Today, physicians and patients are more aware of the relationship between nutrition and disease. Nutrition is an important part of leading a healthy lifestyle. Combined with physical activity, diet can help patients reach and maintain a healthy weight, reduce their risk of chronic diseases (like heart disease and cancer), and promote their overall health.
Unhealthyeating habits have contributed to the obesity epidemic in the United States.One-third of US adults (33.8%) are obese.1 Even for people with ahealthy weight, a poor diet is associated with major health risks that cancause illness and even death. These include heart disease, hypertension, type 2-diabetes,osteoporosis, and certain types of cancer. Also, good dietary habits and goodnutrition are important in the management of various urologic and renaldiseases.
As physicians, it is important for usto establish a link between good nutrition and various urologic and renaldiseases. This article will emphasize the relationship between diet, nutrition,and management of several urologic and renal diseases. The article will provideevidence-based suggestions that we can provide our patients who have thesecommon conditions.
OAB is a sudden involuntarycontraction of the detrusor muscle of thebladdercausing urinaryurgency, an immediate need to urinate. It is one of the causes of urinaryincontinence and affects over33 million Americans.2 Men and women who suffer from OAB often feelembarrassed about their condition and may not seek medical help or bring up theirurinary symptoms with their doctors.
OAB symptoms appear to be multifactorial in both etiology and pathophysiology.Symptoms suggest underlying detrusor overactivity, which can be neurogenic,myogenic, or idiopathic in origin. Neurogenic causes of OAB include multiplesclerosis, dementia, Parkinson disease, and diabetic neuropathy. Inpostmenopausal women, estrogen deficiency can result in OAB symptoms. Estrogendeprivation therapy in younger women with breast cancer has also beenassociated with increased risk for OAB.
The mainstayof OAB management is anticholinergic medications and beta-3 adrenoceptor agonists. Dietary considerations, however, are alsohelpful in ameliorating symptoms. Patients with OAB are often sensitive to caffeinated beverages, andconsuming caffeine can increase OAB symptoms. One of the treatmentrecommendations for those who suffer from OAB is to reduce, or better yet, eliminatecaffeinated beverages, including coffee, tea and energy drinks, which have significantcaffeine content, from their diet. In addition to caffeine serving as a bladderirritant, caffeine is a weak diuretic and increases urine output andcontributes to urinary frequency.3
Other dietaryculprits include acidic fruit juices such as orange or grapefruit juice, whichcan alter the pH of urine and exacerbate OAB symptoms. The goal of dietarytherapy for OAB can include alkalinizing the urine with 2-4 grams of sodium bicarbonatetwice a day. In addition, reducing or eliminating acidic foods such as tomatoesand highly spiced condiments such as chilies and wasabi may also be helpful. Finally,omitting artificial sweeteners such as aspartame and saccharin can also alleviateOAB symptoms.4 Patients can consider eliminating carbonatedbeverages, especially those containing large quantities of caffeine.
A British studyindicated a decreased risk of OAB with increased consumption of raw vegetables,which increases dietary fiber content.5 Raw vegetables provide up to30% of dietary fiber. A low fiber diet is associated with constipation and theaccompanying straining to defecate. Constipation places increased pressure onthe pelvic floor muscles, which are responsible for keeping the urethra closed orcoapted. If these pelvic floor muscles become damaged, such as duringchildbirth, and there is accompanying constipation, then urinary frequency andurgency may occur.
There are alarge number of estrogen receptors located in the bladder and the pelvicmuscles in women. An estrogen deficiency, as occurs in menopause, results inexacerbation of OAB symptoms. When there is evidence of estrogen deficiency,relief may be achieved with hormone replacement therapy unless the use ofestrogen is contraindicated (as in cases of estrogen-positive breast cancer). Cliniciansmay recommend the use of topical estrogen cream, oral estrogen, or estrogenpatches. Topical estrogen such as estradiol vaginal cream every other day ortwice a week is effective as an oral hormone replacement therapy for OAB.6In addition, vegetables such as yam and carrots contain phytoestrogens that maysupplement the natural estrogens in post-menopausal women and reduce OABsymptoms.7
In a longitudinalstudy of 5000 women over age 40 that focused on various dietary inclusions andOAB onset, higher intake of vitamin D, protein, and potassium were associatedwith a decreased onset of OAB. There are vitamin D receptors on the detrusormuscle.8 Adequate vitamin D allows relaxation of the detrusor andresults in a decrease in patients urinary urgency.9 OABpatients may experience improvement in symptoms with 600 units of vitamin D perday.10
The onset andthe symptoms of OAB may be associated with smoking. The mechanism linkingsmoking and OAB symptoms is unclear, but it couldbe related to an anti-estrogenic hormonal effect on the bladder and urethra anda nicotine-induced contraction of the detrusor muscle.11 Mandhu et al. conducteda retrospective study with more than 11,000 women and found that smoking wasassociated with a 14% increased risk of OAB symptoms.12 Thus, in addition to dietary modifications, smokingcessation is advised for patients with OAB.
Perhaps oneof the least expensive yet effective treatments of OAB is fluid restriction. Callanet al. demonstrated that increasing fluid by 25% to 50% could increase daytimefrequency; however, the study did not show a significant effect on urgency.Increasingfluid intakeis associated with worsening of OAB symptomsin observational studies.13 Mild to moderate fluid restriction,however, results in significant improvement in OAB symptoms, especiallynocturia.
Nocturia is one of the mostdistressing symptoms of OAB which is also amenable to fluid restriction. In astudy, investigators managed nocturia using fluid restriction after 6pm. Participants who completed behavioraltreatment that included fluid restriction demonstrated a reduction in meannumber of voids per day from 11.3 in baseline to 9.1 after treatment. Thisdecrease of 2.2 voids per day (18.8%) was statistically significant (P<.001).14
IC or chronic pelvic pain syndrome (CPPS) consists ofpelvic pain and a persistent desire to urinate accompanied by urinaryfrequency, nocturia, and voiding small volumes of urine. The hallmark of IC is thepresence of these urinary symptoms with a negative urine culture. IC affects about700,000 to 1 million Americans, with 90% of patients being women.15 Thisincidence is probably underreported. Many patients may be misdiagnosed ashaving cystitis or prostatitis, as these conditions share similar lower urinarytract symptoms. Possible causes of IC include defects in the lining ofthe urinary bladder that cause irritation, bladder trauma, pelvic floor muscledysfunction, autoimmune disorders, neurogenic inflammation, spinal cord trauma,genetics, or allergy.
Patients withIC are advised to avoid bladder irritants such as citrus food and caffeinatedbeverages for the same reason that caffeine is to be avoided in patients withOAB. A study by Shorter et al identified foods and beverages that worsened thesymptoms of IC. In this study, a questionnaire was administered to 124 patientswith IC. The questionnaire asked patients to indicate whether the foods andbeverages listed improved, worsened, or had no effect on their symptoms. Themost frequently reported foods and fluids that exacerbated their symptoms werecoffee, tea, soft drinks, alcoholic beverages, hot peppers, critic fruits andjuices, and artificial sweeteners.16
Sonmez et al reportedthat a combination of both calcium glycerophosphate and sodium bicarbonateimproved IC symptoms.17 In another study by Shorter et al, patients wereasked to take 2 tablets (0.66 grams) of calcium glycerophosphate over a 4-weekperiod. Patients reported improvement in their symptoms, with a decrease inurgency and dysuria. In addition, these patients also reported a reduction inIC exacerbations, especially from foods such as pizza, spicy food, chocolateand alcohol.18
It isimportant to mention that there is a significant placebo effect in themanagement of IC patients. Patients with moderate tosevere IC have experienced significant improvement after receiving only adviceand support from their physicians. Supportive therapy is risk free, inexpensive,and without side effects. Consequently, proving efficacy of any of the treatments for IC withrigorous placebo-controlled trials is difficult due to a significant effect ofthe placebo intervention.19
Certainly,medications are available for treating IC, such as pentosan polysulfate sodiumand DMSO. Diet modification, however, can supplement pharmacotherapy. Patientsshould be provided with a dietary list of bladder irritants (Figure 1). Sincethe list of bladder irritants is extensive, and in order to identify whichdietary culprits are responsible for symptoms of IC, it is initially advisable toeliminate all possible bladder irritants for 5-7 days and then start addingpotential irritants to the diet, thus enabling identification of the offendingfoods or fluids that might exacerbate the symptoms.
Prostatitisis one of the more common conditions seen in a urologic practice. Although anextensive review of this condition is beyond the scope of this paper,prostatitis, an inflammation of the prostate gland presents as acute orchronic, bacterial or non-bacterial. Non-bacterial, chronic prostatitis is themost common variety. Symptoms include generalized sense of discomfort in thepelvis, and with urination, along with frequency, urgency, pressure sensation,and occasionally low-grade fever
TheUS prevalence of prostatitis is approximately 8.2%. Prostatitis accounts for about 8% of all urologic visits.20 There is a relationship between diet andurinary symptoms associated with chronic prostatitis. Patients with chronic prostatitis may consider avoiding foods and beverages known to exacerbate urinary symptoms. These foods may include spices, hot peppers, alcohol, wheat, and gluten.21 Men find wheat-free or gluten-freediets to be the most beneficial in managing theirprostatitis symptoms.22 Furthermore, drinking ample quantities of water and consuming foods high in fiberand zinc may reduce the symptoms of chronic prostatitis. Also, herbaltea or caffeine-free-tea can be beneficial for controlling chronic prostatitis.22
Goodarzi et.al found that zinc supplementation helps patients with chronic prostatitis inrelieving their symptoms. The conducted a study that included 123 patients aged18-40 years diagnosed with chronic prostatitis.23 All patientscompleted a chronic prostatitis symptom index questionnaire and a pain scorequestionnaire before entering the study. Each patient was given 220 mg/day of zinc sulfate while a controlgroup was given a placebo. At the end of 12 weeks, the zinc sulfate group had areduction in prostatitis symptom index score and pain score compared with thecontrol arm. The effectiveness of zinc can possibly be attributed to itsanti-bacterial and immunomodulatory functions.23 Zinc is a prominentchemical in seminal fluid but its precise role in the management of prostatitisremains unclear. Supplementation with oral zinc appears to be a simple, safeand a potentially effective option for these men.
Benign prostatichyperplasia (BPH) affects approximately 19 million men in the United States,but only about 3 million seek treatment.24 Symptoms include adecrease in the force and caliber of the urine stream, frequency of urination, urgencyto void, a feeling of not emptying the bladder, nocturia, and post-micturitiondribbling. The incidence of BPH increases with age. Only about 10% of men intheir 30s exhibit these lower urinary tract symptoms (LUTS). The incidence increasesto 60% among men in their 60s. Nearly all men over 70 will have some degree ofLUTS.25 By controlling their diet, many patients with BPH cansignificantly improve their urinary symptoms. Benign prostate enlargement islargely driven by the conversion of testosterone to dihydrotestosterone. It isnot known if any foods affect testosterone directly, but there is strongevidence that a plant-based diet consisting of beans, peas, lentils, vegetables,and sesame seedsessentially a Mediterranean dietcan be helpful in men withLUTS and in decreasing the risk of developing LUTS. El Jalby et. al, in their extensiveliterature review on this subject, found 1325 citations and ultimately selected35 studies for their review. Although dietary studies have some built-inchallenges, the studies essentially revealed the above findings with regards todiet and LUTS, in addition to salutary effects on erectile dysfunction.26
Approximately9% of the US population is affected by nephrolithiasis.27 There are 4major types of nephrolithiasis: calcium, uric, struvite, and cystine. Dietary modificationsmay help prevent recurrent nephrolithiasis, and those modifications depend on thetype of kidney stone. For example, uric acid stone formers should decrease intakeof red meat and shellfish because these foods contain high concentration ofpurines which are metabolized into uric acid.28 Increased purine intakemay lead to a higher production of uric acid, which aggregate as crystals inthe collecting system of the kidneys. Patients are advised to reviewinformation readily available listing foods high in purines and be cautious intheir dietary intake of these foods. Patients with uric acid kidney stonesshould follow a diet that consists of fruits, vegetables, and whole grains, andlimit their alcohol intake.
Patients withcalcium oxalate stones, the most common type, should avoid foods high inoxalate such as spinach, nuts, and wheat bran.29 Oxalate is also foundin certain fruits and vegetables, such as rhubarb, beet and potatoes. Patients withcalcium stones are often advised to avoid foods high in calcium, such as dairyproducts.
Althoughexcessive calcium intake is not recommended, either dietary or supplementalcalcium remains important. Calcium restriction does not inhibit the developmentof calcium oxalate stones, but it does have a negative effect on bone health,especially in women who are more prone to osteopenia and osteoporosis.
Patients withcalcium phosphate nephrolithiasis should limit their sodium intake becauseexcess sodium leads to an increase loss of calcium in the urine. With sodium restriction,there is a relative decrease in circulating blood volume. The result is increasedreabsorption of sodium, water, as well as calcium at the level of the proximalconvoluted tubule, thereby decreasing urinary calcium excretion. Foods containinglarge quantities of sodium include salted or canned meat, fish, and poultry, aswell as pizza and nuts, buttermilk, olives, and pickles.30 Inaddition, patients with calcium phosphate stones should also limit their intakeof oxalate-rich foods.
Patients withcystine stones should restrict consumption of meat and other animal proteins andsalt intake. They also should be advised to consume more fruits and vegetablesbecause these foods make the urine less acidic and decrease the excretion ofcystine.31
The time-honored method of prevention for allkidney stones is adequate intake of fluids, especially water. All patients withnephrolithiasis should consume at least 2.5 liters of fluid per day. Patientswith cystine stones are advised to consume 4 liters of fluid per day.31
Increased fluid intake is recommended forpatients in environments with low humidity and who lose water through via perspirationand chronic diarrhea.
A study ofdata from the National Health and Nutrition Examination Survey (NHANES) foundthat the US prevalence of ED in men aged over 20 years was 18.4%, or about 18million men. Not only is ED is strongly associated with age but also in men withdiabetes, hypertension, and a history of cardiovascular disease.32
Since ED iscorrelated with hypertension, it is important to maintain a heart-healthy diet.A study of 555 men with type 2 diabetes demonstrated that patients who followeda Mediterranean diet, which is high in fruits, vegetables, nuts, and wholegrains and low in red meat, had a decreased prevalence of ED and were morelikely to be sexually active than men who did not follow the Mediterranean diet.33
Excessive salt intake can result in hypertension and atherosclerosis, whichcan narrow the lumen of arteries and decease blood flow not only to thecoronary arteries but also to the penis, making erection difficult orimpossible. Therefore, patients with ED should be advised to restrict foodshigh in salt content such as bacon, ham, smoked meat, potato chips, andcrackers.
A systematicreview by Gandaglia et al. showed that ED often precedes cardiovascular disease(CVD). Consequently, ED can be used as an early marker to identify men who areat a higher risk for CVD events.34 It isimportant to note that ED may precede a diagnosis of CVD by as many as 5 years.35The explanation of ED preceding CVD is that the diameter of the penile arterialblood supply is normally one-third the size of the coronary arteries. As aresult, symptoms of ED secondary to hypertension and hypercholesterolemia may occurbefore symptoms of coronary disease,ie, angina or myocardial infarction. Therefore, if a patient has ED,particularly at a young age, a clinician may consider a referral to acardiologist to access occult CVD.
CKD affects approximately31 million Americans, and most CKD cases are undiagnosed because it may beasymptomatic in early stages.36 Type 1 and type 2 diabetes and highblood pressure are the most common causes of CKD.37 The 4 substancesthat patients with CKD need to restrict or avoid are sodium, phosphorus,calcium, and potassium. Excessive sodium impacts blood pressure and waterbalance. CKD and excessive sodium consumption results in a worsening of hypertension.This can be controlled by avoiding foods high in salt such as soy sauce,teriyaki sauce, canned foods, processed foods, and snacks with high sodium content.Patients with CKD should limit their sodium to 2000 mg per day.
As kidney function decreases,phosphorusexcretion by the kidneys decreases and calcium is not absorbed from gastrointestinal tract, leading to low blood levels of calcium. In response to a decrease in calcium,parathyroid hormone (PTH)production increasesand results in the loss ofcalciumand phosphorus from bones, which can lead to osteoporosis. The increase of phosphorus and calcium in the blood stream can cause vascular calcifications and worsening arteriosclerosis.38
Patients with CKD are advised to restrict dietaryphosphorus to less than 800-1,000 mg per day.Foods high in phosphorus to avoid or decrease include milk, ice creamcheese, yogurt, chocolate, and legumes.
Patients withCKD should also avoid excessive quantities of protein, including meat, nuts,and dried beans. Accumulation of excess protein damages glomerular structure,leading to or aggravating CKD. A low-protein diet (0.6-0.8 g/kg/day) isrecommended for patients with CKD.39
Patients withCKD need to be concerned about their potassium level, as hyperkalemia can resultin arrhythmias. Potassium can be regulated by reducing consumption of bananas,melons, milk, and yogurt, as well as poultry and pork. Patients with CKDdisease should limit potassium intake to 2000 mg per day.
Fluidrestriction may be required in patients with CKD, especially those patientswith end-stage kidney disease (ESKD) who are on dialysis. Dialysis patients may need to limit fluids between dialysis treatments. Becausepatients with ESKD have diminished urine output, excessive fluid expands theextracellular fluid space and results in peripheral edema, weight gain,hypertension, and congestive heart failure.
In 2017,approximately 80,000 adults were diagnosed with bladder cancer in the UnitedStates. Worldwide more than 400,000 cases are diagnosed yearly, making it the seventhmost common form of cancer.40 Men are four times more likely to bediagnosed with the malignancy than women, especially white men whose incidencerates are double those of black men. Bladder cancer mostly affects older people,with an average age at diagnosis of 73 years.41
Althoughtobacco use is the single biggest risk factor for bladder cancer, dietarycomponents may alter the natural history of bladder cancer and even reduce therisk of recurrence or progression.
Increasedintake of cruciferous vegetables such as broccoli sprouts, kale, and cabbage isassociated with a decreased risk of bladder cancer. Cruciferous vegetablescontain isothiocynates, which are known to induce anticarcinogenic effectsthrough phase-2 cytoprotective enzymes.42 Evidence also suggests thattea consumption may decrease the risk for bladder cancer. Drinking watercontaminated with arsenicwhich is an issue in some placesis risk factor forbladder cancer.43
A large internationaltrial, the BLEND study, is attempting to address the issue of diet and bladdercancer in a prospective manner. Results of this trial should be forthcoming inthe near future.44
Diet and supplements impact numerous urologic conditions. Although the exact pathophysiology regarding these relationships is not apparent in all cases, it is prudent for healthcare providers to be aware of the relationships and counsel patients regarding proper diet for their particular urologic problem. There clearly are benefits and risks associated with certain foods as they pertain to the urologic problems discussed in this review, but in many respects, patients who consume a prudent diet such as the Mediterranean, the MIND, or the DASH diet can decrease the risks for these diseases or help control their symptoms, in addition to enhancing their overall health.
*David F. Mobley, MD, is Associate Professor of Urology at Weill-Cornell Medicine in Houston. Texas. **Hevin Patel is a pharmacologist at Tulane University in New Orleans. ***Neil Baum, MD, is Profession of Clinical Urology at Tulane University in New Orleans.
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Impact of Nutrition on Urologic and Renal Diseases - Renal and Urology News