During the 5th Yogurt Summit, held in Buenos Aires during ICN2017, Professor Sharon Donovan (University of California, Davis, USA) explained why gut microbiota are recognized today as the intersection between diet and health.

It is widely accepted that obesity and associated metabolic diseases, including type 2 diabetes, are intimately linked to the diet. However, gut microbiota have also become a focus for research at the intersection of diet and metabolic health, said Donovan by introducing her talk during the 5th Yogurt Summit, in the framework of the International Congress of Nutrition. A body of knowledge highlighted the role of the gut microbiota as a mediator of dietary impact on the host metabolic status. Efforts are now focusing on the establishment of causal relationships between diet, gut microbiota and health in people but also on the prospect of therapeutic interventions, such as personalized nutrition.

What are the functions of the microbiome for health maintenance?

Over the past ten years, the rapid development of next generation sequencing (NGS) technologies has had a major impact on the field of metagenomics. In fact, a specific microbiome can be qualitatively and quantitatively characterized in-depth, using NGS-based approaches without the selection bias and constraints associated with cultivation methods. These technologies are also being used in the Human Microbiome Project, of which the aim is to obtain a complete catalogue of the microbes living in the various districts of the human body and to define their functions. The discoveries are exciting! The human microbiome is essential for human health and body functioning:  it intervenes in particular in modulation of bone-mass density, promotion of fat storage and angiogenesis, development and training of the immune system, biosynthesis of vitamins and amino-acids, resistance to pathogens, modification of the nervous system, appetite regulation… And these are the only known functions today. We begin to elucidate the enormous scientific and therapeutic potential of the human microbiome in almost all medical fields, commented Donovan.

Which diseases are linked to the microbiome?

What are the potential mechanisms linking microbiome and health? Gut microbiota contribute to the hydrolysis of complex polysaccharides from dietary fiber, and thereby might contribute to increasing energy harvest and to generating short-chain fatty acids (SCFAs) that affect the host’s metabolism in different ways. SCFAs might activate intestinal hormones that influences gut motility, increase intestinal transit rate, and reduce energy harvest from the diet. SCFAs might also increase insulin sensitivity, and induce satiety. Intestinal dysbiosis, which could be partly caused by “obesogenic” diets rich in saturated fats, may lead to the growth of potential pathogens (Gram-negative bacteria and derived lipopolysaccharide (LPS)) with pro-inflammatory effects in peripheral tissues. Obesity and diabetes represent therefore two examples of diseases mediated by interactions between the gut microbiota and the immune system with subsequent development of specific organ, autoimmunity and/or metabolic dysfunction.

Why is diet the main driver of gut microbiota?

Diet is probably the major factor driving the composition and metabolism of the gut microbiota. Dietary patterns (vegetarian diets, for example), specific nutrients and bioactive dietary components are all playing significant roles in shaping the gut microbiome.  Microbiome composition, metagenome and metabolome are also associated with long-term dietary patterns. However, the short-term consumption of diets entirely composed of animal or plant products alters rapidly the microbial community structure and overwhelms inter-individual differences in microbial genes expression. For example, it has been shown that a high-fat diet adversely reduces A. muciniphila and Lactobacillus, which are both associated with healthy metabolic states. Sharon Donovan also showed how dietary intake of prebiotics positively impacts the gut microbiome, and how fermented food containing live microbial species, such as yogurt or fermented dairy products enriched with probiotics, could benefit gut microbiome and health. However, to date, yogurt has been relatively understudied in terms of effects on the microbiome.

Which other factors influence microbiome composition?

The current ‘omic era promises rapid progress towards understanding how the environment can modulate both the composition and metabolism of the gut microbiota, allowing researchers to provide informed advice that should improve long-term health status. From in utero variations to those that rapidly occur postpartum, our gut microbiome changes with age, environment, stress, diet, and health status as well as medication exposure (like antibiotics) or even geography. In turn, the gut microbiota composition and activity influence host metabolism and disease development. The changing of our gut microbiota across the lifespan is particularly important. Before birth, we’re all more or less “sterile”—we have no microbes. Within a few years, we’re covered in thousands of different species of microbes, and they colonize every millimeter of the body that’s exposed to the outside world. By the time we enter kindergarten, we have vastly different populations living in the different habitats around our bodies. Even as adults and into old age, our gut microbiota continue to shift.

What do we know about the microbiome?

What have we learned about microbiome during this decade of research with “omics”* based approaches? We now know that gut microbiota contain about 1000 different species of microorganisms, which encode much more genes than the human host (100 times more!). The microbiome is the collective genomes of the microbiota. The microbiome is diverse, represents all 3 domains of life (Microbes, Fungi, Archea) and its function is more highly conserved between sites than microbial composition. But despite this variability, some trends have been identified. Microbial populations differ more among body sites than between individuals. For example, the microbes living on the forearms of two different people tend to be more similar than the microbes on the forearm and ear of the same person.  Besides, some species of bacteria only live in the gut, while others only live on the teeth, and so on. Last but not least, recent research in animals has shown the essential role of gut microbiota in normal gastrointestinal, immune, metabolic and cognitive development and function.

How did we study the microbiome?

According to Sharon Donovan, we have totally redefined what it means to be human after the Human Genome Project success, at the beginning of the 21st century. The scientific community agreed that the human gut bacteria community is a major challenge in medical research. As many of these gut bacteria could not be cultivated in a Petri dish in a lab, little is known about this huge community of microorganisms inhabiting our body. It began to be suspected they played a key role in health, but also in diseases. At that time, that is to say 10 years ago, the United States Institutes of Health decided to launch the Human Microbiome Project in which several biomedical research institutes took part. Almost at the same time in Europe, MetaHit was conceived, although unlike the American project, it focused on the link between microbiota and two more and more common diseases, obesity and type 2 diabetes.

Donovan concludes with the observation that if our knowledge of composition has rapidly expanded, our understanding of function remains limited. According to her, longer-term observational studies with detailed metadata and stool samples are needed, as well as prospective yogurt intervention to establish dose and mechanism of actions.

* Omics” refers to innovative technology platforms such as genetics, genomics, proteomics, and metabolomics. These recently developed techniques give us the ability to detect and identify many different molecules, including millions of molecule parts, that are present and expressed in the body. Molecules such as DNA, RNA, proteins, peptides, lipids and metabolites are detected and measured in different biological compartments such as whole blood, plasma and urine.

Consuming fermented milk products such as yogurt is linked with healthy growth of bones when we’re young, reduced bone loss when we’re older, and a lower risk of broken bones in our old age.

These benefits seen at all stages of life are achieved through several mechanisms, say the authors of this review article. Not only do yogurts deliver nutrients vital for strong healthy bones, but they also contain prebiotics and probiotics, which may benefit the bones by modifying the microbiota that inhabit our gut.

A rich source of nutrients

Fermented milk products in the form of yogurts or soft cheese have long been used to preserve milk. They are rich in calcium, phosphorus and protein, all key nutrients for promoting bone growth and maintaining healthy bones.

Yogurt and soft cheeses may be richer in these nutrients than plain milk because of milk powder that is added to yogurt to make it thicker.

Healthy growth for children and teenagers

Intervention trials have shown that giving fermented dairy products to children and adolescents has a positive influence on their bone health especially their bone mineral density.

Protection against age-related bone loss

In adults, fermented dairy product consumption protects against bone loss and maintains bone strength as we get older.

Among the studies reviewed was an Irish study of over 4000 people aged over 60 years. A higher yogurt intake was associated with a lower risk of osteoporosis – a greater effect than that seen with milk intake. In another study of 65-year-old women, bone loss was reduced in those who consumed fermented dairy products and not in those who drank milk or ate cheese.

Dairy products and fractures

Data on the link between dairy product and risk of broken bones are limited but the Framingham Offspring study showed a weak protective trend against hip fracture seen with yogurt consumption but not with other dairy products. In a long-term Swedish study, women who had a high intake of cheese or fermented milk products were less likely to die or to suffer a hip fracture during the follow-up than those who had a low intake.

Prebiotics and probiotics

Additional benefits to our bones may come from prebiotics and probiotics that fermented dairy products may contain.

Prebiotics such as inulin – derived from chicory roots – may be added to yogurt to make it thicker. They are fibre compounds that stimulate the growth and/or activity of the bacteria living in the large bowel. Furthermore, prebiotics may be converted in the large intestine through a process of fermentation to short chain fatty acids. These have several beneficial effects in the bowel including increasing calcium bioavailability and absorption through a reduction in bowel content pH and enhancing intestinal barrier functions.

Probiotics are live micro-organisms which, when administered in adequate amounts, confer health benefits on the host. Probiotics provide a way to deliver beneficial bacteria directly to the gut.

Prebiotics and probiotics in fermented milk products may exert specific effects not seen with other types of dairy foods by modifying the composition and metabolism of the gut microbiota. The gut microbiota has several possible beneficial influences:

• It affects intestinal wall permeability – the gut microbiota is involved in the digestion of dietary nutrients, and can increase calcium absorption.
• It is thought to affect endocrine pathways – the increased calcium absorption may lead to a reduction in parathyroid hormone production which in turn can lead to a reduced bone resorption. The secretion of serotonin may also be modulated thereby increasing bone formation.
• It plays an important role in modulating the immune system – this is significant because inflammation is linked with bone loss.

Eating more yogurt could save money

The authors of this review suggest increasing dairy consumption could lead to cost savings because of its protective effect on our bones. Hence eating one yogurt every day is cost effective in reducing the risk of bone fracture in people aged over 70 years, while eating two yogurts daily is cost effective for reducing fracture risk in those aged over 80 years.

As yogurts tend to be flavoured and sweetened, they may be useful in achieving a higher consumption of milk products, say the authors.

They conclude that further research is needed to clarify whether consuming fermented milk products may be a causal factor or whether it is simply a marker of a healthy lifestyle that promotes healthy bones.

Find out more: read the original article.

Source: Rizzoli R, Biver E. Effects of fermented milk products on bone. Calcif Tissue Int. 2017 Aug 19.

2017 was a year of scientific progress on yogurt. The YINI board of experts has reviewed and compiled a selection of five major studies for you, showing exciting results on the health potential of yogurt consumption, regarding obesity and type 2 diabetes (T2D) risk, but also regarding the health costs associated with T2D and the preventive effect of a globally balanced diet.

These studies show that:

• Replacing traditional snacks, like biscuits and chocolate, for yogurt is associated with a significantly lower T2D risk in older adults at high cardiovascular risk (1)
• An economic model to predict likely cost saving revealed that increased yogurt consumption could potentially help to reduce health service costs associated with T2D (2)
• Higher consumption of whole fat yogurt was associated with a reduction in waist circumference and an increased probability of reversion of abdominal obesity in the elderly (3)
• In obese individuals, yogurt consumption may improve gut health and reduce chronic inflammation by enhancing innate and adaptive immune responses, intestinal barrier function, lipid profiles, and by regulating appetite (4)
• Combined intake of yogurt and fruit offers potential synergistic benefits on health, since they may help to prevent disease (5)

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References:

1. 1 Díaz-López A, Bulló M, Martínez-González MA, et al. Dairy product consumption and risk of type 2 diabetes in an elderly Spanish Mediterranean population at high cardiovascular risk. Eur J Nutr 2016;55:349–60.
2. 2 Lenoir-Wijnkoop I, Mahon J, Claxton L, et al. An economic model for the use of yoghurt in type 2 diabetes risk reduction in the UK. BMC Nutr 2016;2:77.
3. 3 Santiago S, Sayón-Orea C, Babio N, et al. Yogurt consumption and abdominal obesity reversion in the PREDIMED study. Nutr Metab Cardiovasc Dis 2016;26:468–75.
4. 4 Pei R, Martin DA, DiMarco DM, Bolling BW. Evidence for the effects of yogurt on gut health and obesity. Crit Rev Food Sci Nutr 2017;57:1569–83.
5. 5 Fernandez MA, Marette A. Potential health benefits of combining yogurt and fruits based on their probiotic and prebiotic properties. Adv Nutr 2017;8:155S–64S.

This important symposium brought together many nutrition professionals. It was an opportunity for YINI to invite leading experts to talk about the most recent perspective on the benefits of live microbes in fermented foods and gut microbiome. They highlighted what happens in both the pot and the intestine to better understand the health effects of yogurt.

Is the gut microbiota the intersection between diet and health?

The gut microbiota is gradually revealing its secrets. We now know that its ecosystem contains about 1000 different species of microorganisms, which encode more genes than the human host. Sharon Donovan (University of Illinois, USA) explained that these numerous genes interact with the human host through specific receptors located in the gut’s epithelial, neural and immune cells, as well as through the production of hormones and metabolites.

Recent research in animals has shown the essential role of gut microbiota in normal gastrointestinal, immune, metabolic and cognitive development and function. Human studies have highlighted that gastrointestinal conditions, such as inflammatory bowel disease and irritable bowel syndrome, but also other diseases such as obesity, type 2 diabetes and atopy, are linked to an imbalance of the normal gut microbiota (dysbiosis). It is therefore of great interest to better understand the role of dysbiosis in non-communicable diseases and to develop strategies to improve gut microbiota and health outcomes through diet. Review of the literature effectively suggests that diet can modify the intestinal microbiome, which in turn has a profound impact on overall health. This impact can be either beneficial or detrimental, depending on the relative identity and abundance of constituent bacterial populations. For example, it has been shown that a high-fat diet adversely reduces A. muciniphila and Lactobacillus, which are both associated with healthy metabolic states.

On the other hand, Sharon Donovan showed how dietary intake of prebiotics impacts positively the gut microbiome, and how fermented food containing live microbial species, such as yogurt or fermented dairy products enriched with probiotics, could benefit gut microbiome and health. Several groups have reported increased total bacterial load after regular consumption of fermented milk or yogurt. Notable increases in beneficial gut Bifidobacteria and/or Lactobacilli have also consistently been observed with several different types of probiotics. Probiotic-containing yogurt has been shown to significantly reduce counts of the enteropathogens E. coli and Helicobacter pylori.

A diet that is low in sources of prebiotics (soybeans, unrefined wheat and barley, raw oats, fructooligosaccharides (FOS)…) has been shown to reduce total bacterial abundance. On the opposite hand, high intake of these carbohydrates resulted in an increase in microbiota genes richness.

Donovan concludes with the observation that diet can modulate host-microbes interactions, which heralds a promising future therapeutic approach.

What happens in the gut?

Yogurt consumption has been associated with reduced risks of type 2 diabetes, metabolic syndrome, and heart disease, as well as improved weight management. By providing several key nutrients, yogurt is characterized by its live microorganisms (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus), as well as strains of Bifidobacterium and Lactobacillus added specifically for their probiotic properties. Both culture organisms may benefit from the gut environment and, consequently, have an impact on health. These “probiotic” properties are of great interest for research. Robert Hutkins (University of Nebraska, USA) explored the interactions between ingested microorganisms and the gut microbiota, and the way exogenous microorganisms can change the gut environment.

The physiological mechanisms by which these microbes interact with the gut microbiota is the well-known phenomenon of colonization resistance. Recent research report that regular consumption of yogurt appeared to increase the numbers of Lactobacilli. The microbial diversity also appears to slightly increase with yogurt consumption in some subjects. The dairy matrix also matters! Still, dairy foods have long been the main delivery vehicle, and most probiotics do just fine in this matrix.

Clinical studies provide more and more evidence on the health benefits associated with yogurt consumption. Many recent studies have underlined the association between a greater microbial diversity and better health conditions, so this could be an important finding. For instance, it is well demonstrated that yogurt bacteria, via the enzyme β-galactosidase they provide, improve lactose digestion, allowing people with lactose maldigestion to eat yogurt. Research also shows that yogurt containing probiotics improves intestinal and extra-intestinal health, and leads to improved immune and anti-inflammatory responses to infectious diarrhea and respiratory infections. Hutkins also presented the latest areas of research on the microbiota-gut-brain axis, suggesting that probiotics and prebiotics could influence behavior.

In his conclusion, Hutkins also reminds that it is important to address the common misconception that fermented foods are the same thing as “probiotics”—the latter being live bacteria that confer health benefits when consumed in adequate numbers. Not all fermented foods contain live organisms. Beer and wine, for example, undergo steps that remove the organisms. Other fermented foods are heat-treated and the organisms are inactivated. Bread is baked and sauerkraut is often canned. So while these foods may be nutritious, they do not have probiotic activity, but may impact gut microbiota as well, as fermented foods.

What happens in the pot?

What could explain the health benefits of yogurt, reported by numerous epidemiological studies? Yogurt is a nutrient-dense food that contributes to the intake of protein, calcium, bioactive compounds and several micronutrients, which could help to explain some of its health benefits. Andre Marette (Laval University, Canada) presented recent evidence suggesting that dietary proteins can act as key regulators of immunometabolic factors and gut microbiota. Furthermore, he addressed several possible aspects that could explain the role of fermentation in the health benefits of yogurt. During the fermentation process of milk with yogurt cultures, dairy proteins are cleaved, generating in smaller molecules that can have some biological effects. These so-called bioactive peptides could explain the greater beneficial effect of yogurt on metabolic health compared with non-fermented dairy products, such as milk. Marette outlined potential mechanisms related to bacterial constituents and bioactive peptides produced during fermentation, that could be responsible for yogurt’s ability to protect against cardio-metabolic diseases (CMD). For example, the fermentation of yogurt may lead to an increased production of bioactive peptides with physiologic effects such as increased insulin sensitivity and glucose tolerance. Several peptides or peptide fractions have also been investigated for their bioactive properties such as anti-hypertensive, anti-thrombotic, satiety, opioid, immuno-modulatory, osteogenic, and antioxidant activities. Fermented dairy peptides and especially yogurt-type peptides generally exerted greater anti-inflammatory effects than other dairy products. These immunometabolic effects are associated with major taxonomic changes in the gut microbiota. Whether specific bacterial species are modulated by peptides released from fermentation from dairy products remains to be determined. These newly proposed mechanisms require therefore more research before being validated as a key factor in the protection against CMD, like type 2 diabetes or obesity.

A need for new dietary guidelines for fermented foods

Fermented foods and beverages have long been a part of the human diet, and with further supplementation of probiotic microbes, in some cases, they offer nutritional and health attributes worthy of recommendation of regular consumption. Despite the impact of fermented foods and beverages on gastro-intestinal wellbeing and diseases, their many health benefits or recommended consumption has not been widely translated to global inclusion in world food guidelines. Until now, dietary guidelines mainly focused on the nutrient needs, and consequently on the nutritional content of food. But for Seppo Salminen (University of Turku, Finland), it’s time to go further! Indeed, the health benefits associated with the consumption of fermented food, such as yogurt, are more and more evident, and the importance of beneficial microbes such as Lactobacillus in health promotion, by strengthening intestinal mucosal barrier, have been recognised. However, in Europe, only one health claim – on lactose digestion – has been approved for beneficial microbes. National nutrition guidelines or recommendations that include either probiotics or yogurt with live bacteria exist in five EU member states. Given that several physiological effects of probiotics are well established and that yogurt and yogurt with probiotics have benefits to humans, it has been suggested that yogurt should be part of food dietary guidelines. For Salminen, knowledge on health benefits is a real opportunity for evidence-based dietary guidelines with yogurt and yogurt with probiotic bacteria.

* IUNS 21st ICN, Buenos Aires, October 15-20, 2017.

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Children and adolescents who skip breakfast are more likely to be overweight than those in the habit of eating breakfast daily. But drinking milk regularly is associated with a protective effect that helps youngsters remain a healthy weight.

These were the findings of a study that examined the association between body mass index (BMI) and lifestyle in children and teenagers, including their breakfast habits, dairy consumption and physical activity.

It showed that nearly one-third of children skipped breakfast, girls even more often than boys. Children of normal weight were more in the habit of eating breakfast daily than those who were overweight or obese.

Poor nutritional habits and physical inactivity have been blamed for children’s overweight and obesity. Breakfast is considered the most important meal of the day and studies have found that obesity is less common among those who eat breakfast regularly. Milk and other dairy products such as cheese and yogurt are nutrient-rich foods and several studies have suggested an inverse correlation between dairy product consumption and BMI.

This cross-sectional study included 7116 Turkish boys and girls aged 6-18 years who were asked to complete a questionnaire about how often they ate breakfast, their intake of milk and other dairy products, their physical activity, and whether their mother had a job. Their height and weight were measured to calculate their BMI.

Breakfast habits vary with age and gender