The do's and don'ts of foods whilst taking antibiotics

Your body is filled with microorganisms such as fungi viruses and bacteria. In fact, they outnumber human cells by 10 to 1. These microbes play an essential role in your health, making up the immune system and keeping you healthy across the body.

Your gut, otherwise known as your gastrointestinal tract, houses the most bacteria in your body. In the microbiome of the gut, there is a careful balance of the good harmless bacteria (lactobacilli) and the typically bad bacteria known as anaerobes. The ‘good’ bacteria in your gut has many roles. They help break down foods, supply energy, make vitamins, break down harmful toxins and protect your gut against any pathogens.

This means that the lactobacilli, alongside your immune system, work hard to keep the anaerobic bacteria at bay and keep your gut healthy. However, when you take antibiotics this balance is disrupted. This is because most antibiotics cannot discern between the ‘good’ and ‘bad’ bacteria, meaning the biodiversity of the gut flora is reduced overall and good bacteria can be targeted. This is known as dysbiosis.

This reduction of good bacteria during antibiotic treatment means the anaerobic bacteria can grow and lead to an upset stomach, with symptoms such as:

• diarrhoea
• constipation
• bloating
• peptic ulcers (stomach ulcers)
• abdominal pain

Thankfully, these common side effects can be reduced by adjusting your diet.

The most important thing to do is to eat a healthy, balanced diet while being on a course of antibiotics, as to fuel your body with the nutrients it needs, as well as provide healthy bacteria to the gut.

There are two types of nutrients that are good for your gut health: prebiotics and probiotics. Probiotics are living strains of bacteria that add to the population of good bacteria in your digestive system. Prebiotics, on the other hand, are specialised plant fibres that act as food for good bacteria to stimulate its growth.

Below are some foods that you should eat with antibiotics.

Fibre-rich foods

Dietary fibre, or roughage, is a plant-derived food that cannot be broken down by the enzymes in your digestive system. They have a multitude of health benefits such as weight loss and are very good for your heart health.

However, fibre is a great prebiotic and particularly good for gut-health. The lactobacilli feed off of fibre and produce metabolites called short-chain fatty acids (SCFAs), which reduces inflammation and improves metabolism. Fibre has also been linked to improved digestion, and is recommended if you’re suffering from constipation.

Foods that are rich in fibre include:

• whole grains - brown rice, oats and barley
• vegetables - broccoli, kale and cauliflower
• fruits - berries and apples
• legumes - beans and lentils

Polyphenols

Polyphenols are another type of prebiotic as they promote the growth of good bacteria. This is because polyphenol compounds travel through the small intestine without being absorbed, so gut bacteria in the large intestine are mainly responsible for breaking them down.

As well as gut health, polyphenols are powerful antioxidants which means they prevent the production of free radicals. Free radicals are chemical compounds that damage cells, and have been linked to many diseases. They also may contribute to heart health as they reduce the risk of high blood pressure and blood clots. They are also good for high cholesterol, as they are present in many foods that lower bad cholesterol levels.

Polyphenols can be found in a range of foods and spices:

• fruits - berries, blackcurrants, cherries, apples and plums
• vegetables - artichokes, chicory, red onions and spinach
• nuts - hazelnuts, walnuts, almonds and pecans
• cocoa powder and dark chocolate
• soybeans (e.g tofu)
• green and black tea
• cloves, peppermint and star anise

Fermented foods

Unlike the previous two nutrients, fermented foods contain probiotics which replace the good bacteria that has been killed off by antibiotics. Taking probiotics with antibiotics help to prevent any gut problems.

Not only do they promote gut health, probiotics are also good for heart health, mental wellness and some research even suggests that they are good for your skin.

Foods high in probiotics include:

• non-dairy yoghurts
• pickles
• sauerkraut - fermented cabbage
• kefir - fermented non-dairy milk drink
• kimchi - Korean side dish with cabbage as main ingredient
• kombucha - a fermented black or green tea drink
• miso - Japanese seasoning

You can also get probiotics in the form of supplements, since they are less commonly found in foods, and are often recommended to alleviate the side effects of antibiotics.

There are prebiotic supplements available, however you can easily get your prebiotic intake from adjusting your diet.

When taking antibiotics, it's important to avoid certain foods that can upset the balance of your gut bacteria or affect the efficacy of the antibiotics.

Foods to avoid on antibiotics include:

• grapefruit and grapefruit juice - contain compounds known as furanocoumarins which interfere with how the liver and intestines break down the medicine and filter out toxins
• processed, spicy or high-fat foods - can all irritate the stomach and cause stomach upset
• sugary drinks - excess sugar can feed certain types of bad bacteria
• dairy products - the calcium can reduce the effectiveness of the treatment course and worsen certain side effects

As most often advised, excess alcohol is rarely recommended by healthcare professionals. If you are unsure whether alcohol is safe to consume while on any treatment, you should always familiarise yourself with the medicine's patient information leaflet or ask a healthcare professional.

Excessive alcohol consumption can damage the gut lining and lead to gastrointestinal problems, as well as increase the chance of experiencing side effects.

Certain antibiotics should never be combined with alcohol, and some of the most commonly prescribed of those include, but are not limited to:

• doxycycline
• azithromycin
• erythromycin
• metronidazole
• amoxicillin
• penicillin

How long after antibiotics can you drink?

You may have to wait up to 3 days after your last dose of antibiotics. However, this is not the case for everyone and you should always consult your doctor or pharmacist before drinking alcohol.

Antibiotics can interact with the medicines you take and can alter their effectiveness. They can also cause adverse reactions when taken with certain other medicines.

Therefore, you should always inform your prescriber of all medicines you are taking when being prescribed a new treatment. This includes any over-the-counter medicines and supplements, to ensure they are safe to take at the same time.

You should also check the patient information leaflets of the antibiotics as well as the medicines you regularly take to make sure whether they’re safe to take together. However, your pharmacist or doctor will know if there is a potential reaction and whether the antibiotic is safe for you to take.