In earlier studies it was hard to tell which of the three species of the plant were used, but more recently there have been larger trials with well-derived preparations of the herb, and they have been negative on shortening the length of a cold or staving it off.
Bottom line: More studies are leaning toward that echinacea is not all that effective for the common cold, said Bauer. "The studies are conflicting, but most look fairly negative."
What it is: This tiny seed is an inexpensive plant-based source of omega-3 fats, but they are not the same exact omega-3s you would get by eating fish. Oils pressed from the seeds are either placed into capsules or sold as a liquid, yet, unlike consuming the food, they lack the beneficial dietary fiber as well as lignans, which are plant compounds that have estrogen-like activity and may protect against hormone-driven cancers.
What it's supposed to do: Grinding up the seeds and sprinkling them on cereals, salads, and cooked vegetables offers a good source of omega-3 fats in people who don't care to eat fish. "Flax might help keep you regular," explained Lee. And like fish oil, flax is believed to have anti-inflammatory activity. She often suggests ground flax to women with PMS and those with perimenopausal symptoms, and also to people with asthma.
What research suggests: There's less research on flax than there is on fish oil, even though they seemingly overlap in function, says Lee. Flax contains alpha-linolenic acid, a type of omega-3 found in plant foods, and its beneficial effects may not be as compelling as those from fish oils. In human trials, the evidence for any benefits to high cholesterol or triglyceride levels is mixed.
Bottom line: Lee endorses the use of buying whole flax seed, and grinding it up yourself. Ground flax is sensitive to light and heat, so she suggests keeping it refrigerated.
What it is: A plant containing several different species and thought to be an overall tonic for well-being.
What it's supposed to do: Ginseng is considered an adaptogen, meaning that it's an herb believed to help you fight off the stresses in the environment. It's also purported to increase stamina to help you perform better -- physically, mentally, athletically, and perhaps, sexually. The herb is also believed to help boost immune function.
What research suggests: Panax ginseng (also known as Chinese or Korean) is the best studied form, explained Rindfleisch. (There is also an American ginseng and a Siberian form, known as Eleuthero.) He considers the evidence for ginseng as so-so with most of the findings coming from small trials. Rindfleisch said ginseng probably helps with overall thinking, yet he warned that, in some people, the herb might rev them up. He would not recommend that men try it for a sexual problem, such as erectile dysfunction. American ginseng has been studied to help with blood sugar control in people with type 2 diabetes.
Bottom line: Rindfleisch said ginseng might be worth a try in people with chronic fatigue at a dose of 100 milligrams twice a day.