Here at Skeptic North, we’ve often been a sharp critic of those herbal remedies that are unable to withstand the scrutiny of science. Yet nature does indeed house many pharmacologically active compounds, and it stands to reason that some of them will have medicinal value. So today, we’re going to turn the tables and look at 5 herbal remedies that have held up well in repeated studies and are generally regarded as effective.
1) St. John’s Wort for Depression
If there’s one herbal medicine that consistently gets high marks for effectiveness, it’s St. John’s Wort as a treatment for mild depression. A 2008 Cochrane Review looked at 29 trials totaling over 5000 patients, including 18 comparisons with placebo and 17 comparisons with synthetic standard antidepressants, and found significant effects in both cases. The Natural Medicines Comprehensive Database indicates that St. John’s Wort is likely as effective as both first generation antidepressants (low-dose tricyclics) and the current generation of selective serotonin reuptake inhibitors like Prozac, Zoloft, and Paxil.
The National Center for Complementary & Alternative Medicine (NCCAM), the CAM research division of the US National Institute of Health, summarizes the science as follows:
There is scientific evidence that St. John’s wort may be useful for short-term treatment of mild to moderate depression. Although some studies have reported benefits for more severe depression, others have not; for example, a large study sponsored by NCCAM found that the herb was no more effective than placebo in treating major depression of moderate severity.
The American College of Physicians basically agrees, though are notably more cautious in their recommendation, pointing to the lack of standardization and the potential for adverse reactions with other drugs. Standardization is a concern with any natural medicine — preparations can vary widely, so it can be difficult to ascertain what the correct dose should be. As for adverse reactions with other drugs, the list is indeed long — in fact, Health Canada issued a special bulletin on the topic, cautioning against combined use with oral contraceptives, certain blood thinners, anti-epilepsy drugs, HIV medications, antidepressants, and a list of others. For patients not on other medications however, St. John’s Wort is reasonably well tolerated, with a list of side effects that doesn’t seem much worse than that of conventional antidepressants.
Of course the above only applies to St. John’s Wort’s use in treating depression. Like most natural medicines, it is often recommended for a much longer list of conditions, for which the evidence is not so compelling.
St. John’s Wort is probably not effective for
- Hepatitis C
- Irritable Bowel Syndrome
There’s insufficient evidence of St. John’s Wort’s effectiveness for
- Obsessive Compulsive Disorder
- Seasonal Affective Disorder
- Smoking Cessation
- Wounds & Burns
2) African Plum for Enlarged Prostate
Pygeum, an extract of the bark of a plum tree native to sub-saharan Africa, has good evidence of efficacy for reducing the symptoms of enlarged prostate. To be clear, we’re talking about benign prostatic hyperplasia (BPH) — common, age-related prostate enlargement — and not prostate cancer. If you have prostate cancer, note that conventional medical treatments have a 5 year survival rate of 96% and are by far your best bet. But if BPH is your problem, African Plum may be just the thing for you.
A 2002 Cochrane Review is positive but admits the lack of placebo controlled, larger trails. Since that time, one has been initiated and should be completed this year — the CAMUS trial, which will test both African Plum and Saw Palmetto, another BPH remedy which at this time has somewhat less good evidence. Still, the Natural Medicines Comprehensive Database lists it as “likely effective” and lists only nausea and abdominal pain as known side effects. So far, there are no known adverse reactions with other drugs.
It’s also worth noting the list of traditional uses for which pygeum has not been shown to be effective: for the treatment kidney disease, malaria, stomach ache, fever, madness, and as an aphrodisiac.
3) Horse Chestnut for Varicose Veins
Chronic venous insufficiency (CVI) is the inability for the veins to return all of the spent blood to the heart, and often results in swelling, aches, and varicose veins. The Cochrane Review for horse chestnut seed extract has been updated twice since it was first conducted, most recently in 2010, and continues to suggest that horse chestnut is effective at reducing the symptoms of CVI. While calling for better powered studies, the meta-analysis concluded that horse chestnut is “an efficacious and safe short-term treatment for CVI.”
NCCAM goes one step further, pointing to “preliminary evidence that horse chestnut seed extract may be as effective as wearing compression stockings.”
Of course, compression stockings don’t come with quite the list of side effects — from nausea & dizziness to kidney damage — that horse chestnut does. This shouldn’t be surprising considering that the raw seed is poisonous to humans — the medicinal extracts must remove the primary toxic constituent, esculin. While generally safe when prepared in this manner, it is still only recommended for usage terms of less than 12 weeks, which raises the question of its practical therapeutic usefulness, as CVI is typically chronic. Additionally, horse chestnut is unsafe for children (who, admittedly, don’t often suffer from varicose veins) and pregnant women (who certainly do) — as well as anyone taking anticoagulants/antiplatelets, anti-diabetes drugs, or lithium, with which it can interact.
Finally, the long list of traditional uses for which horse chestnut has not been shown to be effective: hemorrhoids, phlebitis, diarrhea, fever, enlarged prostate, malaria, dysentery, eczema, menstrual spastic pain, soft tissue swelling from bone fracture and sprains, complaints after concussion, cough, arthritis, rheumatism, skin ulcers, and lupus.
4) Red Yeast Rice for High Cholesterol
This is a pretty neat one. To quote Science Based Pharmacy:
Red yeast rice is created by fermenting rice with the Monascus purpureus yeast. What’s remarkable about this fermentation process is one of the by-products: A chemical called monacolin K is produced, which is chemically identical to the drug lovastatin (sold by Merck under the brand name Mevacor).
So there’s not really any question that it works — red yeast rice will yield the same cholesterol lowering effect as lovastatin for a given dose. Of course, the same problems with dosing plague red yeast rice as they do other natural medicines, i.e. how to determine the equivalent amount of red yeast rice required to match a standardized dose of lovastatin. This is not insignificant, as there’s simply no way for the consumer to know how much lovastatin is in a given preparation.
Of additional concern, the kidney toxin citrinin has been found in some red yeast rice products. On the flipside, there seems to be some evidence that a known side effect of statin drugs — the elevation of certain dangerous liver enzymes — is not present for red yeast rice. Whether this advantage will withstand better quality trials remains to be seen.
5) Feverfew for Migraines
Feverfew, a variety of chrysanthemum, is a traditional analgesic reputed to reduce both pain and fever. NCCAM summarizes the science as follows: “Some research suggests that feverfew may be helpful in preventing migraine headaches; however, results have been mixed and more evidence is needed from well-designed studies.” A 2000 Cochrane Review that looked at five trials encompassing 343 migraine sufferers came back inconclusive, though did support feverfew’s reasonable safety profile.
The Natural Medicines Comprehensive Database agrees, noting that “feverfew might be better tolerated than some conventional migraine drugs used for prophylaxis.” It calls feverfew “possibly effective,” stating that “there is some evidence that taking feverfew orally can reduce the frequency of migraine headaches and reduce symptoms of pain, nausea, vomiting, and sensitivity to light and noise.” But they also point out conflicts in the data, as well as typical herbal medicine dosing issues, such as the fact that “some feverfew tablet products can contain little or no feverfew.”
Prior to doing the research for this article, I had a vague sense that there were a relatively large number of effective herbal medicines, and was actually surprised by just how few ended up making the cut. Even coming up with a Top 5 list required some nuance (consider the weaker evidence for feverfew), and it would have been a considerable struggle to make it a Top 10 list — at least if we’re relying on science instead marketing and the wishful thinking of herbalists.
First, we need to subtract out those that work but come with an unacceptable safety profile (e.g. kava). Then those with early promise that failed to show significant effects in larger scale trials (e.g. ginko biloba). What we’re left with is a very short list of herbal remedies that are promising but need more research — Valerian for Insomnia, Hawthorn for Heart Failure, and Saw Palmettto for BPH. There may be a few others that I’ve missed (feel free to point them out in the comments), but it’s hardly the “Nature’s Pharmacy” that proponents of phytotherapy claim.
Which says less about nature itself than it does about a basic assumption held by herbalists: that nature is better at producing medicines than science.
It’s certainly true that nature is better at producing novel compounds that have therapeutic value, and a very large percentage of our pharmaceutical research is indeed naturally sourced. A recent paper by the National Cancer Institute found that:
…the utility of natural products as sources of novel structures, but not necessarily the final drug entity, is still alive and well. Thus, in the area of cancer, over the time frame from around the 1940s to date, of the 155 small molecules, 73% are other than “S” (synthetic), with 47% actually being either natural products or directly derived therefrom. In other areas, the influence of natural product structures is quite marked, with, as expected from prior information, the antiinfective area being dependent on natural products and their structures.
So the issue is not that nature doesn’t contain therapeutic remedies, it’s that they’re not often usable in their natural form — either because they’re not safe enough or not effective enough. Isolating and refining the active ingredient through the pharmaceutical development process allows us both to improve drug safety, and to better control efficacy through improved drug purity and more precise dosing.
Indeed, we’ve seen this even in our survey — in the long list of adverse drug interactions with St. John’s Wort, the poisonous nature of raw Horse Chestnut Seed, the kidney toxin in Red Yeast Rice. And these are the best of the best — the herbal remedies that have been held up to the light and passed. If the rest of them are less effective and less safe than these, how can anyone in good conscience make a general case for herbal medicine?