Guide to Ester-C®

Ester-C® is a fat-soluble patented form of vitamin C which has a different composition to regular vitamin C supplements. Standard vitamin C supplements contain ascorbic acid and can sometimes cause stomach upsets in people who have sensitive guts.

Ester-C® is more easily absorbed and stored by the body for longer than its non-patented counterparts, it doesn’t contain ascorbic acid, is pH-neutral and therefore less likely to cause stomach upsets. The supplement is made up from calcium ascorbate (a calcium and vitamin C combination) and is designed to get vitamin C into blood cells fast and stay there for up for 24 hours. It is argued this delivery system gives the immune system 24/7 support.

Dr Sarah Brewer says: ‘Vitamin C plays a crucial role in supporting the immune system. It’s needed to maintain healthy skin; cartilage; teeth and gums; bone and blood vessels. It is also a potent antioxidant used to protect the body’s cells from oxidative damage, and helps to increase the absorption of iron. Ester-C® is particularly beneficial for those who find it difficult to tolerate acidic supplements or foods.’

What does Ester-C® do?

Ester-C®is a fat-soluble form of vitamin C that can be stored in the body’s tissues for up to 24 hours, unlike standard vitamin C which is water-soluble and doesn’t stay in the body for long. Ester-C® has also been shown to enter the white blood cells in the immune system faster than normal vitamin C supplements.

Increased absorption

Ester-C® may enable the body to absorb ascorbic acid more efficiently. A study featured in the publication Advances in Therapy compared differences between Ester-C® and regular vitamin C supplements in 15 men, six of whom were heavy smokers (smoking is known to deplete levels of vitamin C).

After 24 hours, all participants taking Ester-C® had a significantly higher concentration of vitamin C in their white blood cells, compared to those taking regular vitamin C supplements. The study concluded more research into the effects of Ester C® on immunity was warranted.

Gentler on the stomach

Another piece of research published in a 2006 issue of Advances in Therapy tested 50 volunteers that were sensitive to acidic foods. Half were given Ester-C® and half received ascorbic acid. The trial was carried out over nine days and found that patients who took Ester-C® had fewer stomach upsets. The tolerability of Ester-C® was rated ‘very good’ by 72 per cent of participants compared to 54 per cent in the ascorbic acid group.

Getting vitamin C from your diet

Ester-C® is a patented form of vitamin C with a unique delivery system – you cannot get it in this form from food, only from Ester-C® supplements.

Most of us get enough vitamin C from our diet in foods such as citrus fruit, kiwi fruit, red peppers, kale, strawberries, and apples – plus many foods are now fortified with extra vitamin C. However, heavy smokers, heavy drinkers, people who don’t eat enough fruit and vegetables, those with intestinal malabsorption problems and those with kidney disease can be at risk of deficiency.


Ester-C® can sometimes cause heartburn, upset stomach, nausea, diarrhoea, headaches, flatulence and if taken in excessive doses of up 2,000 mg, increased urination. In rare cases, high doses can cause migraine, dizziness, fainting and possibly kidney stones.

If you have diabetes talk to your doctor before taking vitamin C supplements – there are some concerns it could affect some blood glucose tests. The safe upper limit daily intake for vitamin C is 1,000mg.

Correct dosage

There is no UK or EU recommended daily allowance or upper safety limit for Ester-C®. The EU RDA/NRV for vitamin C is 80mg per day. A standard dose of Ester-C® is 1,000mg which contains 765mg of vitamin C.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

Vitamin C plays a crucial role in supporting the immune system. It’s needed to maintain healthy skin; cartilage; teeth and gums; bone and blood vessels.

Dr Sarah Brewer


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