Herbs and spices have been known for their use as flavoring, seasoning, coloring agents and preservatives. More recently, they have also been considered to possess medicinal value. But are there really any benefits? What about risks?

When we think about the properties of herbs and spices, we have to remember that we usually consume these in small quantities (physiological doses). Unfortunately  – similar to other dietary supplements – there are people who think the more they take of a spice, the better. However, overconsumption can lead to toxicological effects of the phytochemicals they contain. And in some cases the high dose of a substance can lead to severe, life threatening complications. 

What makes the properties of herbs and spices so special is the fact that they contain a range of bioactive compounds. It’s hard to deduce a beneficial effect to a single substance though. It’s well accepted among nutrition scientists that the combination (often referred to as synergy) of different compounds is the reason for the effect on the human body. Not one single chemical is the magic bullet, it’s the setting it’s found in. Different substances support each other. One probably wouldn’t work the same way without the others. Said that, it must seem obvious that a high-dose single-nutrient supplement will never have the same effect as the herb or spice used in cooking that contains the nutrient.

In contrast, research studies have actually shown that some beneficial effects of spices and herbs can be reversed and/or lead to life-threatening conditions, especially when they are consumed in large quantities. These then have carcinogenic, neurotoxic, and gastrointestinal toxic effects, and can cause side effects such as insomnia, headaches, rapid heartbeat, blood pressure fluctuations.

Often, we read about beneficial effects of certain substances. Sometimes it’s a research study that tests chemical compounds, sometimes it’s a report on a food that is thought to have certain beneficial properties. When we talk about phytochemicals in culinary herbs and spices, we also face the issue of bioavailability. Can the body absorb the substances and what happens when we process them? Heat, mechanical impact, salt, water, fat…there are many ways of processing and changing the properties of food, and with that also the properties of spices and herbs, and the phytochemicals they contain. There is some evidence that the cooking methods heating, frying and grilling have the most harmful impact on herbs and spices. It is also believed that digestion itself has an impact on the function of phytochemicals.

With all these challenges - What are the benefits?

Spices and herbs contain phytochemicals. Many of these compounds function as antioxidants. Antioxidants provide a protective effect by neutralizing free radicals (= harmful by-products of the natural metabolism) and protecting our cells from damage. Przygodzka and colleagues (2014) analyzed the antioxidant capacity of several spices and rated them as follows:

  • high: clove, cinnamon and allspice
  • medium: star anise and nutmeg
  • low: anise, ginger, vanilla, fennel, cardamom, white pepper and coriander

Besides functioning as antioxidants, herbs and spices also have anti-cancer, antibacterial and anti-inflammatory properties. But despite the high number of papers available scientists are careful with recommendations as many studies show poor study design and differ significantly in their methodology. Furthermore, only a limited number of studies has been done in humans, i.e. more research on certain phenolic compounds is needed to confirm the effects.

Despite many popular claims regarding herbs and spices and significant performance improvements, the number of available high-quality research studies is limited (but growing). Studies vary in design and dose of single phenolic compounds which makes it still difficult to draw clear conclusions.

There has, however, been a very interesting pool of studies that has investigated the effect of polyphenols on exercise and oxidative damage. Quercentin and catechins (e.g. green tea extract) were shown to have some beneficial effect in active people. The understanding of the actions of the polyphenol curcumin is on the rise and some extracts (e.g. pomegranate, montmorency cherry, blackcurrant) are being investigated in regard to exercise performance. Finally, also honey has been studies for many years and considered a substance with antioxidant, anti-inflammatory, and antimicrobial effects.

The evidence for polyphenol supplementation in athletes is still inconclusive. Due to the many different ways of action in the body, it’s also difficult to reduce the effect to solely exercise performance. For now a food first approach with physiological doses is still the safer approach although athletes during high-intensity periods (= high oxidative stress) might benefit from antioxidative 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