Meat and health

The International Congress of Meat Science and Technology is an annual, global
conference where around 430 delegates from the worlds of science and business come together to share knowledge and discuss scientific and technical advances in the meat sector. ‘Think meat, think healthy’ was the central theme of the 61st edition held in August 2015.

This article – part 2 of a report on the congress which revolves around meat-related research – is focused on the relationship between meat consumption and human health. (Click here for part 1)

Packed full of nutrients

Much research has been – and continues to be – done into ‘meat in relation to health’. In his presentation, scientist David Klurfeld (USDA Beltsville) took the audience way back in time to an era when humans became omnivores. It has been proposed that cooking meat allowed for evolution of larger brains and that led to the success of humankind as a species. “Meat is one of the most nutrient-dense foods, providing high-quality protein, haem iron, zinc and vitamins B6 and B12.”

Higher risks?

And yet despite these advantages we hear many negative reports about the impact of consumption of red or processed meat (particularly in large quantities) on our health. Epidemiologic studies have demonstrated a connection between the consumption of red or processed meat and conditions such as obesity, type 2 diabetes, cardiovascular diseases and cancers of multiple organs. Most observational studies report small, increased relative risks. On 26 October 2015, the World Health Organization's IARC identified the consumption of large amounts of processed meat as a hazard and classified it as a cause of cancer.

Stubborn misconceptions

From a scientific perspective, David claimed, there are many limitations of such studies because the researchers did not have sufficient control over a number of factors. Examples include a lack of pre-specified hypotheses, multiple comparisons, the inability to accurately estimate meat intake of the study group and influences from many factors – including body weight, fruit/vegetable intake, physical activity, smoking and alcohol. In a nutshell, the observational studies are heterogeneous and do not fulfil many of the points proposed by AB Hill in 1965 for inferring causality. Nevertheless, accepting small, statistically significant risks as 'real' from observational associations in these studies has resulted in a long list of stubborn misconceptions. For example, links have been drawn between beta-carotene and lung cancer, between low-fat diets and breast cancer or heart disease. These ‘conclusions’ have never been confirmed in randomised trials.

Out of business

David quoted S. Shapiro from Pharmacoepidemiology & Drug Safety (2004): “In adequately designed studies we can be reasonably confident about BIG relative risks, sometimes; we can be only guardedly confident about relative risk estimates of the order of2.0, occasionally: we can hardly ever be confident about estimates of less than 2.0, and when estimates are much below 2.0, we are quite simply out of business.”

Such a research outcome can however be used to design a targeted study based on a hypothesis. During the congress it was put forward that future research should focus on the metabolism of proteins and derived amino acids after the intake of protein-dense foods and meals (instead of isolated protein sources). This proposal was enthusiastically received by the audience.

Muscle protein breakdown in the elderly

Stefan Gorissen (NUTRIM Maastricht University) held a presentation on the muscle protein synthesis response to food ingestion. The preservation of skeletal muscle mass is of great importance for maintaining both metabolic health and functional capacity. Muscle mass maintenance is regulated by the balance between muscle protein breakdown and protein synthesis rates. The daily muscle protein breakdown activities and the synthesis of 1 to 2% occur in muscle tissue. In healthy people breakdown and synthesis are in dynamic equilibrium, but that balance is disrupted in the elderly. ‘Sarcopenia’ is the medical term for the loss of muscle mass and the associated reduction in muscle strength as a direct result of aging.

'What is the ideal approach in terms of nutrition and exercise to optimally stimulate muscle protein synthesis in the elderly?'

Desire for prevention

Both for the breakdown and the synthesis of muscle it has been demonstrated that these processes react very quickly to physiological activity and food intake, and especially to the ingestion of protein. The amount of protein ingested important, but so too is the type of protein. Easily digestible protein with a high level of essential amino acids (such as whey protein) leads to a high response per gram. Other important factors that affect the digestion of proteins are: the timing of the ingestion, the preparation method and the mastication (chewing) process. Furthermore it has been demonstrated that more protein is absorbed by muscles following physical activity than following a period at rest.

Challenge

Needless to say, prevention of sarcopenia is desirable. But what is the ideal approach in terms of nutrition and exercise to optimally stimulate muscle protein synthesis in the elderly? Many older people eat three meals a day, but between their evening meal and breakfast the next morning there can be a gap of around 13 hours during which no food is ingested. Experiments have shown that dietary intake of extra protein in between leads to a clear increase in protein synthesis. Elderly people could perhaps be able to prevent sarcopenia by eating a protein-rich snack in the evening. I challenge the sector to develop a new, protein-rich evening snack especially for older people. There are still many health gains to be made.

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For more information about the presentations and/or the IARC report please contact chief editor Judith Witte or the author of this article, Theo Verkleij.