"Eat to Live, Not Live to Eat"
John H Weisburger, 2000
At one level of analysis, the long-term health benefits of food can be divided into three broad categories. The most basic level is where there's a focus on individual chemical components, eg riboflavin or glucose. At the next higher level it can concern the properties of individual foods, eg apples or olive oil, and at the highest level it can shift to dietry patterns where the makeup of the whole diet is the focus, eg the Mediterranean diet, which inlcudes mainly vegetables, fruits, whole grains, legumes, nuts and olive oil, some sea foods, poultry and dairy, optional red wine and limited red meats.
The first level is obviously the longer term goal in nutrition science, with the example of pure chemical drugs being enormously successful in controlling diseases and also through their development, leading to increased understanding of how they exert their effects in the body. But we're still generations away from understanding how hundreds of individual components in single foods interact and are treated in the body, let alone with normal meals when there is the added complexity of interactions across various foods. Even if eaten in isolation, individual food constituents will still interact with others at various stages of processing and distribution throughout the body before being stored, metabolised or eliminated. Plus, individual chemicals or foods can't supply all the necessary nutrients for long term well-being. So, we're mainly left, for the present, with studying the health effects of particular food patterns. Given the alarming negative trends such as the ever-increasing prevalence of obesity and diabetes in all developed countries, government agencies, health societies and individuals are all looking for direction to improve matters. As a result we have a continuing stream of new diet fads being promoted with full hyperbole, very often without adequate supporting scientific evidence. Consequently they inevitably fail at some stage and the public is sold the next marketing story.
Scientific evidence supporting a particular dietry pattern can be gained in various ways, with controlled human clinical trials being the gold standard. But these are difficult to set up with willing or suitable subjects, very expensive, sometimes have serious ethical limitations and usually take many years to complete. Then depending on the criteria for inclusion in the study they may have to be broadened or extended to cover different scenarios. Another common approach in seeking evidence is to design epidemiological studies where groups of subjects are examined for particular patterns. These are notorious for confounding factors affecting interpretation and they only show associations, but over time can provide valuable insight on promising future directions. The following is a summary of a large epidemiological study (Epidemiology 2007;18: 393-401) examining the impact of different dietry patterns on mortality of Chinese women.
Many foods and nutrients have been suggested to influence life expectancy. However, previous studies have not examined the relationship between dietary patterns and cause-specific mortality. This study prospectively examines the relationship of dietary patterns with total mortality and cause-specific mortality in a population-based cohort study of Chinese women. The Shanghai Women's Health Study is a population-based cohort study of 74,942 women aged 40 to 70 years at the time of recruitment (September 1996 to May 2000). Detailed dietary information was collected using a validated, quantitative food frequency questionnaire. The cohort has been followed using a combination of in-person interviews and record linkage with various registries. Dietary patterns, derived from principal component analysis, were examined for their relation to total mortality and cause-specific mortality using Cox regression models. After an average of 5.7 years of follow-up (423,717 person-years of observation), there were 1565 deaths. We derived three major dietary patterns that these women followed, vegetable-rich, fruit-rich, and meat-rich. The significant adjusted hazard ratios for the fruit-rich diet were 0.94 for all causes of death and 0.89, 0.79 and 0.51 for death caused by cardiovascular disease, stroke, and diabetes respectively. There were non-significant trends for the meat-rich diet pattern, with increased risk of diabetes and a slightly elevated risk of total mortality. There were no significant trends seen with the vegetable-rich diet. In general, a fruit-rich diet was related to lower mortality, whereas a meat-rich diet appeared to increase the probability of death.
It's interesting that the one pattern that was beneficial in a number of chronic diseases was a fruit-rich diet. Although vegetables are normally recommended together with fruit in a healthy diet, a major problem with the former is that usually they are cooked or processed in some way and this can result in major degradation of favourable nutrient properties of the fresh food. Of course many vegetables are not particularly palatable or flavoursome in the fresh state and need some cooking, but the goal in these cases should be to minimise negative outcomes. With a large cohort of more than 70,000 women, it's not surprising to find that the major fruits consumed were the staples of citrus, apples, pears, bananas, watermelon, peaches and grapes. Major vegetables were beans, rice stems, eggplant, celery, cucumber, cauliflower and cabbage. In the meat-rich diet pattern major foods were chicken, animal parts (heart, brain, tongue, tripe and intestines), liver, rice, pig's feet and pork chops. The biggest effect of fruit on specific disease mortality was with diabetes, where women in the top 25% of those conforming to the fruit-rich diet were 81% less likely to die than those in the bottom 25%.
We've all been told in health documentaries, magazines, news reports etc. that chocolate in moderation is good for you. It's delicious and the problem for almost everybody is that it can be hard to stop at only a few squares without eating the whole block in one go. It's a high calorie food because of the high fat content and the usual addition of milk products and sugar. Dark chocolate, where these additives are reduced or absent is healthier but is far less popular because of the reduced sweetness - to many it just tastes unpleasantly bitter. Chocolate is made from ground cacao bean kernels that come from the fruit tree Theobroma cacao. World production is centred in tropical countries, mainly west Africa.
After harvesting, the pods are broken, much of the flesh is removed and the seeds are then fermented, dried and exported worldwide. Kernels are roasted and pressed to extrude the cocoa butter primarily for chocolate production, and the remaining solid cocoa cake is dried and ground to produce cocoa powder. Separation of the two is not complete, but the powder contains a much higher concentration of health-promoting flavonoids (variable but average of 261mg/100g compared to 53 and 15 mg/100g in dark and milk chocolate respectively) and has lower calories (370 and 550kcal/100g respectively). There is also evidence that the milk products and sugars added to chocolates reduce flavonoid activity, and a further consideration is that the average serving size for cocoa powder is 3g, while the size for dark and milk chocolate is 17g and 32g, respectively. So if cacao products are eaten from a nutritional viewpoint rather than straight enjoyment, cocoa powder has the best of both worlds – higher effective flavonoids and lower calories. What does the research say about consuming cocoa powder? The following is a summary of a study published in the International Journal of Medical Sciences (2007), 4, 53-58.
Substantial data suggest that flavonoid-rich food could help prevent cardiovascular disease (CVD) and cancer. Cocoa is the richest source of flavonoids, but current processing reduces the content substantially. The indigenous Kuna Indians living in the Panamanian San Blas islands drink a natural flavanol-rich cocoa as their main beverage. This provides more than 900 mg/day and probably means they have the most flavonoid-rich diet of any population worldwide. We used diagnosis on death certificates to compare cause-specific death rates from year 2000 to 2004 on the mainland and San Blas islands where only Kuna live. In this period there were 77,375 deaths on the mainland and 558 deaths in the San Blas. As anticipated on the mainland, CVD was the leading cause of death (83 age adjusted deaths/100,000) and cancer was second (68). In contrast, the age-adjusted rate of CVD and cancer among island-dwelling Kuna was much lower, 9 and 4 respectively. Similarly, deaths due to diabetes mellitus were much more common on the mainland (24) than in the San Blas (6). This comparatively lower risk among Kuna in the San Blas from the most common causes of morbidity and mortality in much of the world possibly reflects a very high flavanol intake. However, many other risk factors could possibly be involved and an observational study such as the present cannot provide definitive evidence.
The authors are commendably cautious in recognising their study is not the last word on this topic, and recommend further work in the field. But given such a major impact on the common western chronic diseases, the question for individuals is – should I include some cocoa in my diet now while waiting for more exhaustive studies, or is it best to wait till the story has been overwhelmingly settled in perhaps the next 10 years? The authors of the above study did consider or evaluate some of the more obvious possible contributing factors. For example, genetic differences in the two populations are unlikely to be responsible because when the Kuna migrate to the mainland they rapidly acquire the same disease incidence as the mainlanders, they are an older population than the mainlanders which normally would lead to increased disease rates whereas theirs were lower, diet components in the two locations are not significantly different apart from cocoa, and so on. In addition to this study there are now many others focussed on different aspects and using different approaches, and generally they all point in the same direction – cocoa is good for you. The 900mg/day intake of the Kuna compares with average flavonoid intakes in the US, UK, Ireland and Australia of 190, 182, 177 and 130mg/day respectively.
A very common intermediate step in cocoa kernel processing is called alkalisation. This raises the pH, causes colour changes, reduces bitterness and improves water miscibility, but most importantly can destroy a lot of the beneficial flavonoids. If heavily alkalised, less than 5% of what was initially there may be left. Food processors accommodate the dominant sweet preference of consumers by alkalising, so that almost all retail supplies of cocoa powder will have been treated. The US requires alkalised cocoa products to be labelled as such, but here some dogged detective work will be required to track down ‘natural' cocoa powder if you want the full nutritional benefits. After bean fermentation which we have little/no control over, alkalisation is the principal cause of flavonoid loss. Most of the 5000-odd flavonoids known in plant materials are heat labile, but fortunately the main ones in cocoa are more resistant. This means cocoa powder can be incorporated into baked products such as biscuits, muffins and cakes without causing significant loss of nutrient benefits. However if some degree of rising is required, baking soda should be avoided, as it is alkaline and will result in major flavonoid breakdown.