Saturday 31 January 2015
Shrimps or prawns are crustaceans that belonging to the arthropod group of animals, in a subgroup that includes barnacles, crabs, krill, lobsters and crayfish. Prawns have a tough outer shell (like all crustaceans), covering a semi-translucent flesh that can be comprised of various colours. Prawns consumed in Western countries are often pink in colour, but the flesh of prawns can be yellow, grey or brown. Most prawns provided for Western consumers are farmed, but a considerable portion of the World’s shrimp harvest still comes from wild organisms caught from the oceans. Hundreds of varieties of edible prawns are harvested from the oceans each year, and prawns are the second most popular fish Worldwide after tuna (in some countries they are the number one seas food consumed). The popularity of prawns is partly because they are so widely distributed in the oceans of the world and partly because of their nutritional and taste properties.
Nutritionally, prawns are a good source of protein, with a 100 gram serving containing about 20 grams of protein. Prawns are also low in fat, with only 1 gram of fat in the same 100 gram serving. The low content of fat and almost absence of carbohydrate, means that prawns are also low in energy (about 100 calories per 100 grams), with almost all this energy provided by their high protein content. The fat content of the prawns can include around 300 mg of the long chain fatty acids eicosapentaenoic acid and docosahexaenoic acid per 100 grams, although the fat content of the animals depends on their diet. Prawns are therefore not a great source of these fatty acids but can contribute something to omega-3 fatty acid intake. Prawns also contain vitamin B12, which makes them a good food to include in the diet of those who avoid meat. The mineral content of the prawn is notable in that it contains good amounts of selenium.
Sunday 25 January 2015
It is only recently that the importance of the microbiota in the human gut has being fully appreciated as pivotal to human health. This is surprising, because the colonisation of the guts of ruminant livestock is known to provide essential health effects. That the processes in the human colon resemble those within ruminant livestock suggests that a knowledge of the latter may be of interest to the informed nutritionist. Generally ruminant animals possess bacteria, protozoa and fungi within their rumens. Over 60 species of bacteria are known with total bacteria counts equating to between one billion to ten billion organism per mL. Most bacteria in ruminant livestock are non spore forming anaerobes whose main function is the fermentation of cellulose into short chain fatty acids such as butyric, acetic and propionic acid which is then absorbed and used as a source of energy by the animal. Such production of short chain fatty acids is now known to provide substantial energy to humans and may provide up to 5 % of total energy needs.
As well as bacteria, the rumen also contains a lesser number of protozoa (upto 1 million organisms per mL). However, as the protozoa are larger than the bacteria size, the total mass may be similar. Most of the protozoa and ciliates belonging to the holotrich or oligotrich groups. The protozoans belonging to the oligotrichs can ingest food particles, but unlike holotrichous protozoa and bacteria, they cannot ferment cellulose to produce short chain fatty acids. Less is known about the fungi of the rumen which constitute around 10 percent of the microbial biomass. However, as with the bacteria, they are strictly anaerobic and their life cycles include a motile phase as a zoospore and a non-motile phase as a sporangium. As sporangia, they become attached to food particles by rhizoids which penetrate the cells walls where they digest most carbohydrates. The bacteria, protozoa and fungi work as a consorti within the rumen, with fungi invading the plant tissue and the protozoa and bacteria fermenting the product of this invasion. Around 20 % of the nutrients required by ruminants are provided by its microflora and fauna.
Saturday 24 January 2015
Bananas cultivation may have originated in Malaysia over 4000 years ago, but has since spread to Africa, the Middle East and America through colonisation. Bananas are worthy of nutritional consideration because so many are produced and consumed Worldwide. In fact bananas are the second leading fruit crop. There are hundreds of varieties of banana, but they can be split into two main types. Plantain bananas (Musa paradisiaca) are high in starch and low in sugar and as a result are usually cooked before eating. Plantain bananas are used in cooking in a similar way to vegetables such as the potato, and may be cooked often by frying. Plantain bananas are usually green in colour, but can ripen to a black colour. Sweet bananas are also starchy, but can ripen which allows much of the starch to be converted to sugar, and this allows consumption raw. As sweet bananas ripen they pass from green to yellow and finally to black. The most common sweet banana in the West is the Big Mike or Gros Michael (Musa sapientum).
Sweet bananas are renowned for their potassium content, which is high compared to most fruits. However some fruits such as avocados have an even higher potassium content compared to bananas. As well as potassium, bananas also contain high amounts of magnesium. The potassium and magnesium content of bananas makes them a useful food to incorporate as part of a blood pressure lowering diet. This is because these two minerals have been shown to produce blood pressure lowering and other cardioprotective effects in humans. As well as potassium sweet bananas are also a good source of vitamin C, a feature they share with most fruits. The B vitamins in bananas include riboflavin, vitamin B6 (pyridoxine) and biotin. One nutritional property of bananas worthy of consideration is their low water content, in comparison to most fruit. This makes their energy more concentrated that in most other fruits and this favours their use by athletes who require sugars for the resynthesis of glycogen stores following exercise.
Sunday 11 January 2015
It used to be the case that only conventionally grown animal produce was available. However more recently consumer demand has driven a plethora of traditional and alternative farming techniques that provide the market with a range of different quality animal products. The nomenclature of animal products has therefore become confusing to the layman. Deciphering the semantics of the labelling of animal products is therefore worthy of consideration for those interested in health, as the quality of the food eaten will reflect the health benefits derived from those products. The most commonly eaten form of animal product is a result of conventional intensive farming techniques. Conventionally grown livestock are generally fed gains, as these fatten the animals quickly and provide greater profits for the farmers. The grains themselves are often conventionally grown themselves, meaning that the pesticide residues they contain are passed onto the livestock, which is in turn eaten by humans in the animal produce.
The main problem with grain fed animals is that they convert much of the starch in the grain into saturated fatty acids, and this is reflected in a high saturated fat content to their meat or eggs. This saturated fat is an idea reservoir for the storage of the pesticide residues and this creates a conduit with which to siphon the residues into the human food chain. Organic grain fed animals are grown in the same way as conventional grain fed animals, however in this case the grains are of organic origin and so pesticide residues are not present. In addition, many of the drugs and other chemicals administered to conventionally grown animals are not allowed in organically grown produce. However, the diets of all grain fed animals, be it conventional or organic, are devoid of meaningful levels of omega-3 fatty acids, and as a result they provide an imbalanced ratio of omega-6 to omega-3 fats. This can be damaging to the health of the consumer because it produces a proinflammatory state when the products are eaten regularly.
Grass fed animals are generally fed diets more akin to their natural pasture diets. This includes a high intake of grass, which may be supplemented with some grains. Grass fed animals tend to be leaner than grain fed animal and as a result the saturated fat content to the meat is lower. In addition, the omega-3 content of the meat is higher because of the alpha linolenic acid in grass, and this provides a better balance of omega-6 to omega-3 fatty acids in the meat. Organic grass fed animals are fed on grass that is grown in the absence of pesticides and are not administered the same range of drugs as conventionally grown animals, and so the meat should also be absent of many potentially dangerous chemicals. Free range animals are generally allowed to roam freely and in this regard can sources their own food, which supplements their diet. Chickens are increasingly commonly grown as free range. The chicken forage for insects and grubs and this provides a natural more nutrient dense diet that increases the nutrient quality of the meat and eggs they produce. Assume that free range produce is not organic unless specifically stated.
Saturday 10 January 2015
It is estimated that Worldwide more people consume products made from goat’s milk than they do cow’s milk. This likely relates to the historical domestication of the goat which may have occurred as far ago as 8000 years B.C. This is obviously not true in the Western countries such as the United Kingdom and the United States were cow’s milk drinking still predominates. However, in recent times goat’s milk has become more widely available in Western countries and is now stocked by most supermarkets. In addition France, Greece and the Netherlands now produce a range of goat’s cheese that is also widely available throughout Europe. Goats milk has a slightly sweeter taste that cow’s milk, but its reputation for being sour like goat’s cheese is not deserving. Some evidence suggests that allergies are less common with goat’s milk consumption and the nutritional characteristics of goat’s milk might make it more easily digested.
Goats milk shares many of the characteristics of many mammalian milks. In this respect goats milk does not differ significantly from that of cow’s milk. Goats milk is a good source of protein, and as with other milks contains the disaccharide sugar lactose. This can make the consumption of goat’s milk problematic for those with lactose malabsorption, although the levels are lactose are slightly lower in goats milk compared to cow’s milk. As with all milk, the fat content of goat’s milk is low in essential fatty acids as the bacteria in the stomachs of ruminant destroys these fats before they can be absorbed and incorporated into the milk. However, goat’s milk does contain slightly more short and medium chain fatty acids compared to cow’s milk. The mineral content of goat's milk is very similar to cow’s milk, with slightly higher concentrations of potassium and calcium. Goats milk is also a good source of the B vitamins riboflavin and biotin.
Sunday 4 January 2015
Eggs have been part of the human diet since the chicken was first domesticated in Asia over 4000 years ago. Many people believe that eggs are detrimental to the health because they are energy (calorie), saturated fat and cholesterol dense. This is based on the tired old fallacies that saturated fat and cholesterol are the cause of cardiovascular disease, and that high energy foods make you fat. Many nutritional studies have been performed on eggs and egg eaters and when these are viewed in their entirety the evidence for eggs being linked to either weight gain or cardiovascular disease is really non-existent. A shame therefore that many people avoid eggs, because eggs are actually a very good source of nutrients, many of which have been shown to be cardioprotective. Nutritionally eggs contain all the nutrients to create and grow a live chick. Eggs are therefore a good source of essential nutrients including many of the essential nutrients required for human growth and development.
The cardioprotective effects of eggs are evidenced by the nutrients they contain. Betaine is one such nutrient that is known to possess cardioprotective effects. Betaine is able to reduce plasma levels of homocysteine, an amino acid derived chemical that is known to induce oxidative stress in humans. The homocysteine induced oxidative stress is now thought to be a primary driver of the endothelial dysfunction that may be required for the development of cardiovascular disease. Betaine reduces homocysteine levels because it allows conversion of homocysteine to the amino acid methionine, thus reducing tissue levels of the former. Eggs are also a good source of B vitamins, and three of the B vitamins, folic acid, vitamin B12 and vitamin B6 are also able to reduce plasma levels of homocysteine. In this regard, vitamin B12 and folic acid are required as cofactors for the conversion of homocysteine to methionine, and vitamin B6 is required as a cofactor for the conversion of homocysteine to cysteine.
The B vitamins and betaine are therefore key cardioprotective nutrients that can be derived from eggs. However, this is not where the cardioprotective effects of eggs stops. Free range eggs are also a good source of the omega-3 essential fatty acid alpha linolenic acid (ALA, C18:3 (n-3)). The content of omega-3 fatty acids in eggs is dependent on the diet of the chicken. Those given access to a wide range of natural foods tend to accumulate omega-3 fatty acids such as ALA in their eggs, while those fed a restricted and omega-3 deficient diet are not able to do this. Therefore free range eggs tend to be high in omega-3 fats whereas battery reared chicken eggs are not. Omega-3 fats have been shown to be cardioprotective for a number of reasons. Firstly, they reduce inflammation because they are required for the production of anti-inflammatory signal molecules in cells. Secondly, they are able to reduce platelet aggregation. Thirdly, they can alter fat metabolism in the liver and thus reduce triglyceride levels.
The ability to regulate fat metabolism in the liver is an important mechanism by which omega-3 fatty acids prevent cardiovascular disease. However, eggs contain another substance, choline, that may also be cardioprotective because of its effects on liver fat metabolism. Choline is often grouped with the B vitamins, although it can be synthesised in the body from the amino acids methionine and serine. Choline is a lipotropic agent, that is required for the correct metabolism and export of lipids from the liver. This related to the fact that choline is required for the formation of lipoproteins as it is a key component of the phospholipids that are the building blocks of the very low density lipoproteins (VLDL) that export fatty acids from the liver. Choline also plays a role in homocysteine metabolism because it can be converted to betaine, which as mentioned above is a cardioprotective nutrient. Choline is so important to human nutrition that it is now regarded as an essential nutrient, and eggs are one of the best sources.
Saturday 3 January 2015
Turmeric (Cucuma longa) is a member of the ginger (Zingiberaceae) family that is grown commercially in tropical countries for its root (rhizome). The rhizome of the turmeric plant is prized the World over because it has particular medicinal properties in humans and other animals. For medicinal uses the rhizome is dried and powdered where it can be turned into a standardised extract. As well as its medicinal properties, turmeric is also used as a spice in curry powder, mustard and in various foods for its yellow colour. Its antioxidant properties also make turmeric a useful food preserve, one of the reasons it is likely used traditionally in curries. The main active ingredient in turmeric is believed to be a curcumoid called curcumin. However, turmeric also contains a volatile oil comprising of turmerone, bisabolane, curlone, ar-turmerone and zingiberene. This volatile oil gives turmeric its natural aroma. Various sugars, vitamins and minerals are also present in turmeric. Turmeric naturally contains around 0.5 to 5 % curcumin but preparations can be standardised to contain as much as 95 % curcumoids.
Both the volatile oil and the curcuminoids in turmeric are believed to be bioactive and exert significant pharmacological activity in humans. In animals, cell culture and humans studies, turmeric has been shown to possess significant anti-inflammatory, antimicrobial, antioxidant, anticarcinogenic and hepatoprotective effects. The antioxidant effects of turmeric are thought to come primarily from the curcumin content. This is not surprising as curcumin is a phenol (actually a phenylpropanoid) and plant phenols are well researched for their antioxidant capacity. The yellow colour of turmeric means that it can be used in high fat products such as butter margarine and cheese to prevent lipid peroxidation. In humans, curcumin interacts with other antioxidants, sparing cellular levels and boosting overall antioxidant capacity in tissues. This antioxidant effect no doubt confers some protection from cancer. In this regard turmeric has been shown to be beneficial at preventing cancer initiation, propagation and progression.
However, it is the anti-inflammatory effects of turmeric that are most well researched and best understood. The volatile oil fraction of turmeric has been shown to possess significant anti-inflammatory effects in animals, effects which are comparable to currently prescribed anti-inflammatory drugs such as cortisone and other similar drugs. However, the curcumin content is likely the main reason for the anti-inflammatory effects of turmeric. Curcumin has been shown to possess effects against inflammation that are superior to prescribed pharmaceuticals, but in addition shows none of the side effects associated with these compounds. As well as its anti-inflammatory effects curcumin may act in a similar way to capsaicin from cayenne pepper by depleting the nerve ending of substance P. Curcumin is therefore effective at preventing the propagation of pain signals to the central nervous system. In combination with its anti-inflammatory effect this makes curcumin a good treatment for soft tissue injuries.
So how does curcuming inhibit inflammation? Well, the mechanism of action of turmeric on inflammation is not fully understood, but several mechanisms have been suggested and tested clinically in animals and humans. One theory suggests that the curcumoids in turmeric can cause an indirect effect on the adrenal cortex, to modify the release of glucocorticoids (the bodies natural anti-inflammatory compounds). Another theory suggests that the curcumoids in turmeric can decrease the rate of metabolism of glucocorticoids and thus potentiate their action. Alternatively, turmeric may inhibit the 5-lipoxygenase enzyme responsible for the synthesis of pro-inflammatory eicosanoids or inhibit the production of lipopolysaccharide induced cytokines such as tumour necrosis factor alpha (TNF-α) and interleukin-1. Turmeric can also improve liver function and increase bile secretion which may confer beneficial effects against systemic inflammation caused by metabolic dysfunction in the liver.