High-protein, low-carbohydrate diets

O Ketoacidosis is a dangerous condition that is characterized by the acidification of the blood and an acetone odour on the breath. The condition occurs when levels of oxaloacetic acid for the citric acid cycle are low. This leads to a buildup of acetyl CoA molecules, which the liver metabolizes to produce acidic ketone bodies. Since carbohydrates are the main source of oxaloacetic acid in the body, high-protein, low-carbohydrate diets have been linked to ketoacidosis. 

Use this site to explore the issues regarding high-protein, low-carbohydrate diets. 

Our bodies only store a few days worth of carbohydrate, so a high-protein, low-carbohydrate diet can be risky for some people. Raw fruits and vegetables are the best sources of vitamins and minerals. We should be eating five or more generous helpings of fruits and vegetables every day. 

Possibly the most serious nutrition problem in the United States is excessive food consumption, and many people have experimented with fad diets in the hope of losing excess weight. One of the most popular of the fad diets has been the high-protein, high-fat (low-carbohydrate) diet. The premise for such diets is tantalizing because the tricarboxylic acid (TCA) cycle (see Chapter 20) is the primary site of fat metabolism, and because glucose is usually needed to replenish intermediates in the TCA cycle, if carbohydrates are restricted in the diet, dietary fat should merely be converted to ketone bodies and excreted. This so-called diet appears to work at first because a low-carbohydrate diet results in an initial water (and weight) loss. This occurs because... 

Obesity is to be avoided because extra weight places additional stress on the weight-bearing joints. Fktients lose weight more happily on a high-protein, low-carbohydrate, modest-fat, low-caloric diet. 

Low-carbohydrate, high-protein diets are popular these days, but consider the risks. Low-carbohydrate diets cause a significant (but temporary) loss of body water. When you get off the diet, the water returns. A low-carbohydrate, high-protein... 

Due to the popularity of diets such as Atkin s New Diet Revolution (high fat, low carbohydrate, high protein) and The New Pritikin Program (low fat, high carbohydrate, medium protein), there is extensive discussion in the lay media and academic circles regarding the risks, benefits, and outcomes... 

Once again, numerous approaches are widely advertised. We hear of the grapefruit diet, the high-protein diet, the low-carbohydrate diet, the twist-and-tum exercise device. 

Low-carbohydrate diets promote the lipolysis of stored triacylglycerols known as ketosis, reduce glucose and insulin levels, and suppress appetite. As a result, there is an increase in blood uric acid concentration. Some studies have shown that the consumption of high amounts of nondairy protein results in a decline in kidney functions in individuals with mildly compromised kidney function. However, no such effect has been shown in individuals with normal kidney functions. Furthermore, low-carbohydrate diets can have side effects such as bad taste, constipation, diarrhea, dizziness, headache, nausea, thirst, and fatigue. 

The nutrient stress hypothesis can be tested by comparing diet-tissue A N values of animals on low versus normal and high protein diets. Our controlled diet experiments, although primarily designed to trace carbon from different dietary macronutrient fractions (proteins versus carbohydrates, fats and sugars) to animal tissues under different levels of nutrient stress (Ambrose and Norr 1993) may be suitable for testing this hypothesis because they contain diets with 5, 20 and 70% protein by weight. 

Eleven controlled diet and environment experiments have been designed in a way that can be used to investigate the effects of protein nutrition and heat and/or water stress on diet-tissue A N. Laboratory rats were raised on purified, pelletized diets in which the isotopic composition of proteins, lipids and carbohydrates were well characterized and their proportions accurately and precisely measured (Ambrose and Norr 1993). Four experiments involved manipulation of temperature and/or water availability. Of these four experiments, one used a diet with high (70%) protein concentrations and heat/water stress (36°C) and three used normal (20%) protein concentrations. Seven experiments were conducted at normal temperature (21°C) with water ad libitum. Of these seven experiments, two used diets formulated with veiy low protein (5%), three with normal protein and two with high protein concentrations. 

Dietary consumption should be balanced in carbohydrates, protein, and fat. Several diet plans exist that promote weight loss through strict limitation or overabundance of only one macronutrient (e.g., low-fat, low-carbohydrate, or high-protein diets) however, overall energy consumption and expenditure will determine the amount of weight alteration. Consultation with a dietician is recommended when... 

Drug/Food interactions Theophylline elimination is increased (half-life shortened) by a low carbohydrate, high protein diet, and charcoal broiled beef (due to a high polycyclic carbon content). Conversely, elimination is decreased (prolonged half-life) by a high carbohydrate low protein diet. Food may alter the bioavailability and absorption pattern of certain sustained-release preparations. Some sustained-release preparations may be subject to rapid release of their contents when taken with food, resulting in toxicity. It appears that consistent administration in the fasting state allows predictability of effects. 

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