Lost in Spice

Throughout recorded history, spices and herbs have been valued for their culinary properties and curative powers. The U.S. Dept. of Agriculture projects that consumption of these dried, aromatic plant parts in the United States in 2007 will exceed 1.05 billion lb (about 3.5 lb/person), an approximately 5% increase over 2004.

The United States is the largest importer of these food flavor and texture modifiers. Vanilla beans, black and white pepper, capsicums, sesame seed, cinnamon, mustard, and oregano represent the largest portion of spice imports.

The rising domestic use of spices may reflect both a trend toward use of spices to compensate for lower salt and fat levels in foods, and heightened popularity of ethnic foods from Asia and Latin America.

The potential health benefits of spices and herbs have sparked basic studies to identify bioactive components and clinical research to assess mechanisms and dose relationships.

Nearly 70 clinical studies have yielded inconsistent results relative to cardiovascular health assessed by reduction of plasma cholesterol or modulation of lipoproteins. A recent study (Gardner et al., 2007) in which 192 moderately hyperlipemic adults consumed a 4-g clove of raw garlic/day 6 days/week for 6 weeks demonstrated no significant effects on LDL-cholesterol levels.

The overarching problem may be one of dose response; indeed, the classical definition of a spice is a dried seed, fruit, root, bark or other vegetative substance used in nutritionally insignificant quantities for the purpose of flavoring.

Even in small doses, phenolics and flavonoids—possible antioxidants in a variety of herbs and spices such as oregano, marjoram, dill, coriander, basil, thyme, and even garlic—may affect one or more stages of cancer processes. Instead of the typical antioxidant function, such as superoxide sequestrant, the innate phytochemicals or their metabolic products may modulate various enzymic activities, including phase I and phase II detoxification systems responsible for inactivation of some carcinogens.

Similarly, some extracts of curcumin, ginger, capsaicin-laden peppers, lavender, cherries, and mint exhibit natural anti-inflammatory activity in animal models, in-vitro cell cultures, and mutagenicity studies, yet the clinical relevance of these findings to cancer, especially at typical human consumption doses, remains uncertain. Nevertheless, these results are intriguing and suggest a potential chemopreventative role for herbs and spices.

A wider and even more precise definition of spices that acknowledges certain dose ranges for certain compounds might be "pharmacologic foods." This discussion may dovetail with that of functional foods as we struggle to classify what we consume according to possible health benefits.

Several small clinical studies among adult diabetics assessed the impact of ginseng on postprandial blood glucose and glycosylated hemoglobin A_1c, a robust indicator of elevated plasma glucose. We are reminded that the anti-diabetic drug metformin (Glucophage^®) used in the treatment of diabetes was originally isolated from lilac.

More recently, evidence on the relationship between blood glucose and large doses of cinnamon among moderate diabetics provided intriguing but not convincing evidence that this spice may blunt a postprandial glucose response. In-vitro studies with cloves, bay leaves, and turmeric may have a similar response by up-regulating insulin receptor phosphorylation, thus improving cellular uptake of glucose and increasing glycogen synthesis.

Again, while these small clinical trials are intriguing, and the in-vitro studies interesting, larger studies with defined endpoints and dose relationships must be conducted to assess the value of herbs and spices in combating diabetes.

Many medications that have been accepted as standard-of-care in the industrialized countries, such as opium, aspirin, digitalis, and quinine, have a long history of herbal origin. The use of herbs and spices to treat or prevent is almost universal among non-industrialized societies.

Some countries make direct recommendations on consumption of herbs and spices and advocate their health-promoting properties. However, really compelling clinical evidence that supports the notion of health benefits of specific herbs and spices at dose ranges consistent with regular use as part of a healthy diet remains elusive.

by Roger Clemens, Dr.P.H.,
Contributing Editor
Special Projects Advisor, ETHorn, La Mirada, Calif.
[email protected] 

by Peter Pressman, M.D.,
Contributing Editor
Attending Staff, Internal
Medicine, Cedars-Sinai Medical Center, Los Angeles, Calif.
[email protected]

References