The Antiviral Benefits of Honey

Globally, the Covid-19 pandemic is reminding us of just how seriously viruses threaten human health, social cohesion, and economies. Against this backdrop, there is accumulating evidence that honeys, including some New Zealand honeys, display antiviral activity and have related therapeutic benefits.

Kia ora! Greetings from New Zealand. I’m Brenda Tahi, the CEO of Manawa Honey NZ, where we are cautious about claiming anything about the benefits of honey unless it has been the subject of robust published research. So we have reviewed research from across the world regarding the antiviral benefits of honey, and want to share with you a summary of what we have found.

So this article will cover:

• Honey and its Benefits
• The Study of the Antiviral Benefits of Honey
• Demonstrated Antiviral Benefits of Honey
• Other Benefits of Honey Relevant to Virus Infection
• Conclusion on the Antiviral Benefits of Honey

Bees produce honey from the floral nectar of plants or from secretions of other insects (such as for honeydew). The composition of honey is variable and depends mainly upon the floral source. Broadly, honey is a supersaturated solution composed mainly of fructose and glucose, from which honey gets its sweetness. Honey also contains proteins and amino acids, vitamins, certain enzymes (glucose oxidase, catalase), minerals, phenolic acids, and other minor components (Alvarez-Suarez et al. 2010).

Honey brings benefits in human health through its antibiotic, antioxidant, anti-fungal and antiviral properties. Honey’s antibiotic properties stem in part from hydrogen peroxide, the level of which varies in different honeys.

However, even when hydrogen peroxide is removed, some honeys still show antibacterial activity (Allen et al. 1991). In the case of Mānuka honey, the residual anti-bacterial stems from methylglyoxal.

For other honeys, the antibacterial and antifungal activities are also because of the osmolarity (solute concentration), low pH, phenolic acids, and flavonoids in honey (Watanabe et al. 2014). Some of these minor components in honey are also drivers of its antioxidant properties.

Increasingly it is viewed that some of these components and their properties also impart antiviral activity.

Viruses are very small particles of genetic material (either DNA or RNA) that are surrounded by a protein coat. They cannot reproduce on their own and replicate inside the living cells of infected organisms. Viruses infect a host by introducing their genetic material into the cells, hijacking the cell’s internal machinery to make more virus particles, and eventually killing the cells.

There are many kinds of viruses that infect humans: some cause serious illness, others do not, and some can even be beneficial. Examples of common disease-causing viruses are the common cold, influenza, chickenpox, human immunodeficiency virus (HIV), and cold sores (Herpes simplex).

Studies of antiviral activity use a range of approaches that give us differing levels of confidence that the results can be applied in human health. Most commonly, the studies of the antiviral benefits of honey have been done in vitro. These studies are done in a petrie dish or test tube in the laboratory, and not in a living organism.

For example, Watanabe et al. (2014), considered below, demonstrated in a controlled environment, that certain honeys have an inhibitory effect on the replication of the human influenza virus. This virus was grown in a mammalian cell line maintained in the laboratory.

Less commonly, the properties of honey is investigated in vivo, where the study involves the antiviral responses of a living organism to the honey. Rats are often used in such studies as a progression from in vitro research. The next stage in a research progression will then be in vivo studies that test the anitviral benefits of honey in clinical trials involving people.

We found and refer to both in vitro and in vivo studies in addressing the antiviral benefits of honey against specific viruses, to which we now turn.

Littlejohn (2009) found that:

• Mānuka honey appeared to be virucidal against HSV-1 and HSV-2 types, while the other honeys just stopped the development of these viruses.
• The virucidal activity did not appear to be only the result of methygloxal activity in mānuka honey.

French (2002) also showed Mānuka and other honeys limited HSV-1 and HSV-2 virus development in vitro.

Hashemipour et al. (2014) compared the effect of high grade Mānuka Honey and acyclovir dilutions on the HSV-1 virus type. Acyclovir ointment is a common treatment for Herpes simplex lesions. This study showed that mānuka honey and acyclovir had similar inhibitory effects on HSV-1 above certain concentrations.

Al-Waili (2004) showed that topical application in vivo of a multi-floral honey significantly reduced the recovery time of HSV lesions when compared with 5% acyclovir ointment. On the other hand, medical grade Kānuka applied topically did not reduce recovery time when compared with 5% acyclovir ointment (Fingleton et al. 2014; Semprini et al. 2019).

This virus causes chickenpox in young people and shingles in adults. The virus multiplies in the lungs and causes a wide variety of symptoms including serious ones later in life. The survival of the Varicella-zoster virus in cultured cells declined with concentration of both a clover and mānuka honey (Shahzad and Cohrs 2012). The authors argued that the antiviral activity was most likely due to nonspecific osmotic actions of the sugars.

Rubella is a contagious disease caused by a virus that is also known as German Measles. Rubella mostly affects children, and results in a widespread, non-specific rash and swollen lymph glands.  It’s usually mild in kids, but it can be serious in pregnant women, where, it can cause miscarriages and birth defects.

Zeina et al. (1996) added a Tunisian honey and a thyme extract, at a range of concentrations, to a cell culture. These authors used Rubella virus, from a stock used to manufacture vaccine, to inoculate cell cultures while retaining untreated controls. Honey killed the virus at all concentrations, while thyme did not (Zeine et al. 1996). These authors suggest that it is a combination of compounds found in honey that is responsible for the antiviral activity.

This virus is common, and causes infections of the lungs and respiratory tract. Infections with this virus can be serious in babies and anyone with heart and lung disease or weak immune systems. A type of respiratory syncytial virus was cultured in cells and treated with three different mānuka honeys, as well as a rewarewa, honeydew, and clover honeys (Zareie 2011).

All honeys had an inhibitory effect on the development of the infection in vitro, but not when the cell cultures were pre-treated with honey. This suggests a direct effect on the virus rather than on the cells (Zareie 2011). The mānuka honey with the highest non-peroxide activity displayed a much greater inhibition than the other honeys.

Importantly, the development of ways to administer honey solutions into the lungs means that antiviral activity by honey could potentially be used as a therapy for respiratory syncytial infection (Al-Waili 2003).

Some honeys provide therapeutic benefits beyond antiviral activity before, during and after viral infections. A few of the key viral infection relevant therapeutic benefits demonstrated for honeys are considered below (e.g., Molan 2001; Alvarez-Suarez et al. 2014; Pasupuleti et al. 2017).

A weak immune system can lead to viral infections and limit the recovery from infections. There is increasing evidence that honey can stimulate the body’s immune system to fight infections. In cell cultures honey stimulates certain types of white blood cells that activate the immune system (Manyi-Loh et al. 2011).

There are also reports of the stimulation of certain proteins as cell “messengers” that activate immune responses to infection. Moreover, honey boosts the energy production in macrophages (white blood cells) making them more effective in their job to kill infectious micro-organisms (Molan, 2001).

When viral infections weaken the immune system there is a reduction in the body’s ability to clear bacterial infections. Significant antibacterial activity has been demonstrated in vitro for many honeys although this is highly variable. There is also clinical evidence that the antibacterial activity of various honeys can achieve therapeutic benefits (Molan 2001). Mānuka honey, has attracted the attention of the international scientific community for its biological properties, especially for its wide-ranging antimicrobial activity (Carter et al. 2016).

Viral infections can result in, or compound, bacterial infections that can also be treated with honey. For example, bacterial infections can increase wound size and the development of ulcers and abscesses. Honey stimulates wound-healing effectively, even in wounds that do not respond to antibiotics (Alvarez-Suarez et al. 2014).

Oxidative stress can be brought on by excessive or prolonged inflammation resulting from viral infections. Anti-oxidants can assist in coping with oxidative stress, and honey has benefits for this purpose.

A survey of free radical inhibition (anti-oxidant activity) by New Zealand honeys found much variation within and between species, although Rewarewa Honey was relatively consistent with high levels of inhibition (Molan 2012). Honey has also been shown to:

• reduce oxidative reactions in the human body by scavenging free radicals (Gheldof et al. 2002)
• have the potential to exert an antioxidant action by inhibiting the formation of free radicals in the first place (Molan 2001).

Inflammation is the body’s immune system’s response to an irritant such as a virus. When the inflammation is excessive or prolonged it can prevent healing or even cause further damage. The anti-inflammatory properties of honey have been well established and they are free from adverse side effects (Molan 2001; Manyi-Loh et al. 2011).

In a New Zealand example, the inhibition of free radical production was determined in 21 honeys including 14 mānuka, four kānuka, one rewarewa, and one mānuka-kānuka honey. The four kānuka and single rewarewa honeys exhibited the highest in vitro dose-dependent activities, with mānuka being variable (Leong et al. 2012).