Diet Prescription for Hypertensive Patients E-Book

aa.vv

• Herausgeber: SEEd Edizioni Scientifiche
• Kategorie: Fachliteratur
• Sprache: Englisch
• Veröffentlichungsjahr: 2012

Beschreibung

Diet prescription is essential for all patients with hypertension and, together with an adequate pharmacologic treatment, can allow reduction of pressure values even in more severe cases. This booklet summarizes tha basic principles of correlation between sodium and hypertension, describes the rationale for an adequate dietetic approach in this disease and provides some examples of low sodium intake and low calories diets.

Leseprobe

Diet Prescription for Hypertensive Patients

© SEEd srl

Piazza Carlo Emanuele II, 19 – 10123 Torino – Italy Tel. [phone] – Fax [email protected]

First edition April 2012 ISBN -

Modified from: Ipertensione. La gestione integrata del paziente

By Carugo S, Ferrero L, Carra R, Pradelli L. SEEd s.r.l.

Although the information about medication given in this book has been carefully checked, the author and publisher accept no liability for the accuracy of this information. In every individual case the user must check such information by consulting the relevant literature.

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the Italian Copyright Law in its current version, and permission for use must always be obtained from SEEd Medical Publishers Srl. Violations are liable to prosecution under the Italian Copyright Law.

Introduction

The dietary approach is recommendend as the only intervention in individuals at particular risk of arterial hypertension, borderline hypertension, or, in some specific cases, even in mild-to-moderate hypertension (diastolic blood pressure values between 90 and 104 mmHg) and as an adjunct to drug therapy in subjects with moderate-to-severe hypertension.

The combination of dietary therapy to drug treatment can allow an advantageous reduction of the dosages and/or the number of drugs, with positive effects on compliance. In some selected cases, drug therapy can even be withdrawn, continuing with the dietary one alone.

Role of some dietary factors in hypertension

Epidemiological and Clinical Studies

By contrast, in rural Japanese populations a prevalence of hypertension by about 40% (in subjects older than 40) was found, associated with a very high daily intake of salt (about 22 grams per day). In populations with low salt intake, the increased levels of blood pressure with age found in Western industrialized countries isn’t detected.

This age-dependent pressure increase, however, appears as a result of migration of groups of such populations from the original geographic areas, characterized by a low salt consumption, to areas at high consumption: changes of habits seem able to induce an increase in values of arterial hypertension.

Mechanisms of Sensitivity to Sodium

The mechanisms involved in the regulation of sodium metabolism and in the genesis of sodium-dependent hypertension are many. Among them, there are:

reduced ability of the kidney to eliminate sodium;

reduced renin activity;

increased activity of the sympathetic nervous system;

functional alterations of the baroreceptors and systems of ionic transport at the level of vascular smooth muscle.

Approximately 30-50% of hypertensive subjects are sodium-sensitive, but currently there are no indicators to predict with certainty the sensitivity of patients to sodium intake, and hence the effectiveness of a low sodium diet.

According to recent studies, insulin seems to play a fudamental role in hypertension. This hormone, in fact, may influence the mechanisms listed above (sodium retention, increased activity of the sympathetic system, altered transport of ions, increase in intracellular calcium concentration) and also favors the intracellular proliferation of smooth muscle cells of blood vessels.

These actions may result, in conditions of insulin increase and resistance to the hormone, in an antinatriuretic effect, increase in cardiac output and peripheral resistance. Obesity, often characterized by a state of insulin resistance, is often associated with sodium-sensitive hypertension. A state of insulin resistance, however, would be present even in normal-weight hypertensive subjects.

Insulin resistance may, in conclusion, be the key to interpret sodium-sensitive blood pressure.

Calories

Obesity and hypertension are independent factors of cardiovascular risk. Obesity may also be considered a risk factor of hypertension. In pediatric age, hypertension has been shown to be strongly related to overweight. The association between weight gain and hypertension is supported also by numerous observations in several population groups. In the USA, 60% of hypertensive patients is overweight (body weight > 20% of ideal weight). In Australia, 1/3 and 2/3 respectively of hypertensive women between 25 and 64 years of age and hypertensive males between 25 and 44 years are affected by several degrees of obesity.

The anthropometric examination, which has proven to be more predictive of hypertension, is the waist/hip ratio: a high value, which indicates a predominantly abdominal distribution of body fat (android type obesity) is correlated with a higher frequency of hypertension and a higher prevalence of cardiovascular comorbidity and mortality risk. The mechanisms of overweight-dependent hypertension are likely to be complex, multifactorial and only partially known. The Figure shows the relationship between hypertension, insulin resistance and sodium sensitivity in obese-hypertensive subjects.

Potassium

Also potassium intake, probably by acting on natriuresis (which increases), renin secretion (which decreases) and vascular tone (vasodilation) seems able to influence the regulating mechanisms of blood pressure. At epidemiologic level an inverse correlation between dietary intake of potassium and hypertension levels has been demonstrated. Dietary supplements of potassium led to equivocal results: they seem more effective in hypertensive subjects with a high intake of sodium, while they seem to loose their effectiveness during sodium restriction. These data suggest an adequate potassium intake.

Calcium and Magnesium

Both of these cations seem to be able to act on smooth muscle tone and are probably involved also in other pressure mechanisms still poorly explored (increased parathyroid hormone (PTH) levels or CGRP (calcitonin gene-related peptide with strong vasodilator action, etc.)). However, the role of supplemental calcium or magnesium in the control of hypertension requires further study, before allowing the application of safe nutritional guidelines. A diet low in calcium intake may, however, potentiate the pressor effects of high sodium intake.

Lipids

Some fatty acids are precursors of vasodilators such as prostaglandins. It is possible, therefore, that lipid intake, and even more the proportions among the various fatty acids with different saturation characteristics, may play a role in the regulation of blood pressure levels. A diet that restricts the global intake of lipids and cholesterol and promotes proper proportions between saturated, monounsaturated and polyunsaturated fats, however, falls among the control interventions of cardiovascular risk and may also limit the overall energy intake.

Alcohol

Alcohol seems to play a role which is not dependent on other environmental or gender- or age-related factors in influencing the onset of hypertension. A direct correlation between hypertension and ethanol intake (> 30 g/day in men and > 20 g/day in women, who seem to be more susceptible to the effects of alcohol on blood pressure) was also found. In obese subjects the short-term limitation of the consumption of alcoholic beverages has proven effective in favoring the control of blood pressure. Taken together, these considerations has led to the indication for hypertensive patients to abstain from alcoholic beverages, or at least, to keep their consumption moderate.

Therefore, it is recommended to limit as much as possible the consumption of alcohol, which in any case should not exceed the maximum weekly value of 21 standard units for men and 14 for women.

Since the alcohol content varies depending on the beverage, the alcohol consumption is usually measured in standard units.

A standard unit of alcohol (equivalent to 8-10 g of pure alcohol) is equivalent to:

A small glass of wine250 ml of blonde beer125 ml of dark beerA cocktailA small glass of spiritsA small glass of sherry

Practical aspects of dietary therapy

Low-sodium Diets

Sodium requirements

In Italy the discretionary consumption of sodium is quite high, accounting for nearly 36% of the total, while the daily amount of salt daily ingested with foods with no added salt is about 2-4 g and fully satisfies the requirements of sodium (which is about 575-3500 mg/day).

Sodium in foods

Sodium is widely distributed in foods of animal origin (meat, milk, egg white, etc.), while it is very low in those of plant origin (but some contain a fair amount: turnips, radishes, celery, carrots, artichokes, spinach, chard, and kale).

As sodium chloride, it forms the common salt, which has an ever more widespread and abundant use in the food (bread, bread sticks, crackers, biscuits, and cakes), and in the preservation of food (preserved vegetable products canned or under glass, frozen, or dehydrated).

The sodium content in the water, both of the network and bottled, is variable in relation to the intrinsic characteristics and the features related to possible treatments. The processes of softening of hard water, for example, increase the sodium content by 1 mg/l. Even some low-sodium sweeteners contain sodium.

Foods high in sodium

Salt, meat extracts, cubes or flavouring powders, also plant-basedCanned or dehydrated soups containing monosodium glutamateSausages, cheeses, smoked or canned meats, smoked fish, pickled or in oil, corned tongueCanned, in oil or vinegar vegetables, sauerkraut, mashed potato flakes, olivesPotato chips, peanuts, popcorn with added saltSome frozen foods, especially fish products, or some vegetables like peas or spinachReady-made sauces: mayonnaise, mustard, ketchup, tomato, Worcestershire, tuna, basil (pesto), or anchovy, garlic, walnut, olive pasteMixes for cakes, pies or pizza or baked goods containing artificial leavening agents

Additives and preservatives containing sodium

Product

Food

Disodium phosphate

Grain, cheese, ice cream, soft drinks

Monosodium glutamate

Dehydrated soups, cubes, condiments

Sodium alginate

Ice cream, chocolate drinks