Siam rice is a polished white rice which contains about 0.25% phosphorus pentoxide and has more often been associated with severe outbreaks of beriberi than Rangoon rice, which has about 0.32%, this latter, however, being a well-recognized beriberi-producing rice. Unpolished rice contains about 0.55% of phosphorus pentoxide. Natives generally prefer the polished rice because it is clean and free from weevils, while the undermilled kind is dirty. Parboiled rice has a disagreeable odor.
Voegtlin has recommended a P2O5 requirement of 0.5% for corn products and 1% for wheat ones. Thus whole wheat contained 1.12% while highly milled flour had only 0.114%. Fowls fed on this flour developed polyneuritis in twenty to thirty-two days.
Whole corn contains 0.76% P2O5, while highly milled corn grits has approximately 0.2%, and highly milled corn meal about 0.3%. These highly milled corn products produced polyneuritis within from thirty to thirty-five days.
With rock ground corn meal, containing 0.7% P2O5 the fowls remained well.
Experiment of Fraser and Stanton.—While there have been numerous instances reported to show the connection between polished rice and beriberi, when such rice was the predominating article of diet, it will suffice to refer to the experiments of Fraser and Stanton and of Strong.
In 1909, Fraser and Stanton experimented with 493 Javanese coolies who were employed in building a road far removed from any village which might introduce the factor of bacterial etiology into the problem. They noted that the Javanese prefer white rice, and reference is made to the fact that many cases of beriberi occurred among these laborers in 1906, which outbreak ceased upon requiring them to eat parboiled rice at the suggestion of Doctor Braddon. They state that they informed the coolies of the danger of white rice but, notwithstanding, they all expressed a preference for the white rice over parboiled rice. For the purpose of comparison, only one-half were allowed the white rice diet. The two parties were quartered in virgin jungle and were isolated from each other by an interval of 7 miles. Of 220 individuals on white rice there were 20 cases of beriberi recorded while among 273, who lived on parboiled rice, no cases occurred.
Prolonged Continuation of Faulty Diet Necessary.—It appeared that a considerable period of continuance of white rice diet was necessary before the appearance of the disease (eighty-seven days). As against the infectious nature of the disease they note that contact of persons on a parboiled rice diet with the beriberi cases was without result. Substitution of parboiled rice for white rice brought about a cessation of the outbreak.
The Philippine scouts, numbering about 5000 natives, gave 618 cases of beriberi in 1908 and 550 cases in 1909. In 1910 undermilled rice was substituted for polished rice and they were required to eat 1-6 oz. beans daily. No other change in their mode of living was made. By 1913 beriberi had disappeared among them, although the disease still prevailed among the native population in contact with them.
Experiment of Strong and Crowell.—Strong and Crowell stated that the object of their study was to determine whether beriberi, as it occurs in the Philippines, is an infectious disease or whether it is one which has its origin in disturbances of metabolism, due chiefly to the prolonged use of polished rice as a staple article of diet.
The experiments were carried out in Bilibid prison. Prisoners, who had been condemned to death, were informed of the nature of the experiment and were told of the diet on which it was proposed to place them. They were also told that they might contract beriberi. Twenty-nine volunteered and each signed a statement in his own dialect that he undertook the experiment voluntarily.