Coronary heart disease epidemics: not all the same.

BACKGROUND: Coronary heart disease (CHD) was an important epidemic in many developed countries in the 20th century and there is concern because the epidemic has affected Eastern Europe, Russia and Central Asia and is starting to affect developing countries. METHODS: The epidemic curves of CHD mortality for 55 countries, which had reliable data and met other selection criteria, were examined using age-standardised death rates 35-74 years from the World Health Organization. Annual male mortality rates for individual countries from 1950 to 2003 were plotted and a table and a graph used to classify countries by magnitude, pattern and timing of its CHD epidemic. RESULTS: The natural history of CHD epidemics varies markedly among countries. Different CHD patterns are distinguishable including "rise and fall" (classic epidemic pattern), "rising" (first part of epidemic) and "flat" (no epidemic yet). Furthermore, epidemic peaks were higher in Anglo-Celtic countries first affected by the epidemic, and subsequent peaks were less, except for the recent extraordinary epidemics in Russia and Central Asian republics. There were considerable differences among some continental or regional geographical areas. Eastern European, South American and Asian countries have quite different epidemic characteristics, including shorter epidemic cycles. CONCLUSIONS: It cannot be assumed that WHO regions or any other geographical regions will be useful when analysing CHD epidemics or deciding upon strategic policies to reduce CHD in individual countries. The needs for action that are urgent in some countries are less so in others, and even regional country groups can have quite different epidemic characteristics.

Some problems with Cochrane reviews of diet and chronic disease.

The sum of evidence-based nutrition has to be more than a Cochrane-type meta-analysis of randomised controlled trials (RCTs). Most of the evidence base in nutrition is observational, especially cohort studies. RCTs of diet change through to disease outcome are uncommon and the change has usually been addition or removal of only a single food component. Trials with whole diets through to disease outcome are rare and dietary changes made by individuals are unlikely to be an exact copy of the prescription. It is hard to even imagine a trial in which half (randomised) of a large group of middle-aged people agree to avoid vegetables for 5 y and be followed up to see who will develop cancer. Most of the USA's health claims, permitted by the Food and Drug Administration, are not supported by RCTs. But where controlled trials of nutritional change and disease outcome have been achieved, they must be reviewed very carefully. Two Cochrane reviews on diet and cardiovascular disease (CVD), published in the widely read British Medical Journal (BMJ), were criticised after their publication and the conclusions have not been subsequently adopted by expert committees. The first of these reviews was 'Dietary fat and prevention of CVD: a systematic review'. The second was 'Systematic review of long term effects of advice to reduce dietary salt in adults'. A critique of these two Cochrane reviews is presented here as a contribution to our discussion of the potential of Cochrane methodology to the reliability of knowledge about diet and disease.

The A2 milk case: a critical review.

This review outlines a hypothesis that A1 one of the common variants of beta-casein, a major protein in cows milk could facilitate the immunological processes that lead to type I diabetes (DM-I). It was subsequently suggested that A1 beta-casein may also be a risk factor for coronary heart disease (CHD), based on between-country correlations of CHD mortality with estimated national consumption of A1 beta-casein in a selected number of developed countries. A company, A2 Corporation was set up in New Zealand in the late 1990s to test cows and market milk in several countries with only the A2 variant of beta-casein, which appeared not to have the disadvantages of A1 beta-casein. The second part of this review is a critique of the A1/A2 hypothesis. For both DM-I and CHD, the between-country correlation method is shown to be unreliable and negated by recalculation with more countries and by prospective studies in individuals. The animal experiments with diabetes-prone rodents that supported the hypothesis about diabetes were not confirmed by larger, better standardised multicentre experiments. The single animal experiment supporting an A1 beta-casein and CHD link was small, short, in an unsuitable animal model and had other design weaknesses. The A1/A2 milk hypothesis was ingenious. If the scientific evidence had worked out it would have required huge adjustments in the world's dairy industries. This review concludes, however, that there is no convincing or even probable evidence that the A1 beta-casein of cow milk has any adverse effect in humans. This review has been independent of examination of evidence related to A1 and A2 milk by the Australian and New Zealand food standard and food safety authorities, which have not published the evidence they have examined and the analysis of it. They stated in 2003 that no relationship has been established between A1 or A2 milk and diabetes, CHD or other diseases.

Meat consumption and cancer of the large bowel.

Since the major reviews on diet and cancer by the World Cancer Research Fund (WCRF) and by the British Department of Health's Committee on Medical Aspects of Food Policy (COMA) in 1997 and 1998, additional epidemiological studies relating (red) meat consumption and colorectal cancer have been published or found by search. These are collected here. Thirty adequate case-control studies have been published up to 1999 (from 16 different countries). Twenty of them found no significant association of (red) meat with colorectal cancer. Of the remaining 10 studies reporting an association, some obtained statistical significance only in rectal or colon cancers, another only in men, not women, or found a stronger association with pasta and rice, or used an inadequate food list in the food frequency questionnaire. Fifteen cohort studies have now been published. Only in three were significant associations of (red) meat found with colorectal cancer. Two of these positive studies were from the same group in the USA (relative risk 1.7). The results of the third positive study appear to conflict with data from part of the vegetarians follow up mortality study. Here, five groups of vegetarians (in three different countries) with socially matched controls were followed up (total 76 000 people). Mortality from colorectal cancer was not distinguishable between vegetarians and controls. While it is still possible that certain processed meats or sausages (with a variety of added ingredients) or meats cooked at very high temperature carry some risk, the relationship between meats in general and colorectal cancer now looks weaker than the 'probable' status it was judged to have by the WCRF in 1997.

Cereal grains and coronary heart disease.

Cereal grains and their products provide around 30% of total energy intake in British adults, (much more than any of the other major food groups). Coronary heart disease (CHD) is the largest single cause of death in Britain and many other Western countries. This review examines the question whether there is a relation between cereal consumption and CHD. Several of the nutrients in cereals have known potential for reducing risk factors for CHD: the linoleic acid, fibre, vitamin E, selenium and folate. Cereals also contain phytoestrogens of the lignan family and several phenolic acids with antioxidant properties. Processing generally reduces the content of these nutrients and bioprotective substances. Although cereals at the farm gate are very low in salt, processed cereal foods, eg bread and some breakfast cereals, are high-salt foods and thus could contribute to raising blood pressure. Human experiments have clearly shown that oat fibre tends to lower plasma total and LDL cholesterol but wheat fibre does not. Rice bran and barley may also lower cholesterol but most people do not eat enough barley to have an effect. Cereal foods with low glycaemic index such as pasta and oats are beneficial for people with diabetes and might lower plasma lipids. Between 1996 and 2001 an accumulation of five very large cohort studies in the USA, Finland and Norway have all reported that subjects consuming relatively large amounts of whole grain cereals have significantly lower rates of CHD. This confirms an earlier report from a small British cohort. The protective effect does not seem to be due to cholesterol-lowering. While cohort studies have shown this consistent protective effect of whole grain cereals, there has been (only one) randomised controlled secondary prevention trial of advice to eat more cereal fibre. In this there was no reduction of the rate of reinfarction. The trial had some weaknesses, eg there were eight different diets, compliance was not checked objectively, and duration was for only 2 y. It appears valid to make health claims (as now permitted by the US FDA) that whole grain cereal foods and oat meal or bran may reduce the risk of CHD.

There are many Mediterranean diets.

Interest in Mediterranean diet began 30 years ago, when Ancel Keys published the results of the famous Seven Countries Study, Since 1945, almost 1.3 million people have come to Australia from Mediterranean countries as new settlers. There are 18 countries with coasts on the Mediterranean sea: Spain, southern France, Italy, Malta, Croatia, Bosnia, Albania, Greece, Cyprus, Turkey, Syria, Lebanon, Egypt, Libya, Malta, Tunisia, Algeria and Morocco. This study from which this report derives aims to investigate the influence of the food habits of immigrants from Mediterranean countries on Australian food intake. Here we look at the 'traditional' food habits of the above Mediterranean countries as told by 102 people we interviewed in Sydney, who came from 18 Mediterranean countries to Sydney. Most of the informants were women, their age ranged from 35 to 55 years. The interview was open-ended and held in the informant's home. It usually lasted around 1 1/2 hours. The interview had three parts. Personal information was obtained, questions relating to the food habits of these people back in their original Mediterranean countries and how their food intake and habits have changed in Australia were also asked. From the interviews, we have obtained a broad picture of 'traditional' food habits in different Mediterranean countries. The interview data was checked with books of recipes for the different countries. While there were similarities between the countries, there are also important differences in the food habits of the Mediterranean countries. Neighbouring countries' food habits are closer than those on opposite sides of the Mediterranean Sea. We suggest that these food habits can be put into four groups. The data here refer to food habits in Mediterranean countries 20 or 30 years ago, as they were recovering from the Second World War. There is no single ideal Mediterranean diet. Nutritionists who use the concept should qualify the individual country and the time in history of their model Mediterranean diet.

Family physicians and patients: is effective nutrition interaction possible?

This article summarizes presentations from an international workshop held in Heelsum, Netherlands, 14-16 December 1998 that was sponsored by the Dutch Dairy Foundation on Nutrition and Health, the Department of Nutrition at Wageningen Agricultural University, the Dutch College of General Practitioners, and the International Union of Nutritional Sciences. Twenty-one speakers and 12 other participants were invited from 9 countries: the Netherlands, the United States, the United Kingdom, Australia, Canada, Denmark, New Zealand, Spain, and Sweden. The workshop was chaired by GJAJ Hautvast and the scientific secretary was GJ Hiddink. Family physicians are highly trusted. Many consultations include a nutritional aspect, but physicians do not discuss nutrition with their patients as often as they could. Major barriers include short visit times, the paucity of nutrition teaching in medical schools, and poor compliance of patients with physicians' dietary prescriptions. Problems, practicalities, operational research, and some solutions were discussed at this meeting of leading family doctors with interested nutritionists. Family physicians have to distill the essentials for their patients from many different specialties ranging from ophthalmology to podiatry. They look for clarity of recommendations from nutrition researchers. Among developments discussed at the meeting that can increase nutritional work in family medicine are 1) new opportunities to teach nutrition in vocational training programs, 2) some manuals and a new journal specially written by nutritional scientists for family physicians, 3) nutritional advice being incorporated into computer software for family physicians, 4) more dietitians working with family physicians, and 5) nutrition training for practice nurses in some countries.

Comparing palmolein with different predominantly monounsaturated oils: effect on plasma lipids.

Our group has compared plasma lipids in randomised crossover trials in which approximately half the fat intake of subjects was changed from palmolein to each of three predominantly monounsaturated oils in a series of experiments in free living volunteers. With canola oil total cholesterols were lower than on palmolein; part of this reduction was due to lower HDL-cholesterol (HDL-c) so that total cholesterol/HDL-c was only 2% lower. With olive oil mean total cholesterols were the same as on palmolein but HDL-cholesterols were a little lower and LDL-cholesterols a little higher. Plasma lipid fatty acid patterns confirmed the diet change, showing 5% higher 16:0 on palmolein and 11% higher 18:1 on olive oil. To test the possibility that lack of effect of the extra palmitic acid in the palmolein-olive oil comparison was because subjects were young, thin and active, comparison of a third oil, high oleic sunflower oil (HOSO) with palmolein was made in both young and middle-aged subjects. Plasma total and LDL-cholesterols were 7% lower in the whole group on HOSO but HDL-c was also 5% lower so total cholesterol/HDL-c was only 3% lower than on palmolein. There was no difference in lowering of LDL-c on HOSO between young and older subjects. In comparisons of all three predominantly monounsaturated oils with palmolein a higher HDL-c on palmolein reduced the presumed health benefit of lower total cholesterols on canola and high oleic sunflower oil. The reason for no reduction of total cholesterol on olive oil compared with palmolein was presumably due to the higher linoleic and higher phytosterols in palmolein and higher squalene in the olive oil.

What nutrition knowledge and skills do primary care physicians need to have, and how should this be communicated?

The last Heelsum workshop agreed that general practitioners should concentrate on dietary advice for treatment or secondary prevention, though nutritional advice for health is part of the doctor's work with pregnancy, infants and the very old. Nutrition prescriptions contrast with drug prescriptions. For drugs information is authoritative, evidence-based and easily available. Drug prescriptions are potentially liable to litigation. Dietary prescriptions are less serious and more the patient's responsibility. Nutrition information comes in a plethora of different forms, some of it unscientific, some out of date, some commercially biased. While waiting for some system (?authoritative, ?electronic) that can help general practitioners (GPs) organise nutrition information, there are three modern books that have been written by nutrition specialists for GPs in the English language (there may be others in North America) and another was written for practice nurses. As well as general books like this most large countries have expert reports on some nutritional topics by government committees available for reference. In relating foods and food components to disease, most of the reliable evidence is about their effect on risk factors-plasma cholesterol, blood glucose, blood pressure or body weight. A smaller amount of evidence relates food intake data from large cohort studies to incidence of disease. Very few randomised controlled trials (the ultimate evidence-based medicine) have been achieved for nutrition. Dietary recommendations may have to change with time because of new research-and drugs. Advice for secondary prevention of coronary heart disease is shown as an example of this.