The scientific literature also includes laboratory and animal studies as well as clinical trials. Although some findings suggest promise, it is difficult to compare cranberry products across studies. Many of these studies have methodological issues such as:
- Not being randomized or controlled
- Being small in size
- Having quality issues in design or reporting
- Using products that are not standardized.
Research on cranberry for urinary tract conditions is ongoing, including in NCCAM-supported studies using well-standardized, research-grade cranberry products.
Benign Prostatic Hyperplasia
BPH is common in men but rarely produces symptoms before age 40. Not all men with BPH have symptoms. The cause of BPH is not well understood but is thought to be connected with hormones, such as the levels of dihydrotestosterone and/or estrogen. More than half of men aged 50 or older, and as many as 90 percent of men in their 70s and 80s, have symptoms of BPH. As a condition, it is estimated to account for at least 1.7 million office visits to physicians and over $4 billion in health care costs per year in the United States. As the population ages and life expectancy continues to rise, the incidence and prevalence of BPH are expected to rise as well.
Lower urinary tract symptoms (LUTS) associated with BPH can range from mild to very bothersome, and include frequency or urgency of urination, nocturia, slow stream, and leakage. Urinary retention associated with BPH potentially can lead to complications, although these are less common, such as UTI, or bladder or kidney damage. Having BPH is not a risk factor for prostate cancer, although both can occur simultaneously.
An increasing number of men are treating their BPH symptoms with botanical preparations sold over-the-counter, using them as individual agents or in combination with prescribed drugs. A 2006 estimate placed the sales of botanicals marketed for BPH symptoms at over $6 billion per year.
Saw palmetto (Serenoa repens, made from ripe berries of the American dwarf palm) is the botanical that is most used for symptoms of BPH and most studied in clinical trials. In the 2007 national survey on Americans' use of CAM, among respondents who used natural products as CAM, about 5 percent used saw palmetto (translating to about 1.7 million Americans).
Basic research on saw palmetto in laboratory and animal studies has revealed some findings, such as the following, that may be relevant to its potential application in treating BPH:
- Saw palmetto appears to contain components that have activity similar to (but weaker than) 5-alpha-reductase inhibitors, which prevent conversion of testosterone to dihydrotestosterone.
- Saw palmetto contains substances, including certain fatty acids, that may have weak antiandrogenic effects as well as antiproliferative and anti-inflammatory properties.
Snapshots of the Evidence