Immune Support

30 capsules |1 month's supply

Dr Sasivimol Ahmed PhD, PG Dip (Personalised Nutrition), BSc (Food Science)
A personal favourite of mine! I use it daily and all year round, it's perfect for those with busy and demanding lifestyles; especially helpful during the winter months.
Dr Sasivimol Ahmed
Dr Sasivimol Ahmed PhD, PG Dip (Personalised Nutrition), BSc (Food Science)

Who is it for?

Immune Support is a 2-in-1 supplement with 5 billion scientifically proven Lactobacillus paracasei CASEI 431 and Vitamin C.

FREE UK delivery on orders over £40.

UK express - Monday to Friday delivery.

See our Delivery & Returns for more information.

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  • Vegan


  • No dairy

    No dairy

  • Gluten free

    Gluten free

  • No added sugar

    No added sugar

  • During pregnancy

    During pregnancy

  • Artificial colour free

    Artificial colour free

Key benefits

Friendly bacteria with Vitamin C for the immune system

A supplement with added Vitamin C designed for those wishing to support their immune system. This strain has been extensively researched in thousands of people and is recommended for daily use. It is suitable for those aged 4 years onwards.

  • Digestive supplement Optibac Immune Support contains 5 billion live cultures of the strain L. paracasei CASEI 431®, which complements the natural gut bacteria
  • Extensively researched friendly bacteria strain L. paracasei CASEI 431® has been studied in over 20 scientific trials
  • Contains 100% NRV of Vitamin C Vitamin C supports a healthy immune system and helps reduce tiredness and fatigue.
  • Scientifically proven supplement High quality friendly bacteria shown to reach the gut alive
  • For daily use High-quality, daily immune support in just one easy-to-swallow capsule
  • Natural and vegan Vegan, dairy free and gluten free, with absolutely no artificial flavourings or colourings
  • From the UK's most recommended brand Optibac is the brand of friendly bacteria supplements most recommended by UK consumers

Optibac Probiotics strains

  • Lactobacillus paracasei CASEI 431®

Added nutrients

  • Vitamin C
See full ingredients list

General digestive


Complements gut bacteria

Customer Reviews

Customer reviews have been collected on our website or independently through Trustpilot where no moderation is possible. Reviews are not endorsed by us and should not be regarded as medical or health advice. For supplement advice, you can speak to one of our qualified experts. The top 3 reviews have been selected from our website, please click view all to explore more customer feedback.

Help & advice

Our team of qualified experts are available for free personalised supplement advice. If you're not sure where to start or your needs have recently changed, please get in touch.

Louise Mason
Louise Mason BA(Hons) DipCNM Nutritional Therapist, DipCNM Naturopath, mANP

Why choose us?

We are the UK's most trusted & recommended brand of friendly bacteria supplements as determined in an independent survey of 1000 people 

We use the most researched strains of friendly bacteria in the world with each supplement designed to target individual needs and life stages.

  • How to use

  • Ingredients

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  • Delivery & returns

  • How to use

    Recommended use

    Immune Support can be given to adults and children, from 4 years onwards, with the following recommendations:

    • For best results take 1 capsule daily with food, preferably with breakfast, or as professionally directed.
    • For those unable to swallow capsules, open and mix contents with cool drink/food.
    • May be used on an ongoing basis

    Storage instructions

    • For best results, do not remove desiccant sachet from the glass jar and close lid firmly after each use.
    • Store in a cool, dry place below 25°C and out of direct sunlight. For maximum potency, can be refrigerated after opening.


    Live cultures are not recommended for those with serious medical conditions e.g. those who are severely immunosuppressed, have pancreatitis, are in the ICU, have melaena, have a central venous catheter, short bowel syndrome, or patients with open wounds following major surgery; unless under a doctor's care. Keep out of reach of children.

    Gut health supplements are not intended to prevent, treat or diagnose any medical conditions. If taking probiotic supplements for gut health, note that these should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. If you are taking any medications or have a serious medical condition, consult a doctor before use. Optibac supplements will not cause dependency and may be used on an ongoing basis.

  • Ingredients


    Vitamin C (80mg, 100% NRV*); stabiliser: maltodextrin (natural source); vegetarian capsule: hydroxypropyl methylcellulose; Live cultures: Lactobacillus paracasei CASEI 431®; anti-caking agent: vegetable magnesium stearate.

    Each capsule guarantees 5 billion micro-organisms.

    *Nutrient Reference Value.


    • Vegan
    • Vegetarian
    • No dairy
    • Gluten free
    • No added sugars
    • Yeast free
    • Free from artificial flavourings, colourings and preservatives
    • No chemicals or parabens
    • GMO free
    • Suitable during pregnancy
    • Suitable during breastfeeding

    Following the taxonomic updates published in April 2020 which are intended to be adopted globally, this strain may now also be referred to as Lacticaseibacillus paracasei subsp. paracasei CASEI-431.

    Format Capsule
    No. Live Cultures 5 billion
    Added Ingredients Vitamin C
    Recommended Use 1 capsule daily
    Age Range Adult
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  • Delivery & returns

    UK Delivery

    Free UK Delivery over £40 
    Free standard UK delivery is automatically applied at the checkout when you spend £40.

    Standard 2nd class: £2.50
    Allow 4-10 working days (Monday - Friday) for delivery 

    1st class: £3.95
    Allow 1-3 working days (Monday - Friday) for delivery 

    Express Next Day, order before 2pm (Tracked): £6.95 
    Allow 1-2 working day delivery to most of the UK*. Orders placed on Friday will be delivered on Monday (next working day). Requires signature.

    Shipments will be dispatched via DHL or FedEx, the service will be selected depending on the delivery location.

    *Express delivery may exclude the Channel Islands, Herm Island, Isle of Man, Isle of Wight, Northern Irish postcodes BT18 & upwards, Sark, Scottish borders and offshore and a small number of remote mainland destinations as determined by our delivery courier. 

    Good to know

    • We'll send you an email to confirm once your parcel has been dispatched.
    • For delivery queries, please call us on +44 (0)1264 339 770 or email
    • Orders placed before 2pm are typically dispatched on the same working day.
    • Delivery within the UK and Northern Ireland has a fixed price, regardless of the size and weight of your order. 
    • Delivery times are estimates and not guaranteed unless otherwise stated.

    International Delivery

    We offer an excellent worldwide delivery service. For more details, please take a look at our delivery FAQ.


    If you have changed your mind, you can return goods, at your cost, unopened within 14 days for refund or exchange, this does not affect your statutory rights.

Customer Questions

All questions answered by probiotic experts Dr Kate Stephens PhD (Food and Microbial Sciences) BSc(Hons) Medical Biology and Helen Morton BSc (Hons) DipION Nutritional Therapist

Yes! It’s not possible to overdose on live cultures supplements as your gut naturally contains trillions of friendly bacteria. Friendly bacteria have been researched for decades, and daily use is both safe and recommended, without risk of dependency or overdose1,2,3.

Read references

Various factors affect immunity, including cold weather or stress, but you can do things to help support your immune system. Eat plenty of fruits and vegetables, limit alcohol intake, get a good night’s sleep, exercise daily, wash your hands properly, and consider taking a supplement like Optibac Immune Support, which is designed to support the immune system during the winter cold and flu season.

Choose highly researched immunity supplements containing ingredients like Vitamin C, proven to support a healthy immune system and your body’s resistance to infection. Optibac Immune Support contains 100% of your daily requirement of Vitamin C, along with one of the world’s most researched1 bacterial strains, Lactobacillus paracasei CASEI 431®.

Read references

Vitamin C and friendly bacteria supplements for immune support are generally safe for daily use by everyone, including children (from 1 year) and older people1,2,3. However, they may not be appropriate for adults or children who are immune-compromised – read our safety information for more details. If you have a serious health condition, speak to your doctor before taking any supplement.

Read references

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