Lutein and Zeaxanthin in Foods: Eye Health

Lutein and zeaxanthin are carotenoids that have a particular role to play in human health. Both compounds accumulate in the macula of the eye, and here they protect the retina and other parts from free radicals through their antioxidant activity. A diet high in lutein and zeaxanthin is therefore beneficial to eye health and can significantly reduce the risk of specific eye disorders related to free radical damage. Dietary sources of lutein and zeaxanthin tend to have strong yellow colours as these pigments reflect the light waves necessary to be visualised as yellow. Foods such as egg yolks and yellow flower petals are often rich sources of lutein and zeaxanthin. However, lutein and zeaxanthin can also be found in green leafy vegetables such as kale, parsley and spinach, with the green chlorophyll pigment masking the yellow colour of the carotenoids. Generally, plant diets are high in both lutein and zeaxanthin, but eating foods that contain higher amounts can be a good strategy to optimise eye health and protect eyesight. 

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RdB

Abdel-Aal, E.S.M., Akhtar, H., Zaheer, K. and Ali, R. 2013 Dietary Sources of Lutein and Zeaxanthin Carotenoids and Their Role in Eye Health. Nutrients. 5: 1169-1185
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Chlorophyll in Human Nutrition

Chlorophyll is one of the most ubiquitous chemicals in the human diet and makes up a considerable amount of the micronutrient intake when a high plant food diet is eaten. Chlorophyll is a pigment in plants that is structurally similar to human haemoglobin apart from the presence of magnesium ions rather than iron ions. Chlorophyll may have a number of health effects in humans and in particular it may be able to modify the process that can lead to the formation of cancers. One way this may occur is through the modification of oxidative stress through an antioxidant process that is present in certain chlorophyll metabolites. Of course one of the major benefits of eating more chlorophyll from plants is that with the chlorophyll many other useful and health giving nutrients are consumed. High chlorophyll diets therefore tend to be high in many beneficial phytochemicals, many of which possess antioxidant, anti-cancer, cardioprotective and anti-inflammatory effects. 

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Hayes, M. and Ferruzzi, M.G. 2020. Update on the bioavailability and chemopreventative mechanisms of dietary chlorophyll derivatives. Nutrition Research. 81: 19-37
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The Functions of Glycine

Glycine represents around 11.5 % of the total amino acids in humans and roughly 20 % of the nitrogen from amino acids in proteins. However, glycine is not essential because it can be synthesised from other chemicals including choline, glyoxylate and the amino acid threonine. Glycine is used by the body for a number of functions and the wide variety of its uses means that the body has a high requirement to synthesise it. For example glycine is required for the formation of collagen, where it forms every third residue in the triple helical structure. Glycine is also required for the formation of the cellular antioxidant glutathione. The energy system of the body relies on glycine because it is needed for the synthesis of creatine, which forms the high energy creatine phosphate compound in cells. Purine in the form of DNA and RNA both require glycine, as does the oxygen carrying compound haem. Another highly important function of glycine is the formation of bile acids, which are pivotal in the digestion and absorption of lipids. 

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Wang, W., Wu, Z., Dai, Z., Yang, Y., Wang, J. and Wu, G. 2013. Glycine metabolism in animals and humans: implications for nutrition and health. Amino Acids. 45(3): 463-477
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The Temporal Component of Food

Unless considerable time and effort is spent learning about nutrition, the superficial viewpoint will never fully uncover the secrets it possesses. One great example of this is how the nutritional component within foods change over time. Looking at a particular food at time point A can give a different picture of the same frood at time point B. Bananas for example when unripe and high in starch. As the banana ripens the starch is converted to sugar and therefore the nutritional quality of the banana changes. This can have significant effects on the consumer as not only are the macronutrients they ingest different, but those macronutrients affect metabolism in different ways. Another great example of this are fatty acids, that slowly degrade over time and become rancid. A healthy food at time point A, can therefore become an unhealthy food at time point B. Understanding the changing nutrition of foods is part of understanding nutrition, and without this knowledge, the one-size fits all advice will likely mislead the consumer to ill health. 

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RdB

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Edible Flowers

Flower petals are brightly coloured as the purpose of the petals is to attract insects that can pollinate the plant. The plant uses a variety of phytochemicals to colour its petals and some of these have interesting nutritional properties. Two of the most commonly used phytochemicals that plants accumulate in petals include anthocyanins, which have a red, blue or purple colour, and carotenoids, which can be red, yellow or orange. Traditional Japanese, Chinese and Indian medicine all incorporate flowers from plants as part of their medical treatments in certain forms, and teas such as jasmine tea (Jasminum), made from Jasmine flowers, has become popular in the West for its calming effects.  In Europe, marigold (Calendula officinalis), geranium (Geranium macrorrhizum), bougainvillaea (Bougainvillaea spectabilis) and Jerusalem artichoke (Helianthus tuberosus) are all edible and have a traditional culinary use. Health effects of flowers generally derive from their high antioxidant content. 

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Petrova, I., Petkova, N. and Ivanov, I. 2016. Five edible flowers–valuable source of antioxidants in human nutrition. International Journal of Pharmacognosy and Phytochemical Research. 8(4): 604-610
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How Costly is Chicken and Fish Farming?

Chicken and salmon farming both have considerable environmental impacts when compared to more sustainable plant based practices of agriculture. Studies show that chicken farming is more efficient when compared to salmon farming and also cod fishing with a trawler. This likely relates to the fact that chickens are easy to feed and house and grow quickly. Salmon is more intensive as a method of farming, particularly as salmon farming requires a high use of chemicals in order to prevent the fish becoming ill. Cod fishing is also energy intensive because of the requirement to use a trawler, which necessitates the use of expensive equipment. Another factor is the huge area required for fishing compared to the small area required for growing chickens. However, compared to plants, all animal protein is significantly more costly in terms of time, energy and resources, with planting, harvesting and storing taking up most of the energy needs.  

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Ellingsen, H. and Aanondsen, S.A. 2006. Environmental impacts of wild caught cod and farmed Salmon-a comparison with chicken (7 pp). The International Journal of Life Cycle Assessment. 11(1): 60-65
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The Best Antioxidant for Your Brain?

The human brain is composed of a high concentration of lipids, many of which are phospholipids and their derivatives. Diets rich in essential fatty acids improve brain function and efficiency. However, the essential fatty acids are polyunsaturated, and this increases the susceptibility of the brain to free radical damage. Free radical damage is highly detrimental to the long term health of the brain and a significant factor in the development of dementia and mood disorders. Because the brain is composed of high amounts of fat, the best antioxidants are those that protect fats. Of these the most useful is perhaps the vitamin E vitamers that are composed of the tocotrienols and the tocopherols. These vitamins accumulate in cell membranes and protect the fatty acids for free radicals which lower the risk of lipid peroxidation and disease. Nature has cleverly packages polyunsaturated fatty acids with vitamin E in the most common source, nuts and seeds, and so consumption of these foods negates the necessity to consume additional vitamin E. 

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Why Honey is Not The Same as Sugar

Evidence shows that refined crystalline sugars, including sucrose and fructose are detrimental to the health. This relates to the way the fructose molecule is able to decrease the insulin sensitivity of cells, something that causes metabolic dysfunction, weight gain and fatty liver disease. Honey contains sucrose and fructose in high amounts, and yet studies consistently show that honey does not have the same negative effects. It is not fully understood why this might be so, but a number of lines of evidence exist. In particular, honey contains high amounts of antioxidants in the form of polyphenols, and these may protect the consumer from the negative effects of the sucrose and fructose by reducing the risk of insulin resistance developing. This may be because for insulin resistance to develop a free radical process must happen, but the polyphenols interfere with the generation of free radicals and therefore prevent the negative effects. However, as with all foods honey should still be moderated if consumed as part of a healthy diet. 

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Some of the Problems with Artificial Sweeteners

Artificial sweeteners are popular as a food ingredient, mainly because most individuals naturally have a sweet tooth. Food manufacturers play on people’s desire to avoid sugar and add artificial sweeteners to foods. In many cases these are sweeteners with little or no energy content such as aspartame, acesulfame K or sucralose. Some evidence suggests that certain artificial sweeteners can be toxic, and this is most commonly associated with aspartame because it can cause neuronal over stimulation. However, there are more problems with sweeteners other than their alleged toxicity. Another major problem with artificial sweeteners is that they tend to be added to junk food and this encourages its overconsumption. In relation to this, artificial sweeteners also negatively affect insulin levels, and as a result can increase the risk of weight gain, despite being energy free. Minimising artificial sweetener intake can be achieved by eating a high quality diet centred on plant foods and high quality meat with high intakes of antioxidants and fibre.  

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Mental Function and Dehydration

A reasonably large body of evidence from the literature shows a correlation between the hydration level of the subject and physical performance. As dehydration reaches about 5 %, performance drops off significantly. Athletes have known this for some time, and maintaining proper hydration is a significant priority of the serious and determined athlete. As with physical performance, mental performance also shows a correlation with hydration levels. In this regard, even small amounts of dehydration can cause significant cognitive impairments. For example, one study observed that a dehydration level of 2 % causes significant impairment in tasks that require attention, psychomotor, subjective state assessment and immediate memory skills. However, long-term memory and executive mental functions are not so detrimentally affected, as might be expected. Maintaining correct hydration levels should therefore be a priority to those that wish to optimise mental function and maintain optimal health. 

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Adan, A. 2012. Cognitive performance and dehydration. Journal of the American College of Nutrition. 31(2): 71-78
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