties eat the most fibre, people in Portugal, Italy and Spain eat the least. Conclusion: even with equal access to a range of foods, different ethnic groups have different diets, demonstrating the influence of culture and dietary history on food preferences.

Issues and debates: Reductionist: Biological explanations, especially the evolutionary approach imply that much of our diet is determined by nature rather than nurture (genetics rather than environment) this ignores cultural and social changes in food availability and choice over the years of human evolution. The study of feeding behaviour and its disorders has focused largely on western and other industrialised societies. It has ignored third word countries whose main aim is to avoid starvation rather than cope with obesity. This is an example of research that is culturally biased. Diet can show clear cultural variations, as Leshem’s work demonstrates. However we cannot conclude that these are environmental or ‘nurture’ effects rather than inherited tendencies (nature) where groups such as the Bedouin have lived in the same environment for many generations, it may be that their diet today is a mixture of innate factors and culturally transmitted preferences.