Practitioner's Guide to Nutritional Supplements
Practitioner's Guide to Nutritional Supplements
Lack of communication between doctors and patients poses a serious problem for the healthcare industry, especially when it comes to complementary and alternative medicine (CAM). According to the National Center for Complementary and Alternative Medicine (NCCAM; Bethesda, MD), only about 12% of Americans who tried CAM between 1997 and 2004 consulted a licensed healthcare practitioner.
The average doctor’s office visit lasts just 15 minutes and involves about six different topics, according to the American Medical Association (AMA; Chicago). Unfortunately, CAM seldom tops the agenda. In a January 2007 survey administered to 1559 people aged 50 and older, about 42% of the respondents said they did not discuss CAM during office visits because their practitioners never asked about it, NCCAM noted. Another 30% said they didn’t know they should discuss CAM, and 19% said they didn’t have enough time during office visits to broach the subject.
The problem doesn’t just involve seniors and their doctors, however. Young adults are also reluctant to discuss CAM, and about 80% of teens have tried CAM at least once, according to NCCAM, which also notes that many patients believe that practitioners are uninformed about CAM and unlikely to be supportive of CAM use.
There may be some truth to that perception. NCCAM notes that in a 2001 survey of 745 members of the American Academy of Pediatrics (AAP; Elk Grove, IL), fewer than 5% of the respondents said they felt very knowledgeable about CAM, despite the fact that 87% had been asked about it within the past three months. Moreover, negative statements about CAM that have appeared in the mainstream press over the past decade may have added to the overall impression that doctors are not interested in CAM. On the other hand, the AAP survey took place six years ago, when doctors and researchers knew less about CAM’s risks and benefits.
CLOSING THE INFORMATION GAP
To gauge the level of CAM education among the nation’s healthcare practitioners, the National Institutes of Health’s (NIH; Bethesda, MD) Office of Dietary Supplements (ODS) recently completed a comprehensive survey of academic institutions. ODS conducted the survey from October 2006 to January 2007 by sending questions about educational programs involving dietary supplements to all U.S. schools offering degree programs in disciplines such as nursing, food science, medicine, dentistry, pharmacy, and kinesiology. As part of the survey, ODS asked faculty members to provide information about course materials and asked for suggestions about what resources would be useful for instructors.
ODS is already putting the information to good use. On May 21–25, the office will host a free practicum on dietary supplements for faculty and graduate students. The practicum will offer several days of lectures and presentations about supplements from officials from ODS, NIH, academic institutions, and federal agencies, along with one day of meetings with industry stakeholders in Washington, DC. Additional instruction in the use of databases relevant to supplements will also be provided. ODS hopes to use the practicum to provide participants with resources and encourage interest in the field of supplement research. The office also plans to publish a report on the survey’s findings.
In addition, NCCAM and ODS have taken other steps to promote knowledge of dietary supplements and other CAM therapies to healthcare professionals, helping to close the information gap between practitioners and patients. NIH-sponsored resources, such as ODS’s Annual Bibliography of Significant Advances in Dietary Supplement Research and Computer Access to Research on Dietary Supplements (CARDS) database convey some of the latest information.
Moreover, other resources, like this second-annual Practitioner’s Guide to Nutritional Supplements, can offer backgrounds, summaries, and other data on popular nutritional supplement ingredients. While last year’s Practitioner’s Guide contained information on supplements such as hoodia, saw palmetto, and vitamin E, this year’s edition covers ingredients including black cohosh, lignans, and DHEA, among others.
Table of Contents
BACKGROUND: Lignans are a class of phytoestrogens found in numerous plant-based foods, such as rye grains, linseeds, spinach, broccoli, carrots, and other vegetables. Some researchers believe that lignans may possess antioxidant and anticancer properties. Because their shape closely resembles human estrogen, lignans may latch onto estrogen receptors and block the uptake of estrogen linked to tumor growth. Data on lignans are limited, however.
Flaxseed is a common source of plant ligans.
Photo by Steven Foster.
HISTORY OF USE: Foods that are rich in phytoestrogens are popular in Asia. However, phytoestrogen intake is much lower in the west, where the main source of lignan intake is flax.
RESEARCH: Most data on lignans come from observational studies. One of the largest studies involving lignans consumed by a western population was published in the March 21, 2007, issue of the Journal of the National Cancer Institute. In that study, researchers analyzed responses to dietary questionnaires filled out by more than 58,000 postmenopausal French women who did not eat soy. After an average 7.7 years of follow up, the researchers calculated that women with the highest levels of lignan intake had a 17% lower risk of developing breast cancer than women with the lowest levels. The results were specific to estrogen and progesterone receptor cancers, however. The researchers wrote that although scientists are still debating the role of lignans in preventing breast cancer, a strategy of increasing dietary lignan intake “may be an interesting potential approach.”
CONVENTIONAL WISDOM: Interest in flax and other phytoestrogens rose after the Women’s Health Initiative uncovered some negative health effects associated with hormone replacement therapy. However, the current evidence for lignans is not extensive, and researchers still disagree over the role and identity of lignans that may be involved in cancer prevention. In February 2007, several major flax producers announced that they are collaborating on the development of a validated analytical method for the main flax lignan secoisolariciresinol diglucoside (SDG), which may lead to standardized and more effective lignan supplements. Moreover, studies on other sources of lignans, such as Norway spruce (Picea abies), are currently under way. These new products could create greater interest in lignans.
SUMMARY: While there is some evidence that dietary intake of phytoestrogens may be related to cancer risk, more data are needed to support health claims involving lignans. Greater government and industry involvement in lignan research, however, could fuel new discoveries.
BACKGROUND: More than 20 million people in the United States currently suffer from osteoarthritis (OA). However, aside from nonsteroidal anti-inflammatory drugs (NSAIDs), there aren’t many treatment options for OA. People with joint pain who are worried about the side effects of NSAIDs like Vioxx therefore are increasingly turning to products like glucosamine and a related supplement, chondroitin sulfate.
HISTORY OF USE: People with OA and other joint mobility problems have used chondroitin, a polysaccharide constituent of cartilage, as a supplement since the 1960s.
RESEARCH: Although many clinical trials have found that chondroitin provided strong relief to people with OA, a study published in the April 17, 2007, issue of the Annals of Internal Medicine concluded that use of the supplement should be discouraged because its benefits were “minimal or nonexistent.” In the review, researchers analyzed 20 studies involving chondroitin and excluded data from all but three on the grounds of poor study design.
The Annals study findings are controversial because they contradict positive results reported in several earlier studies, including a similar meta-analysis that appeared in the March 15, 2000, issue of the Journal of the American Medical Association (JAMA). The JAMA study rated chondroitin’s effects as “moderate to large.” However, the study also noted evidence of some publication bias and exaggeration in the trials covered in the meta-analysis. For instance, one study claimed that chondroitin was as effective as a total knee replacement.
The Annals study findings also appeared to partially contradict the results of the recent Glucosamine/ Chondroitin Arthritis Intervention Trial (GAIT), which was published in the February 23, 2006, issue of the New England Journal of Medicine. In that trial, chondroitin appeared to have statistically significant positive effects on 67% of people with mild OA.
Critics of the Annals study say that the meta-analysis is not an accurate representation of people who use chondroitin. Two dietary supplement trade associations, the Council for Responsible Nutrition (CRN; Washington, DC), and Natural Products Association (NPA; Washington, DC), pointed out that many previous studies showed positive results for some patients. According to CRN vice president of scientific and regulatory affairs Andrew Shao, PhD, the meta-analysis provided “a narrow view of the entire body of evidence on the effect of chondroitin supplementation.”
Additionally, NPA vice president of scientific and regulatory affairs Daniel Fabricant, PhD, noted that most consumers actually use a combination of glucosamine and chondroitin, rather than chondroitin by itself. Perhaps anticipating some of these objections, the authors of the Annals study stated that most of the trials in the meta-analysis involved heterogenous populations that made comparisons difficult. The authors also wrote that instead of contradicting earlier findings, their conclusions simply present a more-accurate picture over time by incorporating data from newer, better-designed trials.
In an editorial accompanying the Annals study, one author observed that because chondroitin appears to be safe and well tolerated, patients should continue to take the supplement if they think it helps.
CONVENTIONAL WISDOM: Intense media coverage of the 2004 withdrawal of Vioxx revealed strong consumer demand for alternatives to NSAIDs. Moreover, many consumers already are convinced that the supplement offers relief. As long as consumers have knee pain and think chondroitin is safe, they will continue to take it.
SUMMARY: While the Annals study is unlikely to change consumer beliefs about chondroitin sulfate, the results of the next stage of the GAIT trial are expected soon and should keep the ingredient in the news. Scientists still need more data about the supplement’s effects on a variety of study populations, however, before they will know for certain who it will benefit.
BACKGROUND: There is nearly universal agreement among scientists that fish is one of the world’s healthiest foods. Recent studies suggest that fish intake may be positively associated with overall health, as well as cardiovascular and cognitive fitness. However, many consumers don’t like the taste or odor of fish; others fear that fish is contaminated with heavy metals or pesticides. Because of these concerns, supplements and functional foods containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), two omega-3s found in fish oil, are growing in popularity among health-conscious consumers.
HISTORY OF USE: In the early 20th century, children grimaced when their parents forced them to swallow foul-tasting cod liver oil. In the early 21st century, however, omega-3 oils are much more palatable to consumers, thanks to new manufacturing technologies. As manufacturers have learned how to purify and deodorize fish oils, and harvest omega-3s from vegetarian sources such as flax and algae, products containing the healthy oils have proliferated. Consumers now can obtain their omega-3s through capsules and foods such as beverages, breads, and candies.
RESEARCH: Much omega-3 research has focused on their effects on the cardiovascular system. In a study published in the October 18, 2006, issue of the Journal of the American Medical Association (JAMA), Harvard School of Public Health (HSPH; Boston) researchers noted that intake of fish or fish oil reduces total mortality by 17% and lowers the risk of heart disease by 36%. According to the HSPH researchers, fish’s benefits stem from its omega-3 content.
The HSPH study also suggested that omega-3s may improve brain development in children who obtain the nutrients through pregnant or nursing mothers. Similarly an analysis of the Avon Longitudinal Study of Parents in Children that appeared in the February 15, 2007, issue of the Lancet found that mothers who had a low intake of seafood were less likely to give birth to children with high motor, communication, and social development scores.
Scientists have also studied the effects of omega-3s on adult cognition. At the March 7, 2007, annual meeting of the American Psychosomatic Society (McLean, VA) in Budapest, researchers from the University of Pittsburgh reported that people with high blood levels of omega-3s tend to have higher volumes of grey matter in areas of the brain linked to emotional arousal and regulation. Moreover, a study in the November 2006 issue of Archives of Neurology concluded that participants with the highest blood levels of DHA had a 47% lower risk of developing dementia and a 39% lower risk of developing Alzheimer’s than participants with lower levels.
Omega-3s may have indications that extend beyond cardiovascular and cognitive health. But researchers exploring the potential effects of omega-3s on diabetes, inflammatory conditions, and cancer have turned up mixed or disappointing results. For instance, in a study that appeared in the September 20, 2006, issue of JAMA, scientists from the Karolinska Institute in Stockholm concluded that Swedish women who ate at least one serving of fatty fish per week lowered their risk of developing renal cancer by 74%, compared with women who never ate fatty fish. However, in a January 25, 2006, meta-analysis of 38 studies involving more than 700,000 people reported in the Journal of the National Cancer Institute, researchers found “little to suggest that omega-3 fatty acids reduce the risk of any single type of cancer.”
CONVENTIONAL WISDOM: Manufacturers launched a plethora of new supplements, foods, and beverages enriched with omega-3s in 2006, betting that the time was ripe to market DHA/EPA products with mass appeal. Moreover, a series of positive reports on omega-3s issued by the Agency for Healthcare Quality and Research (Bethesda, MD) in 2004 helped propel the ingredients into the scientific mainstream.
SUMMARY: Studies suggest that fatty fish and the omega-3 fatty acids DHA and EPA may have beneficial effects on cardiovascular and cognitive health, as well as overall mortality. However, much of the research is based on epidemiological studies that track fish intake, rather than prospective trials that test the effects of specific omega-3 fatty acids. New research should help provide more information about omega-3s, which are attracting a new audience thanks to improvements in manufacturing technology.
BACKGROUND: Multivitamins comprise the largest segment of the dietary supplement market. Until recently, health experts considered multis a nutritional safety net. A National Institutes of Health (NIH; Bethesda, MD) meeting in October 2006 challenged this assumption. Currently, nutritionists are at odds about multivitamins. Some advocate multis for specific micronutrients such as folic acid; B vitamins; calcium; and vitamins A, D, K, and E. Others believe far more research is needed to prove efficacy.
HISTORY OF USE: “Vital Amines” first appeared in 1913 when physicians began prescribing thiamin for beriberi. Food fortification began in 1924 when iodine was added to table salt to prevent goiter. By the mid-1930s, milk was fortified with vitamin D to stop rickets and flour was sold with thiamin, riboflavin, niacin, and iron. A decade later, Miles Laboratories introduced “One-A-Day” multivitamin tablets.
Today, one-third of all Americans take multivitamins. Most do so because they doubt their diet provides adequate amounts of essential nutrients. Nutrition cognoscenti tend to agree. The Harvard School of Public Health (Boston) believes “taking a daily multivitamin makes sense for most adults.” The American Dietetic Association (Chicago) feels multivitamins offer benefits for certain subsets of healthy people, including pregnant women, some vegetarians, and women of childbearing years.
RESEARCH: In 2006, NIH held a landmark conference concerning multivitamin use and chronic disease prevention. The conference reported that few high-quality clinical trials had been conducted to determine whether single-use or paired vitamins and minerals prevent chronic diseases, and fewer are generalizable to the U.S. population.
Since then, studies involving single vitamins regularly make headlines. The April 5, 2007, issue of the New England Journal of Medicine included a Harvard study that suggested distributing multivitamins, such as B complex, C, and E vitamins, to pregnant women could be a cost-effective way of reducing low infant birth weight—a significant risk factor for infant mortality and other afflictions like heart disease and diabetes. The study also showed better outcomes for HIV-negative women taking multivitamins, with an 18% decrease in low birth weight, defined as weights less than 5.5 lb, for those HIV-negative women taking daily vitamin supplements.
On February 28, the Journal of the American Medical Association (JAMA) published a meta-analysis that found a significant correlation between antioxidant supplements and all-cause mortality. The supplement industry sharply criticized the study’s methodology, particularly in the way studies were selected for the meta-analysis. However, the study highlighted the lack of clinical work involving vitamin combinations. “Right now, the term multivitamin encompasses hundreds, if not thousands, of products with varied content and dose of vitamins and minerals,” said Irwin Rosenberg, MD, university professor and director of the Nutrition and Neurocognition Laboratory at the Jean Mayer USDA Human Nutrition Research on Aging at Tufts University (Boston). “It’s really difficult to guide customers if we don’t even know what is in the vitamins they are taking. Standards would be helpful to both consumers and industry by rewarding those companies that do science-based marketing, rather than those that make unjustified health claims.”
CONVENTIONAL WISDOM: While the debate behind multivitamins heats up, marketers continue to meet demand for new products. Recent introductions include Bayer’s (Morristown, NJ) New Bayer Nutritional Science Daily Multivitamin Vital Body & Cells Formula with pomegranate and alpha-lipoic acid, Pharmavite’s (Northridge, CA) Nature Made Multivitamins with Optimized Nutrient Levels, and McNeil Nutritionals’ (Fort Washington, PA) Viactiv Multi-Vitamin Flavor Glides containing 24 vitamins and minerals, including vitamins A, C, D, E, K, B1, B2, niacin, B6, folic acid, B12, biotin, pantothenic acid, and calcium.
SUMMARY: People know that their diets lack essential nutrients. They also know they don’t have the time or the inclination to eat properly. Multivitamins are an inexpensive insurance policy. Americans will keep taking their multivitamins until a definitive study persuades them to stop. Meanwhile, watch for specific vitamins to be recommended for targeted applications, such as the recent findings with vitamin D and vitamin K.
BACKGROUND: Selenium is an antioxidant mineral that might offer protection against some forms of cancer. While most people obtain adequate amounts of selenium from water and food—especially seafood, meat, and nuts—some research suggests that poor soil quality in certain parts of the world may result in a selenium deficiency.
HISTORY OF USE: Selenium supplement use is common among men who are attempting to ward off prostate cancer. In a study published in the May 2004 issue of the British Journal of Urology International, more than half of the 333 men who filled out a 420-item questionnaire reported using supplements to prevent prostate cancer. While letter vitamins were the most commonly used supplement, about a third of the men also said they used minerals such as zinc, calcium, and selenium.
RESEARCH: Selenium’s potential cancer-protective effects may be related to the body’s levels of selenoproteins. According to a study that appeared in the May 23, 2006, issue of the Proceedings of the National Academy of Sciences, lower levels of selenoproteins are associated with faster cancer development in animals. In the study, the offspring of one mouse that was genetically manipulated to be likely to develop prostate cancer and another that had low levels of selenoproteins experienced accelerated cancer development. There are more than 25 selenoproteins in the body, but the study’s authors theorized that one, glutathione peroxidase, may be the most important.
National Institutes of Health (NIH; Bethesda, MD) researchers are currently working on the Selenium and Vitamin E Prevention Trial (SELECT), the most comprehensive study to focus on selenium’s possible cancer-preventive abilities. Launched in 2001, SELECT involves about 35,000 participants. NIH researchers divided the volunteers into four arms: one group received two placebos, one group received 200 µg of selenium and 400 IU of vitamin E, one group received 200 µg of selenium and a placebo, and one group received 400 IU of vitamin E and a placebo. The study is expected to continue through 2008.
CONVENTIONAL WISDOM: As with other antioxidant vitamins and minerals, studies involving selenium intake suggest that the ingredient is associated with improved health, but studies involving selenium supplementation have yielded mixed results. Interest in selenium should remain strong, however, due to the pending results of the SELECT trial.
SUMMARY: Selenium may offer men some protection against prostate cancer. However, much of the data that scientists have about selenium was gleaned from studies that did not focus directly on the mineral’s effects on prostate cancer. The results of the SELECT trial should help clarify what potential role, if any, selenium may have in cancer prevention.
BACKGROUND: A naturally occurring steroid hormone produced by the adrenal gland, dehydroepiandrosterone (DHEA) is a key component of many anti-aging supplements. DHEA levels normally peak when a person reaches their early 20s and later decline with age. Although DHEA, a precursor to testosterone and estrogen, is sometimes confused with anabolic steroids, it does not produce the same changes on muscle growth, and instead exerts only weak androgenic and estrogenic effects.
HISTORY OF USE: DHEA is popular among baby boomers who use it as an anti-aging supplement and to restore libido. Some studies suggest that DHEA may benefit elderly patients by supporting immune and cognitive function, maintaining bone health, and reducing fat mass. However, other studies show few if any positive effects on younger people.
RESEARCH: In a study published in the November 10, 2004, issue of the Journal of the American Medical Association, researchers from Washington University School of Medicine (St. Louis) gave 56 elderly people either 50 mg of DHEA or a placebo for six months and found that DHEA produced a significant decrease in both visceral and subcutaneous abdominal fat. The decrease in visceral fat ranged from 10.2% in women to 7.4% in men, while the decrease in abdominal fat was about 6% in both sexes. Noting the small size and duration of the study, the researchers called for larger, longer clinical trials.
Two years later, Mayo Clinic (Rochester, MN) researchers published the results of a more extensive trial in the October 19, 2006, issue of the New England Journal of Medicine (NEJM). In the NEJM study, researchers gave 154 men and women either DHEA, testosterone, or a placebo for two years. Men received 75 mg of DHEA or 5 mg of testosterone per day, while women took 50 g of DHEA and did not receive testosterone. The researchers recorded changes in body composition, physical performance, insulin sensitivity, and quality of life for two years and concluded that DHEA did not have an anti-aging effect or benefit quality of life.
However, according to the Council for Responsible Nutrition (CRN; Washington, DC), a trade group for manufacturers of dietary supplements, the study’s conclusions downplayed DHEA’s beneficial effects on bone mineral density and did not explore outcomes related to sexual performance. CRN also noted that the most important outcome of the study was that it demonstrated DHEA’s long-term safety.
CONVENTIONAL WISDOM: The Mayo Clinic study was well designed but unlikely to deter elderly consumers who want to feel younger. Because few safety concerns have been reported for DHEA, consumers and healthcare practitioners will probably wait for further studies before reaching a final verdict.
SUMMARY: DHEA may offer health benefits for elderly consumers, but clinical trial results have been mixed. Future research should clarify its effects and potential as an anti-aging supplement.
BACKGROUND: One of the most promising supplements for people with diabetes and metabolic syndrome may be chromium picolinate. Chromium picolinate has been studied extensively over the past decade and is a featured ingredient in many products marketed for blood sugar control.
HISTORY OF USE: Consumers use chromium picolinate for a range of applications, including blood sugar control, weight loss, and maintenance of cardiovascular health.
RESEARCH: Although scientists are still attempting to discover how chromium affects blood sugar levels, some research suggests that the mineral may enhance the activity of a protein related to insulin production. At the 18th International Diabetes Federation Congress (Paris) in 2003, researchers from the University of Vermont College of Medicine (Burlington, VT) presented the results of a study indicating that chromium picolinate affects insulin metabolism by enhancing the activation of Akt phosphorylation, which increases the uptake of glucose into cells.
A review of 15 clinical studies involving 1690 subjects published in the January 2007 issue of Diabetes Technology & Therapeutics found that chromium picolinate produced improvements in one or more measurements of diabetes management, such as fasting and postprandial glucose, fasting and postprandial insulin, glycated hemoglobin, and insulin sensitivity. Moreover, the review’s authors concluded that the high bioavailability of chromium picolinate might explain its beneficial effects on glycemic control.
Moreover, a placebo-controlled, double-blind trial of Diachrome, a supplement containing chromium picolinate and biotin, published in the December 2006 issue of Diabetes Technology and Therapeutics, found that the chromium and biotin combination improved blood glucose levels and cholesterol metabolism in overweight people with type 2 diabetes who also were taking diabetes medication. The trial, which involved 36 overweight people, lasted 30 days. The researchers are planning to publish the results of a larger, 400-patient, 90-day trial later this year.
CONVENTIONAL WISDOM: Diabetes is rapidly becoming one of the most significant health problems facing Americans and has already reached epidemic proportions. Because chromium picolinate appears to be safe, effective, and well-tolerated, it could turn out to be an inexpensive tool for weight management.
SUMMARY: More than 15 clinical studies support the use of chromium picolinate, and additional studies support the use of competing forms of chromium such as chromium polynicotinate and chromium chloride. While there are disagreements over which form is the most bioavailable, there is substantial agreement about chromium’s potential.
BACKGROUND: Many women seeking relief from menopausal symptoms such as hot flashes have turned to the herb black cohosh (Actaea racemosa and Cimicifuga racemosa). Herbal preparations extracted from the roots and rhizomes of black cohosh, a member of the Ranunculaceae family of plants, contain phytoestrogens that may mimic the effects of hormone replacement therapy (HRT). Some research suggests that black cohosh binds to human opiate receptors that regulate body temperature, pain, and appetite.
HISTORY OF USE: Black cohosh, which grows in the Eastern United States, was a staple of Native American medicine. While its use in North America diminished by the turn of the twentieth century, German doctors have prescribed it for decades. One popular black cohosh extract, Remifemin, has been in use since at least the 1950s.
RESEARCH: Considerable data exists to support the safety and efficacy of black cohosh. However, in 2006, a major study funded by the National Institutes of Health (NIH; Bethesda, MD) found the herb to be ineffective. Critics have offered several potential explanations for the NIH study’s negative results and conclusions. One of the largest studies to examine the safety of black cohosh appeared in the July 2003 issue of the Journal of the North American Menopause Society. The research, a comprehensive review of all available scientific literature on black cohosh, uncovered a low rate of adverse-event reports (5.4%), which were overwhelmingly minor (97%). Tieraona Low Dog, MD, lead author of the report, NIH advisor, and former member of the White House Commission on Complementary and Alternative Medicine, wrote that the review “should reassure health professionals that they can safely recommend black cohosh to their menopausal patients who cannot or choose not to take HRT.”
A newer study published in the January/February 2007 issue of the same journal also appeared to support the safety of black cohosh, at least in the short term. In that study, an open, uncontrolled, prospective trial, 65 women received 40 mg of black cohosh per day for six months. The researchers performed mammograms and also took percutaneous needle aspiration biopsies of breast tissue at the beginning of the study and after six months. After comparing the baseline and end-of-study data, the researchers concluded that none of the women experienced an increase in breast density or breast cell proliferation.
Another recent study on black cohosh appeared in the April 1, 2007, issue of the International Journal of Cancer. In that study, researchers compared the medical histories of 949 women with breast cancer and 1524 women in a control group. The researchers found that women who said they had taken black cohosh had a 61% lower risk of developing breast cancer, but they qualified the results by noting that black cohosh may produce side effects and influence breast cancer severity in animals. Moreover, the authors added that the contents and quality of black cohosh supplements on the market vary widely. According to the researchers, “Substantial additional research must be undertaken before it can be established that black cohosh, or some compound found in black cohosh, is a breast cancer chemopreventive agent.”
In 2006, a major NIH-funded study published in the December 19 issue of the Annals of Internal Medicine concluded that black cohosh did not relieve hot flashes in menopausal or perimenopausal women. The 12-month trial, known as the Herbal Alternatives for Menopause Study (HALT), divided 351 women aged 45–55 into five groups that received one of the following: a placebo, HRT, a multibotanical supplement and dietary counseling to increase intake of soy foods, a multibotanical supplement, or black cohosh. In the middle of the trial, data from the Women’s Health Initiative linking HRT to cardiovascular side effects prompted the researchers to give participants an opportunity to leave the HRT group. While the women in the HRT group reported experiencing an average of 4.6 fewer hot flashes than the women in the placebo group by the end of the study, the women in the other treatment groups did not see any improvement.
According to the American Botanical Council (ABC; Austin) and other botanical experts, however, the study’s conclusions were not representative of previous studies, which tended to report positive results. ABC suggested several potential flaws with the research. For instance, although the study involved a large number of participants, it also separated them into five groups, which diluted the statistical power of the trial. In addition, the supplements were not sealed in blister packaging that would have preserved their potency throughout the study. Critics also noted that some black cohosh preparations used in previous trials contained a 40 mg dose of an isopropanolic extract, whereas the preparation used in the NIH study contained a 60 mg dose of an ethanolic extract. According to ABC, the results of the NIH trial, while interesting, were not definitive and should be viewed within the context of the entire body of research on black cohosh.
CONSUMER TRENDS: Roughly 2 million women turn 50 every year, creating a huge potential market for black cohosh and other supplements that may offer relief from menopausal symptoms. The herb is the most widely used natural alternative to HRT, ranking eighth in retail sales for all single-herb supplements, according to 2005 data from Information Resources Inc. (Chicago). About 90% of women aged 40–60 who participated in a 2006 poll conducted by Stanford University researchers reported having experienced at least one menopausal symptom, and 37% reported using HRT. A slightly smaller number, 31%, reported using herbs to treat menopausal symptoms, while 13% said they used supplements. Roughly 75% of the women who had used HRT stopped because of concerns about adverse effects, and 55% of the women who had used herbal supplements said they chose the therapies because of concerns about HRT. The results of the poll appeared in the May/June 2006 issue of the Journal of the North American Menopause Society.
CONVENTIONAL WISDOM: Strong negative publicity created the NIH study may dent the popularity of black cohosh, at least in the short term. On the other hand, the herb has a long history of use and appears to work better than many other herbal alternatives. Future studies that address some of the concerns raised by ABC may also yield positive results.
SUMMARY: There are many black cohosh supplements on the market, and most contain varying amounts and forms of the herb, making it difficult for researchers to compare the supplements. While the NIH study raised questions about the efficacy of black cohosh, other studies support its use. Additional studies are needed to settle disputes about its efficacy.
Useful Online Resources for Healthcare Practitioners
• FDA Center for Food Safety and Applied Nutrition:
• National Center for Complementary and Alternative Medicine (NCCAM):
• Office of Dietary Supplements (ODS):
• Recalls and Safety Alerts:
• Medwatch Online Adverse-Event Reporting Form:
Health Claims for Dietary Supplements:
• List of Health Claims Meeting FDA’s Significant Scientific Agreement Standard:
• List of Qualified Health Claims:
• FDA’s Guide to Structure/Function Claims:
Supplement Research Databases:
• NIH Computer Access to Research on Dietary Supplements (CARDS) Database:
• International Bibliographic Information on Dietary Supplements Database:
• Dr. James Duke’s Phytochemical Database:
Natural Products Trade Associations:
• Council for Responsible Nutrition:
• Natural Products Association:
• American Herbal Products Association:
• American Botanical Council:
• ODS’s Annual Bibliography of Significant Advances in Dietary Supplement Research: