Eutrophication

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Information is on file in the Rockefeller Institute, if it's ever decided that it should be released. It does not provide formal guidelines or recommendations for making health care decisions. Another trial used megestrol alone versus megestrol plus L-carnitine, celecoxib, and antioxidants to treat women with gynecologic malignancies. On March 29, , the state's Joint Committee on the Flint Water Public Health Emergency held a hearing on the crisis in Flint during which residents and local experts testified. Batty and Lawrence M. Choose foods that are easy to chew, i. Aurora at pole of Jupiter is similar to earth polar auroral ring that is always there day and night days of the year

Impediments to Adequate Nutrition

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He disagreed with the "experts" who used their resources to label him a crackpot. The symptoms of biotherapy that are most likely to impact nutrition status are fatigue, fever, nausea, vomiting, and diarrhea. HCT patients can have special nutrition requirements. Before cell transplant, patients receive high-dose chemotherapy and may be treated with total-body irradiation. Patients may also experience acute or chronic graft-versus-host disease GVHD.

The goal of nutrition support is to maintain adequate nutrition status and protein stores. In addition, transplant patients are at very high risk of neutropenia, an abnormally small number of neutrophils in the blood that increases susceptibility to multiple infections.

To reduce the risk of infections related to HCT, patients can receive dietary counseling regarding safe food handling and avoidance of foods that may pose an infection risk.

Optimizing nutrition for patients with cancer involves early detection of malnutrition or risk of malnutrition so that intervention may be initiated in the early stages of disease or treatment.

The goal of nutrition screening is to rapidly identify patients who are at risk of developing malnutrition and refer them to a health care professional, ideally a registered dietitian, who can perform a complete nutrition assessment and implement a nutrition care plan. There are no standard definitions or indices of malnutrition. Without more context, these characteristics are not acceptable measures by which to determine malnutrition. A growing body of literature examines the prevalence of malnutrition in obese cancer patients.

In a study of clinical data obtained from 1, patients with metastatic primary cancers, Malnutrition, even in the presence of obesity, has been found to be an independent predictor of survival,[ 9 ] with patients presenting with sarcopenic obesity having the poorest prognosis. Obesity has been shown to increase the risk of cancer recurrence, and it negatively impacts overall survival.

Cancer survivors with the highest rates of increasing obesity are colorectal and breast cancer survivors and non-Hispanic blacks. Early recognition of nutrition-related issues is necessary for appropriate nutrition management of cancer patients.

Nutrition screening can be performed with a validated tool before treatment begins and at regular intervals over the course of treatment.

In the outpatient oncology setting, it is recommended that patients be screened initially before treatment begins and re-screened at planned intervals. Five screening tools are validated for use in oncology: The Nutrition Risk Screening has not been validated in the oncology setting, but it has been used in several studies of oncology patients. Scores are correlated to general outcomes associated with malnutrition, such as hospital length of stay, complications, and mortality.

When a screening method is being chosen, it is recommended to consider who will be performing the screen, how much time may be devoted to the process, and what the process will be for referring the patient for a full nutrition assessment. The two tools validated for both inpatient and outpatient in oncology settings are presented in further detail below.

The MST is a short questionnaire comprising two questions. Depending on the answers to these questions, patients are stratified into two categories: It is well validated and consistently shows high sensitivity and specificity in identifying patients at risk of malnutrition. The PG-SGA is the most commonly accepted tool for screening and assessment, backed by many studies and validated in both inpatient and outpatient oncology settings.

The remainder of the PG-SGA is completed by a health care practitioner, accounting for information about disease and metabolic demand and the completion of a physical exam. Responses are then scored and, on the basis of the score, patients are stratified into four nutrition triage categories: The drawback is that the PG-SGA takes more time to administer and requires a trained health care practitioner to complete the physical assessment portion. In screening, it is important to use a validated tool and to consider the needs of the clinical practice.

In centers where a registered dietitian is readily available, the MST may be the screening tool of choice because it is quick and can be performed by many members of the office and practice staff; patients found to be at risk may then be referred to the dietitian for further assessment.

In practices where a registered dietitian is not readily available, the PG-SGAsf may be more appropriate because it helps better determine which patients may receive sufficient information from the nurse, advanced-practice provider, or physician and which patients would best be referred to a registered dietitian for more in-depth assessment and intervention.

Nutrition assessment is a comprehensive approach to evaluating and diagnosing nutrition problems and designing interventions. Within the nutrition assessment, the following factors are considered in making a diagnosis of malnutrition: The assessment of anthropometric measurements evaluates weight loss, takes into account the time frame of weight loss, and is considered in the context of physical findings such as dehydration or fluid retention. The physical exam of the following areas determines loss of subcutaneous fat or muscle:.

In addition to the issues described above, the oncology nutrition assessment also takes into account the following: The goal of an oncology nutrition assessment is to collect the information necessary to determine current or anticipated nutrition issues and to formulate a plan with the patient, caregivers, and other members of the health care team involved with nutrition interventions.

Additionally, this multidisciplinary team approach may also include metabolic, pharmacologic, and functional interventions to address and prevent the identified or anticipated nutrition issues. Decisions about the best approach for therapy are informed by symptom severity and function of the gastrointestinal GI tract.

Treatment could include multiple strategies based on these factors. Nutrition goals during and after cancer therapy are integrated with goals related to nutrition status and the presence of malnutrition. A healthy diet with an emphasis on plant-based foods, regular physical activity, and achievement of a healthy weight has been recommended for all patients after cancer treatment on the basis of extensive reviews of the evidence.

Prompt and aggressive nutrition intervention is required for patients with precachexia or cancer cachexia. Intervention is more likely to be effective when started early. Interventions include an individualized approach to oral, enteral, and parenteral nutrition using evidence-based recommendations, guidelines, and program and regulatory standards.

The dietitian works with the patient, caregivers, and members of the health care team to 1 improve compliance and the effectiveness of pharmacotherapy interventions prescribed to manage cancer and cancer treatment—related symptoms; and 2 counsel patients about behavioral strategies to alleviate nutrition impact symptoms.

The Association of Community Cancer Centers Cancer Program Guidelines [ 7 ] specify having a registered dietitian as the nutrition professional available to work with patients and their families, especially those at risk of developing nutrition problems.

Registered dietitians work with the patient, family, and medical team to manage the nutrition and hydration status and maintain optimal nutrition status across the continuum of care through appropriate screening, assessment, and intervention.

The registered dietitian provides individualized care to each patient with nutrition- and diet-related needs, incorporates current research and utilizes evidence-based nutrition practice, and collaborates with the medical team to ensure integration of care with the overall treatment plan during active treatment and into survivorship. Registered dietitians also serve as a resource and provide education related to reducing cancer risk and the risk of recurrence to patients and communities.

A systematic review of randomized controlled trials led to the recommendation that patients be referred for nutrition counseling because of strong evidence of the beneficial effects it has on the prevention and reduction of malnutrition. Cancer and cancer treatment result in a range of side effects, described as nutrition impact symptoms, that impede oral intake.

While some patients experience few of these effects, others may have multiple symptoms, including anorexia, early satiety, constipation, diarrhea, dysphagia, fatigue, mucositis, nausea, taste and smell changes, and xerostomia. These symptoms can result in a decline in nutrition status and quality of life.

Behavioral strategies are essential in alleviating the impact of these symptoms and promoting adequate nutrient intake; pharmacologic interventions may be used in combination with these strategies to minimize symptom severity.

The following lists describe behavioral strategies to help alleviate nutrition-related symptoms of cancer treatment. Additional information about nutrition strategies during treatment is available from oncology-focused organizations such as ACS and AICR.

Commercially available oral nutrition supplements e. Patients with cancer need adequate protein to maintain and rebuild lean body mass. A systematic review of multinutrient, high-protein oral nutrition supplements found significant improvement in total energy and protein intake and reduced incidence of complications. In patients with resectable gastric cancer, supplementation did not change postoperative weight loss or complication rates.

Although supplements containing fish oil alone do not seem to be beneficial in cachexia or surgery recovery, studies of immune-enhancing IE formulas containing fish oil, as well as arginine and nucleotides, suggest benefit for individuals undergoing GI surgery.

A Cochrane review found significant reduction in postoperative complications and infections when IE oral supplements or enteral feeding were given before GI surgery. Studies of both preoperative and postoperative use found that noninfectious complications and hospital length of stay were also reduced.

There is concern that long-term use of oral nutrition supplements can result in taste fatigue and decreased compliance with recommendations. A systematic review of compliance with oral nutrition supplements suggested that compliance is good, especially with higher-energy-density supplements. Nutrition support is the delivery of nutrition that bypasses oral intake.

Every measure is employed to sustain patients and improve their condition through oral intake before consideration is given to nutrition support. Enteral nutrition tube feeding provides nutrition directly into the GI tract. Parenteral nutrition is the intravenous IV infusion of nutrients.

The use of enteral and parenteral nutrition in the oncology population may be indicated when oral nutrition strategies are not possible or fail because of tumor location or severe side effects. Although nutrition support is not recommended as standard treatment, it may be beneficial for patients who are malnourished and expected to become unable to take in adequate nutrition by mouth for an extended period of time. However, if nutrition support is clinically indicated, it should not be withheld because of concerns about tumor promotion.

Enteral nutrition is preferred over parenteral nutrition in most instances. Enteral nutrition continues to use the gut, is associated with fewer infectious complications, is often easier to administer, and is more cost-effective than parenteral nutrition. Indications for nutrition support include the following: Providing nutrition support routinely to patients undergoing chemotherapy or radiation therapy is not recommended; rather, nutrition support is reserved for patients who meet any of the criteria listed above.

It is sometimes difficult to know which patients will have a prolonged period of inadequate oral intake or malabsorption and will benefit from nutrition support. Although aggressive nutrition support has been shown to improve quality of life in patients with advanced cancer,[ 29 ] it is generally not recommended if life expectancy is shorter than 40 to 60 days.

Several effective methods for the delivery of enteral nutrition exist. Factors affecting a choice of the enteral route include anticipated length of need, aspiration risk, tumor location, and side effects. Assessment of need is best performed early. If a malnourished patient requires surgery for an unrelated event, a feeding tube may be placed at that time to avoid an additional procedure.

The risk of aspiration is considered in the determination of the proper termination point of the tube: Tubes are constructed of silicone or polyurethane and can vary in length from 30 to 43 inches, with the shorter tubes used for nasogastric feedings.

Diameters range from 5F catheters to 16F catheters. Tubes may have weighted tips to help passage through the gut. If a patient with cancer is at very high risk of aspiration, enteral nutrition may be contraindicated, and parenteral nutrition can be considered.

Percutaneous tubes may be placed endoscopically, surgically, or with fluoroscopy by interventional radiology. Percutaneous tube placement has a number of advantages: Administration methods vary depending on where in the GI tract the tube terminates and may be affected by treatment side effects. For tubes terminating in the stomach, a bolus or intermittent gravity drip may be possible and is preferable because it mimics normal feeding, requires less time and equipment, and offers greater flexibility to the patient.

For tubes terminating in the duodenum or jejunum, an infusion pump is required because a slower administration rate is necessary.

The following lists summarize infusion methods and considerations for initiation and administration of enteral nutrition. Enteral formulas vary in nutrient composition and source. Most commercially available formulas are lactose free, kosher, and halal. Semi-elemental and elemental formulas are available for patients with malabsorption who do not or will not tolerate standard formulas.

The use of whole-food blenderized formulas is gaining in popularity. Some products are commercially available, and there are published recipes for home-made formula.

It is important for a dietitian to thoroughly review the nutrient content of these home-blenderized formulas to ensure adequacy. For patients in the perioperative setting, evidence supports the use of IE formulas. The most widely studied formula in this category contains a combination of arginine, omega-3 fatty acids, and nucleotides. If parenteral nutrition is determined to be beneficial and appropriate, it can be administered via central or peripheral venous access.

Many patients with cancer already have central IV catheters to accommodate multiple IV therapies. For patients who do not already have central line access or will not have it for a period of time, a peripheral catheter can be placed; however, care must be taken to avoid overuse of the peripheral IVs, as this can result in vessel sclerosis. To minimize venous complications, the use of peripheral parenteral nutrition is limited. Parenteral nutrition is a combination of dextrose carbohydrate , amino acids protein , and lipid emulsions fat with added electrolytes, vitamins, and trace elements.

It is recommended that parenteral nutrition management include clinicians with expertise in nutrition support and be made up of a multidisciplinary team, including a registered dietitian and clinical pharmacist. Parenteral nutrition is typically initiated as a hour infusion. After tolerance is established and generally after daily macronutrient goals are achieved, parenteral nutrition may be cycled typically to an infusion time of 10—14 hours. For patients who will be receiving home parenteral nutrition, a cyclic infusion is preferred.

Only if the benefits of home initiation far outweigh the risks should it be considered, and only for patients who are hemodynamically stable, at low risk of refeeding syndrome, and nondiabetic. Many treatments have been suggested for cachexia-anorexia syndrome CAS , but few of these treatments have resulted in consistent improvement, probably because of the multifactorial mechanisms involved.

The first issue widely studied for treatment has been anorexia associated with CAS. The use of agents that improve appetite and resultant caloric intake have been widely studied; these agents include corticosteroids, progesterone analogs, androgens, cannabinoids, and cyproheptadine.

Perhaps the earliest agents studied for the management of cancer cachexia are dexamethasone and prednisolone. Used in cancer treatment for their anti-inflammatory, antimalignancy, and antiemetic properties, steroids have produced side effects such as increased appetite and weight gain, probably because of their effects in the hypothalamus. Several large placebo-controlled studies have shown increases in appetite and weight gain associated with steroid use in this setting.

In a study of tumor-bearing rats, use of megestrol acetate resulted in a reversal of muscle wasting and improved physical performance. No definitive conclusions about other outcomes related to lean body mass, quality of life, or fatigue could be drawn. No improvement in survival was found. A placebo-controlled study looked at megestrol acetate at a dose of 7. The megestrol group had a mean weight gain of Interest in the use of cannabinoids in CAS is ongoing because of their effects on appetite and potential benefit in HIV-related cachexia.

Cyproheptadine is a serotonin and histamine antagonist developed as an antihistamine. Side effects include increased appetite and weight gain. Seventy-six percent of the patients were classified as responders, experiencing either weight gain or no further weight loss. Patients also showed a significant increase in serum leptin levels. An increase in serum leptin has been correlated with an increase in body mass index. Increases in cytokines associated with cancer—including tumor necrosis factor-alpha TNF-alpha , interleukin-6 IL-6 , and interleukin-1—have been shown to be important in the etiology of this disorder.

Specific targeted agents have also been studied. These include agents targeting TNF-alpha, such as etanercept, infliximab, and pentoxifylline, which, in small trials, have not had a significant impact. Several studies using thalidomide, a nonspecific antagonist to TNF, have been performed. Thalidomide patients had a statistically significant reduction in weight loss compared with placebo patients. There has been interest in several other agents for the management of CAS, including mirtazapine,[ 76 ] metoclopramide, formoterol, melatonin, and olanzapine.

Given the multifactorial etiology of, and multiple mechanisms involved in, the development of CAS, it is possible that combining multiple agents with different mechanisms of action might result in greater efficacy. In this study, the combination arm was found to be superior.

Another trial used megestrol alone versus megestrol plus L-carnitine, celecoxib, and antioxidants to treat women with gynecologic malignancies. Researchers also looked at the combination of formoterol, an anabolic beta-2 adrenergic agonist, and megestrol acetate in 13 patients. Six of seven evaluable patients achieved a major response, with increases in muscle mass.

For these reasons, there is no recommended combination at this time. In addition, combining drug therapy with nutrition support and increased physical activity may have even greater efficacy.

CAS is a complex, multifactorial complication of cancer and its therapy, resulting in weight loss and decreased lean body mass. As understanding of the mechanisms of CAS improves and new agents that selectively target these proposed pathways become available, more efficacious treatments are also expected to become available.

Trials of new agents must be able to compare similar groups of patients. In addition, treating preventatively in high-risk patients, as opposed to treating patients already suffering from CAS, may be associated with better outcomes. Further clinical trials are essential to determine the best possible therapies. Patients with advanced disease often develop new, or worsening, nutrition-related side effects associated with disease progression, treatment, or both.

In a large systematic review of symptom prevalence in patients with incurable cancer, the most common nutrition impact symptoms were anorexia, xerostomia, constipation, and nausea.

Other symptoms among advanced-cancer patients receiving care in inpatient palliative care units,[ 2 , 3 ] cancer cachexia specialty clinics,[ 4 ] hospice, or non-hospice settings [ 3 ] included bloating, constipation, dysphagia, chewing difficulties, early satiety, mucositis, taste changes, and vomiting. Clinically refractory cachexia develops as a result of very advanced cancer or rapidly progressive disease that is unresponsive to antineoplastic therapy.

It is associated with active catabolism and weight loss that is unresponsive to nutrition therapy. At the end of life, patients often have severely restricted oral intake of food and fluids as part of the normal dying process. The primary objective of nutrition intervention in patients with advanced cancer is to conserve or restore the best possible quality of life and control any nutrition-related symptoms that cause distress.

Nutrition goals for a patient with advanced cancer may depend on the overall plan of care. These patients may be receiving anticancer therapy with or without concurrent palliative care , may be receiving palliative care alone, or may be enrolled in hospice. Regardless of the care setting, patients are screened to determine the need for nutrition intervention. As the focus of care shifts from cancer-modifying therapy to hospice or end-of-life care, nutrition goals may become less aggressive, with a shift in emphasis toward comfort.

Continued assessment and adjustment of nutrition goals and interventions is required throughout this continuum to meet the changing needs of the patient receiving palliative or hospice care services. Ethical issues may arise when patients, families, or caregivers request artificial nutrition and hydration when there is no prospect of recovering from the underlying illness or accruing appreciable benefit from the intervention.

When there is uncertainty about whether a patient will benefit from artificial nutrition, hydration, or both, a time-limited trial may be useful. Clear, measurable endpoints are outlined at the beginning of a time-limited trial. The caregiving team will explain that, as with other medical therapies, artificial nutrition and hydration can be stopped if the desired nutrition effects are not produced.

Randomized controlled trials of enteral or parenteral nutrition in cancer patients receiving formal palliative care are lacking. Patients with a life expectancy shorter than 40 days may be palliated with home intravenous IV fluid therapy, although this practice is controversial. Patients and caregivers often consider the provision of food and fluids to be basic care. However, the use of artificial nutrition and hydration at the end of life is a complex and controversial intervention that is influenced by clinical, cultural, religious, ethical, and legal factors.

Patients and families often believe the use of these interventions will improve quality and length of life, but evidence of clear benefit is lacking. In addition, agitated or confused patients receiving artificial nutrition and hydration may need to be physically restrained to prevent them from removing a gastrostomy tube, nasogastric tube, or central IV line.

Patients at the end of life who have increased difficulty with swallowing have less risk of aspiration with thick liquids than with thin liquids. For patients at the end of life, the goals of nutrition therapy are directed at alleviating symptoms rather than reversing nutrition deficits. The pleasure of tasting food and the social benefits of participating in meals with family and friends can be emphasized over increasing caloric intake. Other studies found no effect on terminal delirium, thirst, chronic nausea, or fluid overload.

The American Academy of Hospice and Palliative Medicine suggests that providers facilitate respectful and informed discussions about the effects of artificial nutrition and hydration near the end of life among physicians, other health care professionals, patients, and families.

Ideally, patients will make their own decisions on the basis of a careful assessment of potential benefits and burdens, consistent with legal and ethical norms that permit patients to accept or forgo specific medical interventions.

Decisions about whether to provide artificial nutrition and hydration to patients in the late stages of life are complex and influenced by ethical, legal, cultural, and clinical considerations, and by patient and family preferences.

Guidelines on the ethical considerations about whether to forgo or discontinue hydration and nutrition support have been published by a number of organizations, including the American Medical Association,[ 25 ] the American Academy of Hospice and Palliative Medicine,[ 11 ] the Hospice and Palliative Nurses Association,[ 18 ] the American Society for Parenteral and Enteral Nutrition,[ 26 , 27 ] and the Academy of Nutrition and Dietetics.

Religion and religious traditions provide a set of core beliefs about life events and an ethical foundation for clinical decision-making. To provide an optimal and inclusive healing environment, all palliative team members need to be aware of their own spirituality and how it may differ from that of fellow team members and the spirituality of the patients and families they serve.

Religious beliefs are often closely related to cultural views. Individuals living in the midst of a particular tradition can continue to be influenced by it, even if they have stopped believing in or practicing it. Patients may rely on religion and spirituality as important means to interpret and cope with illness.

The wide range of practices related to neutropenic diets reflects the lack of evidence regarding the efficacy of dietary restrictions in preventing infectious complications in cancer patients. Studies evaluating various approaches to diet restrictions have not shown clear benefit.

A meta-analysis and a systematic review of articles evaluating the effect of a neutropenic diet on infection and mortality rates in cancer patients found no superiority or advantage in using a neutropenic diet over a regular diet in neutropenic cancer patients. Even after the observational study was omitted from the analysis, the results persisted.

The review concluded that these individual studies provided no evidence showing that the use of a low-bacterial diet prevents infections. Other studies have demonstrated potential adverse effects of neutropenic diets.

One group of investigators [ 6 ] conducted a retrospective review of patients who had undergone hematopoietic cell transplantation HCT. The patients who received the neutropenic diet experienced significantly more documented infections than did the patients receiving the general hospital diet that permitted black pepper and well-washed fruits and vegetables and excluded raw tomatoes, seeds, and nuts.

The neutropenic diet group had a significantly higher rate of infections that could be attributed to a gastrointestinal source, as well as a trend toward a higher rate of vancomycin-resistant enterococci infections. Without clinical evidence to define the dietary restrictions required to prevent foodborne infection in immunocompromised cancer patients, recommendations for food safety are based on general food safety guidelines and the avoidance of foods most likely to contain pathogenic organisms.

The effectiveness of these guidelines is dependent on patient and caregiver knowledge about, and adherence to, safe food handling practices and avoidance of higher-risk foods.

Leading cancer centers provide guidelines for HCT patients and information about food safety practices related to food purchase, storage, and preparation e. Comprehensive food safety information designed by the U. Food and Drug Administration for people with cancer and for transplant recipients is also available online. Recommendations support the use of safe food handling procedures and avoiding consumption of foods that pose a high risk of infection, as noted in Table 7.

Maintaining adequate nutrition while undergoing treatment for cancer is imperative because it can reduce treatment-related side effects, prevent delays in treatment, and help maintain quality of life. Patients are likely to search the Internet and other lay sources of information for dietary approaches to manage cancer risk and to improve prognosis.

Unfortunately, much of this information is not supported by a sufficient evidence base. The sections below summarize the state of the science on some of the most popular diets and dietary supplements.

A vegetarian diet is popular, is easy to implement and, if followed carefully, does not result in nutrition deficiencies. There is strong evidence that a vegetarian diet reduces the incidence of many types of cancer, especially cancers of the gastrointestinal GI tract. There are no published clinical trials, pilot studies, or case reports on the effectiveness of a vegetarian diet for the management of cancer therapy and symptoms.

There is no evidence suggesting a benefit of adopting a vegetarian or vegan diet upon diagnosis or while undergoing cancer therapy. On the other hand, there is no evidence that an individual who follows a vegetarian or vegan diet before cancer therapy should abandon it upon starting treatment.

One pilot study has suggested that following a plant-based diet can prevent tumor progression in men with localized prostate cancer. It is a high-carbohydrate, low-fat, plant-based diet stemming from philosophical principles promoting a healthy way of living. Although there are anecdotal reports on the effectiveness of a macrobiotic diet as an alternative cancer therapy, none have been published in peer-reviewed, scientific journals.

No clinical trials, observational studies, or pilot studies have examined the diet as a complementary or alternative therapy for cancer. Phosphorus is a necessary nutrient for plants to live, and is the limiting factor for plant growth in many freshwater ecosystems.

Phosphate adheres tightly to soil, so it is mainly transported by erosion. Once translocated to lakes, the extraction of phosphate into water is slow, hence the difficulty of reversing the effects of eutrophication. Cultural eutrophication is the process that speeds up natural eutrophication because of human activity.

Extra nutrients are also supplied by treatment plants, golf courses, fertilizers, farms including fish farms , as well as untreated sewage in many countries. When algae die, they decompose and the nutrients contained in that organic matter are converted into inorganic form by microorganisms.

This decomposition process consumes oxygen, which reduces the concentration of dissolved oxygen. The depleted oxygen levels in turn may lead to fish kills and a range of other effects reducing biodiversity. Nutrients may become concentrated in an anoxic zone and may only be made available again during autumn turn-over or in conditions of turbulent flow. Enhanced growth of aquatic vegetation or phytoplankton and algal blooms disrupts normal functioning of the ecosystem, causing a variety of problems such as a lack of oxygen needed for fish and shellfish to survive.

The water becomes cloudy, typically coloured a shade of green, yellow, brown, or red. Eutrophication also decreases the value of rivers, lakes and aesthetic enjoyment. Health problems can occur where eutrophic conditions interfere with drinking water treatment. Human activities can accelerate the rate at which nutrients enter ecosystems. Runoff from agriculture and development, pollution from septic systems and sewers , sewage sludge spreading, and other human-related activities increase the flow of both inorganic nutrients and organic substances into ecosystems.

Elevated levels of atmospheric compounds of nitrogen can increase nitrogen availability. Phosphorus is often regarded as the main culprit in cases of eutrophication in lakes subjected to "point source" pollution from sewage pipes. The concentration of algae and the trophic state of lakes correspond well to phosphorus levels in water.

Studies conducted in the Experimental Lakes Area in Ontario have shown a relationship between the addition of phosphorus and the rate of eutrophication. Humankind has increased the rate of phosphorus cycling on Earth by four times, mainly due to agricultural fertilizer production and application. Between and , an estimated ,, tonnes of phosphorus was applied to Earth's surface, primarily on croplands.

Although eutrophication is commonly caused by human activities, it can also be a natural process, particularly in lakes. Eutrophy occurs in many lakes in temperate grasslands, for instance. Paleolimnologists now recognise that climate change, geology, and other external influences are critical in regulating the natural productivity of lakes.

Some lakes also demonstrate the reverse process meiotrophication , becoming less nutrient rich with time. Eutrophication is a common phenomenon in coastal waters. In contrast to freshwater systems, nitrogen is more commonly the key limiting nutrient of marine waters; thus, nitrogen levels have greater importance to understanding eutrophication problems in salt water.

Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated where run-off enters a confined channel. Upwelling in coastal systems also promotes increased productivity by conveying deep, nutrient-rich waters to the surface, where the nutrients can be assimilated by algae.

Examples of anthropogenic sources of nitrogen-rich pollution include seacage fish farming and discharges of ammonia from the production of coke from coal. In addition to runoff from land, fish farming wastes and industrial ammonia discharges, atmospheric fixed nitrogen can enter the open ocean.

Terrestrial ecosystems are subject to similarly adverse impacts from eutrophication. Many terrestrial plant species are endangered as a result of soil eutrophication, such as the majority of orchid species in Europe. In meadows, tall grasses that can take advantage of higher nitrogen levels may change the area so that natural species may be lost. Species-rich fens can be overtaken by reed or reedgrass species.

Forest undergrowth affected by run-off from a nearby fertilized field can be turned into a nettle and bramble thicket. Chemical forms of nitrogen are most often of concern with regard to eutrophication, because plants have high nitrogen requirements so that additions of nitrogen compounds will stimulate plant growth.

Nitrogen is not readily available in soil because N 2 , a gaseous form of nitrogen, is very stable and unavailable directly to higher plants. Terrestrial ecosystems rely on microbial nitrogen fixation to convert N 2 into other forms such as nitrates.

However, there is a limit to how much nitrogen can be utilized. Ecosystems receiving more nitrogen than the plants require are called nitrogen-saturated. Saturated terrestrial ecosystems then can contribute both inorganic and organic nitrogen to freshwater, coastal, and marine eutrophication, where nitrogen is also typically a limiting nutrient.

However, because phosphorus is generally much less soluble than nitrogen, it is leached from the soil at a much slower rate than nitrogen.

Consequently, phosphorus is much more important as a limiting nutrient in aquatic systems. Eutrophication was recognized as a water pollution problem in European and North American lakes and reservoirs in the midth century. Many ecological effects can arise from stimulating primary production , but there are three particularly troubling ecological impacts: When an ecosystem experiences an increase in nutrients, primary producers reap the benefits first.

In aquatic ecosystems, species such as algae experience a population increase called an algal bloom. Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water.

Oxygen is required by all aerobically respiring plants and animals and it is replenished in daylight by photosynthesizing plants and algae. Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae.

When dissolved oxygen levels decline to hypoxic levels, fish and other marine animals suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off. Zones where this occurs are known as dead zones. Eutrophication may cause competitive release by making abundant a normally limiting nutrient. This process causes shifts in the species composition of ecosystems. For instance, an increase in nitrogen might allow new, competitive species to invade and out-compete original inhabitant species.

This has been shown to occur [27] in New England salt marshes. In Europe and Asia, the common carp frequently lives in naturally Eutrophic or Hypereutrophic areas, and is adapted to living in such conditions. The eutrophication of areas outside its natural range partially explain the fish's success in colonising these areas after being introduced. Some algal blooms , otherwise called "nuisance algae" or "harmful algal blooms", are toxic to plants and animals.

Toxic compounds they produce can make their way up the food chain , resulting in animal mortality. When the algae die or are eaten, neuro - and hepatotoxins are released which can kill animals and may pose a threat to humans.

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