In this article, we consider the theory that some food cravings are physiological or biochemical in origin. We also take a look at whether they could be caused by an imbalance in hormonal and chemical substances in the brain and nervous system. Particular emphasis is places on serotonin.
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A complex situation
It is important to understand that research in this field is relatively recent and that there are many things we don't yet know about body chemicals and their effect on food cravings and excessive food intake that can lead to obesity.
New chemicals and hormonal substances are constantly being discovered and the bottom line is that we don't yet know exactly what chemical triggers can affect food intake.
Also keep in mind that the biochemistry of food intake is very complex and that much more research will be required before we can solve the problem of food cravings.
Serotonin
A study of the scientific literature shows that a chemical or so-called neurotransmitter (a chemical that transmits messages in the brain and nervous system), called serotonin (also referred to as 5HT), may play an important role in the control of food intake.
Research has shown that serotonin regulates carbohydrate intake and that tryptophan (one of the common amino acids) increases serotonin release from the brain. When serotonin levels in the brain drop, or are deficient, we develop cravings for carbohydrate-rich foods. So any treatment that can increase brain serotonin levels will help to counteract this drop in serotonin and help to curb carbohydrate cravings.
Most people 'self-medicate' themselves when they experience a drop in brain serotonin levels by eating carbohydrate-rich food like sugar, sweets, cakes, and chocolate. This often uncontrolled gorging inevitably leads to weight gain.
The serotonin-alcohol connection
Some research has also shown that drinking alcohol will increase brain serotonin levels, so that certain people suffering from alcohol addiction will crave carbohydrates when they are unable to drink alcohol.
A study conducted by Moorhouse and co-workers (2000) with alcohol-dependent subjects, who were either carbohydrate cravers or non-carbohydrate cravers, found that when the carbohydrate cravers were given a low-carbohydrate diet, they suffered from pronounced mood changes and had low serotonin levels.
This would explain why this type of alcohol-dependent person will crave carbohydrates to boost serotonin levels and tend to overeat carbohydrates when deprived of alcohol, in an attempt to boost serotonin levels.
Serotonin, mood disorders and cravings
Many studies have identified a link between mood changes, low serotonin levels and food cravings.
Dr Wurtman (1988, 1990, 1993) of the Massachusetts Institute of Technology, has published extensively on the association between depressed serotonin levels and affective disorders such as seasonal affective disorder (SAD – bouts of depression especially in winter), carbohydrate craving obesity (CCO) and premenstrual syndrome (PMS).
Researchers such as Wallins & Rissanen (1994) also suggest that other conditions such as atypical depression, anorexia, bulimia and binge eating disorder are associated with low serotonin levels that are, in turn, linked to food cravings.
In some of these conditions, the low serotonin levels lead to excessive food intake, particularly of highly refined carbohydrates (e.g. depression, bulimia and binge eating disorder), while in anorexia the disordered serotonin biochemistry causes cravings that the patient does not satisfy with food.
Food cravings and PMS
Many women experience food cravings at certain times of their menstrual cycle. Readers often report that they cannot stop themselves from gorging on sugar and sweets or from drinking litres of sugar-sweetened cold drinks at 'that time of the month'.
A team of South African researchers lead by Dr Buffenstein (1995) believe that cyclical fluctuations in food intake occur in women at various time during the menstrual cycle, with a drop in food intake just before ovulation and a peak just after ovulation.
In some cases, the changes in food intake in response to changes in the hormones produced by the ovaries, can amount to as much as 2500kJ per day. These researchers suggest that the hormone-induced changes in food intake could contribute to excessive energy intake and weight gain.
In addition to the influence exerted by ovarian hormones, a publication by Moller (1992) from the Department of Clinical Pharmacology in Denmark, suggests that serotonin participates in the regulation of mood and impulsive behaviours, including food cravings. It also governs eating patterns.
Solutions?
In view of the central role played by serotonin in regulating cravings for sweet carbohydrate foods and mood swings associated with depression, SAD, CCO, and PMS, the question now arises as to how we can influence our serotonin levels without overeating and causing weight gain.
There are a number of potential solutions.
Medication
a) Selective serotonin re-uptake inhibitors
Many antidepressant medications contain so-called selective serotonin re-uptake inhibitors, which increase the levels of serotonin in the brain and keep these levels steady.
If you suffer from depression associated with weight gain (a common combination) or SAD, CCO, or PMS, then it may be a good idea to ask your doctor about the use of selective serotonin re-uptake inhibitors that control the serotonin levels in the brain.
b) Weight-reduction medications
At present, there are only a few weight-reduction medications available in South Africa that influence serotonin levels.
One of these is Reductil, which contains sibutramine. According to my copy of the MDR, this chemical "is a serotonin(5-HT) and noradrenaline re-uptake inhibitor", that reduces body weight gain by a dual action to decrease calorie intake and increase energy expenditure.
This medication must be used with an energy-controlled diet and is primarily indicated for obese patients (BMI exceeding 30). The recommended duration of treatment is three months if the patient responds.
If a patient doesn't experience weight loss with Reductil, the manufacturers recommend that treatment should be stopped.
Dietary interventions
We know that eating carbohydrates and foods that contain the amino acid tryptophan will boost brain serotonin levels.
If you suffer from food cravings due to low brain serotonin levels, you may be able to control your cravings by making sure you eat a diet that is rich in carbs. However, the carbs you eat should not be loaded with additional fat, or be excessively high in energy. This excludes all chocolate, cakes, tarts, biscuits, desserts and sugar-sweetened cold drinks.
Concentrate on eating carbohydrates with a high-fibre content that are minimally processed, e.g. unsifted maize meal, Maltabella, high-fibre bran cereals, and oats for breakfast, plenty of fruit and starchy vegetables (especially sweet potatoes that are rich in fibre), and unprocessed grains such as brown rice and wholegrain wheat.
To boost your tryptophan intake, you need to have some protein, such as fat-free milk, yoghurt, and cottage cheese, lean meat, fish or eggs (stick to four eggs a week for heart health).
When next you experience a food craving, try having some fat-free yoghurt, or a wholewheat cracker, or dried/fresh fruit.
Food cravings are caused by many different factors, some of which are psychological in origin, while others are due to physiological derangements of the chemical balance in the body.
Try following a high-carbohydrate, high-fibre diet that includes some protein at each meal to prevent food cravings and mood swings, or ask your doctor for medical treatment if these food cravings are totally out of control. – (Dr Ingrid van Heerden, DietDoc, September 2006)
References:
(Reductil Package Insert; Other references available on request)
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