This is a religiously motivated idea. And it is very probably a quite terrible idea from a health perspective. It is definitively a terrible idea from a taste perspective. After reviewing the available literature for claims and results we have to conclude that there is no evidence to support these claims. Two experts who should really know the literature on this confirm this with testimonials found quoted at the end of this answer.
There are some studies in scientific journals that seem to indicate some qualities of bovine urine that may point into the therapeutic direction:
Kuldeep Dhama: "Anti-Cancer Activity of Cow Urine: Current Status and Future Directions", International Journal of Cow Science, 1(2): 1-25, 2005
Cow urine has a unique place in Ayurveda and has been described in ‘Sushrita Samhita’ and ‘Ashtanga Sangraha’ to be the most effective substance/secretion of animal origin with innumerable therapeutic values. It has been recognized as water of life or “Amrita” (beverages of immotality), the nector of the God. In India, drinking of cow urine has been practiced for thousands of years. It is an important ingredient of panchgavya, a term used to describe five major substances (urine, milk, ghee, curd and dung), obtained from cow. All the five products possess medicinal properties, and are used singly or in combination with some other herbs against many diseases, even those not curable by allopathic treatments. This kind of alternative treatment, termed as ‘panchgavya therapy’ or ‘cowpathy’, has been reported to be beneficial even for dreaded diseases like cancer, AIDS and diabetes. Practitioners of Ayurvedic medicine from India routinely use cow urine as a remedy and the medicines made from it are used to cure several diseases. Improvements have been shown or reported with those suffering from flu, allergies, colds, rheumatoid arthritis, bacterial/viral infections, tuberculosis, chicken pox, hepatitis, leucorrhoea, leprosy, ulcer, heart disease, asthma, skin infections, aging, chemical intoxication etc. Cow urine can kill the number of drug resistant bacteria and viruses. Recently the cow urine has been granted U.S. Patents (No. 6896907 and 6,410,059) for its medicinal properties, particularly for its use along with antibiotics for the control of bacterial infection and fight against cancers.
The whole substance is thought of as miracle drug –– in some regions and belief systems –– that is said to fight almost all diseases at once,
‘The cow’ is a mobile medical dispensary and cow urine is a panacea of all diseases. (Mohanty: Int J Pharm Pharm Sci, Vol 6, Issue 3, 20-22, 2014.)
The arguments found in favour of this substance often emphasise that it has US patents granted to its use in medicine and even comes from a sacred animal as its waste product, that is without harming the animal?
Let's start to look at the patents:
US6410059 and US6896907. They were granted on the basis that cow urine is a "bioenhancer", not a medicine in itself. That may have some value. But the argument is peripheral to the claim of cow urine as health drink and scientific or medical information found in patents does not have be reliable.
What quality is to be found in those research articles that claim to find and present evidence? Usually it goes like this:
N. K. Jain et al.: "Efficacy Of Cow Urine Therapy On Various Cancer Patients In Mandsaur District, India - A Survey", International Journal of Green Pharmacy, Vol 4, No 1 (2010)
Evaluation of cow urine therapy on cancer patients in 8 days camp at Mandsaur district was carried out. The object of this survey was to evaluate efficacy of cow urine therapy on various cancer patients who were reported across from different state of India. Total 68 cancer patients reported during the survey from 8 April 2007 to 15 April 2007. A questionnaire was developed to assess the efficacy of cow urine therapy. During survey, out of 68 patients, 7.35% patients withdraw themselves from the treatment and 63 (92.64%) patients continued the therapy. There was a high proportion (30.87%) of throat cancer and the other prevalent cancer was breast cancer (14.70%) followed by cervix and uterine cancer (5.88%), buccal cavity cancer and sinus (4.41%) lung cancer, lymphoma and bone cancer (2.94%), both throat and buccal (5.88%) and other cancer (8.82%), respectively. The symptoms (pain, inflammation, burning sensation, difficulty in swallowing, irritation, etc.) of cancer patients were categorized into severe, moderateand mild categories, respectively. Intensive study of the data of cancer patients revealed that the degree of severe, moderate and mild symptoms were 82.16%, 15.8% and 1.58% on the first day and 7.9%, 55.3% and 36.34% on the eighth day, respectively. It was evaluated that patients who were receiving cow urine therapy since 2-3 months were most benefited. Hence, this traditional therapy may really a boon to cancer patients.
A short, small study with little controls. As a first exploration this might do. For a "medicine" that is thousands of years old this will not do. The scientific quality of the evidence presented here is absolutely abysmal. And the quality of the publishing venues is not considered in this verdict.
In vitro studies might show interesting results, like Antioxidant and Antimicrobial Activities of Cow Urine and Cow Urine Concentrate: A potent agent with Antimicrobial and Anthelmintic activity. But in almost every case the authors state that they are rooted in the tradition and wanted to prove the value of a traditional treatment option. They very often jump to conclusions that have no scientific or even logic basis: "a boon to cancer patients"?
As a traditional treatment option this juicy medicine might also be applied to treat eye/vision problems. Judging the efficacy with just the alternative medicine adage of "who heals is right" it has to be said that cow urine does not seem to help very much:
A total of 1420 new patients attended the eye clinic during the study period (January to December 2009). Forty eight (3.4%) applied various substances into their eyes after sustaining ocular injury. Substances applied include Kerosene 25%, cassava water 20.8%, breast milk 12.5%, personal urine 10.8%, and cow urine 8.3%. Nearly half of the patients 23 (47.9%) presented with low vision and after treatment there was no visual improvement in almost all of them, 22 (45.8%).
Prevalence of Harmful/Traditional Medication Use in Traumatic Eye Injury Glob J Health Sci. 2013 Jul; 5(4): 55–59.
Cow urine, or Gomutra has little scientific investigations really in its favour, but some quite heavily against it.
Evaluation of antidiabetic, antioxidant effect and safety profile of gomutra ark in Wistar albino rats
The effect of Gomutra ark (GoA) on experimental alloxan-induced diabetes in rats was studied. For this purpose, Wistar albino rats of either sex weighing 200-250 g were used. The biochemical parameters like blood sugar, vitamin C, and malondialdehyde release were measured. The safety profile of GoA was evaluated using acute and chronic toxicity studies. GoA significantly lowers blood glucose in diabetic rats although the observed effect was found to be less than glibenclamide. It significantly lowers the level of malondialdehyde and vitamin C in diabetic rats. No toxicity was observed even when cow urine was given 32 times of the study dose in acute toxicity and no significant changes were seen when it was used chronically, which suggests that cow urine is having a very high therapeutic index. This study supports the traditional use of GoA in diabetes and is having a high therapeutic index and is safe for chronic use. However, further studies are needed to elucidate the mechanism of action of Gomutra ark.
But the caveats that rats might be different from humans are not to be dismissed. Rats are apparently already different enough from dogs or mice:
DD Oyebola; RA Elegbe (1975). "Cow's urine poisoning in Nigeria. Experimental observations in mice". Tropical and geographical medicine. 27 (2): 194–202.
The method of preparation and administration of "cow's urine" and the signs and symptoms of cow's urine poisoning have been described. Experimental investigations were carried out in mice to assess the toxicity ot this concoction. Effect of the preparation was compared with that of pure nicotine. The effect of each component used in preparing the concoction was also tested. Results of the experiments show that both "cow's urine" and nicotine cause excitement in low doses and cause convulsion and/or death in higher doses. Both also depress respiration. The role of "cow's urine" toxicity following administration to patients with convulsion and the possible aetiology of the neurological sequelae of "cow's urine" poisoning are discussed.
The most dangerous aspect found recently seems to lie in the danger of even catching a prion-disease via urine: A Protease-resistant Prion Protein Isoform is Present in Urine of Animals and Humans Affected with Prion Diseases (2001).
While it might be that Western Medicine is a bit prejudiced or uninterested in this regard and just does not look into the matter properly, as long as only ayurvedic practitioners, esotericists and Hindu nationalists continue to claim any health benefits were associated with drinking traditional preparations of cow urine, the known dangers seem to outweigh the dubious claims of benefits.
From a theoretical thought experiment perspective that this practice is said to be widely used in India, and India is neither leading in death from drinking cow urine nor leading in successful treatment of cancers: health benefits of drinking cow urine are unfounded.
Or in the words of other experts as reported via abc-news:
Curing cancer with cow urine? Cancer prevention experts said this seems like an unlikely stretch.
"It's a claim from somebody that does not have any distinction or credentials, and it's an empty claim without scientific basis," said Dr. Sam Epstein, emeritus professor of environmental and occupational medicine at the University of Illinois Chicago School of Public Health.
Dr. Donald Hensrud, chairman of the Division of Preventive Medicine at the Mayo Clinic in Rochester, Minn., agreed. "I think I'm perfectly comfortable in saying that I'm aware of no data that cow's urine –– or any other species' urine –– holds any promise … in treating or preventing cancer."