̽��ֱ�� of Cambridge - Dairy

Opinion: Dairy got the all-clear this week - but was it justified?

cjb250 — Wed, 17 May 2017 08:55:43 +0000

A new study, published recently in the European Journal of Epidemiology, appeared to give dairy products a clean bill of health. ̽��ֱ��researchers found no evidence for an increased risk of cardiovascular disease or death from consuming dairy products – even full-fat dairy products.

These findings were widely covered in the media – headlines mostly singled out cheese, saying it does not increase the risk of heart attack or stroke. Some of the reports claimed that saturated fats do not increase the risk of cardiovascular disease, but the study didn’t examine saturated fat consumption itself.

It’s worth taking a closer look at the science behind the headlines.

Key findings

This new study is a type of study known as a meta-analysis because it pools data from earlier studies and analyses the combined data. In this instance, there were 29 studies that the researchers felt were of sufficiently high quality to include in their analysis. There were 783,989 participants in all, with an average age of 57 years. Each of the studies had asked healthy people about their usual diet and then followed them up over five to 25 years. Over the course of the follow up, 93,158 participants died (from any cause), 28,419 developed coronary heart disease and 25,416 developed cardiovascular disease (heart attack and stroke).

̽��ֱ��international team of researchers who conducted the meta-analysis found no statistically significant link between any of total dairy consumption (high- and low-fat combined), high-fat dairy consumption, low-fat dairy consumption, and risk of death, risk of coronary heart disease or risk of cardiovascular disease.

Among individual dairy products, milk consumption was not associated with cardiovascular disease or death, and neither was yoghurt consumption. For cheese and fermented dairy products (including sour milk products, cheese or yoghurt), there was a minor reduction in the risk of cardiovascular disease, but it seemed to be because of one large study. When this study – which showed an extreme result – was removed from the analysis, the link disappeared.

Strengths and weaknesses

Although not new, this research included the largest sample of participants to date on this topic and investigated both total and individual types of dairy products. ̽��ֱ��researchers applied sound meta-analysis methods and were careful to use extra analyses (called sensitivity analyses) to check their initial findings. However, there are some limitations of the individual studies, and meta-analysis, which are worth mentioning.

Although up to 29 studies were identified for the meta-analysis, the actual number available for each analysis was considerably less than 29. For example, for high-fat there were five studies for looking at death, nine for heart disease and seven for cardiovascular disease. And for yoghurt consumption, there were only three studies. This can compromise the confidence we can place in some of the results. For example, we can’t be certain that the association of yoghurt intake with cardiovascular disease is indeed null, as fermented dairy products – especially yoghurt – have been associated with reductions in cardiovascular risk, weight gain and type 2 diabetes in other research.

Another weakness is that the meta-analysis combined data from observational studies. Observational studies are not as robust as clinical trials. But this is a common limitation of studies of diet as it’s often not possible to keep people under close scrutiny – as required in clinical trials – for many years while comparing one type of diet with another.

With observational studies, there is always a risk that some other factor – one not being investigated – is the actual reason for the observed associations. To get around this, researchers take “confounding factors” into account when analysing the data. In this instance, the studies took into account such factors to very different degrees – some only including a very limited number of factors such as age, sex, smoking, or social status (such as education), while there are also other important factors such as obesity, physical activity, alcohol intake, ethnicity and other foods consumed that were missed in some studies. It is possible such health and lifestyle factors not taken into account by the researchers may have influenced the results.

Inconsistency in the definitions of groups of dairy products might also obscure interpretation. For example, some studies might include full-fat yoghurt in high-fat dairy products, whereas other studies might include both types of yoghurt in low-fat dairy products. Some dairy products such as cream and butter were not individually assessed in the meta-analysis.

Wider context

There is emerging evidence from other research, that not all foods that are rich in saturated fats have the same impact on health. This is probably because foods rich in saturated fat also contain many other ingredients. For instance processed red meat is associated with an increased risk of type 2 diabetes, whereas
dairy products, particularly yoghurt, are associated with a decrease in risk of type 2 diabetes, as we have also shown in two studies (EPIC InterAct and EPIC-Norfolk).

Most dietary research relies on people reporting their dietary habits, and this can be prone to error and inaccuracies, which can mask the detection of links between diet and health. Our own research has shown that measuring biomarkers of food intake in blood or urine can open up new possibilities for understanding links with disease and bypass errors due to self-reporting in questionnaires.

New evidence suggests that saturated fat in dairy may not be as bad for us as we once thought, but there isn’t enough evidence, just yet, to change dietary guidelines which, in the UK, recommend that saturated fats should make up fewer than 11% of all calories consumed from food.

Eirini Trichia, PhD student, MRC Epidemiology Unit, ̽��ֱ�� of Cambridge and Nita Forouhi, Programme Leader, MRC Epidemiology Unit, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

When it comes to health claims around the food we eat, it’s worth taking a closer look at the science behind the headlines, say Eirini Trichia and Professor Nita Forouhi from the MRC Epidemiology Unit, writing for ̽��ֱ��Conversation.

Jules Morgan

Cheese

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Yoghurt cuts risk of type 2 diabetes

fpjl2 — Thu, 06 Feb 2014 12:33:47 +0000

Published in the journal Diabetologia, the study showed that eating yoghurt in place of a portion of other snacks such as crisps also reduced the risk of developing type 2 diabetes.

̽��ֱ��study found that higher consumption of yoghurt, compared with no consumption, can reduce the risk of new-onset type 2 diabetes by 28%, and that higher consumption of low-fat fermented dairy products – including all yoghurt varieties and some low-fat cheeses – also reduced the relative risk of diabetes by 24% overall.

According to lead researcher Dr Nita Forouhi, from the Medical Research Council Epidemiology Unit at the ̽��ֱ�� of Cambridge: “This research highlights that specific foods may have an important role in the prevention of type 2 diabetes and are relevant for public health messages.”

̽��ֱ��research was based on the large EPIC-Norfolk study, which includes more than 25,000 men and women living in Norfolk, UK.

It compared a detailed daily record of all the food and drink consumed over a week at the time of study entry among 753 people who developed new-onset type 2 diabetes over 11 years of follow-up with 3,502 randomly selected study participants.

This allowed the researchers to examine the risk of diabetes in relation to the consumption of total dairy products as well as individual dairy products.

Total dairy, total high-fat dairy or total low-fat dairy consumption was not associated with new-onset diabetes once important factors like healthier lifestyles, education, obesity levels, other eating habits and total calorie intake were taken into account. Total milk and cheese intakes were also not associated with diabetes risk.

However, those with the highest consumption of low-fat fermented dairy products (such as yoghurt, fromage frais and low-fat cottage cheese) were 24% less likely to develop type 2 diabetes over the 11 years, compared with non-consumers.

Previous studies on the link between dairy product consumption (high fat or low fat) and diabetes have proved inconclusive, prompting this more detailed assessment of diary product consumption.

Type 2 diabetes is common and its incidence is increasing. In 2013, there were 382 million people worldwide with diabetes and by 2035 that number will increase to 592 million, according to the International Diabetes Federation.

While this type of study cannot prove that eating dairy products causes the reduced diabetes risk, dairy products do contain beneficial constituents such as vitamin D, calcium and magnesium. In addition, fermented dairy products may exert beneficial effects against diabetes through probiotic bacteria and a special form of vitamin K (part of the menaquinone family) associated with fermentation.

“At a time when we have a lot of other evidence that consuming high amounts of certain foods, such as added sugars and sugary drinks, is bad for our health, it is very reassuring to have messages about other foods like yoghurt and low-fat fermented dairy products, that could be good for our health,” said Dr Forouhi.

Eating more yoghurt can reduce the risk of new-onset type 2 diabetes, researchers at Cambridge have found.

It is very reassuring to have messages about other foods like yoghurt and low-fat fermented dairy products, that could be good for our health

Nita Forouhi

jules:stonesoup

Home made yoghurt

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New strain of MRSA discovered

gm349 — Fri, 03 Jun 2011 09:10:27 +0000

Scientists have identified a new strain of methicillin-resistant Staphylococcus aureus (MRSA) which occurs both in human and dairy cow populations.

̽��ֱ��study, led by Dr Mark Holmes at the ̽��ֱ�� of Cambridge, identified the new strain in milk from dairy cows while researching mastitis (a bacterial infection which occurs in the cows’ udders).

̽��ֱ��new strain’s genetic makeup differs greatly from previous strains, which means that the ‘gold standard’ molecular tests currently used to identify MRSA - a polymerase chain reaction technique (PCR) and slide agglutination testing - do not detect this new strain. ̽��ֱ��research findings are published today in the journal ̽��ֱ��Lancet Infectious Diseases.

Dr Laura García-Álvarez, first author of the paper, who discovered the new strain while a PhD student at the ̽��ֱ�� of Cambridge’s Veterinary School, said: “To find the same new strain in both humans and cows is certainly worrying. However, pasteurization of milk will prevent any risk of infection via the food chain. Workers on dairy farms may be at higher risk of carrying MRSA, but we do not yet know if this translates into a higher risk of infection. In the wider UK community, less than 1% of individuals carry MRSA – typically in their noses – without becoming ill.”

̽��ֱ��scientists discovered the antibiotic resistant strain while researching S. aureus, a bacterium known to cause bovine mastitis. Despite the strain being able to grow in the presence of antibiotics, when they attempted to use the standard molecular tests available – which work by identifying the presence of the gene responsible for methicillin resistance (the mecA gene) - the tests came back negative for MRSA.

When Dr Matt Holden and a research team at the Wellcome Trust Sanger Institute sequenced the entire genome (decoding all of the genes in the bacteria’s DNA) they realised that the new strain possessed unconventional DNA for MRSA. They found that the new strain does have a mecA gene but with only 60% similarity to the original mecA gene. Unfortunately, this results in molecular tests (which identify MRSA by the presence of the mecA gene) giving a false negative for this strain of MRSA.

Subsequent research revealed that the new strain was also present in humans. During the study, the new strain was found in samples from Scotland, England and Denmark (some from screening tests and others from people with MRSA disease). It has since been identified in Ireland and Germany. Additionally, by testing archived S. aureus samples, the researchers have also identified a recent upward trend in the prevalence of the antibiotic resistant bacteria.

Dr Mark Holmes said: “ ̽��ֱ��majority of MRSA testing in British hospitals is performed by seeing if the bacteria will grow in the presence of antibiotics, typically oxacillin and cefoxitin, rather than methicillin - which is now no longer manufactured. This type of testing detects both the new MRSA and conventional MRSA.

“However, it is important that any of the MRSA testing that is based on detection of the mecA gene - i.e. PCR based testing, or slide agglutination testing - be upgraded to ensure that the tests detect the new mecA gene found in the new MRSA. We have already been working with public health colleagues in the UK and Denmark to ensure that testing in these countries now detects the new MRSA.”

̽��ֱ��new research also raises questions about whether cows could be a reservoir for the new strains of MRSA.

Dr Holmes added: “Although there is circumstantial evidence that dairy cows are providing a reservoir of infection, it is still not known for certain if cows are infecting people, or people are infecting cows. This is one of the many things we will be looking into next.

“Although our research suggests that the new MRSA accounts for a small proportion of MRSA – probably less than 100 isolations per year in the UK, it does appear that the numbers are rising. ̽��ֱ��next step will be to explore how prevalent the new strain actually is and to track where it is coming from. If we are ever going to address the problem with MRSA, we need to determine its origins.”

Scientists at the Health Protection Agency (HPA) co-authored this paper, providing the analysis of the human samples of the new strain. Dr Angela Kearns, head of the HPA’s Staphylococcus Reference Laboratory said: “There are numerous strains of MRSA circulating in the UK and the rest of Europe. Even though this new strain is not picked up by the current molecular tests, they do still remain effective for the detection of over 99 per cent of MRSAs. This new strain can be picked up by another type of test, which has shown to be effective in trials in the UK and elsewhere in Europe.

“This is a very interesting find and the HPA is currently involved in further research to screen a wider population of MRSA samples to ascertain how prevalent it is. It’s important to remember MRSA is still treatable with a range of antibiotics and the risk of becoming infected with this new strain is very low.”

With funding from the Medical Research Council, the researchers will next be undertaking prevalence surveys in people and in dairy cattle in the UK to determine how much new MRSA is present in these populations. They will also be performing an epidemiological study on farms to identify any factors that may be associated with infection by the new MRSA, to look for further new MRSA strains, and to explore the potential risks of the new strain to farm workers.

Antibiotic resistant bacteria found in both humans and dairy cows.

Although our research suggests that the new MRSA accounts for a small proportion of MRSA – probably less than 100 isolations per year in the UK, it does appear that the numbers are rising. ̽��ֱ��next step will be to explore how prevalent the new strain actually is and to track where it is coming from. If we are ever going to address the problem with MRSA, we need to determine its origins.

Dr Mark Holmes, Department of Veterinary Medicine at the ̽��ֱ�� of Cambridge

Royalty-free image Collection by Flickr

Cow

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