Fighting Free Radicals With Lemons

  • Saira Loane Master's of Toxicology, Institute of Biomedical Research, University of Birmingham

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Is lemon a citrus fruit capable of shielding us from free radicals? Yes, you read it right. Lemon, a fruit which we consume as a part of our regular diet or as part of food or beverages, is also an antioxidant and the antioxidants are capable of neutralising the free radicals in the body.

Apart from being a souring agent in our diet, lemon helps with digestion, boosting immunity, maintaining a healthy pH and most importantly fights the free radicals.

The free radicals can be called as a product of unhealthy habits, stress, carcinogenic exposures and our regular biological mechanism. The changes caused by them can be balanced only with the help of antioxidants which are present in fruits like lemon.

Free radicals and their impact on health

Free radicals are formed as a result of normal cellular metabolism. 

A free radical is defined as an atom or molecule containing one or more unpaired electrons in valence shell or outer orbit and is capable of independent existence. The odd number of electrons in the outer shell makes it unstable and highly reactive.

Lemon as a potential natural remedy

Lemon, the yellow coloured citrus fruit, has a good number of beneficial nutrients. The fruit is also a very good source of dietary fibre and contains a number of other nutrients including calcium, iron, copper, potassium, folic acid, magnesium, manganese, phosphorus, zinc, sodium, phytonutrients.

Health benefits of lemon includes:

  • Boosts the immune system
  • Helps in weight loss
  • Home remedy for acnes
  • To manage nausea and vomiting
  • Low glycemic fruit
  • Prevents anaemia
  • Use of lemon maintains a healthy pH of our body
  • Relieves indigestion and constipation

Understanding free radicals

Formation of free radicals

Biological processes that take place in the human body such as breathing, metabolising therapeutic agents, digesting food and conversion of fat into energy, produce damaging compounds known as reactive oxygen (ROS), and nitrogen species (RNS), ROS and RNS respectively, together named as RONs.

During conditions of stress, the formation of RONs overpower the antioxidant defences, resulting in a redox imbalance which produces oxidative stress and irreversible alterations in cell compounds. Oxidative stress is the leading factor that produces damage in cell structures, i.e., in membranes, lipids, proteins and DNA.

An ideal antioxidant should be readily absorbed, successful in removal of RONs and also chelate metals at physiologically suitable concentrations.

Types of reactive oxygen species(ROS)

  • Hydroperoxide (O 2 H),
  • superoxide (O 2 -),
  • hydroxyl radical (OH.)

Singlet oxygen and Reactive nitrogen species(RNS) are derived from nitric oxide (NO) and superoxide (O 2•−) produced via the enzymatic activity of inducible nitric oxide synthase 2 (NOS2) and NADPH oxidase respectively. The antioxidants can be of endogenous or exogenous sources.

Endogenous Antioxidants may not be sufficient to avoid oxidative stress so we must incorporate dietary exogenous antioxidants.

Sources of free radicals in the body

The endogenous sources of reactive oxygen species include different cell organelles such as endoplasmic reticulum, mitochondria and peroxisomes where the oxygen usage is high. The other endogenous sources of ROS include prostaglandin synthesis, auto-oxidation, phagocytic cells, reduced riboflavin, FADH2, cytochrome P 450, immune cell activation, inflammation, mental stress, excessive exercise, infection, cancer, ageing, ischemia.

Role of oxidative stress in health

Oxidative stress can damage cells, proteins and DNA. All these contribute to early ageing, and other conditions like diabetes, and cancer.

Oxidative stress is due to imbalance between production and accumulation of reactive oxygen species (ROS) in cells and tissues. ROS has several physiological roles and they are normally generated as by-products of oxygen metabolism, environmental stressors and xenobiotics cause an increase in ROS production, thus causing an imbalance leading to cell and tissue damage.

Lemon and its antioxidant properties

Composition of lemon

Lemon comes from Rutaceae Family and genus Citrus. They are indigenous to Asia. Citrus fruits are commonly known for nutritional, pharmaceutical and cosmetic properties. The genus Citrus includes evergreen plants, shrubs or trees. The leaves are ovoid or elliptical in shape. Some of them have spikes.

Both the fruit (as frozen pulps, juices, dried pulp or peel) and parts of the plant are used as an ingredient in diet and products like dishwashing liquids, essential oils, creams, serums.

Antioxidant Compounds present in lemon are mainly flavonoids, limonoids, phenolic acids, kaempferol, quercetin and ascorbic acid. The sourness of lemon is contributed by limonoids, and triterpene derivatives which gives the specific aroma for the citrus fruits.

Wide consumption of lemons and other citrus fruits were started to prevent scurvy as lemons are rich in ascorbic acid, an essential dietary nutrient. Vitamin C and Flavonoids are major antioxidants in Lemon.

The highest amount of vitamin C is found in Lemons. The recommended dietary allowance (RDA) of Vitamin C is 60 mg. Around 53 mg of vitamin C is present per 100 grams of lemon without peel and this makes up a major part of the RDA.

Vit C prevents cell damage, boosts the immune system and supports collagen production for maintaining skin health. Flavonoids, another group of antioxidants found in lemons, has numerous health benefits, including reducing inflammation and contributes to heart health. 

Scientific evidence supporting lemon's anti-free radical effects

Studies on lemon and oxidative stress

Oxidative stress is an imbalance between oxidants and antioxidants levels in biological systems. Highly reactive atoms or molecules such as free radicals and reactive oxygen species(ROS) are the main cause of oxidative stress.

Lemon is a natural antioxidant. With respect to its antioxidant function, it can neutralise both ROS and nitrogen oxide species by donating a hydrogen atom, thus forming an ascorbic radical which could be obtained back as Vitamin C. Vit C can act both on the intracellular and extracellular side, as it is water soluble.

Animal studies have proven the antioxidant effect of lemon juice on some haematological and biochemical parameters after their exposure to free radicals like H2O2. Analytical studies are still carried out to separate the flavonoid from citrus fruits to reach a standardised method. 

Incorporating lemon into a healthy lifestyle

A balanced diet includes vegetables, fruits, milk, eggs and meat.

Also, there is a recommended daily allowance of all the vitamins, minerals and nutrients as per our body requirement. The pectin fibre found in lemons expands once its ingested, giving a feel of fullness. Lemon water is often consumed as an effective tool in weight loss and weight maintenance. The citric acid content may help to prevent kidney stones. Lemons are used as a preservative.

The chance of having citrus allergy is also to be kept in mind even if it is rare. The symptoms include:

  • Itching
  • Blisters
  • Redness
  • Contact dermatitis
  • Oral allergy syndrome(OAS)

Lemon-based recipes for antioxidant boost

Including lemon as part of our daily diet helps the human body fight against free radicals. As we could consume both the peel and pulp of lemon and can be consumed in fresh or in dried form.

Healthier ways of Lemon consumption includes:

  • Lemon juice with water
  • Simply squeezing on salads and foods
  • Dry lemons
  • Lemon crush

Many recipes are there across the world using lemons.

  • Marmalade
  • Lemonade mimosas
  • Low calorie lemon cakes
  • Lemon curd
  • Lemon doughnuts
  • Lemon pies 

Potential risks and considerations

Side effects or contraindications

The easiest way of lemon consumption is in the form of lemon water or juice. But drinking too much of this causes enamel erosion.

It's always advised to have a moderate consumption of lemons as they are an acidic fruit, especially when having the juice, also try to have it in the diluted form.

Overconsumption of lemon can lead to:

  • Enamel erosion
  • Cause migraines due to a component called tyramine 
  • Worsens mouth ulcers
  • Burning sensation and can trigger Gastroesophageal reflux disease(GERD)
  • Nausea

Lemons are used as a home remedy for a great number of health issues such as obesity, dandruff, wound healing etc. But before going for these remedies it's always advised to take a physician consultation as these can also be symptoms of any chronic disease.


Lemon is one of widely produced and consumed fruit worldwide due to its health benefits and unique flavour.

The antioxidants in lemon neutralise the free radicals. These free radicals are proven to be causing chronic inflammation, different cancers, atherosclerosis and other neurodegenerative disorders.

In this period of people being more concerned about health, the addition or continuing use of lemons as per RDA can contribute towards better health. An antioxidant in lemon the Flavonoids show radical scavenging activity and are found to reduce risk for certain chronic diseases and the prevention of some cardiovascular disorders, cancerous processes. Also possesses antiviral antimicrobial and anti-inflammatory activities and an ability to inhibit human platelet aggregation, antiulcer and antiallergenic properties.

Projects on improving pharmacological activity of antioxidants with nanotechnology-based formulations, and recent nanoformulations including nanoparticles, polymeric micelles, liposomes, phytosomes and solid lipid nanoparticles are carried out. These are giving promising outcomes in improving the potential and bioavailability of antioxidants.

Research shows even the lemon seed has antioxidant properties. Many studies are ongoing to separate the antioxidants present in lemon. Lemon juice is a rich antioxidants source that can be used as a safe, cheap and acceptable drink at different concentrations.


  1. Liu S, Li S, Ho CT. Dietary bioactives and essential oils of lemon and lime fruits. Food Science and Human Wellness [Internet]. 2022 Jul 1 [cited 2023 Nov 17];11(4):753–64. Available from:
  2. Knight A. Antioxidants in lemons: fighting free radicals for better health [Internet]. Fischer Institute. 2023 [cited 2023 Nov 17]. Available from:
  3. Losada-Barreiro S, Sezgin-Bayindir Z, Paiva-Martins F, Bravo-Díaz C. Biochemistry of antioxidants: mechanisms and pharmaceutical applications. Biomedicines [Internet]. 2022 Nov 25 [cited 2023 Nov 17];10(12):3051. Available from:

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Keerthana Hareendran

Bachelor of Dental Surgery – BDS, Pondicherry University

Keerthana is a General Dentist with analytical skills who is passionate in crafting Dental as well as writing aesthetics.

She has several years of experience as a General Practice Dentist and also in the Oncology data analysis also in writing and editing articles.

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