Formulators and marketers have delectable opportunities to promote one of the most sensorial antioxidant sources available to the palate. Emma F Pickford explores the research
All these years, chocolate may have been falsely accused of promoting heart disease, weight gain and obesity; of being detrimental to diabetics; and of being the devilish cause of 'chocolate cravings.' A literature review substantiates that these accusations are unfounded.1From a nutritional point of view, when chocolate is consumed as part of a varied, balanced diet, it can provide important nutrients—including antioxidants in cocoa—not to mention a unique source of sensorial pleasure.
The chocolate that we enjoy today is a pleasurable, simple, confectionery snack consisting of only five essential components: cocoa materials (cocoa liquor, cocoa butter, cocoa powder), milk materials (milk solids, milk fat), sugars (sucrose, lactose), emulsifiers (usually lecithin) and flavours (usually vanillin). Often, chocolate is combined with other high-quality ingredients, called inclusions, such as nuts, cereals and fruit. (See Table 1)
Data support neither greater palatability nor craving for chocolate, nor higher consumption of chocolate confectionery in the obese. Thus, in the absence of any longitudinal data, there is no evidence to implicate chocolate consumption in the aetiology of obesity.2 Becoming overweight is a result of a complex interplay between physiological factors, including energy intake that exceed expenditure and/or gene-nutrient interactions, along with socio-psychological factors, such as how we make our food choices when faced with a wide variety of readily available, inexpensive, tasty, energy-dense foods.
Dieticians suggest that people with diabetes should balance their diet and maintain a normal level of blood sugar before and after meals. This advice applies to both type 1 diabetes (insulin dependent) and type 2 diabetes (non-insulin-dependent). The potential for foods to cause a blood-glucose response is described by its glycaemic index (GI). This index compares a food's effect on blood sugars after consumption with a standard, usually glucose or white bread. Alongside this, the insulin index of a food is a measure of the amount of insulin the body produces in response to a particular food.
The majority of chocolate products produce glycaemic and insulin responses that are lower than those of white or wholemeal bread (the average glycaemic index of chocolate products being 49). One reason for the relatively low glycaemic index is the high fat content, since fat in food is well known to slow gastric emptying. The quantity and quality of the protein may be another explanation.3 In some cases, chocolate products produce high insulin responses, which could lead to rebound hypoglycaemia (low blood-sugar levels).
However, this is not a universal finding, and therefore concerns about rebound hypoglycaemia are considered to be scientifically unfounded.4 Scientific opinion is that chocolate confections are harmless, within moderation, in the diets of people with diabetes. People with type 1 and type 2 diabetes should ask their health professional to help them to incorporate chocolate into their diet.
Cocoa butter—the fat in cocoa—consists of approximately 35 per cent stearic acid, 34 per cent oleic acid and 26 per cent palmitic acid.5 Researchers demonstrated that consumption of stearic acid elicits a neutral cholesterolaemic response with no effect on total cholesterol. Also, when study participants ate one milk chocolate bar daily as a substitute for a high-carbohydrate snack, it increased HDL cholesterol and decreased plasma triglycerides.6
Concerning blood-clotting, stearic acid does not adversely affect platelet function and appears to play no role in the thrombogenic events that can lead to heart disease.7
Recently, cocoa and chocolate products have been identified as a dietary source of antioxidants called polyphenols. Studies have shown that certain cocoa powders have an antioxidant activity equivalent to, or greater than, many fruits and vegetables. Researchers discovered that the antioxidant activity of dark chocolate is more than twice that of prunes, which had the highest rating of the fruits and vegetables tested.8
Researchers found that when healthy humans consumed a flavonoid-rich cocoa beverage, it inhibited platelet activity and increased the time for blood to clot.9 Furthermore, cocoa flavonoids may benefit cardiovascular health by improving immune function,10 helping prevent inflammation of blood vessels,11 reducing thrombosis, promoting normal endothelial function and blocking the expression of cellular adhesion molecules.12
The consumption of a cocoa rich in flavonols, a subgroup of flavonoids, may be associated with the modulation of nitric oxide,13 which is produced in the lining of blood vessels and exerts protective properties that are important for cardiovascular health. In a recent study (the first of its kind), researchers compared a low-dose aspirin with a flavonol-rich cocoa beverage and found reductions in platelet aggregation in both.14
In response to this emerging evidence, the US Department of Agriculture is developing a food composition database on the flavonoid content of various foods.15
There are many theories regarding the reasons people report chocolate cravings. One involves the pharmacology of chocolate, which contains biologically active methylxanthines. Theobromine is the main methylxanthine in cocoa, with a lower level of caffeine and traces of theophylline. Caffeine concentrations in solid chocolate bars are approximately 10-30mg/40g serving,16 whereas levels in coffee are approximately 80-100mg per cup.17 Chocolate products contribute very little to the average daily intake of caffeine (0.03 mg/kg adults, 0.09 mg/kg for children).
Although the theobromine content of chocolate is higher than the caffeine content, the physiological effect of theobromine is much weaker. Scientists seem to agree that the low methylxanthine content of chocolate products per ratio of one's total diet is unlikely to cause a noticeable physiological or mood effect in the majority of individuals.18
The neurophysiological theory of chocolate craving suggests that it could be due to the effect of carbohydrate consumption on serotonin metabolism. Although this can be demonstrated in the laboratory, a food item that contains minimal amounts of protein does not produce this effect.19 If this were true, humans would be equally likely to crave boiled potatoes.20 We don't!
The premenstrual phase has been associated with cravings for sweet items, possibly due to low progesterone levels. However, there is no consistent evidence that an increase in chocolate consumption occurs, and increased craving might generally reflect an increase in premenstrual appetite. Also, when progesterone levels are increased, this does not influence the level of craving.21
A more plausible explanation for chocolate craving lies in its sensory characteristics.18 Chocolate delivers a unique combination of aroma, taste and texture. Cocoa butter has a melting point just below body temperature, providing a luxurious texture and sensation upon melting in the mouth, along with the sweetness of a high sugar content.
Then there is the influence of culture and gender. Comparing Americans with Spaniards, in both cultures women crave sweet rather than savoury foods, while the reverse is true of men. Among sweet cravers, chocolate craving is much more frequent among American women (44.6 per cent) than men (17.4 per cent), but no such gender difference occurs for Spaniards (28.6 per cent for women and 22.2 per cent for men).22
These studies indicate that there may not be any validity in the accusations against chocolate—either for its role in heart disease, obesity or diabetes. On the other hand, there is a rich body of research now developing that suggests that the opposite may be true—that the antioxidant components of cocoa and chocolate may have significant health benefits. The fact that some people may crave chocolate is linked to its unique sensory characteristics. Chocolate is intended to bring pleasure, and in addition can contribute some useful nutrients—as part of a balanced and varied diet.
1. Rössner S. Chocolate—divine food, fattening junk or nutritious supplementation? Eur J Clin Nutr 1997;51:341-45.
2. Bolton-Smith C, Hetherington MM. Obesity: taste preferences and chocolate consumption. In: Knight I, editor Chocolate and cocoa: health and nutrition. Oxford: Blackwell Science 1999. 177-94.
3. Brand Miller JC. Chocolate consumption and glucose response in people with diabetes. In: Knight I, editor. Chocolate and cocoa: health and nutrition. Oxford: Blackwell Science 1999.
4. Wolever TMS, Brand Miller J. Sugar and blood glucose control. Am J Clin Nutr 1995;62:871S-93S.
5. Kris-Etherton PM, et al. The role of fatty acid saturation on plasma lipids, lipoproteins and apolipoproteins: I. Effects of whole food diets high in cocoa butter, olive oil, soybean oil, dairy butter and milk chocolate on the plasma lipids of young men. Metabolism 1993;42:121-9.
6. Kris-Etherton PM, et al. Effects of milk chocolate bar per day substituted for a high-carbohydrate snack in young men on an NCEP/AHA Step 1 diet. Am J Clin Nutr 1994;60:1037S-42S.
7. Kris-Etherton PM, Etherton TD. Cardiovascular health: role of stearic acid on atherogenic and thrombogenic factors. In: Knight I, editor. Chocolate and cocoa: health and nutrition. Oxford: Blackwell Science 1999.
8. Hammerstone JF. Identification of procyanidins in cocoa and chocolate using high-performance liquid chromatography/mass spectrometry. J Ag Food Chem 1999:47:490-6.
9. Rein D. Cocoa inhibits platelet activation and function. Am J Clin Nutr 2000:72:30-5.
10. Mao T. Cocoa procyanidins and human cytokine transcription and secretion. J Nutr 2000;130:2093S-9S.
11. Schramm DD. Chocolate procyanidins decrease the leukotriene-prostacyclin ratio in humans and human aortic endothelial cells. Am J Clin Nutr 2001;73:36-40.
12. Kris-Etherton PM, Keen CL. Evidence that the antioxidant flavonoids in tea and cocoa are beneficial for cardiovascular health. Curr Opin Lipidol 2002;13:41-9.
13. New research suggests potential link between eating flavanol rich chocolate and improved blood vessel function. Findings presented at American Heart Association annual meeting provide further indications that certain chocolates may support heart health. Chicago 2002 Nov 20.
14. Pearson DA, et al. The effects of flavanol rich cocoa and aspirin on ex vivo platelet function. Thrombosis Res 2002;106:191-7.
15. Bhagwat DB. Development of USDA's Flavonoid Database for Foods, Beltsville Human Nutrition Research Center, ARS, USDA, Beltsville (Md); Jean Mayer USDA HNRC on Aging; Tufts University Schools of Medicine and Nutrition, Boston; General Mills, Agricultural Research Service, Minneapolis.
16. Agpar JL, Stanley Jr MT. Methylxanthines, In: Knight I, editor. Chocolate and cocoa: health and nutrition. Oxford: Blackwell Science 1999.
17. Binns NM. Caffeine. Brit Nutr Foundation Nutr Bull 2000;20(suppl):278S-85S.
18. Rozin P, et al. Chocolate craving and liking. Appetite 1991;17:199-212.
19. Leathwood PD. Tryptophan availability and serotonin synthesis. Proc Nutr Soc 1987;146:143-56
20. Benton D. Chocolate craving: biological or psychological phenomenon? In: Knight I, editor. Chocolate and cocoa: health and nutrition. Oxford: Blackwell Science 1999.
21. Michener W, et al. The role of low progesterone and tension as triggers of perimenstrual chocolate craving: some negative experimental evidence. Physiol and Behav 1999;67:417-22.
22. Zellner DA. Food liking and craving: a cross-cultural approach. Appetite 1999;33:1, 61-70.