Effect of a Low Refined Carbohydrate High-Protein Diet Upon the Urinary pH

Introduction

A previous report (Ringsdorf et al., to be published) has shown that significant changes in urinary specific gravity follow the introduction of low-refined-carbohydrate high-protein diet. Specifically, it was observed that urinary specific gravity levels above 1.018 decreased to or about that point whereas values below 1.018 rose to or about that value.

This report is designed to describe the changes in urinary pH which follow the introduction of a low-refined-carbohydrate high-protein dietary regime.

Review of the Literature

A number of reports have been published showing the effect of diet upon the pH of the urine in lower animals and in the human.

Lower animal studies

In the only lower animal study noted in the literature, Langwill et al. (1945) observed that, when rats were fed a supplement of horse meat in addition to their basic diet, there was a slight increase in the urinary pH. Conversely, when these same rats were provided with sucrose supplementation, the urine became more acid.

Human studies

Effect of carbohydrate upon urinary pH.–Brunton (1933), in a study of four subjects, observed that foods high in carbohydrate, such as lima beans and potatoes, caused a rise in urinary pH. Stenstrom (1922) studied eleven infants with dystrophia and found that the urinary pH was not altered when he increased the carbohydrate content of breast milk. Lyon (1938) states that individuals subsisting on a high-carbohydrate diet show an elevated urinary pH, while those with low carbohydrate intake have an acid urine.

Effect of protein upon urinary pH.–Ryberg (1943) observed that, with a protein-rich diet, the postprandial alkaline tide was extended beyond the normal period. In contrast, a low-protein diet significantly shortened the alkaline tide. Lyon (loc. cit.) and Cotar (1937), however, observed a lower urinary pH in subjects with high-protein intake and an alkaline urine following a low protein meal. The general consensus among these and other authors (Colby, 1956; Barnes and Hadley, 1954; Wohl and Goodhart, 1960; Cantarow and Trumper, 1956) is that there is a negative correlation between the protein content of the diet (acid ash) and the urinary pH.

Effect of a high-carbohydrate low-protein diet.–Miller et al. (1941) determined the urinary pH of ten healthy subjects supplied with a high carbohydrate low-protein diet. They found that this diet yielded an increase in urinary pH. However, Bischoff et al. (1934) observed just the opposite (an increase in acidity of the urine when subjects were placed on essentially this same type of diet).

Effect of a low-carbohydrate high-protein diet.–Miller et al. (loc. cit.) observed a lowering of the pH in the urine when individuals were fed a low-carbohydrate high-protein test diet. On the same type of diet, however, Bischoff et al. (loc. cit.) found a slight elevation in pH.

Effect of fruits and fruit juices.–There are a number of publications which deal with the effects of the ingestion of fruits and fruit juices upon the urinary pH. Among the fruits which cause an elevation in pH are grapes (Saywell, 1932), raisins (Saywell, 1932a), figs (Saywell and Lane, 1933), pears (Saywell, 1933), apricots, (Saywell, 1933), peaches (Saywell, 1933) and bananas (Brunton, loc. cit.). Fruits and fruit juices which are reported to increase the acidity of the urine are prunes (Brunton, loc. cit.; Mark et al., 1934; Blatherwick and Long, 1923), raisins (Brunton, loc. cit.), and cranberries (Fellers et al., 1933). As a general rule, it may be stated that the alkaline ash foods (most fruits and vegetables) (Brunton, loc. cit.) tend to reduce urinary acidity (Colby, loc. cit.; Barnes and Hadley, loc. cit.; Wohl and Goodhart, loc. cit.; Cantarow and Trumper, loc. cit.). According to literature reports, orange juice (Saywell and Lane, loc. cit.; Blatherwick and Long, loc. cit.), tomato juice, (Saywell and Lane, loc. cit.) and guava juice (Ross and Hartzler, 1946) all tend to cause an increase in urinary pH.

Miscellaneous factors.–The administration of solutions of lactose (Neff, 1935), glucose (Eggleton, 1947), gluconic acid (Gold and Civin, 1939; Chenoveth et al., 1941) and cola beverages (Bowers, 1941) have been reported to decrease the urinary pH. In one instance, however, patients were given dextrose and the urinary pH was increased (Luhrs, 1935).

Normal pH.–It is generally accepted in the literature that there is a normal diurnal variation in urinary pH (Lyons, loc. cit.; Ryberg, loc. cit.). This physiologic variation is affected by the ingestion of food. This phenomenon is known as the alkaline tide and normally lasts for three to four hours after eating. Following a meal, there is a transient decrease in pH for one hour after which there is an elevation for approximately three hours. There is also evidence that the body is physiologically adapted to excrete an acid urine with a pH approximately 5.5 to 6.0 (Lyons, loc. cit.; Cotar, loc. cit.; Miller et al., loc. cit.; Bischoff et al., loc. cit. Saywell, 1932, 1932a, 1933, 1933a; Mark et al., loc. cit.; Johnson, 1949).

Method of Investigation

Twenty-five ambulatory subjects were studied with regard to urinary pH. Generally, the sample was divided almost equally between the two sexes. Subjects range in age from the second to the eighth decades.

Each patient presented in the clinic between 9.00 and 12.00 a.m. after a customary breakfast meal. A urine sample obtained upon arising in the morning was brought in by the patient and the urinary pH measured immediately upon receipt in the clinic. The scores so derived will hereafter be referred to be based on a regular diet.

The patient was then instructed with regard to diet. He was informed that, for the next three days, to consume as much meat, fish, fowl, vegetables, whole grain (as breads, cereals, vegetables), eggs, nuts, and butter as desired.

The patient was also permitted weak tea, decaffeinated coffee, and water ad libitum. Specific instructions were given not to eat sugar and refined sugar products, white flour foods, fruit and fruit juices, milk and milk products (except butter). The only dietary supplement given to the patient for the three-day period was a 75 mg. tablet of vitamin C. Hereafter, in the interest of conservation of space, this regime will be referred to as basic or preparatory diet (preparatory to blood tests). In order to be as certain as possible that the instructions were followed, the patient was given a form on which all foods eaten were to be recorded during the three-day period.

Finally, the patient was instructed to return on the fourth day between 9.00 and 12.00 a.m. after a breakfast based on the recommendations above. At this second visit, the urine sample obtained upon arising was again measured for pH.

Results

The initial urinary pH findings of the 25 patients and the findings following a three-day low-refined carbohydrate high-protein diet are shown in the Table. The mean initial pH for the group proved to be 5.7 with a standard deviation of 0. This can be interpreted to mean that approximately two-thirds of the patients, specifically 68 per cent, ranged from 5.1 to 6.3. This is quite in accord with supposedly physiologic values (Lyons, loc. cit.; Cotar, loc. cit.; Miller et al., loc. cit.; Bischoff et al., 1934; Saywell, 1932, 1932a, 1933, 1933a; Mark et al., loc. cit.; Blatherwick and Long, loc. cit.; Johnson, loc. cit.). Three days after subsisting on the preparatory diet, the mean urinary pH decreased to 5.5 and the standard deviation was reduced to 0.5. Thus, at the end of the three-day dietary period, two-thirds of the sample ranged from 5.0 to 6.0.

Table–Comparison of nonfasting urinary pH with regular diet and after a three-day low-refined carbohydrate high-protein diet.

The scores obtained for the 25 patients initially and after the dietary regime are represented in the Graph. Shown along the abscissa are the initial urinary pH findings. The difference between the initial scores and the observations three days later are charted on the ordinate. It is very clear from the Graph that there is a definite line of regression. The coefficient of correlation for the group was found to be -0.769 with a P<.001. Thus, the evidence seems reasonable that, under this dietary regime, patients with urinary pH levels above 5.5 tend to be reduced to or about 5.5. Also, it appears that those scores below 5.5 tend to rise toward 5.5.

Graph–Comparison of nonfasting urinary pH initially (shown on the abscissa) and after a three-day low-refined carbohydrate high-protein diet (demonstrated on the ordinate) in 25 patients.

Initial nonfasting urinary pH. 

Discussion

The evidence from these 25 subjects indicates that there is a tendency for the urinary pH to approach 5.5 under the conditions of a high-protein low-refined-carbohydrate diet. This is underscored by the very clear-cut line of regression and the significant negative correlation. These findings are at variance with previously published information (Miller et al., loc. cit.; Bischoff et al., loc. cit.). However, it should be pointed out that these investigators simply reduced carbohydrates and increased protein. In contrast, only refined carbohydrates were eliminated while increasing protein intake in this study. Whether this is the sole or only partial explanation for the different results cannot be made from the observations in this study.

It is, of course, hazardous to draw conclusions as to what physiologic urinary pH should be from these limited data. However, the evidence at least suggests that 5.5 might well be the ideal physiologic score.

It should be emphasized that similar findings were observed with regard to the effect of a low-refined-carbohydrate relatively high-protein diet upon blood sugar (Page et al., 1961), serum calcium (Page et al., 1962), serum phosphorus (Page et al., 1931), calcium phosphorus relationships (Page et al., 1962), serum cholesterol (Page et al. to be published), serum protein (Ringsdorf and Cheraskin, 1962), and urinary specific gravity (Ringsdorf et al., loc. cit.). In all of these instances, the particular biochemical values decreased to within a relatively narrow range indicating the possibility that the physiologic spreads for blood sugar, serum calcium, serum phosphorus, calcium-phosphorus relationships, serum cholesterol, serum protein, urinary specific gravity, and urinary pH may be more limited than currently held.

There is one other curious point which should be made. A detailed study of all the biochemical values indicates the same patients who migrated most within the narrow range of 5.5 for urinary pH were the very same individuals who migrated most closely to urinary specific gravity of 1.018, blood sugar 100 mg. per cent, serum calcium 9.7 mg. per cent, serum phosphorus 3.7 mg. per cent, calcium-phosphorus product 35, serum cholesterol 220 mg. per cent, and serum protein 7.1 g. per cent.

Summary

1. Urinary pH analyses of 25 patients were made initially (during a period of regular diet) and three days after a relatively high-protein low-refined-carbohydrate regime.
2. Evidence is presented to show that, under this dietary programme, the urinary pH tends to seek a more narrow physiologic range than is currently recognized.
3. It would appear, at least presumptively, that 5.5 may be the ideal (physiologic) pH value.

This investigation was supported in part by a traineeship grant (2G-15) from the Epidemiology and Biometry Section, Public Health Service and (A-2899) the National Institute of Arthritis and Metabolic Diseases.

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