I recently read a piece in the newspaper - a little AP notice saying that a decade after the government embarked on a massive effort to study herbal remedies, there has been little positive news. The "lone exception" cited in the article is the suggestion that ginger may alleviate nausea caused by chemotherapy.
But that doesn't really tell the whole scientific story of herbal remedies. Sure, the popular (and lucrative) herbal remedies have generally not lived up to their reputation in clinical studies. The placebo effect is strong with us, but seems to be the main benefit of such.
However, the herbal remedies the AP article is referring to are hardly the whole story of herbal medicine. Many herbs have potent medicinal effects affirmed by studies. Cilantro does interesting things with heavy metals; cinnamon affects blood's cholesterol and glucose balances; turmeric (the orange spice that gives curry powder and many curries their distinctive yellowness) plays a role in suppressing histamines. Garlic really does have an impact on the immune system's behavior.
Willow bark does indeed alleviate pain, and also has potentially beneficial cardiac effects - you've probably taken a concentrated form of the same chemical, marketed under the name of aspirin. Camellia sinensis and coffea arabica share a remarkable effective stimulant chemical released when parts of the plants are steeped in hot water - caffeine.
So when I read that article, I thought to myself that it overstated the case. There certainly are herbal remedies that work. There may be many, such as echinacea, which fail to live up to the hype of their fans under scientific scrutiny, but even if the government-funded studies in question picked out only one significant effect, the things you put in your food will affect the systems of your body.