What did the research involve?
The researchers needed to obtain several sets of data to fill their model. Data for UK deaths from coronary heart disease, stroke and cancer were obtained from the Office for National Statistics, the General Register Office for Scotland and the Northern Ireland Statistics and Research Agency. Information on the population's intake of foods and nutrients was obtained from two sources: the average intake of fatty acids, fibre, and fruit and vegetables for 2005–7 was derived from the Expenditure and Food Survey, while estimates of salt intake came from the National Diet and Nutrition Survey, 2006.
The modelling also incorporated several meta-analyses of individual studies looking at diet and disease risk factors. The researchers looked at reviews that had pooled data from randomised trials, cohort studies or case-control studies, giving priority to meta-analyses of randomised trials. These different studies were combined in the model to calculate the change in risk of disease for an individual who changes his or her diet. To estimate the change in health outcomes with a change in diet at a population level, the model used the difference between current average consumption levels and recommended levels of different foods in the UK.
What were the basic results?
In a general summary of the main findings, the researchers calculated that:
About 33,000 deaths a year would be avoided if UK dietary recommendations were met. There would be a reduction in deaths from coronary heart disease of 20,800 (95% credible interval 17,845 to 24,069), a reduction of 5,876 for deaths from stroke (3,856 to 7,364) and a reduction of 6,481 for deaths from cancer (4,487 to 8,353). About 12,500 of these avoided deaths would be in people aged 75 or under. About 18,000 of the avoided deaths would be men and 15,000 would be women. More than 15,000 of the avoided deaths (nearly half the total figure) would be due to increased consumption of fruit and vegetables. Reducing average salt intake to 6g a day would avoid 7,500 deaths annually. The greatest number of deaths avoided would be in Northern Ireland and Scotland, whose populations are furthest from achieving dietary recommendations.
How did the researchers interpret the results?
The researchers say their study suggests that increasing average consumption of fruits and vegetables to five portions a day is the target likely to offer most benefit in terms of deaths avoided. They also say that reducing recommended salt levels to 3g daily and saturated fat to 3% of total energy would achieve a similar reduction in mortality.
They conclude that their calculations based on the Dietron model are robust, pointing out that their estimate of deaths avoided is lower than a previous government survey which calculated that 70,000 deaths a year could be avoided if government dietary recommendations were met. The estimates could be used in calculating the allocation of resources for interventions aimed at reducing chronic disease.
This well-conducted modelling study used various data sources to link consumption of different dietary components with disease risk factors (for example blood pressure, cholesterol and obesity) and subsequent mortality from coronary heart disease, stroke and cancer. The study supports previous research showing that diet plays a crucial role in health and that a diet with plenty of fruit and vegetables, fibre and low fat and salt levels can reduce the risk of chronic disease, in particular coronary heart disease. However, its predictions are made at the population level. A model such as this cannot predict individual risk, which will depend on many factors, including family history, smoking and other lifestyle habits.
It is important to note that the figures are based on the estimates and assumptions made when using a mathematical model, and not on reality. As the authors themselves note, the modelling technique they used may have led to “some degree of double counting” and that, therefore, their estimate of reduced mortalities if dietary recommendations were met is likely to be an overestimate. Also, the accuracy of the model depends to some extent on the quality of the meta-analyses that were included, and the quality of the individual studies that were pooled within these reviews in order to establish associations between diet and particular disease risk factors.
Overall, this study supports current dietary recommendations and even though it cannot predict how diet influences risk for individuals, it does indicate that keeping to dietary recommendations reduces the risk of disease.
Dietary recommendations include eating five portions of fruit and vegetables a day (about 440g) and 18g of fibre (provided by wholegrain foods and some fruit and vegetables). It is recommended that salt intake is limited to a maximum of 6g a day and that a third of total energy is provided by fats, with saturated fat comprising 10%. The researchers point out that in 2007, according to the estimated average intakes in the sources they used, none of the UK countries met these recommendations.
Metabolic syndrome is a cluster of risk factors which can result in heart disease and diabetes. Researchers have now found that poor diet and lack of exercise that lead to an imbalance in metabolism may also increase a child's risk of developing asthma.
Dr. Giovanni Piedimonte and researchers from West Virginia University School of Medicine analyzed data from nearly 18,000 children aged 4 to 12 years who were taking part in the Coronary Artery Risk Detection in Appalachian Communities (CARDIAC) project. Factors considered included triglyceride levels and evidence of acanthosis nigricans, which are raised patches of brown skin that are often biomarkers for insulin resistance.
The team also considered body mass index or BMI, and almost 21% of the children were considered obese. Fourteen percent of the children had asthma.
The researchers found that asthma prevalence among the children was strongly associated with certain symptoms of metabolic syndrome including dyslipidemia and abnormal glucose metabolism, but not weight status. Although those who were obese were more likely to have asthma, even children of a healthy weight who had imbalanced metabolism were at increased risk.
Certain metabolic factors participate in the asthma disease process by contributing to inflammation of the airways in the lungs and hyperreactivity (contraction of smooth muscle in the bronchial walls), says Dr. Piedimonte. He says that strict monitoring and control of triglyceride and glucose levels early in life may play a role in the management of chronic asthma in children.
Dr. Piedimonte would like to see the findings used as further support for universal lipid screening in children. “The rationale is that by using selective screening, we would have missed over a third of children with significant genetic dyslipidemia,” he said.
Both poor diet – one lacking in antioxidants but high in fat – and inadequate exercise play a role in the metabolic syndrome, a group of risk factors that increase the risk for coronary artery disease, stroke, and type 2 diabetes. The goal of treatment is often weight loss (if overweight), a minimum of 30 minutes of daily moderate intensity exercise, and a lowering of cholesterol, blood pressure and blood sugar through diet or medication.
Cottrell L, et al “Metabolic abnormalities in children with asthma” Am J Respir Crit Care Med 2010; DOI: 10.1164/rccm.201004-0603OC.
Eating red meat and processed meats like bacon sharply increased heart disease risk in women, U.S. researchers say.Researchers at Harvard School of Public Health in Boston suggest eating healthier protein-rich foods — such as fish, poultry, low-fat dairy and nuts — instead of red and processed meats, may reduce heart disease risk.
“There are good protein-rich sources that do not involve red meat,” first author Dr. Adam Bernstein says in a statement. “You don't need to have hot dogs, hamburgers, bologna or pastrami, which are all fresh or processed meats.”
The study, published in the journal Circulation: Journal of the American Heart Association, finds women having two servings per day of red meat had a 30 percent higher risk of developing coronary heart disease than those who had half a serving per day.
The risk of heart disease was lowered 30 percent when a daily serving of red meat was replaced by nuts. Another red-meat replacement — fish — lowered cardiac risk 24 percent and poultry reduced heart risk by 19 percent.
Bernstein and colleagues examined medical history and lifestyle — including diet — for 84,136 women, ages 30-55, enrolled the Nurses' Health Study from 1980 to 2006. During the 26-year period, the researchers documented 2,210 non-fatal heart attacks and 952 deaths from coronary heart disease.
Due to the many different ways that previous studies have investigated the association between height and heart disease, Dr Paajanen and her colleagues decided to compare the shortest group to the tallest group instead of using a fixed height limit.
From the total of 1,900 papers, the researchers selected 52 that fulfilled all their criteria for inclusion in their study. These included a total of 3,012,747 patients. On average short people were below 160.5 cms high and tall people were over 173.9 cms. When men and women were considered separately, on average short men were below 165.4 cms and short women below 153 cms, while tall men were over 177.5 cms and tall women over 166.4 cms.
Dr Paajanen and her colleagues found that compared to those in the tallest group, the people in the shortest group were nearly 1.5 times more likely to die from cardiovascular disease (CVD) or coronary heart disease (CHD), or to live with the symptoms of CVD or CHD, or to suffer a heart attack, compared with the tallest people.
Looking at men and women separately, short men were 37% more likely to die from any cause compared with tall men, and short women were 55% more likely to die from any cause compared with their taller counterparts.
“Due to the heterogeneity of studies, we cannot reliably answer the question on the critical absolute height,” write the authors in their study. “The height cut-off points did not only differ between the articles but also between men and women and between ethnic groups. This is why we used the shortest-vs.-tallest group setting.”
The findings have clinical implications. Dr Paajanen said: “The results of this systematic review and meta-analysis suggest that height may be considered as a possible independent factor to be used in calculating people's risk of heart disease. Height is used to calculate body mass index, which is a widely used to quantify risk of coronary heart disease.”
It is not known why short stature should be associated with increased risk of heart disease. Dr Paajanen said: “The reasons remain open to hypotheses. We hypothesize that shorter people have smaller coronary arteries and smaller coronary arteries may be occluded earlier in life due to factors that increase risk, such as a poorer socioeconomic background with poor nutrition and infections that result in poor foetal or early life growth. Smaller coronary arteries also might be more affected by changes and disturbances in blood flow. However, recent findings on the genetic background of body height suggest that inherited factors, rather than speculative early-life poor nutrition or birth weight, may explain the association between small stature and an increased risk of heart disease in later life. We are carrying out further research to investigate these hypotheses.”
Dr Paajanen said that it was important that short people should not be worried by her findings. “Height is only one factor that may contribute to heart disease risk, and whereas people have no control over their height, they can control their weight, lifestyle habits such as smoking, drinking and exercise and all of these together affect their heart disease risk. In addition, because the average height of populations is constantly increasing, this may have beneficial effect of deaths and illness from cardiovascular disease.”
In an editorial on the research published at the same time , Jaakko Tuomilehto, Professor of Public Health at the University of Helsinki, Helsinki, Finland, welcomed the study, writing: “The systematic review and meta-analysis on this topic . . . is well justified 60 years after the first observation and the hundreds of other papers which have been published since then on this topic. The results are unequivocal: short stature is associated with increased risk of coronary heart disease. This meta-analysis provides solid proof for this, but, as the authors conclude 'The possible pathophysiological, environmental, and genetic background of this peculiar association is not known'.”
He suspects that environmental events affecting growth before and after birth may be involved. “Socio-economic adversity in childhood is . . . associated with delayed early growth and shorter adult stature. The so-called catch-up growth during the first years of life among children who are born small has negative health effects in adulthood; much of the early growth is due to greater fat accumulation. Thus, it is most likely that short stature is the link to coronary heart disease, and that tallness is not a primary factor in preventing the disease, although it indicates healthy growth. Short stature seems to be a marker for risk.”
While more work is needed to understand the exact nature of the mechanisms at work, he writes that information on height can be used now for the prevention of heart disease and other chronic diseases linked to shortness. “Full term babies who are born small are likely to be short as adults. They should receive preventive attention early on. The primordial prevention of chronic diseases should start during foetal life, and health promotion should be targeted to all pregnant women with the aim of health development of the foetus. Low birth weight and some other birth characteristics can reveal potential problems during this period of life. After that, in babies with low birth weight, it is important to avoid excessive catch-up growth, i.e. early-life fatness.”
In adult life it becomes more difficult to discover best practices, but Prof Tuomilehto, thinks it is likely short adults would benefit from more aggressive risk factor reduction.
He concludes: “Most of us know approximately our own height ranking, and, if we are at the low end, we should take coronary risk factor control more seriously. On the other hand, tall people are not protected against coronary heart disease, and they also need to pay attention to the same risk factors as shorter people.”
Over the past several decades, the food industry has reduced the amount of saturated fat in many products, and the public has reduced the amount of saturated fat in their diet. However, there has been a wide variation in the types of nutrients that have replaced this saturated fat. For example, in many products saturated fats were replaced with trans fats, which have since been determined to be detrimental; and in the overall American diet saturated fat was generally replaced with increased consumption of refined carbohydrates and grains.
“The specific replacement nutrient for saturated fat may be very important,” said lead author Dariush Mozaffarian, assistant professor in the department of epidemiology at HSPH and the department of medicine at Harvard Medical School. “Our findings suggest that polyunsaturated fats would be a preferred replacement for saturated fats for better heart health.”
Results from prior individual randomized controlled trials of saturated fat reduction and heart disease events were very mixed, with most showing no significant effects. Other trials focused only on blood cholesterol levels, which are an indirect marker of risk. Large observational studies have also generally shown no relationship between saturated fat consumption and risk of heart disease events; for example, earlier this month in the American Journal of Clinical Nutrition, researchers from HSPH and Children's Hospital Oakland Research Institute performed a pooled meta-analysis of prior observational studies and found no evidence that overall consumption of saturated fat was related to risk of coronary heart disease or stroke events.
Some of these mixed findings may relate to absence of prior focus on the specific replacement nutrient for saturated fat; in other words, was saturated fat replaced primarily with carbohydrate, monounsaturated fats such as in olive oil, or polyunsaturated fats such as in most vegetable oils?
Mozaffarian and his HSPH colleagues, Renata Micha and Sarah Wallace, performed a systematic review and meta-analysis of all randomized controlled trials through June 2009 in which participants specifically increased their polyunsaturated fat consumption as a replacement for saturated fat and in which coronary heart disease events were documented. Eight trials met the inclusion criteria, totaling 13,614 participants with 1,042 coronary heart disease events.
The meta-analysis of the trials showed that increasing polyunsaturated fat consumption as a replacement for saturated fat reduced the risk of coronary heart disease events by 19%. For every 5% increase (measured as total energy) in polyunsaturated fat consumption, coronary heart disease risk was reduced by 10%. This is now just the second dietary intervention–consuming long-chain omega-3 fatty acids is the first — to show a reduction in coronary heart disease events in randomized controlled trials.
Currently, the Institute of Medicine guidelines recommend that a range of 5%-10% energy consumption come from polyunsaturated fats. In addition, some scientists and organizations have recently suggested that consumption of polyunsaturated fats (largely “omega-6” fatty acids) should actually be reduced due to theoretical concerns that such consumption could increase coronary heart disease risk.
The results from this study suggest that polyunsaturated fats from vegetable oils may be an optimal replacement for saturated fats, an important finding for dietary guidelines and for when food manufacturers and restaurants are making decisions on how to reduce saturated fat in their products. The findings also suggest that an upper limit of 10% energy consumption from polyunsaturated fats may be too low, as the participants in these trials who reduced their risk were consuming about 15% energy from polyunsaturated fats.
Support for this study was provided by the National Heart, Lung, and Blood Institute, NIH and a Searle Scholar Award from the Searle Funds at the Chicago Community Trust.
Increased intakes of omega-3 fatty acids may decrease the risk of heart disease and heart attack in people with low fish intakes, says a new study from The Netherlands. Daily intakes of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) of about 240 milligrams was associated with a 50 per cent reduction in the risk of coronary heart disease (CHD), compared with intakes of about 40 milligrams, according to findings published in the Journal of Nutrition. Furthermore, the highest average intake of DHA and EPA was associated with a 38 per cent reduction in the heart attack, said researchers from Wageningen University following a study with over 21,000 people with low fish intakes.
The heart health benefits of consuming oily fish, and the omega-3 fatty acids they contain, are well-documented, being first reported in the early 1970s by Jorn Dyerberg and his co-workers in The Lancet and The American Journal of Clinical Nutrition. To date, the polyunsaturated fatty acids (PUFAs) have been linked to improvements in blood lipid levels, a reduced tendency of thrombosis, blood pressure and heart rate improvements, and improved vascular function.
Omega-3 fatty acids, most notably DHA and EPA, have been linked to a wide-range of health benefits, including reduced risk of cardiovascular disease (CVD) and certain cancers, good development of a baby during pregnancy, joint health, and improved behaviour and mood.
Intakes of EPA plus DHA, and fish were assessed in 21,342 people aged between 20 and 65. Fish intakes ranged from 1.1 to 17.3 grams per day. Over the course of an average of 11.3 years, the researchers documented 647 deaths, of which 82 were linked to coronary heart disease, with 64 of these being heart attack.
According to the results, the highest average intake of EPA plus DHA (234 milligrams per day) was associated with a 51 per cent reduction in the risk of fatal CHD, compared to the lowest average intake (40 mg per day).
“In conclusion, in populations with a low fish consumption, EPA+DHA and fish may lower fatal CHD and [heart attack] risk in a dose-responsive manner,” wrote the researchers.
Source: Journal of Nutrition
“Marine (n-3) Fatty Acids, Fish Consumption, and the 10-Year Risk of Fatal and Nonfatal Coronary Heart Disease in a Large Population of Dutch Adults with a Low Fish Intake”
Authors: J. de Goede, J.M. Geleijnse, J.M. A. Boer, D. Kromhout, W. M.M. Verschuren