Anouk Frieling, MSc Equine Sciences, BSc (Hons)
Turmeric, also known as the golden spice due to its yellow colour, is an equine supplement that is commonly used due to its supportive functions in the body. For many years turmeric has been used as a health product for humans to soothe health issues such as abdominal pains, sinusitis, sprains and swellings. Turmeric has also been shown to have anti-inflammatory, anti-parasitic and antimicrobial effects in humans. More recently, research studies have evaluated the beneficial effects of turmeric supplements in equine nutrition. Therefore, this article will focus on the composition, bioavailability and health benefits of turmeric as an equine supplement.
COMPOSITION OF TURMERIC
The spice turmeric originates from South Asia and is a rhizome of the Curcuma longa plant (Ali et al., 2014), which is related to the ginger family (Gupta, et al., 2013b) (Figure 1). For humans the spice is distributed in many forms such as ground turmeric powder (loose or in capsules), turmeric extract, turmeric tea and turmeric oil and is also often used for cooking purposes. Turmeric supplements for horses are mainly distributed in the form of turmeric powder or oil and are ingested orally. Not every horse is instantly fond of the bitter taste of turmeric powder and therefore the powdered form of turmeric should be introduced gradually in the diet so that the horse can get used to the taste. Currently 235 different compounds in turmeric have been identified through research (Li, 2011). From these 235 components, curcuminoids (part of the diarylheptanoids components) have been recognised as the active components (Meng et al., 2018). Turmeric contains three types of curcuminoids: curcumin, demethoxycurcumin and bisdemethoxycurcumin (Kotra et al., 2019).
Figure 1. Turmeric is a rhizome from the Curcuma longa plant. Turmeric owes its yellow colour to the curcuminoid curcumin, which is one of the composites in turmeric. Due to the yellow/golden colour of turmeric and the many beneficial functions it is also known as ‘the golden spice’
All three curcuminoids have been studied separately to gather better understanding about their function in the body. Demethoxycurcumin and bisdemethoxycurcumin have shown to have anti-cancerous properties in humans (Yodkeeree et al., 2009). Curcumin is the main active component and the most abundant curcuminoid, comprising 2 to 5% of turmeric. It is also the component that gives turmeric its bright yellow colour (Gupta et al., 2013a).
TURMERIC BIOAVAILABILITY
Both turmeric in its whole form and extracts of curcumin have poor bioavailability and therefore only a small portion of the ingredient will be directly absorbed in the small intestine that can be used for biological activities (Shishu & Maheshwari, 2010; Aller, 2019). Besides poor bioavailability, turmeric and curcumin become unstable at a physiological pH, are insoluble in water, are absorbed very slowly by body cells and are rapidly metabolised in the body (Siviero et al., 2015). Studies have compared the individual bioavailability of whole turmeric and curcumin extract. Turmeric had a greater significant effect on pro-inflammatory genes and feeding turmeric resulted in a higher level of curcumin in the digestive tract than when feeding a curcumin extract, suggesting that turmeric is more stable and bioavailable (Martin et al., 2012). Turmeric is curcumin's precursor and therefore consists of multiple components, as mentioned before. These other components, in combination with curcumin, are more resistant against rapid metabolisation in the body, which explains why whole turmeric is more bioavailable (Martin et al., 2012). Even though turmeric has a higher bioavailability than curcumin extract, there has been an interest in increasing the bioavailability of turmeric to improve the effects of supplementing this spice. A common ingredient that is added to turmeric and increases bioavailability is piperine, the active component of black pepper (Figure 2). Shoba et al. (1998) found that supplementing a combination of curcumin and piperine to rats, increased blood curcumin levels compared to levels after only supplementing curcumin. Adding lipids, such as linseed oil, has also shown to have a positive effect on the bioavailability of turmeric (Chang et al., 2013; Mohammed et al., 2021). Therefore, it is commonly advised to feed oils in combination with turmeric to the horse to optimise the supplement's effect.
EFFECTS OF TURMERIC SUPPLEMENTATION ON THE HORSE
Turmeric has been used for many years as a health product for humans and more recently is also distributed as an equine supplement as research in horses has analysed and evaluated the positive effects of turmeric. For example, turmeric supplementation has been associated with the reduction of gastric acid in the stomach which causes gastric ulcers in horses (Fletcher & Gough, 2019).
Figure 2. To increase bioavailability studies have analysed the effects of adding piperine and lipids. Both have shown to improve the bioavailability of turmeric and curcumin
Fletcher & Gough (2019) demonstrated that supplementation of 20 grams of turmeric powder, to adult horses weighing about 500kg, reduces severe gastric ulcers caused by dietary change and does not create or worsen them. As mentioned before turmeric has an effect on proinflammatory genes (Martin et al., 2012). Turmeric reduces the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β), which are related to osteoarthritis and therefore supplementing turmeric works positively for horses with joint issues (Farinacci et al., 2009). Due to reducing inflammatory responses, turmeric may also provide pain relief to horses that suffer from osteoarthritis. In humans turmeric has also shown to have anti-parasitic purposes. Unfortunately, studies have not been able to confirm the same effect after supplementation to horses (Wuest et al., 2017).
Supplementation of turmeric has also shown to have an effect on the microbiome abundances of rats (Han et al., 2020). Rats are small hindgut fermenters and share similar microbiome abundances with horses (Han et al., 2018). For that reason, there has been an interest to study the effect of turmeric on the hindgut of the horse. Results of the small number of studies suggest that turmeric alters caecal characteristics such as the total volatile fatty acid production (VFA) (Bland et al., 2017). Future research is needed to be able to identify the effect turmeric has when it reaches the hindgut and the microbiome.
SUMMARY
Turmeric has been an established supplement for human consumption and has become a popular equine supplement in recent years. The working component of turmeric is curcumin. Both whole turmeric and curcumin extract have poor bioavailability. Research has shown that combining turmeric and curcumin with black pepper, piperine or lipids increases this bioavailability and therefore allows the supplement to work optimally. In humans turmeric has shown to have many beneficial effects. The equine supplement is primarily known for its anti-inflammatory properties and ability to reduce gastric acid in the stomach. There is an interest to further analyse the effect of turmeric on the hindgut and further research will be needed to measure these effects.
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