Phytochemicals, Herbs & Spices - Health and Performance vs. Toxic Effects

Herbs and spices have long been known and popular for enhancing flavor, color, and serving as preservatives in food. A relatively recent perspective is that they can also have medicinal value. However, is this mode of action even present? Are there risks? When considering the properties of herbs and spices, it is essential to keep in mind that we typically consume them in small quantities (physiological dose). Unfortunately, similar to other supplements, there are many who believe that the more of these spices one consumes, the better. However, the highly concentrated consumption can lead to toxic effects of the phytochemicals they contain. In some cases, this can result in serious, life-threatening complications.

More is not always better.
Excessive intake can cause toxic, life-threatening effects.

The special aspect of herbs and spices is the fact that they contain a variety of bioactive compounds. It is challenging to attribute a favorable effect to a specific part of them. There is consensus among nutrition scientists that the combination often makes the difference (often referred to as synergy), creating the effect in the human body. Not a single chemical substance is the miracle cure, but the environment in which it is found. Different substances support each other. Alone, one would probably not function in the same way without the others. Therefore, it must almost seem logical that individual, high-dose substances will never have the same effect as the spice used in cooking.

On the contrary, scientific studies have shown that some beneficial effects of herbs and spices can be reversed and/or lead to life-threatening conditions, especially when taken in large quantities. These can then have carcinogenic, neurotoxic, and gastro-toxic effects and may cause insomnia, headaches, palpitations, and blood pressure fluctuations.

The influence of processing on bioactive compounds
Baking in the oven, frying, and grilling significantly reduce the beneficial effects of herbs and spices.

Often, we read about the beneficial effects of certain substances. Sometimes it's a research study testing chemical compounds, sometimes it's a report highlighting a food that supposedly has special properties. When we talk about phytochemicals in herbs and spices, we also need to consider bioavailability. Can the body absorb these substances, and what happens when we metabolize them? Heat, mechanical impact, salt, water, fat... there are many ways to process and alter our foods, including herbs and spices and their phytochemicals. There is evidence that cooking methods like heating, frying, and grilling have the greatest impact. Additionally, it is believed that digestion also influences the effects of phytochemicals.

In the face of all these challenges - What are the benefits?

Herbs and spices contain phytochemicals. Many of these compounds act as antioxidants. Antioxidants have a protective effect by neutralizing free radicals (= harmful metabolic by-products) and protecting our cells from destruction. Przygodzka and colleagues (2014) investigated the antioxidant capacity of some spices and classified them as follows:

• High: Clove, Cinnamon, and Allspice
• Moderate: Star Anise and Nutmeg
• Low: Anise, Ginger, Vanilla, Fennel, Cardamom, White Pepper, and Coriander

In addition to their role as antioxidants, spices and herbs also possess anticarcinogenic, antibacterial, and anti-inflammatory properties. However, despite the abundance of scientific articles, researchers are cautious with recommendations due to many studies having poor design and significant methodological differences. Moreover, only a few studies have been conducted in humans, indicating that more research is needed to confirm the effects of phytochemicals.

Any benefits for athletes?
There is currently a limited number of high-quality scientific studies on the topic of herbs and spices in athletic performance. In recent years, phytochemicals, especially in the realm of polyphenols, have garnered interest.

Despite many popular claims about herbs and spices leading to a significant improvement in performance, the number of high-quality research studies on this topic is limited (but increasing). Studies vary in design and the dosage of individual compounds used, making it challenging to draw definitive conclusions.

However, there is a group of studies that has examined the effects of polyphenols on exercise and oxidative stress. Quercetin and catechins (e.g., green tea extract) seem to have beneficial effects in active individuals. The mechanism of action of turmeric is also better understood, and some extracts (e.g., pomegranate, Montmorency cherry, blackcurrant) are being investigated for their impact on sports. Additionally, honey is among the substances that have been well-studied, with suggested antioxidant, anti-inflammatory, and antimicrobial properties.

The evidence for polyphenol supplementation in athletes is not yet clear. Due to the various ways these compounds interact in the body, it is challenging to limit their effects solely to athletic performance. For now, it is better to obtain physiological doses through food, which is also a safer approach. However, athletes under high training loads (associated with high oxidative stress) might benefit from the antioxidant properties of polyphenols.

Further Reading

Opara & Chohan (2014) Culinary Herbs and Spices. Their Bioactive Properties, the Contribution of Polyphenols and the Challenges in Deducing Their True Health Benefits. DOI: 10.3390/ijms151019183

Przygodzka et al (2014) Phytochemicals of herbs and spices: Health versus toxicological effects. DOI: 10.1016/j.fct.2018.05.050

Sommerville et al (2017) Polyphenols and performance. A systematic review and meta-analysis. DOI: 10.1007/s40279-017-0675-5