Some herbs are standardized for a certain level of an active compound, meaning they've been processed in a way that isolates and measures the key constituent or constituents — something that makes it a whole lot easier for consumers to know what they're buying. However, the issue of standardization is fairly controversial.

Medicinal herbs that are sold in Europe are typically standardized to contain a certain amount of the constituent responsible for their therapeutic effect, also known as the active ingredient or marker. Thus, milk thistle (Silybum marianum) is standardized for silymarin, the compound that seems to be behind its medicinal effects.

Standardization makes sense for several reasons. From a quality-control standpoint, it allows manufacturers to ensure consistency of their products from batch to batch. It also guarantees that the product contains a therapeutic dose of the medicinal ingredients that made you want to buy it in the first place.

Ideally, the compounds that are used for standardization would be the ones that are responsible for the herb's beneficial effects. In this way, every time you bought an herb in 250 mg capsules, you'd know exactly how many milligrams of the active ingredient you were getting and what effects you could expect.

But in the majority of cases, the exact compounds that are producing the effect is unknown, meaning you can't know which ones to pick for standardization. In many cases, we also don't always know what other compounds, or cofactors, must be present in order for the active constituent to do its job.

Consider Saint John's wort (Hypericum perforatum), one of the most popular and well-researched herbs around. Scientists continue to debate over which of the plant's many chemical constituents (there are about sixty) is or are responsible for its medicinal effects. A few years back, everyone seemed to agree that it's the hypericin, and commercial products standardized for hypericin started appearing. Then researchers began to wonder if another chemical, hyperforin, was the real active ingredient. As of this printing, the jury is still out.

What's more, the practice of standardization itself isn't exactly standardized. Different U.S. manufacturers standardize for different amounts of marker compounds and use different methods of testing.

Meanwhile, many herbalists and natural health practitioners advocate using extracts of the whole herb (or the whole herb part, such as the root) instead of any isolated components. These are called crude extracts. Aside from the question of picking the right ingredient to isolate, they argue that this is the best strategy because herbs have been used for centuries as intact organisms, not individual chemicals, and there's evidence that the various constituents in herbs work together synergistically.

Unfortunately, this isn't an ideal solution, either. Because there can be such disparity among crops of plants, there can be enormous variation among their crude extracts — meaning some batches may have higher levels of active constituents than others.

Right now, the best approach seems to be using standardized crude extracts wherever possible. This means you're getting the whole herb and all of its components but are ensured of getting a therapeutic dose of the active ingredient (or at least the ingredient that seems to be the active one). For more on buying herbal preparations, see Chapter 18.