Barbara Walther

Natural Vitamin D Content in Animal Products

Humans derive most vitamin D from the action of sunlight in their skin. However, in view of the current Western lifestyle with most daily activities taking place indoors, sun exposure is often not sufficient for adequate vitamin D production. For this reason, dietary intake is also of great importance. Animal foodstuffs (e.g., fish, meat, offal, egg, dairy) are the main sources for naturally occurring cholecalciferol (vitamin D-3). This paper therefore aims to provide an up-to-date overview of vitamin D-3 content in various animal foods. The focus lies on the natural vitamin D-3 content because there are many countries in which foods are not regularly fortified with vitamin D. The published data show that the highest values of vitamin D are found in fish and especially in fish liver, but offal also provides considerable amounts of vitamin D. The content in muscle meat is generally much lower. Vitamin D concentrations in egg yolks range between the values for meat and offal. If milk and dairy products are not fortified, they are normally low in vitamin D, with the exception of butter because of its high fat content. However, as recommendations for vitamin D intake have recently been increased considerably, it is difficult to cover the requirements solely by foodstuffs.

Hot topic: Changes in angiotensin-converting enzyme inhibition and concentrations of the tripeptides Val-Pro-Pro and Ile-Pro-Pro during ripening of different Swiss cheese varieties.

The angiotensin-converting enzyme (ACE) inhibitory activity and the concentration of the 2 ACE-inhibiting tripeptides Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) were studied during cheese ripening in 7 Swiss cheese varieties. The semi-hard cheeses Tilsiter, Appenzeller 1/4 fat, Tête de Moine, and Vacherin fribourgeois and the extra-hard and hard cheeses Berner Hobelkäse, Le Gruyère, and Emmentaler were investigated. Three loaves of each variety manufactured in different cheese factories were purchased at the beginning of commercial ripeness and investigated at constant intervals until the end of the usual sale period. Good agreement was found between ACE-inhibitory activity and the total concentration of VPP and IPP at advanced ripening stages. In most of the investigated varieties ACE-inhibitory activity and the concentration of the 2 tripeptides initially increased during the study period. A decline in the concentration of VPP and IPP was obtained toward the end of the investigated period for Tilsiter and Gruyère. The ratio of VPP/IPP decreased during ripening in all varieties with the exception of Emmentaler. However, large variations were observed among the cheese varieties as well as the individual loaves of the same variety. Chemical characterization of the investigated cheeses revealed that qualitative differences in the proteolysis pattern, not quantitative differences in the degree of proteolysis, are responsible for the observed variations in the concentrations of VPP and IPP. The presence of Lactobacillus helveticus in the starter culture was associated with elevated concentrations of VPP and IPP. The results of the present study show that concentrations of VPP and IPP above 100 mg/kg are attainable in semi-hard cheese varieties after ripening periods of about 4 to 7 mo and that stable concentrations of the 2 antihypertensive tripeptides can be expected over several weeks of cheese ripening.

Bioactive proteins and peptides in foods.

Increasing amounts of data demonstrate a bioactive role of proteins and peptides above and beyond their nutritional impact. The focus of the investigations has mainly been on vitamin- and mineral-binding proteins, on antimicrobial, immunosuppressing/-modulatory proteins, and on proteins with enzyme inhibitory activity as well as on hormones and growth factors from different food proteins; most research has been performed on milk proteins. Because of their molecular size, intact absorption of proteins in the human gastrointestinal tract is limited. Therefore, most of the proteins with biological functions show physiological activity in the gastrointestinal tract by enhancing nutrient absorption, inhibiting enzymes, and modulating the immune system to defend against pathogens. Peptides are released during fermentation or digestion from food proteins by proteolytic enzymes; such peptides have been found mainly in milk. Some of these released peptides exert biological activities such as opiate-like, antihypertensive, mineral-binding, antioxidative, antimicrobial, immuno-, and cytomodulating activity. Intact absorption of these smaller peptides is more likely than that of the larger proteins. Consequently, other organs than the gastrointestinal tract are possible targets for their biological functions. Bioactive proteins as well as bioactive peptides are part of a balanced diet. It is possible to accumulate bioactive peptides in food, for example by using specific microorganisms in fermented dairy products. Although bioactive peptides have been the subject of several studies in vitro and in vivo, their health potential is still under investigation. Up to now, the Commission of European Communities has not (yet) authorized any health claims for bioactive proteins and peptides from food.

Milk Consumption Does Not Lead to Mucus Production or Occurrence of Asthma

There is a belief among some members of the public that the consumption of milk and dairy products increases the production of mucus in the respiratory system. Therefore, some who believe in this effect renounce drinking milk. According to Australian studies, subjects perceived some parameters of mucus production to change after consumption of milk and soy-based beverages, but these effects were not specific to cows’ milk because the soy-based milk drink with similar sensory characteristics produced the same changes. In individuals inoculated with the common cold virus, milk intake was not associated with increased nasal secretions, symptoms of cough, nose symptoms or congestion. Nevertheless, individuals who believe in the mucus and milk theory report more respiratory symptoms after drinking milk. In some types of alternative medicine, people with bronchial asthma, a chronic inflammatory disease of the lower respiratory tract, are advised not to eat so-called mucus-forming foods, especially all kinds of dairy products. According to different investigations the consumption of milk does not seem to exacerbate the symptoms of asthma and a relationship between milk consumption and the occurrence of asthma cannot be established. However, there are a few cases documented in which people with a cow’s milk allergy presented with asthma-like symptoms.

Inflammatory and metabolic responses to high-fat meals with and without dairy products in men

Postprandial inflammation is an important factor for human health since chronic low-grade inflammation is associated with chronic diseases. Dairy products have a weak but significant anti-inflammatory effect on postprandial inflammation. The objective of the present study was to compare the effect of a high-fat dairy meal (HFD meal), a high-fat non-dairy meal supplemented with milk (HFM meal) and a high-fat non-dairy control meal (HFC meal) on postprandial inflammatory and metabolic responses in healthy men. A cross-over study was conducted in nineteen male subjects. Blood samples were collected before and 1, 2, 4 and 6 h after consumption of the test meals. Plasma concentrations of insulin, glucose, total cholesterol, LDL-cholesterol, HDL-cholesterol, TAG and C-reactive protein (CRP) were measured at each time point. IL-6, TNF-α and endotoxin concentrations were assessed at baseline and endpoint (6 h). Time-dependent curves of these metabolic parameters were plotted, and the net incremental AUC were found to be significantly higher for TAG and lower for CRP after consumption of the HFM meal compared with the HFD meal; however, the HFM and HFD meals were not different from the HFC meal. Alterations in IL-6, TNF-α and endotoxin concentrations were not significantly different between the test meals. The results suggest that full-fat milk and dairy products (cheese and butter) have no significant impact on the inflammatory response to a high-fat meal.

The NutriChip project--translating technology into nutritional knowledge

Advances in food transformation have dramatically increased the diversity of products on the market and, consequently, exposed consumers to a complex spectrum of bioactive nutrients whose potential risks and benefits have mostly not been confidently demonstrated. Therefore, tools are needed to efficiently screen products for selected physiological properties before they enter the market. NutriChip is an interdisciplinary modular project funded by the Swiss programme Nano-Tera, which groups scientists from several areas of research with the aim of developing analytical strategies that will enable functional screening of foods. The project focuses on postprandial inflammatory stress, which potentially contributes to the development of chronic inflammatory diseases. The first module of the NutriChip project is composed of three in vitro biochemical steps that mimic the digestion process, intestinal absorption, and subsequent modulation of immune cells by the bioavailable nutrients. The second module is a miniaturised form of the first module (gut-on-a-chip) that integrates a microfluidic-based cell co-culture system and super-resolution imaging technologies to provide a physiologically relevant fluid flow environment and allows sensitive real-time analysis of the products screened in vitro. The third module aims at validating the in vitro screening model by assessing the nutritional properties of selected food products in humans. Because of the immunomodulatory properties of milk as well as its amenability to technological transformation, dairy products have been selected as model foods. The NutriChip project reflects the opening of food and nutrition sciences to state-of-the-art technologies, a key step in the translation of transdisciplinary knowledge into nutritional advice.

Short communication: Dairy consumption among middle-aged and elderly adults in Switzerland

Different studies have shown that people are aware of the benefits of dairy products, but a sizeable part of the worlds population still does not consume the recommended amount of dairy produce. The aims of the present research were to determine which dairy products are consumed by the middle-aged and elderly (50-81yr old) living in Switzerland and to explore why some of this population segment are actually reducing their consumption of dairy products. On average, older Swiss adults consumed 2.6 portions of dairy products per day, which is slightly less than the recommended 3 to 4 portions a day. Additionally, about one-quarter of the respondents indicated that they have reduced their milk or dairy consumption. The main reasons given for this decision were to reduce fat or cholesterol. A reported difficulty in digesting some dairy products may be a further reason for limiting dairy intake, particularly cheese. It follows that a need for the propagation of appropriate nutritional information about dairy products to the middle-aged and elderly exists.

Nutrition behavior of the middle-aged and elderly: Compliance with dietary recommendations of the food pyramid

BACKGROUND & AIMS During the aging process, human physiology changes noticeably, mostly to the disadvantage of the individual. A healthy lifestyle that includes sufficient physical activity as well as a balanced and diverse diet contributes to healthy aging. One key factor that elderly people need to be aware of is compliance with nutritional recommendations. There is very little data concerning eating patterns, consumption behavior, and compliance with food guides (food pyramid) and nutritional recommendations among the Swiss, particularly for the middle-aged and elderly. The objective of this study was to gather new and representative information about these issues, concentrating on people aged 50+ and living in Switzerland. METHODS A questionnaire in online and written form was distributed to a representative sample of middle-aged and elderly people living in Switzerland. RESULTS In total, 632 people returned the survey. Of those respondents, 71% knew the Swiss Food Pyramid but only 38% said they comply with it. Based on self-reports, only a few participants met the recommendations for the different food groups listed in the food pyramid, whether in the pyramid-comply or pyramid-non-comply group. CONCLUSION The survey shows that the middle-aged and elderly living in Switzerland need more nutritional guidance to help them to meet dietary recommendations. As usage and understanding of food guides seem limited among this population group, new tools must be explored for transfer of recommendations to real applications.

Menaquinones, Bacteria, and Foods: Vitamin K2 in the Diet

Vitamin K2 is a collection of isoprenologues that mostly originate from bacterial synthesis, also called menaquinones (MKs). Multiple bacterial species used as starter cultures for food fermentation are known to synthesize MK. Therefore, fermented food is the best source of vitamin K2. In the Western diet, dairy products are one of the best known and most commonly consumed group of fermented products. Although intensive research on metabolism and the biological effect of vitamin K2 continues today, data about vitamin K2 production and content in foods remain scarce. Dietary recommendations are still based on the classic role of vitamin K as an enzyme cofactor for coagulation proteins and do not consider differences in bioavailability and bioactivity between the various MKs and the possibly higher requirements for health effects apart from coagulation, such as bone or cardiovascular health. Here, we provide a global view of foods rich in vitamin K2 and their interactions together with other nutrients in selected health effects such as bone and cardiovascular health.

Caloric dose-responsive genes in blood cells differentiate the metabolic status of obese men

We have investigated the postprandial transcriptional response of blood cells to increasing caloric doses of a meal challenge to test whether the dynamic response of the human organism to the ingestion of food is dependent on metabolic health. The randomized crossover study included seven normal weight and seven obese men consuming three doses (500/1000/1500 kcal) of a high-fat meal. The blood cell transcriptome was measured before and 2, 4, and 6 h after meal ingestion (168 samples). We applied univariate and multivariate statistics to investigate differentially expressed genes in both study groups. We identified 624 probe sets that were up- or down-regulated after the caloric challenge in a dose-dependent manner. These transcripts were most responsive to the 1500 kcal challenge in the obese group and were associated with postprandial insulin and oxidative phosphorylation. Furthermore, the data revealed a separation of the obese group into individuals whose response was close to the normal weight group and individuals with a transcriptional response indicative of a loss of metabolic flexibility. The molecular signature provided by the postprandial transcriptomic response of blood cells to increasing caloric doses of a high-fat meal challenge may represent a sensitive way to evaluate the qualitative impact of food on human health.