Sunday, 30 August 2015
Taurine and Blood Pressure
Taurine is a non-essential non-protein forming amino acid. It is non-essential because it can be synthesised in humans from methionine and cysteine. Both methionine and cysteine contain a sulphur atom and so it is no surprised that taurine is also a sulphur containing amino acid. However, the sulphur atom in taurine replaces the carboxyl group normally present on amino acids and in this way is structurally distinct from most amino acids. Supplemental taurine has been researched with regard its blood pressure lowering effects. Initial studies on rodents showed that taurine had beneficial effects on the blood pressure of hypertensive rats. Later human studies confirmed the earlier rodent studies. In human studies, hypertensive subjects supplemented with 6 grams of taurine per day experienced significant reductions in blood pressure in as little as 7 days. Therefore taurine seems to produce blood pressure lowering effects in mammals, that are rapid and effective.
The reason that taurine is beneficial to hypertensive mammals is not fully understood. However, the beneficial effects may be dependent on an overactive sympathetic nervous system. The role of taurine in physiology is still being researched, but taurine is known to be critical in maintaining cell membrane potential and also in maintaining a regular heart beat. Interestingly, taurine may also benefit other cardiovascular problems, suggesting that it has more than one mechanism of action. In particular taurine can benefit congestive heart failure, and improve general heart function, and this likely relates to its ability to maintain membrane potential. A taurine rich diet can provide up to 2.5 grams of taurine per day. Cheese, cottage cheese, granola, pork, milk and wild game are good sources of taurine, but it is also available in supplements. Generally animal products are better sources of taurine that plant products. However, to get the cardiovascular benefits supplements are likely necessary.
Saturday, 29 August 2015
More on Selenium And Cancer
The clues that selenium is protective of cancer date back many decades. In fact evidence in the nutritional literature dating back to at least the 1970’s suggests that low selenium diets increase the risk of cancer significantly. Selenium is protective of cancer, possibly because it is required as a cofactor for the cellular antioxidant glutathione peroxidase. Low selenium diets cause significant reductions in plasma levels of glutathione peroxidase, and this likely increase oxidative stress in cells and may cause damage to DNA, which initiates cancer formation. Low selenium crops may cause low intake of selenium in a given population if that population relies on that crop as a staple food. However, selenium is also present in meat, with fish being a particularly good source. Epidemiological studies show that as intakes of selenium drop, breast cancer rates increase significantly1 (figure 1). Studies on rodent confirm that low selenium diet cause significant increases in cancer rates amongst the animals.
|Figure 1. The inverse association between selenium intake and breast cancer mortality1.|
1Schnauzer, G. N., White, D. A., Schneider, C. J. 1977. Cancer mortality correlation studies - IV: associations with dietary intakes and blood levels of certain trace elements, notably Se-Antagonists. Bioinorganic Chemistry. 7: 35-36
Sunday, 23 August 2015
Dates: Sugary, But Good For the Health
Dates are the fruits of the date palm tree (Phoenix dactylifera). The tree itself is similar in appearance to the coconut palm, with mature tree reaching a height of around 30 meters. Date are an important Worldwide food and may be one of the oldest agricultural crops. Records suggest that dates have been harvested for around 8000 years. In particular the date is an important crop in the Middle East, where the date is part of the traditional diets of local populations. One of the advantage of dates over other crops is that although they are harvested in the autumn, they store well and so are available all year round. The amount of dates produced by the date palm trees is immense, with clusters of dates weighing up to 10 kg, and each tree containing multiple clusters. Because the trees can live for eighty years or more, and bear fruit after about year 5, it can be seen how economically important dates are as a fruit crop. Around 75 % of the World’s dates are grown in the Middle East, although California, Texas and Arizona also contribute significantly.
Nutritionally dates are very interesting. The carbohydrate content of dates is high, as they contain around 60 to 70 percent sugar. The predominant sugars in dates are sucrose and fructose, as is common in most fruits. However, while the sugar content is high the total energy in a single date only amounts to roughly 20 to 25 kcals. The high carbohydrate content may be seen as a disadvantage, based on the negative connotations associated with sugar. However, dates also contain considerable amounts of fibre, and this improves the glycaemic profile considerably. In fact dates are not associated with negative effects from the sugars, and this likely relates to both the high fibre content and the high levels of certain vitamins, particularly of B vitamins including niacin, folate, pyridoxine, thiamine and pantothenic acid. In addition minerals such as copper, zinc, selenium, potassium, manganese and magnesium can also accumulate in dates, depending on the soil conditions on which the palms are grown.
The fibre in dates is a beta-D-glucan fibre that may have particular health benefits. One physiological effects that beta-D-Glucan fibre has been shown to possess is one of limiting cholesterol absorption. Studies using oats for example have shown beneficial lipid lowering effects, a factor that has been attributed to the soluble beta-D-glucan fibre they contain. However, as oats possess other components that can lower blood cholesterol this is controversial. Beta-D-Glucan can for example limit the rate at which glucose is absorbed. This produces beneficial glycaemic effects that may improve insulin sensitivity, and this decrease metabolic dysfunction, particularly in the liver, that can include detrimental changes to blood lipid levels. The presence of beta-D-glucan fibre may make dates an effective weight loss food, as has been shown for oats. Dates are also rich in antioxidants and this may be another route by which dates provide important health benefits.
Saturday, 22 August 2015
Eczema is considered an allergic reaction of the skin, and is often idiopathic in nature. Eczema is characterised by redness, pain, swelling, loss of function and heat, which are the symptoms of inflammation. If eczema is particularly bad and scratching of the affected area is allowed, blisters can develop which may become infected, leading to further inflammatory responses. Eczema may result from contact with an allergen or through ingestion of an allergen. In the case of the former, poison ivy for example is a known irritant that induces contact dermatitis. Household cleaning products are also commonly implicated in contact dermatitis. In the case of the latter, any number of foods or food ingredients may be able to cause eczema in particularly sensitive individuals. Interestingly eczema is more common in children, and many children outgrow eczema, which suggests that it might be related to hypersensitivity in the immune system, something that is not so prevalent as an individual ages.
As allergens are implicated in the development of eczema, the most obvious solution is to identify the allergen and avoid it. This is easy in the case of ivy as it is not commonly encountered and the dermatitis is easy to identify when contact occurs. However, in the case of household cleaning products, cosmetics and food ingredients this is much more difficult to achieve. Further, because multiple foods can trigger eczema, it can be extremely difficult to identify the food or foods involved. However, eggs, peanuts and milk account for the vast majority of cases of childhood eczema, and so these foods are a good place to start. An elimination diet can help identify the foods responsible for triggering eczema. In addition, eczema suffers also appear to have deficiencies of the delta 5-desaturase enzyme necessary for the metabolism of the essential fatty acids. Supplemental fish oils and gamma linolenic acid from starflower oil or evening primrose oil can therefore also be effective treatments.
Sunday, 16 August 2015
Fluoride in Toothpaste: Is It Just An Antimicrobial Agent?
Proponent of the fluoridation of drinking water claim that the addition of fluoride compounds to water reduces the incidence of dental caries in children. This is controversial because the scientific evidence for a protective effect in healthy nutritionally replete populations is quite weak. In addition, the mass medication of all humans for the benefit of a small group is unethical and of questionable logic. If fluoride is beneficial to teeth there are better ways to administer it to children than through drinking water. Further, fluoride is already ubiquitous in the diets on most individuals. Most foods and drink contain a small amount of fluoride and it is therefore very doubtful that any human with a balanced healthy diet would develop a fluoride deficiency. Even if fluoride were to be proved to be essential to the health, it would only be needed in minute amounts. Although fluoride is claimed to be essential to human health based on its supposed effects on teeth, fluoride does not satisfy classification to that of an essential minerals in humans.
However, irrespective of the ethical and health implications of this practice, biological mechanisms to explain how the fluoridation of water could affect teeth are available. Proponents of the fluoridation of drinking water state that for fluoride to be beneficial, it must be consumed and absorbed. Fluoride in drinking water increases the fluoride content of tissues and this may then be incorporated into the growing tooth along with other minerals most notably calcium. However, studies have questioned the necessity to actually consume fluoride for it to have beneficial effects. This is because fluoride may be absorbed to teeth through topical application. It is very hard to separate the topical effects of fluoride from the systemic effects, because all systemic fluoride passes through the mouth and comes into contact with teeth. Therefore the systemic effects of fluoride ingestion are confounded by the topical application of fluoride to teeth and studies investigating the two separately have not been forthcoming.
The topical application of fluoride is often used as evidence to support the addition of fluoride in toothpaste. However, controversy also surrounds this practice. The growth in the availability of fluoride free toothpastes would suggest that the public as a whole is becoming suspicious of the medical establishment and their obsession with fluoride. The mineral fluoride and its role in tooth decay receives huge amounts of public campaign money, and yet selenium, a mineral that has been shown to decrease the rate of cancer mortality by 50 % is completely ignored. The use of fluoride in toothpaste is also interesting because fluoride has antimicrobial properties and can significantly reduce the growth of bacteria on tooth enamel, which in turn would prevent dental caries and strengthen the teeth. This fact alone could explain the beneficial effect of fluoride containing toothpaste. However, safer and more effective antimicrobial agents are available to add to toothpaste. The role of refined crystalline sugar in tooth decay is also largely ignored.
Saturday, 15 August 2015
Plasticiser Chemicals and Cancer
Man made chemicals may be contribute significantly to the increase in rates of diseases in Western nations. Evidence suggests that chemicals belonging to the organochlorine and organophosphate group of synthetic chemicals, used extensively in agriculture, may be damaging to the health. In particular, exposure to the organophosphate chemicals has been shown to be particularly damaging to the nervous system. In this regard exposure to high concentrations of organophosphate compounds acutely, or lower concentrations chronically, may lead to neurological problems. Exposure to various organophosphate compounds for example has been shown to increase the risk of dementia significantly. In addition, the organochlorine molecules such as DDT (dichlorodiphenyltrichloroethane), PCB (polychlorinated biphenyl), lindane and dioxins may be hormone disrupting chemicals through their ability to interact with various hormone receptors. The DDT metabolite DDE for example is a known anti-androgen.
Some organochlorine molecules have been banned because of their known damaging effect, including DDT. However, many of the banned organochlorine chemicals remain in the environment as they do not readily biodegrade and can also bioaccumulate in animals due to their fat soluble nature. These chemicals tend to concentrate as they pass up the food chain, and high concentrations have been detected in those animals at the top of the food chain such as birds of prey, where they disrupt the ability of the birds to produce healthy eggs. This effect is suspected as responsible for the decline in the populations of birds of prey in some areas. As humans are at the top of the food chain, it is not surprising that high levels of DDT have also been found in human adipose tissue, despite the chemical being banned in the countries where the human subjects were tested. It is unclear how long it will take for DDT to be removed from the food chain, but this is likely to take decades.
However, of more concern are the plasticisers. These include the nonylphenols such as alkylphenols, the octaphenols, as well as the bisphenols which include the notorious bisphenol A. The plasticisers are of more nutritional importance than the organochlorine and organophosphate molecules because plastic food packaging used for example in fruit juices, milk, bottled drink and the plastic lining of canned foods all contain plasticisers that can leach into the foods they contain. These chemicals are still widely produced and evidence suggests that they bioaccumulate in humans fat tissue, are released to the blood, and then have oestrogen-like effects. The plasticisers are thought to be at least partly responsible for the increase in the rates of hormone dependent cancers in humans that are particularly prevalent in Western nations. Evidence suggest that the chemicals may have synergistic effects and so the large variation in plasticisers may produce additive effects on hormonal disruption.
It is virtually impossible to eliminate the organophosphate, organochlorine and plasticiser from the diet. This is because they are now so widespread and used in so many products that modern life exposes even the most careful avoider to quite considerable concentrations of these chemicals. Minimising exposure is therefore highly important. Many pesticides belonging to the organochlorine and organophosphate groups can be avoided by eating organic meat and animal produce. These chemicals are not allowed to be used in organic farming by law and so the concentration in organic meat is much lower, although they are still present in some organic foods due to environmental contamination. Avoiding food in plastic containers, particularly milk and other fat containing foods is also effective at reducing exposure. Fatty foods tend to accumulate more plasticisers because the chemicals are fat soluble. Exposure of plastic containers to heat and light may also increase the release of the chemicals to the foods, and plastic containers for food should not be exposed to these conditions.
Friday, 14 August 2015
Sunday, 9 August 2015
Avidin: Raw Eggs and Biotin
Biotin is a member of the B vitamin family of vitamins. Biotin is required in the diet as it is used as a cofactor in the acetyl CoA carboxylase, propionyl CoA carboxylase and pyruvate carboxylase enzymes. Plant sources such as grains are good sources of biotin, but animal foods with the exception of liver and eggs are poor sources. The fact that eggs contain a good supply of biotin is interesting because raw egg white may be potent inhibitors of biotin absorption. Initial observations about the interactions of raw egg whites and dietary effects were made when it was observed that laboratory animals on healthy diets did not do well if raw egg white was added to their diets. In particular, experiments showed that animals lost some of their hair, and developed dermatitis, particularly around their eyes. It was observed that addition of high amounts of B vitamins to the diets reversed these symptoms, and by carefully changing the B vitamin administered, it was found that biotin was the vitamin responsible for this effect.
Further tests of chick, rats, rabbits, monkeys and guinea pigs showed similar dermatitis and skin lesions in the animals when fed raw egg whites at about 50 % of their total diet. These symptoms were similar to the deficiency symptoms of biotin that had previously been established by feeding animals biotin deficient diets. Observations of eczema in children eating raw eggs have also been made as far back as 1939. In 1942 human studies were performed whereby humans were fed 30 % of their energy intake as raw eggs. Only a handful of subjects completed the study, and these subjects developed dermatitis, a grey pallor to the skin, as well as a dryness and scaliness to the skin. Other symptoms including depression, lassitude, sleepiness, muscle pains, numbness, and appetite suppression also developed. Some of the subjects also developed heart irregularities, and cholesterol concentrations increased in the blood. Addition of biotin to the diet reversed all of the symptoms quickly.
The symptoms of egg white induced biotin deficiency were referred to as ‘egg white injury’. Subsequently, the discovery that egg white inhibit the absorption of biotin lead to the identification of a protein in egg whites called avidin. In chicken eggs, avidin makes up around 0.05 % of the total protein in egg whites, a reasonably large amount. However, avidin is secreted into the egg white of other birds as well as the eggs of amphibians, although the function of avidin is not understood. Each avidin molecule can bind up to four molecules of biotin. Because avidin is a protein it is able to be denatured, and this removes its biotin binding capacity, something that is dependent on the shape of the molecule. Heating egg white will denature avidin, and so cooked egg whites are not able to bind biotin and has no effect on the absorption of biotin. Some denaturation of avidin may occur in the hydrochloric acid of the stomach, although clearly this does not occur quickly enough to prevent the binding of most biotin.
Saturday, 8 August 2015
Sugar Sugar Everywhere
Sugar is increasingly being linked to the development of Western lifestyle diseases including tooth decay, obesity, cardiovascular disease, cancer, dementia and type 2 diabetes. Sugar is detrimental for the health because it contains a molecule of fructose. Refined crystalline fructose used as a food ingredient is damaging to the health because it can only be processed by the liver. In excessive amounts it overloads the liver with energy because it is rapidly absorbed in its unrefined state. Excessive fructose intakes shift the metabolism of the liver to one of synthesising fatty acids through the de novo lipogenesis pathway, and the resultant fatty acids accumulate in skeletal muscle and the liver. Here the fatty acids interfere with the insulin signal cascade and contribute significantly to the development of insulin resistance, a cause of weight gain and disease. The typical Western diet contains too much fructose because sugar is a common ingredient in many foods, many of which do not really need added sugar.
Ready to eat breakfast cereals often contain hidden sugar. Many breakfast cereal manufacturers claim their cereals are ‘healthy’ or ‘whole grain’, when they are neither of these things. Adding sugar to breakfast cereals is done to improve the taste, and this is often necessary because the consumer is used to the taste of high sugar foods. Without the addition of sugar, the cereals taste bland and unpalatable to the typical Westerner who has been raised on a high sugar diet. Sugar is also often added to the cereal by the consumer for the same reason. The added sugar content in some cereals is not large. This added sugar would likely not be detrimental if it was not for the fact that sugar intake is cumulative. So many foods now contain sugar that intakes of small amounts of sugar are detrimental when the diet as a whole is considered. Avoiding Western diseases necessitate avoiding added sugar and this means the careful reading of food labels to find that sugar which has been hidden in foods by the manufacturers.
Figure 1. The ingredients of a brand name ready to eat breakfast cereal clearly shows added sugar.
Sunday, 2 August 2015
How Do Vitamins and Minerals Work?
Vitamins and minerals are terms that most people are familiar with. However, few really understand their role in nutrition. Vitamins and minerals should really be thought of as the nuts and bolts that hold human health together. This is because their role centres on their function as cofactors to enzymes in metabolic pathways. In this role vitamins and minerals tend to function in the same way, with just minor nuances. Vitamins are organic compounds synthesised by plants, or in some cases microorganisms. Vitamins are therefore derived from eating plants, but eating animals that have previously eaten food containing vitamins also supplies humans with some vitamins. In contrast minerals are inorganic compound derived from rock. Plants absorb minerals to their tissues from the soil, and then animals eat the plants to obtain minerals. Some animals obtain their minerals through eating clay or soil. If the minerals are absent from the soil then they will also be absent from the plants and animals living on those soils.
Vitamins and minerals act as cofactors to enzymes in metabolic pathways. A metabolic pathways is a number of chemical reactions that are linked together to form a chain of reactions. These reactions can be catabolic if they break a substance down or anabolic if the synthesised new chemicals. The sum of the anabolic and catabolic pathways is called metabolism and it is this that accounts for the energy required at rest. Enzymes catalyse many of the metabolic reactions in the body. Enzymes are proteins with specific shapes and charges that allow them to speed the rates of particular reactions by lowering the activation energy of the reaction. However, many enzymes require vitamins or minerals to provide particular conditions within the active site of the enzyme. If these vitamins and minerals are missing, the enzymes stops working and the pathway ceases to exist. This leads to a specific deficiency disease and ultimately death. Vitamin and mineral deficiencies can be reversed before death by addition of the missing nutrient to the diet.
Saturday, 1 August 2015
Pycnogenol: Antioxidant Bark
Antioxidants are protective of disease because they inhibit free radical chain reactions, and this reduces oxidative stress. Oxidative stress is associated with many Western lifestyle diseases including cancer, cardiovascular disease, type 2 diabetes, arthritis and obesity. Oxidative stress may initiate disease because the free radicals generated during oxidative stress overwhelm the natural antioxidant defences of tissues and this causes tissue damage, cellular destruction and DNA mutations. Plants synthesise antioxidants for the same reason as animals, as this protects them from environmental stress that can initiate free radical formation. When we eat plants we consume these antioxidants, many of which are biologically active and contribute towards protection of our own tissues from oxidative stress. However, many plants not commonly consumed also contain highly beneficial antioxidants. One such plant is a pine tree Pinus maritima, the bark of which contains an antioxidants called proanthocyanidins.
The native North American Indians used the bark of the pine tree as a decoction to provide high levels of vitamin C, proanthocyanidins and other beneficial nutrients to supplement their diet. It may have been the French explorer Jacques Cartier that first highlighted the antiscorbutic effects of the pine bark extract to Europeans, when he used it to treat scurvy ridden sailors under his command. A discuvery likely aided by the local knowledge of the Native American Indians. It was some centuries later that a Canadian researcher Jacques Masquelier identified the health effects of pine bark extracts and attributed many of these effects to the proanthocyanidins in the bark. From his research a patented formula containing a specific amount of proanthocyanidins was formulated, and this supplemental extract was called pycnogenol. Proanthocyanidins are actually polymers of the catechin compounds found in tea, and evidence suggests they are biologically active and have antioxidant effects in humans that confer health benefits.
However, the proanthocyanidins in pine bark extract are not unique. They are also present in high concentrations in grapes, berries, cocoa, wine, cinnamon as well as in lower amounts in many other fruits and vegetables. A diet rich in fruits and vegetables therefore provides high amounts of proanthocyanidins that should confer the same health effects as pine bark extract. The benefits of consuming proanthocyanidins through the diet is that many other antioxidants and essential nutrients will be consumed in the whole foods. Supplements of proanthocyanidins are also available having been extracted from grape seeds, and these tend to be cheaper than the pine bark extracted equivalents. Further, as the proanthocyanidins are polymers of the catechin, it may be possible to experience much of the beneficial antioxidant effects of proanthocyanidins from tea. It is not clear if the high molecular weight proanthocyanidins are absorbed intact, or more likely digested to smaller monomers, dimers and trimers, before absorption.
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