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Some investigators contend that a high protein intake leads to a reduction in blood pressure.1-3 Other researchers argue that increased protein consumption serves as a hypertensive agent.4-7 Finally, a large group of authorities holds that protein exerts no effect.8-12
Thus, the effect of protein upon blood pressure continues to be a controversial issue. This study is designed to cast additional light upon the subject through a study of the effect of protein versus placebo supplementation upon blood pressure in a group of healthy young men.
Forty-four junior dental students participated in this project. Blood pressure was recorded in all subjects by 1 examiner at 10 A.M. on Monday of a week. On a random basis, one-half of the students were given 40 gm. per day of a protein supplement (see table). The remaining 22 students received 40 gm. daily of an indistinguishable placebo (methylcellulose). The blood pressure was retaken Friday of the same week at 10 A.M. by the same examiner, with no knowledge of the original values or the type of supplementation.
Table–Composition of Protein Tablets
|Average weight||760 mg.|
derived from soybean protein concentrate, casein, gelatin
Essential amino acid content
(per 12 tablets)
Figures 1 and 2 list the actual systolic and diastolic findings in all of the subjects before and after protein versus placebo supplementation. It is well to point out that, according to present blood pressure standards, none of the subjects was hypertensive or hypotensive. Also included in these charts are the means, standard deviations, and probability values. Statistically significant changes occurred only in the protein-treated groups. Specifically, the systolic values changed from 120.3 ± 8.8 to 114.7 ± 7.8 (P< 0.050) and the diastolic values from 72.3 ± 6.4 to 68.5 ± 4.4 (P< 0.050). In contrast, the preplacebo versus postplacebo values for both systolic and diastolic pressures were not significantly different.
The evidence presented here appears to indicate that protein supplementation, in the amount given and for the period administered, exerts a small but nonetheless significant effect upon both systolic and diastolic pressure. The conclusions are even more interesting in view of the fact that, according to present standards for blood pressure, all subjects were within physiological limits.13,14 This raises the question as to whether present parameters for blood pressure are correct.
These data are also interesting because of the similarity to blood pressure changes previously reported after the administration of a low-refined-carbohydrate, high-protein dietary regime.15
The coefficient of correlation between the initial pressure and the amount of change after three days of supplementation was significant for both systolic (r = 0.472, P < 0.050) and diastolic (r = 0.726, P < 0.005) readings in the protein group. In contrast, the low correlations for the placebo group indicated no significant change (systolic, r = 0.013, P = 0.500) (diastolic, r = 0.451, P > 0.050). The negative regression of the individually plotted blood pressure changes is demonstrated in figures 3 and 4.
The systolic pressures for the protein-supplemented group appear to decrease when above approximately 118 mm. Hg and increase when below this value (figure 3). The point of change for the diastolic pressures is approximately 70 mm. Hg (figure 4).
The small, significant changes in both systolic and diastolic blood pressure are emphasized by a relatively narrow margin of error in measuring. Reproducibility of the systolic reading was within 2 mm. for 82 percent of the group. Eighty-six percent of diastolic readings were consistent with this degree of error.
A study of 44 dental students (healthy males) subjected to protein versus placebo supplementation for four days resulted in small but orderly and significant changes in systolic and especially diastolic blood pressure for the protein-treated group. The systolic and diastolic pressure changes made it appear, at least presumptively, that approximately 118/70 mm. Hg is the ideal physiological nonfasting blood pressure for young adult males. These observations confirm earlier reported findings of a narrower blood pressure range following a low-refined-carbohydrate, high-protein diet.
- Harris, I., Aldred, C. N., and English, A. G. H.: “The effect of high protein diet on arterial pressure in cases of hypertony.” Lancet 1:1327, 1935.
- Allen, F. M., and Cope, O. M.: “Influence of diet on blood pressure and kidney size in dogs.” J. Urol. (Baltimore) 47: 751, 1942.
- Alvarez, W. C.: “Does meat-eating influence blood pressure?” Gastroenterology 1:536, 1943.
- Breed, T. M.: “Amino acids and hypertension.” Calif. Med. 17: 371, 1919.
- Saile, F.: “Influence of vegetarian diet on blood pressure; comparative study of monks from orders which permit meat in diet and those which allow only vegetarian diet.” Med. Klin. 26:929, 1930.
- Handler, P., and Bernheim, F.: “Physiologic basis for effects of low-protein diets on blood pressure of subtotally nephrectomized rats.” Amer. J. Physiol. 162:368, 1950.
- Wilhelmj, C. M., Meyers, V. W., Milani, D. P., McDonough, J. R., Racher, E. M., McGuire, T. F., Waldmann, E. B., and McCarthy, H. H.: “Effect of diet on blood pressure and heart rate of normal dogs; protein and carbohydrate.” Circulat. Res. 1:419, 1953.
- Philipsborn, H., Katz, L. N., and Rodbard, S.: “Effect of high protein diets on experimental animal hypertension.” J. Exp. Med. 74:591, 1941.
- Alpert, L. K., and Thomas, C. B.: “Studies in experimental hypertension. II. The effect of dietary protein on the urea clearance and arterial blood pressure in chronic hypertension.” Bull. Johns Hopk. Hosp. 72:274, 1943.
- Guerrant, J. L., Scott, J. K., and Wood, J. E., Jr.: “Effect of high protein diet and urea administration on the blood pressure of normal dogs and of dogs with experimental hypertension.” Amer. Heart J. 26:232, 1943.
- Danford, H. G., Dieter, D. G., Christofferson, J. W., and Herrin, R. C.: “Effect of dietary restriction of salt and protein on blood pressure of hypertensive rats.” Amer. J. Physiol. 163: 190, 1950.
- Dubey, J. D.: “A study on blood pressure amongst industrial workers of Kanpur.” J. Indian Med. Ass. 23:495, 1954.
- Master, A. M., Garfield, C. I., and Walters, M. B.: Normal Blood Pressure and Hypertension. Philadelphia: Lea & Febiger, 1952.
- Brest, A. N., and Moyer, J. H.: Hypertension, Recent Advances. Philadelphia: Lea & Febiger, 1961.
- Ringsdorf, W. M., Jr., Cheraskin, E., and Hollis, C. F.: “Effect of a low-refined-carbohydrate diet upon nonfasting blood pressure.” Ala. Dent. Rev. 9:1, 1962.