Vitamin A: Gaining A Better View Of Its Benefits
Thursday, September 21st, 2017 | 131 Views
Vitamin a might be the most underrated of all vitamin alphabet hybrids, never really gaining the scurvy-beating, capsule-pushing fame of vitamins c and d. Recent research exploring the health benefits of vitamin a though, has pushed the vitamin’s relevance up a few notches. By Nyi Nyi Thet
There has been some breakthrough in treating colon cancer. The disease, which is one of the leading causes of cancer-related deaths, kills more than 50,000 people annually, and is notorious for being almost impossible to completely get rid of. Even after undergoing chemotherapy, a group of persisting cancer cells remain in the colon, and are not typically alleviated by conventional methods. One of the more novel treatments being proposed involves reversing the HOXA5, a homeobox protein that prevents the growth of the cancerous stems in the colon. Researchers needed a way to reactivate the HOXA5, such as a chemical structure that could turn the HOXA5 gene on. They might have found the solution in an unlikely source, Vitamin A.
Vitamin A is not actually a single nutrient but a group of unsaturated nutritional organic compounds, consisting of retinol, retinoic acid, retinal and various other pro-vitamin A carotenoids and beta-carotene. The complex weave of compounds not only determines the nature of vitamin A, but in many ways dictates the equally fascinating path to discovering the vitamin.
History Of Vitamin A
The winding history of the plucky vitamin started in the early 1800s and has only recently found a semblance of closure. The first sign of vitamin A was noticed by a physiologist called Magendie in 1816 who, while conducting nutritional deprivation experiments, found that malnourished dogs tended to develop corneal ulcers and suffered an elevated threat of death. Further along the 17th century, Nicolai Lunin discovered an unknown substance in milk that was essential for nutrition, even though neither the word vitamin nor the letter A was close to being used.
English biochemist Frederick Gowland Hopkins took the vitamin to the cusp of discovery with his initial conclusion that there were unsuspected dietetic factors that were necessary for life. He followed up that finding with a claim that there were in fact incredibly small amounts of accessory factors present in milk that supported life. That discovery would later be compounded by the trio of scientists, Elmer McCollum, Lafayette Mendel and Thomas Burr Osbourne. They found that the nutritional value of butter and egg yolk exceeded that of lard and olive oil. This ‘accessory factor’ was christened ‘fat-soluble A’ before landing on the more marketable ‘vitamin A’ in 1920.
Once the name was in place, the pieces of the puzzles were laid down hard and fast, with Swiss organic chemist Paul Karrer describing the chemical structure in 1932, chemists Harry Holmes and Ruth Corbet isolating and crystallising the vitamin in 1937 and methods for synthesis being developed in 1946. The research on effects of vitamin A carried well into the ‘90s, with extensive work done on the role of immunity and child survival.
The Two Forms Of Vitamin A
The foundations led to the discovery of two major forms of vitamin A found in food, retinoids and carotenoids. The first form, carotenoids, is the form most people associate with vitamin A. It is found most commonly in brightly coloured vegetables that have been proven to enhance eyesight. The carotenoid forms of vitamin A commonly function as antioxidant and anti-inflammatory nutrients.
Interestingly, not every food rich in vitamin A serves to improve your eyesight; the only carotenoids found inside the retina of the human eye are the xanthophylls lutein and zeaxanthin, commonly found in corn, wolfberries and paprika. The ocular health-conscious consumer might therefore wish to aim for a diet that is rich in both (e.g. spinach, kale, Spanish chard) as the results on improving eyesight based on a diet of just one of the two is still inconclusive.
Retinoids offer an almost diametrically opposed stance from carotenoids, both in source of origin and health effects. They are found typically in meat, dairy products and some seafood, with the highest levels of retinoid found in shrimps, eggs and cheese. While retinoids do quite little to improve eyesight, except perhaps boost night vision, they provide numerous other forms of immunity, inflammatory, genetic and reproductive benefits. They are adept at boosting cell division and enhancing cell communications, and provide heightened resistance to infectious diseases and increased red cell production.
Despite the wildly differing nutritional sources suggesting the necessity for a good mix of both, vegetarians might want to hold off on that quarter pounder for just a bit. While there are indeed some groups of people who, due to genetic factors or prolonged exposure to toxic chemicals, are unable to convert carotenoid forms of vitamin A into retinoid forms, most people will generally be fi ne in their vitamin A intake if they follow an all carotenoid diet.
Vitamin A Conversion
Not all carotenoids are converted equally though, beta carotenes for example, are far more effectively converted into retinoid, producing twice as much retinoid as compared to alpha-carotene.
It is thanks in large part to the high conversion rate that sweet potato emerges as the vegetable with the highest vitamin A count. Sweet potatoes possess the highest concentration of beta carotene among any vegetables, an astonishing 23,018 micrograms, more than twice the amount of micrograms found in their closest competitor, spinach (11,318 micrograms).
A system based on retinol activity equivalents (RAE) and retinol equivalents (RE) that measures the retinoid-converting potential of carotenoids also placed sweet potatoes head and shoulders above competition. They score a 1,922 in mcg RAE, with carrots and spinach trailing behind with scores of 1,019 and 943 respectively.
Sweet potato’s status as the best source of vitamin A fits nicely into the general stereotype of colourful foods having higher vitamin A. However, if you are hankering for something other than vegetables, there are animal foods that possess a relatively high amount of vitamin A as well, namely shrimps, cheese and eggs, with RAE scores of 102, 77 and 75 respectively.
Another extremely potent source of vitamin A is liver. A tablespoon of cod liver alone delivers a mind boggling 136 percent of the established daily tolerable upper intake level (UL). The sheer excess of vitamin A, and the potential for vitamin toxicity, found in liver therefore makes it somewhat unfeasible for liver products to be properly marketed as a primary source of vitamin A.
Reasons For Deficiency
Despite the relatively abundant nature of vitamin A, there is still an epidemic of deficiency prevalent through certain parts of the world. The worst hit areas, according to the World Health Organisation, of the deficiency lies primarily in Africa and the developing parts of Asia, with the hardest hit demographics being young children and pregnant women from low income countries. There are estimated to be 250 million preschool children who are vitamin A deficient, and a majority of women in these low income areas most likely suffer from vitamin A deficiency as well.
Vitamin A deficiency is the leading cause of preventable blindness in children, with 250,000 to 500,000 vitamin A deficient children becoming blind every year, and half of them dying within a year of losing their sight. Other diseases that might occur in children due to the deficiency include heightened risk of severe illness, or even death, from common childhood infections such as diarrhoea disease and measles.
For pregnant women, the main timeframe of risk occurs during the third trimester, when nutritional demand by both the unborn child and the mother is at its absolute peak. The vitamin deficiency at this stage usually manifests itself in the form of night blindness. Persistent vitamin A deficiency might also be responsible for an increased likelihood in maternal mortality.
One of the major causes of vitamin A deficiency in these regions is the dearth of preformed vitamin A usually found in meat. Supplementary causes that factor into overall deficiency also includes iron deficiency, excessive alcohol intake and fat mal-absorption issues such as pancreatitis, cystic fibrosis, tropical sprue and biliary obstruction.
Solutions For Deficiency
The need for a radically altered diet in these regions provides an interesting and necessary opportunity for marketing an increased uptake in vitamin A. One of the dietary restrictions which caused this pandemic of malnutrition in the first place was the establishment of rice as a staple food in many of these cultures. Rice, while excelling in providing energy, provides absolutely no vitamin A at all.
A possible substitute, or more likely supplement, to the grain might come in the form of vitamin A-fortified milk and cereals. A recent research carried out in the Philippines, one of the countries that experiences high levels of vitamin A deficiency, found that not only is fortification one of the most viable methods of infusing much needed vitamins into the daily diets of needy people, it actually might be extremely cost-efficient as well.
Studies have shown that cost is a significant factor for rural populations when purchasing food, which leaves healthier food items in relatively low demand compared to less nutritious, but cheaper foods. A Chinese study found that compared to other methods which add vitamin A into a household diet, including supplementation and dietary diversification, food fortification was significantly cheaper.
While cost is definitely essential in propagating the adoption of more vitamin A-heavy food, there are other factors that have to be taken into account as well, including colour and texture of the fortified food item in question. It is due to these inherent local preferences that fortifying food items already favoured by the rural population might serve as a necessary jump off point for any attempt at breaking into relatively less globalised markets.
A good instance of fortifying established food items was when China, in response to continued iron deficiency, started to produce iron-fortified soy sauce over three years, at which point over 50 million residents in seven provinces were regularly consuming iron. The trial showed significant reduction of iron deficiency anaemia in comparison to the control group. This intricate blending of fortification methods while adhering to the strict cultural and societal guidelines of the respective markets of interest is integral for optimum assimilation.
Future Of Vitamin A
Vitamin A has always been correlated with improving eyesight, and for the most part, that is spot on; vegetables high in vitamin A are incredibly good for the eyes, but considering only that particular aspect is just scratching the metaphorical retinoid coated surface.
They also provide an invaluable solution to enhance immune systems, provide anti-inflammatory antioxidants, boost cell division and improve cell communications. All of these contribute immensely to the resistance of infectious diseases and increasing red cell production.
Despite all the positives, vitamin A is far from finished in its nutritional evolution. One of the more recent revelations about vitamin A is its ability to induce differentiation of stem cells in the skin, with the retinoids blocking tumour progression and normalising tissues by turning HOXA5 off. The idea of vitamin A having any effect on cancer might seem farfetched for eyesight-improving vitamins, but this is just another step in vitamin A’s slow but inexorable march forward.
Vitamin A might not have the brand recognition of vitamins C or D, two of the most popular vitamins according to some researchers, but their health benefits are slowly but surely being uncovered. It is a lengthy process laden with neither pomp nor glamour, but vitamin A has always been a slow simmering concept, progressing steadily over the centuries instead of bursting onto the scene, and the challenge for any marketer is to continually exploit that untapped potential.
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