Current Nutrition & Food Science - Volume 2, Issue 4, 2006

Numerous studies have shown suboptimal vitamin D status in populations at high geographical latitudes, owing to a reduced capacity to synthesise vitamin D, especially during wintertime. Vitamin D supplementation has been shown to be effective at maintaining adequate vitamin D status throughout the year in these countries. Classically reported to play a central role in bone health, vitamin D has more recently been shown to modulate immune function by promoting an anti-inflammatory response, which may be related to onset or progression of autoimmune inflammatory disorders. One such condition is multiple sclerosis (MS). There is an increasing incidence of MS with increasing latitude, with higher prevalence reported in countries further away from the equator, where vitamin D synthesis is inadequate. Vitamin D has been shown to have positive effects on the animal model of MS, experimental autoimmune encephalomyelitis. However, there have been few human intervention studies to investigate the effect of vitamin D supplementation on symptoms of MS or indeed of other autoimmune disorders. Further research is required to examine the potential beneficial role of vitamin D in MS to ultimately determine the optimal vitamin D status required to alleviate symptoms and possibly prevent this and other chronic diseases.

Diet and lifestyle influence morbidity and mortality. Among the elderly it is of particular importance to adopt diet and lifestyle practices that minimize their risk of morbidity and maximize their prospects for healthful aging. The Mediterranean diet is a model of a healthy diet that represents the dietary pattern among populations of the Mediterranean area. Most studies that were published in the last decade evaluated its effect on specific diseases such as cardiovascular disease and cancer. However, it may also interfere with the aging process and result in greater longevity and successful aging. Therefore, it is not surprising that interest in the effect of the Mediterranean diet on the aging process and longevity is increasing. In the current paper we will focus on the effect of the Mediterranean diet on aging and longevity. Our literature review identified seven studies which focused on assessing the impact of the Mediterranean diet on longevity and successful aging. All these studies demonstrated that the Mediterranean diet has a positive effect on survival and longevity. The paper also includes proposed mechanisms for the beneficial effects of the Mediterranean diet.

This review deals with the applications of cyclodextrins (CDs) to food manufacture, focusing on the technical advantages of their use in food processing and as food additives. Their beneficial effects essentially derive from the ability to form stable inclusion complexes with sensitive lipophilic nutrients and constituents of flavor and taste. Toxicological data are examined and an assessment of CDs from the standpoint of safety for human consumption is made. Regulations are covered, showing a general trend towards a wider acceptance of CDs as food additives. The growing health consciousness of consumers and expanding market for functional foods and nutraceutical products are opening up to CDs a promising future in food industry.

Dietary factors, in particular dietary fat intake, are discussed as potential determinants for the development of allergic diseases. However, studies analyzing the relationship between dietary fat intake and allergic outcomes reported inconsistent and even conflicting findings. Therefore, this strategic review summarizes the findings from observational studies estimating the association of dietary fat intake with allergic diseases and allergic sensitization, and additionally outlines the results of supplementation studies with fatty acids. According to this, margarine intake seemed to be a risk factor for allergic diseases, and some studies reported beneficial effects of fish intake on asthma. Butter might also be a protective factor against allergies, even though this association is less clear. Observational studies analyzing fatty acid intake in relation to allergic diseases, as well as supplementation studies with essential fatty acids, have given inconsistent results and could not prove any beneficial effect. In summary, it is not evident yet, whether dietary fat intake has an impact on the development of allergic diseases and, if so, whether only subgroups of the population are affected by this mechanism. Therefore, future studies might target at subgroup identification of susceptible individuals, and focus on preventive supplementation in subjects at high risk.

The discovery of leptin in 1994 revolutionized our knowledge of the role of adipose tissue in nutrition. This hormone is synthesized in adipocytes, and the cell membrane of most cells bears leptin receptors, but it exerts its action mainly in the hypothalamus by inhibiting the production of neuropeptide Y and diminishing appetite. Free and bound leptin is present in plasma, where it has a soluble receptor: sOb-R. The proportion of bound leptin varies during the lifetime according to the amount of fat in the body: the more fat, the higher the production of free leptin. The active form is considered to be free leptin, because it is able to cross the blood-brain barrier (BBB) and is the form found in the cerebrospinal fluid (CSF). Moreover, the direct injection of leptin in the hypothalamus effectively inhibits appetite and increases thermogenesis. Leptin acts in the cell via interactions with its membrane receptor. Seven isoforms of this receptor have been identified, the short (Ob-Ra) and long (Ob-Rb) forms being the best known. Ob-Ra is the membrane carrier for free leptin across the BBB from the plasma to the CSF. Although this receptor is present in many tissues, the highest concentrations are found in the choroid plexus and especially in the arcuate nucleus. Furthermore, a small proportion of plasma free leptin also reaches the brain by passive diffusion. Once it reaches the CSF, leptin binds to the Ob-Rb receptor in the neuronal membrane. This molecule is then phosphorylated by protein-kinase JAK2 in the cytosol, and the leptin-receptor complex interacts with STAT3 to inhibit peptide Y and reduce energy intake. In the periphery, leptin stimulates the oxidation of fat stores in adipocytes and other cells by means of peroxisome proliferator-activated receptor (PPAR) -alpha, subsequently reducing the lipotoxicity in cells that are not designed to store excess lipids. In addition, leptin has been found to interfere in insulin metabolism, cellular growth, placental tropism, reproduction, and immunity. In lean individuals the ratio of free to bound plasma leptin is 1:1. However, in obese persons this equilibrium is altered and the free/bound ratio can be as high as 25:1. The paradoxical finding that obese people have elevated concentrations of free leptin (an active anorexigenic) can be explained by the existence of resistance to leptin transport across the BBB. It has been shown that hypertriglyceridemia is an important cause of this resistance. The well known existence of hypertriglyceridemia in starvation has been interpreted as a natural mechanism to block the access of leptin to the CSF, which keeps the person hungry and seeking food. During the 20th century, however, a new phenomenon appeared: overnutrition and a sedentary lifestyle in large population groups. As a consequence we now confront widespread hypertriglyceridemia, for which natural evolution has not had the time to create an adaptive mechanism. Humans have fallen into a vicious circle of overfeeding with low access of leptin to the hypothalamus, and as a consequence obesity has reached the dimensions of a global epidemic. A therapeutic solution focused on leptin transport could lessen the severity of obesity in many persons. However, before we can focus on this goal, we need to identify the specific site of triglyceride-induced resistance, and then search for agonistic drugs that can act at this site. Nevertheless, to control the epidemic we also need measures to reduce the amount of fat in our diet.

Volatile fatty acids (VFA) are the main energy source for ruminants, generally accounting for 50-75% of energy digested. They are produced from microbial fermentation of food in the rumen and are known to control food intake. Propionic acid, which is a major VFA produced in the rumen, is responsible of a feeding-induced behavior regulation in ruminants and its absorption results in a down-regulated energy intake in these animals. Although hypophagic effects of propionate have been extensively documented in ruminants and other farm animals, such evidence is almost nonexistent in humans. Interestingly, one human investigation tested the glycemic and insulinemic responses to ingestion of breads enriched with different additives. Amongst tested breads, propionic acid-enriched bread prolonged the duration of satiety compared with other breads tested. Therefore, the current literature survey reviews the physiological understanding of satiety control established in ruminants to bring up novel insights of feeding behavior control in human. Eventually, these challenging hypophagic properties of propionate could be transposed to the field of human obesity management.

Taurine, a beta-sulphur amino acid with a zwitterionic function, plays an important role in several biological processes. In humans taurine synthesis is limited. Therefore, intake by food is important. A normal diet, including animal products, contains a sufficient amount of taurine to provide the physiological necessary quantity of taurine. Taurine is a component of bile salts, which function as detergents for emulsification of dietary lipids and fat-soluble vitamins. Also, taurine is involved in the development of the brain and retina, which makes it an essential nutritional substrate in neonates and small children, who are limited in the synthesis of taurine. Moreover, taurine can act as an osmoregulator and antioxidant, which makes it an important amino acid during pathological conditions such as ischemic reperfusion injury, inflammation and brain oedema. Its osmolytic function helps to prevent alteration in the intra-cellular concentrations of all substances. In many models of oxidant-induced injury, taurine was shown to be tissue-protective as a non-toxic endogenous antioxidant. This review focuses on the biological actions of taurine, to illuminate possible clinical benefits of taurine.

Epidemiological studies on historical and contemporary populations indicate that the uterine environment is a major factor contributing to later health and disease in the resulting offspring. These findings are supported by experimental studies which indicate that both macro and micronutrient deficiencies have long-term health implications for the offspring. Maternal nutrition directly determines foetal and placental growth and influences the in utero endocrine environment. A reduction in maternal food intake at defined stages of gestation does not necessarily compromise foetal growth but reprogrammes foetal sensitivity to later stress. When nutrient restriction is targeted over the period of maximal placental growth placental size is restricted in conjunction with a reduction in maternal plasma concentrations of counterregulatory hormones including cortisol. These maternal adaptations appear to be accompanied by an increased sensitivity to these hormones in their resulting offspring. In late gestation, foetal growth can be compromised by a reduction in nutrient supply, but long term outcomes from nutrient restriction in early, early to mid or late gestation are very different. The maternal nutrient and endocrine environments therefore have pronounced influences on foetal endocrine sensitivity that depends on stage of gestation and result in long term outcomes predicted to compromise later health and well being.

Secreted by goblet cells, intestinal mucins play a crucial role in cytoprotective functions against mechanical insults, colonisation by pathogenic bacteria and their toxins, luminal proteases and potential carcinogens. The present paper provides a review of the effect of nutrients on intestinal mucin secretion. In the small intestine, the secretion of mucus is modulated by hydrolysates of milk proteins and by β-casomorphins (a family of peptides derived from β-casein). Other factors present in milk, like EGF, also stimulate mucus discharge. In the new-born baby, such an effect of proteins of milk or bioactive peptides on the secretion of mucus could play a role in the control of the mechanism of defence and similar protective effects could be expected in the adults. In the colon, some dietary fibres increase the discharge of mucus. The metabolic product of dietary fibres, the short chain fatty acids (SCFA), also induce mucus secretion in the colon. Additionally, butyrate modulates mucin expression, suggesting that SCFA are influential in increasing the synthesis and secretion of colonic mucin. In conclusion, bioactive peptides, fibres and SCFA appear to be liable nutrients to induce mucus secretion. New researches are required to determine whether they can be used to achieve preventive or therapeutic effects in human.

Among various nutritional strategies to combat iron deficiency, fortification of food is generally considered to be the best and cost effective long-term strategy. Iron is a key micronutrient and an integral part of haemoglobin, required for the transport of oxygen and carbon dioxide in blood. Among the cereals, which the ability of being successfully fortified with iron, wheat has additional advantage to be used as a vehicle. The bioavailability of iron added to wheat is several times greater than other staple foods such as maize and rice. As breads and leavened flat bread are the major portion of routine diet of a large number of population segments in developing countries, so wheat could be used as a vehicle for iron fortification, as the fortification of iron in flour does not show any direct effect on product quality and taste and also it is a low cost staple routine diet. Reduced or elemental iron and FeEDTA do not react with fat in flour and thus do not promote rancidity. The stability of different forms of iron depends on various factors including the nature of the food it is added to, the particle size and the exposure to heat and air. Among the various forms of iron, ferrous sulphate has excellent bioavailability. It is the fortificant of choice when used in bakery flour and other types of low extraction wheat flours and is the best iron source because of its high bioavailability and low cost. Iron fortification of wheat flour and its bakes products is steadily expanding around the world and is expected to remain so with the intend to combat in the battle against the global health problem of iron deficiency anaemia.