Over a five year period McCarrison noted no case of illness, no death from natural causes, no maternal mortality and no infantile mortality amongst this group of rats. They were of course kept clean and had exposure to the sun daily and were generally well cared for, but the same conditions and care were given during these years to thousands of other rats fed deficiently on southern Indian diets, amongst which a wide variety of illness was observed. It was the altered diet which provided a disease-free environment for the rats, and this corresponded with a sturdier physique, just as McCarrison had observed amongst humans following these different dietary patterns.

He concluded that if attention is paid to three things cleanliness, comfort and food - it is possible to exclude disease from a colony of cloistered rats, and that it is possible greatly to reduce disease by the same means in human beings.

McCarrison's final experiments
Having found that the Sikh diet provided an ideal for good health and long life, McCarrison then took two groups of 20 matched rats and fed one on a Sikh diet and the other on a typical British diet (white bread, margarine, sweetened tea, a little milk, boiled potatoes and cabbage, tinned meat and tinned jam). The differences between the two groups of rats were dramatic and rapidly observable. The Sikh-diet fed rats were, as in previous studies, contented and healthy. The British-diet fed rats did not flourish:

Their growth was stunted; they were badly proportioned; their coats were sparing and lacked gloss; they were nervous and apt to bite; they lived unhappily together, and by the 60th day began to kill and eat the weaker ones amongst them.

The experiment continued for 187 days - around 16 years in human terms. The 'British' rats showed a tendency to diseases of the lungs and gastrointestinal disease, while those on the 'Sikh' diet were free of such problems. McCarrison noted that when he kept rats on either the deficient Madrasi diet, an even worse Travancore diet or a Sikh diet, for 700 days (50 human years) many animals died, and peptic ulcers developed in 29 per cent of the Travancore-diet group, in 11 per cent of the Madrasidiet group and in none of the Sikh-diet group. This is precisely the pattern of ill-health seen in humans living on the same diets. 'Here again, we see that a disease common in certain parts of a country can be produced in rats by feeding them on the faulty diets in common use by the people of these parts.'

McCarrison has proved similar dietary connections in numerous other disease patterns found in humans, including skin diseases (ulcers, abscesses, dermatitis); diseases of the eye (cornea! ulceration, conjunctivitis, cataracts); diseases of the ear (otitis media); diseases of the nose (rhinitis, sinusitis); diseases of the lungs and respiratory passages (adenoids, pneumonia, pleurisy); diseases of the alimentary tract (dental disease, gastric ulcer, cancer of the stomach, duodenal ulcer, enteritis, colitis); diseases of the urinary tract (pyonephrosis, pyelitis, renal stones, nephritis, cystitis); diseases of the reproductive system (endometritis, premature birth, uterine hemorrhage, testicular disease); diseases of the blood (anaemia, pernicious anaemia); diseases of the Iymph glands (cysts and abscesses); diseases of the endocrine glands (goitre, adrenal hypertrophy, atrophy of the thymus, hemorrhagic pancreatitis); diseases of the heart (cardiac atrophy, cardiac hypertrophy, myocarditis, pericarditis); diseases of the nervous system (polyneuritis, beri-beri, degenerative lesions); diseases of the bone (crooked spine); general diseases (malnutrition oedema, scurvy). 'All these conditions had a common causation: faulty nutrition with or without infection.'