Different To Typical Artificial Dietary supplements Is Wanted, Say Specialists
Entire meals dietary supplements is at the moment a subject of worldwide curiosity. A profusion of proof has lately come to gentle suggesting that unusual artificial multivitamin dietary supplements could also be hazardous to your well being. Goran Bjelakovic, a revered scientist from the College of Copenhagen, headed up a large meta-study that seemed on the outcomes of 67 placebo-controlled trials beforehand undertaken to find out the results of vitamin and anti-oxidant dietary supplements on longevity. Ultimately, the research mixed observations of 232 000 take a look at topics. By utilizing such a big inhabitants pattern, a research can develop into far more highly effective close to recognizing large-scale tendencies and overcoming human bias.
The outcomes of the evaluation, printed within the Journal of the American Medical Affiliation, had been nothing lower than surprising. sufferers with diabetes, coronary heart illness and lung most cancers, in addition to wholesome, regular people, there was no obvious profit to taking standard fractionated dietary supplements like Vitamin A, Vitamin E, Vitamin C, Selenium, or beta-Carotene. Actually, the outcomes went in the wrong way – there was an elevated likelihood of dying (16 %) amongst Vitamin A customers, a 7 % greater dying price amongst beta-Carotene customers, and a 4 % mortality enhance in Vitamin E customers. Beta-Carotene and Retinol, promoted as anti-carcinogenic brokers, could promote lung most cancers. That is proper – capsules marketed as serving to you in direction of an extended, more healthy life are the truth is correlated with a speedier demise. This research used typical dietary supplements available on the market constituted of artificial nutritional vitamins.
So as to add insult to damage, a latest research printed within the British Journal of Vitamin beneath the unimaginative title of “Ascorbic Acid Supplementation Does Not Attenuate Submit-Train Muscle Soreness Following Muscle-Damaging Train However Might Delay The Restoration Course of” indicated that supplementation with anti-oxidants from artificial sources could reverse most of the helpful results of bodily coaching.
Now, this isn’t to say that anti-oxidants or nutritional vitamins are dangerous for you. Removed from it – these dietary supplements had been created on the premise of stable science. Anti-oxidants are nonetheless believed to guard cells from the ravages of free radicals. The issue, reasonably, is the concept that you may get these advantages from artificial remoted compounds. Illness and the growing older course of are normally way more sophisticated than test-tube research can account for. Moreover, the problem of bioavailability is an ever-present concern. Many typical artificial dietary supplements embody enormous quantities of the marketed vitamin, however lack the extra compounds wanted to make sure that their key elements are literally absorbed by the physique. Passing straight via the digestive tract, these ‘miracle well being cures’ usually wind up doing little past giving individuals costly urine. To the rescue…Entire Meals Dietary supplements.
What the layperson ought to take from all this isn’t a way that we have made no progress within the final century concerning uncovering sufficient means of private well being upkeep. There’s one factor that no person is disputing, and that is the significance of a wholesome, well-rounded weight-reduction plan replete in fruit, orange, yellow and darkish inexperienced leafy greens, entire grains, legumes, seeds, nuts, top quality carbohydrates and lean proteins and supplementation from entire meals dietary supplements. . While you keep away from taking in dangerous chemical compounds corresponding to these in meals preservatives, flavorings, taste enhancers and ‘artificial vitamin components’, you may not solely scale back your consumption of poisons. You may even be pressured to faucet into probably the most nutritionally dependable supply obtainable, specifically pure diet. Human beings have advanced to eat unprocessed plant and animal meals sources. Latest analysis means that the prevalence of pure ratios and formulations has been massively undervalued.
Entire meals dietary supplements are meals that have not been processed or refined, or have undergone as little processing as attainable for preservation or human consumption. A lot as is the case with natural meals, entire meals dietary supplements name for the avoidance of chemically assisted agriculture. The idea is considered one of a minimization of human interference with the processes of nature. That is primarily based on the tenet that nature’s merchandise make for more healthy merchandise than the merchandise of human trade.
Whereas this can be a declare met by a lot resistance from the refined meals and pharmaceutical industries, it is being repeatedly borne out by the outcomes of analysis. A research of girls shifted from a weight-reduction plan excessive in processed meals to at least one replete with entire meals and entire meals dietary supplements resulted in a 61% lower in saturated fats consumption. In addition they skilled will increase in dietary fiber of 60 %, a forty five % enhance in vitamin E, a 60 % enchancment in vitamin C consumption, and a five-fold enhance in carotene consumption. The web results of this new phytochemical-rich weight-reduction plan was an induced drop in whole ldl cholesterol of 13 % – which means much less danger of coronary heart illness and stroke, statistically nonetheless the most important killers of individuals in first world international locations. Within the brief time period, additionally they noticed huge enhancements in bowel perform and total perceived well being. Clearly entire meals dietary supplements are preferable to typical artificial supplementation.
So the message, really, appears to be reasonably clear. Eat a weight-reduction plan comprised primarily of entire meals and entire meals dietary supplements, and you will be a shoe-in for lengthy life and an important, wholesome previous age. It sounds easy, however there’s a downside with that strategy, not less than in our present period of fixed trade and nine-to-five workdays. Progressively, individuals in developed international locations are struggling to maintain up with the clock. At the same time as work-induced stress makes the disciplinary problem of sticking to a weight-reduction plan extra daunting, so spending what little free time one has on grocery procuring can appear to be its personal particular type of waste. In contrast to processed meals, entire meals aren’t very simply saved, which means that to eat in accordance with such a weight-reduction plan, you may want to go to a farmer’s market and purchase your meals recent each few days. That is the place well-meaning eaters so usually falter within the journey in direction of well being enchancment and a trimmer waistline, coming into the lifelong development of yo-yo weight-reduction plan.
Moreover, many meals could not even be obtainable in sure international locations. Inform somebody that lives in South Africa to eat extra kale and also you may as nicely be informing them of the helpful results of zero gravity.
Bent on discovering their means round these obstacles to easy well being upkeep, scientists have labored an angle that will sound, at first blush, a bit of counterintuitive. The purpose of pharmaceutical supplementation has all the time been to protect or enhance upon the dietary efficacy of entire meals in pill and powder type. By a rigorous strategy of trial and error, it was found that, by curing greens, herbs and different nutrient sources, grinding them up into powder, and forming that powder into tablets or capsules, it was attainable to retain a lot of their nourishing worth .That is solely true of entire meals dietary supplements which were processed utilizing little or no warmth. And so, it seems, one can lastly get pleasure from the advantages of wholesome consuming through the straightforward act of popping a number of capsules. The profit over unusual consuming is within the mixtures of nutrient sources (and the portions thereof) chosen, designed to enrich one another and assist in probably the most full, favorable absorption of the elements. Because of the unbelievable lower in measurement that desiccation brings, it is also attainable to eat way more of stated vitamins, avoiding the generally undesirable must stuff one’s face with greens.
The impact of entire meals dietary supplements has been very favorably contrasted with synthetic dietary supplements corresponding to multivitamins. The explanation entire meals dietary supplements come out on high is easy: your physique acknowledges the ratios of vitamins in entire meals and processes them way more simply than dietary supplements consisting of remoted or fractionated vitamins.The physique acknowledges entire meals dietary supplements as diet and is ready to metabolize and make the most of them effectively.
The perfect concept, say specialists, relating to figuring out your entire meals dietary supplements necessities is to determine on the available meals that you may and can eat constantly, then fill within the gaps from there. A basic record of probably the most extremely beneficial greens close to anti-aging and well being advantages would come with kale, chard, spinach, broccoli, Brussels sprouts, cauliflower, pink and inexperienced peppers, garlic, onions, candy potatoes, tomatoes, inexperienced peas, asparagus and carrots. At Rutgers College, New Jersey, dietary and meals science Professor Paul A. Lachance headed up a research, printed within the Journal of The American Faculty of Vitamin, to guage 29 standard fruit, and ranked them in descending order of worth in accordance with the advantages they confer. His high ten record learn as follows: kiwi, papaya, cantaloupe, strawberry, mango, lemon, orange, pink currant, mandarin orange and avocado. To be efficient these meals should be eaten uncooked.
When it comes to supplementing past this record, relating to choosing the right entire meals dietary supplements in your functions, you may most likely wish to search for a lot the identical belongings you may need seemed for in synthetic dietary supplements prior to now – compounds to advertise joint well being, mind well being, immunity and so forth, by means of anti-oxidants like resveratrol, beta-carotene together with different amino acids and nutritional vitamins. The distinction could not lie within the listed elements, however reasonably within the method these elements had been derived – from frequent (and a few not-so-common) crops, greens, fruits, herbs and so forth. That is how pure entire meals dietary supplements firms supply their vitamins.
What Dietary supplements Ought to You Take?
Whether or not you employ important vitamins as your barometer of what and the way a lot to eat, or the information in figuring out what wholefood dietary supplements you want, figuring out their presence or lack thereof might be the easiest way to guage a weight-reduction plan. Under are listed a few of the important vitamins most individuals ought to contemplate supplementing of their diets – those persons are usually poor in, and those who present probably the most advantages. Included are the meals by which these vitamins could be discovered.
Anti-oxidant supplementation is, clearly, wanted for its promised results of safety in opposition to illness, mobile breakdown, most cancers and in the end growing older. In 2004, a research by the USDA revealed one of the best dietary sources of anti-oxidants. Printed within the peer-reviewed publication of the American Chemical Society, the Journal of Agricultural and Meals Chemistry, the research confirmed that meals like beans and artichokes take delight of place within the anti-oxidant-rich-food hierarchy. The research additionally demonstrated powerfully helpful results from pecan nuts, cinnamon and russet potatoes.
The B-Nutritional vitamins play a extremely necessary function in cell metabolism. As soon as regarded as a single vitamin, these had been later found to be a bunch of chemically distinct nutritional vitamins that often coexist particularly meals. Well being dietary supplements that comprise the total roster of eight B-Nutritional vitamins are known as Vitamin B Advanced dietary supplements. These nutritional vitamins assist to keep up good muscle and pores and skin tone, selling cell progress, notably of pink blood cells, and thereby offering safety from anemia. They assist and enhance the speed of metabolism, which means that they’ll additionally help in sustaining a wholesome weight. Notably, they lower the danger of pancreatic most cancers, however solely when consumed as an entire meals, not as an artificial fractionated pill. Most B-vitamins should be consumed every day, as any extra is speedily excreted within the urine. Good sources embody potatoes, bananas, lentils, chile peppers, brewer’s yeast, entire meals dietary supplements, molasses, tuna, animal livers and meat. For the reason that vitamin B12 can’t be produced by vegetable sources, deficiency on this nutrient is of explicit concern for vegetarians, who must get it by consuming dietary supplements or fortified breakfast cereals to keep away from attainable sick penalties on well being. For the extra omnivorous amongst us, good sources are fish, meat, poultry and eggs.
A famed member of the antioxidant household, Beta-Carotene is price mentioning alone, particularly for its help within the uptake of vitamin A. It is the substance that colours carrots orange, and assists within the buildup of epidermal retinol, liable for defending the pores and skin from solar injury. It is ample in crude palm oil and Vietnamese gac, which have the very best Beta-Carotene content material of any vegetable or fruit. These are, sadly, usually filtered for readability earlier than sale, a course of which removes all carotenoids. Different sources embody papayas, mangoes, carrots, yams, spinach, kale and candy potato leaves and high quality entire meals dietary supplements.
It is the fifth most ample factor within the earth’s crust, however that does not imply that conscientious calcium consumption should not be a priority of anybody trying to stay to a sturdy, wholesome previous age. Calcium is crucial for a lot of important mobile processes. “Calcium performs an necessary function in constructing stronger, denser bones early in life and holding bones robust and wholesome later in life,” says the Nationwide Osteoporosis Basis, and it is a advice that has been hammered into us via media to the purpose of filtering into commonsense and standard tradition. Extended calcium deficiency results in rickets, poor blood clotting and an elevated danger of fractures.
The perfect recognized sources of calcium are dairy merchandise. Sadly, lactose intolerance is much from a uncommon dysfunction, and varied different illnesses and private philosophies (corresponding to veganism) maintain sure people from consuming dairy merchandise. Fortunately, there are quite a few good vegetable sources of calcium, together with nuts, seeds, seaweed, oranges, figs, beans, broccoli and fortified merchandise like soy milk. One poorly acknowledged sources of calcium is floor eggshell. For info on the calcium content material of meals, go to the USDA Nationwide Nutrient Database on-line. The simplest option to eat calcium that the physique will acknowledge as meals is to take entire meals dietary supplements.
It performs an important function in regulating neuromuscular actions, most notably these of the guts. It assists in sustaining good blood strain, wholesome muscle tone and good pores and skin pallor. It helps us metabolize calcium and vitamin C, and as such deficiency in magnesium can lead to calcium depletion, kidney stones, muscular irritability, nervousness and confusion. But the gorgeous reality is that almost all of individuals on earth (round 80%) are recognized to be poor in Magnesium. Typical charges of consumption are between 143 and 266 mg per day – considerably decrease than the FDA’s beneficial every day consumption of 350 mg. Deficiency in Magnesium has additionally been implicated within the growth of power illnesses like bronchial asthma, osteoporosis and a spotlight deficit hyperactivity dysfunction. Good meals sources embody nuts, seeds, spices, bran cereals, quinoa, soybeans, espresso, cocoa, tea and inexperienced, leafy greens. It has been speculated that the diminished consumption of dietary magnesium in developed international locations could be correlated with the rise of meals refinement and using fashionable, magnesium-free fertilizers. Amongst dietary dietary supplements, magnesium citrate has been recurrently confirmed as probably the most bioavailable, beating the oxide and amino-acid chelate kinds for its price of absorption. Artificial dietary supplements can’t be absorbed: use entire meals dietary supplements to keep up correct ranges.
Higher generally known as vitamin C, L-ascorbic acid is probably the preferred of dietary supplements, and has been used to deal with illness ever for the reason that French explorer Jacques Cartier boiled the needles of the arbor vitae tree to deal with scurvy in 1536. The resultant tea was later proven to comprise 50mg of vitamin C per 100 grams. Like Magnesium, with out common uptake vitamin C is rapidly eradicated via the urine, so it is simple to develop into poor with out supplementation. Whereas oranges are well-known for his or her vitamin C content material, the extra obscure however vastly stronger sources, corresponding to kakadu plums, camu camu, rose hips and Indian gooseberries are slowly gaining standard recognition, as are frequent sources like blackcurrants, pink peppers, parsley and guava. Animal sources of this nutrient embody oysters, pork, beef, calf and rooster livers, cod roe and, as unpalatable as it could sound, lamb mind. The simplest option to keep correct ranges is with entire meals dietary supplements.
An oil-soluble, vitamin-like substance present in most crops and animals, CoQ10 is liable for supporting the method of ATP era, liable for ninety 5 % of the human physique’s vitality. The organs with the very best vitality necessities – such because the liver and coronary heart – thus require probably the most Co-Q10. Recognized for this strengthening impact on the guts muscle, CoQ10 has been used to deal with many types of cardiac situation, though the extent of its function in vitality manufacturing continues to be not absolutely understood. It has been proven to have helpful results on victims of migraine complications, to decrease blood strain, reverse gum illness, and assist in weight reduction. It’s recognized for its skill to sluggish the shrinkage of the thymus gland, thus stopping the weakening of the immune system that usually accompanies previous age. It’s also being investigated for its potential to mitigate the results of most cancers.
The perfect dietary sources of CoQ10 are sardines, mackerel, the livers of beef, pork and lamb, eggs, spinach, broccoli, peanuts, wheat germ and entire grains. The simplest option to keep ranges is with entire meals dietary supplements for fast absorption.
Whereas it could be a little bit of stretch to name it a nutrient, dietary fiber or ‘roughage’ is significant to the well being of the digestive system, and thus to the efficacy with which all different vitamins get absorbed. Roughage is comprised of the indigestible elements of plant meals that simple the progress of meals via the digestive system, easing defecation.
Good plant sources of fiber embody psyllium seed husk, bran flakes, legumes, oats, rye, barley, prune juice, plums, lentils, beans, quinoa, berries, bananas, broccoli, carrots, artichokes, potatoes, candy potatoes, onions, entire grain meals, wheat, corn bran, flax seed, inexperienced beans and tomatoes.
Soluble fiber or probiotic dietary supplements can be helpful to easing the signs of diarrhea, constipation, and irritable bowel syndrome. The FDA stories that research have discovered that “diets low in saturated fats and ldl cholesterol and excessive in fiber are related to a diminished danger of sure cancers, diabetes, digestive issues, and coronary heart illness.”
Omega 3 Fatty Acids
The nutritionally necessary Omega 3 fatty acids – Alpha Linoleic Acid (ALA), Eicosapentanoic Acid (EPA) and Docosahexanoic Acid (DHA) – have been credited with supporting cardiovascular well being, circulation and wholesome imaginative and prescient, in addition to selling higher perform of the mind and immune system. DHA and EPA are made by microalgae which, residing in seawater, are consumed by fish and plankton, accumulating to excessive ranges of their inner organs.
Use of omega 3’s within the type of fish oil has been proven to scale back danger of coronary heart assault, decrease blood strain, and offset the results of arthritis. It additionally causes a lower in LDL, the ‘dangerous’ type of ldl cholesterol. Moreover, there may be some proof that it helps in ameliorating despair and nervousness. Amongst most cancers sufferers, fish oil clearly diminished tumor progress, elevated survival occasions, and assist sufferers retain muscle mass throughout therapy. It has additionally demonstrably diminished the signs of victims of psychological issues, together with power aggression and ADHD.
The perfect dietary supply of omega 3’s might be fish. Nonetheless, a a lot publicized danger of standard fish ingestion lies within the potential for heavy steel poisoning by the buildup of poisonous parts within the intestine – notably mercury, lead, nickel and arsenic. Nonetheless, a 2004 research by the FDA has indicated that, of the 44 standard industrial fish oils examined, all handed contaminant security requirements. Thus it is suggested that well being aware people get their omega 3’s this manner – by mixing fish oil into their meals, or taking gel complement capsules. Omega 3 supplementation has was a meals advertising development, with many firms promoting the whole lot from fortified yoghurts and juices to take advantage of, eggs and pasta. Flax seeds, which produce linseed oil, even have a really excessive omega 3 content material, and are most likely probably the most broadly obtainable botanical supply of omega 3. Different sources embody chia, kiwifruit, perilla , lingonberry, butternut, black raspberry, broccoli and strawberries. The perfect and best option to get hold of that is by taking exceptionally pure, chilly processed oils in entire meals dietary supplements.
These plant secondary metabolites are greatest recognized for his or her antioxidant exercise. This impression could also be a bit of inaccurate. The huge enhance within the antioxidant capability of the blood after the consumption of flavonoid-rich meals is likely as a consequence of elevated ranges of uric acid. In essence, the physique sees flavonoids as overseas, invading compounds, and does its greatest to get rid of them. This induces the exercise of Part II enzymes, which assist to get rid of carcinogens. Most cancers researchers at UCLA discovered that individuals who eat meals containing sure flavonoids seem like nearly proof against lung most cancers. The perfect amongst these seem like strawberries, inexperienced and black teas, Brussels sprouts, apples, beans and onions, parsley, pulses, pink wine, and gingko biloba. Evidently, solely small portions of such flavonoids is required to see the specified results, an overindulgence can reverse them into unfavourable territory. Different functions of flavonoids consists of the therapy of simple bruising, hemorrhoids and varicose veins.
Found by Japanese virologists at Tokyo College within the 1950’s, interferons are cell-signaling proteins produced by the immune techniques of vertebrates in responds to viruses, parasites and different threats. They help the response of the immune system by dampening viral replication, thus growing the resistance of host cells to an infection. That is an impact that can be utilized protectively by the administration of interferon medicine. Interferon remedy is often used as a therapy for most cancers, in addition to within the therapy and management of autoimmune dysfunction and a number of sclerosis.
All through Jap Europe and Russia, interferon is taken intranasally as a way of stopping and treating respiratory illnesses of viral origin, like flu and chilly. Good meals sources of this substance embody quark cheese and flax oil, however one of the best methodology of ingestion might be by supplementation. The one pure compound components created by the discoverers of interferon is a Shaklee unique Nutriferon beneficial dose is 2 tablets every day. For extra info go to http://www.thenutritionnurse.com
Essential to the functioning of all recognized organisms, Iron is a crucial element of hemoglobin, the compound in blood liable for delivering oxygen from the lungs to different elements of the physique. It additionally performs an necessary function in enzyme reactions in varied tissues. Iron deficiency is the most typical recognized type of dietary deficiency, and is most prevalent in youngsters and pre-menopausal girls – an estimated 90% of girls fail to get the beneficial every day quantity. The end result is iron deficiency anaemia, which ends up in fatigue, impaired focus, impaired immune perform and a sallow, yellow pallor, amongst different disagreeable maladies. Infants and pregnant girls usually require iron supplementation for optimum well being.
Good entire meals dietary supplements sources of iron embody pink meat, fish, poultry, tofu, beans, lentils, leafy inexperienced greens, peas, and fortified merchandise like bread and breakfast cereals. In supplementary phrases, probably the most bioavailable type of iron is that which has been chelated into amino acids. That is also known as iron glycinate.
That is a type of dietary parts that most individuals have not heard of. It is acquired a tough identify, and there aren’t any main diseases related to deficiency in it. Nonetheless, the potential advantages to consuming it are great. Suppose improved liver, mind, reproductive and cardiovascular well being. Actually, it is generally marketed as a nootropic drug for the enhancements to neurotransmitter efficacy that it could actually convey. Analysis signifies that phosphatidyl choline is intimately concerned within the mediation of temper, reminiscence and cognitive perform.
Probably the most broadly obtainable supply of this nutrient is lecithin, which could be derived from soy or egg yolks – the truth is, the phosphatidyl choline element of this substance is so nice that the 2 phrases are generally used interchangeably. Different meals wealthy in phosphatidyl choline are beef, veal, rooster and turkey livers, brewer’s yeast, fish, peanuts and cauliflower.
As with quite a lot of the nutritional vitamins, Vitamin E is the collective identify for a set of associated tocopherols and their corresponding tocotrienols, which have been tied to colon, coronary heart, prostate and immune system well being.
Meals sources highest in Vitamin E embody avocado, asparagus, egg, seeds, nuts, palm oil, spinach, milk, vegetable oils, wholegrain meals, wheat germ, rice and olive oil.
This phytoalexin, which is produced naturally by a number of crops when beneath assault by pathogens, has been correlated with a decreased danger of most cancers, elevated life expectancy, and lowered blood sugar ranges in diabetics. It has additionally been seen to affect on the 4 main indicators of growing older. It’s discovered within the pores and skin of pink grapes (and the seeds of muscadines), and as such could be had simply sufficient by consuming a glass of pink wine, which accounts for the cardioprotective results of the favored beverage. Nonetheless, it seems that reasonably excessive doses are required for strongly constructive results on people – ranges usually solely reached via supplementation. The fruit of the mulberry has additionally been proven to comprise notable ranges of resveratrol. Probably the most potent and bioavailable type is VIVIX. It is a Shaklee exculsive anti growing older tonic and is 10 occasions simpler than taking resveratrol alone. Solely obtainable from an unbiased Shaklee distributor. See the above hyperlink to the Vitamin Nurse.
Over 200 enzymes within the human physique rely on zinc for his or her perform. A vital mineral liable for selling regular progress, growth and immune perform, zinc is nonetheless not current in adequate portions within the diets of most individuals within the growing world, two billion of whom are estimated to be zinc poor. Zinc deficiency is related to many illnesses, together with, amongst youngsters, delayed sexual maturation, progress retardation, diarrhea and susceptibility to an infection. Actually, zinc deficiency has been linked to the dying of over eight hundred thousand youngsters yearly.
Zinc ranges in meals differ in accordance with the degrees of important vitamins in soil, a degree which should be maintained by soil conservation. Assuming that ranges of zinc in soil are equal, probably the most zinc-rich crops are wheat germ and bran, seeds, beans, nuts, and blackcurrants. Many cereals are additionally fortified with zinc sulfate and oxide. Nonetheless, many individuals complement this factor of their diets as an insurance coverage coverage in opposition to poor consuming habits.
The Backside Line
Planning and growing a weight-reduction plan in order to not be poor in any of the important vitamins is usually a difficult, some may say nearly not possible process. Certainly, it is most likely solely by the mixture of proper consuming and a powerful base of dietary supplements that an unusual individual can make sure that they’re getting the whole lot they should stay a protracted, wholesome, completely satisfied existence. Stay conscious of the restrictions of each entire meals and artificial capsules, and you will have gone a good distance in direction of making that future yours. Clearly the prudent plan of action is to provoke a routine together with high quality entire meals dietary supplements.
* These statements haven’t been evaluated by the Meals and Drug Administration. These merchandise aren’t supposed to diagnose, deal with, treatment, or stop any illness.
By Anthony Antolics RN,BSN The Vitamin Nurse