Lemons: Vitamin C, Iron Absorption and Lemon Water

By Nikola · Precision Nutrition L1 · Updated 4 November 2026

Lemons (Citrus limon) are sour citrus fruits used far more as a seasoning than as a fruit to eat on its own. Per 100 g, lemon flesh has only 29 kcal and 9.3 g of carbohydrate, but 53 mg of vitamin C, so a small lemon of 58 g gives about 31 mg. The most useful thing lemon does in a kitchen goes beyond its own nutrients: the NIH notes that vitamin C improves the absorption of non-haem iron, the form found in plant foods, which makes a squeeze of lemon a smart habit with lentils, beans and leafy greens. Lemon juice is also acidic, so it is worth protecting your teeth if you drink it daily.

Lemon nutrition per 100 g and per lemon

Nutrient	Per 100 g, flesh without peel	Small lemon, 58 g
Energy	29 kcal	17 kcal
Water	89 g	52 g
Protein	1.1 g	0.6 g
Fat	0.3 g	0.2 g
Carbohydrate	9.3 g	5.4 g
of which sugars	2.5 g	1.5 g
Fibre	2.8 g	1.6 g
Vitamin C	53 mg	31 mg
Potassium	138 mg	80 mg
Calcium	26 mg	15 mg
Folate	11 µg	6 µg

Source: USDA FoodData Central, SR Legacy, “Lemons, raw, without peel”, FDC ID 167746, checked 4 November 2026. USDA gives 58 g for a lemon about 5.4 cm across, 84 g for one about 6 cm across (around 45 mg of vitamin C) and 7 g for a wedge (one eighth of a small lemon, about 3.7 mg of vitamin C). The small-lemon column is calculated from the 100 g values. These figures are for the flesh; lemon juice has its own USDA record, which is not used here, so do not assume all the fibre in the table ends up in your glass. Values rounded.

Glycemic index

Lemons are not listed in the international GI tables (Atkinson 2008), so we do not give a number. They have little carbohydrate: 9.3 g per 100 g of flesh, and a typical squeeze over a salad or into a glass of water contains a few grams of lemon at most. Lemonade is a different story, because its effect on blood sugar comes from the added sugar, not the lemon.

Health benefits: what the evidence says

Vitamin C. 100 g of lemon flesh gives 53 mg of vitamin C, a small lemon about 31 mg. The NIH lists citrus fruits among the best food sources of vitamin C, together with peppers, kiwifruit, broccoli, strawberries and Brussels sprouts.
Better iron absorption from plant foods. The NIH Office of Dietary Supplements states that vitamin C improves the absorption of non-haem iron, the form in plant foods. In practice: lemon juice on lentils, chickpeas, spinach or kale helps your body use the iron in the meal.
Flavour without salt or sugar. Lemon juice and zest add a sharp, fresh taste to fish, vegetables, grains and dressings, which makes it easier to cook with less salt. This is a practical point rather than a clinical finding.
Colds: keep expectations modest. According to the NIH, regular vitamin C supplements of at least 200 mg a day do not reduce how often the general population catches a cold, though they may modestly shorten colds. Taking vitamin C only after symptoms start does not seem to help. A slice of lemon in tea gives a few milligrams, far below the doses tested, so enjoy the drink without expecting it to work as a remedy.

Ayurveda: lemons in the traditional system

In Usha and Vasant Lad’s food guidelines, lemons are favourable for Vata and favourable in moderation for Kapha. For Pitta they are on the list of foods to avoid. If you are Pitta and use lemon, a small squeeze in a dish is a different thing from daily glasses of lemon water. This is a traditional view, not a clinical finding.

How to use lemons

With legumes and greens: finish lentil soup, chickpea salad or sautéed spinach with lemon juice for flavour and better iron absorption.
Add it at the end: the NIH notes that vitamin C is sensitive to heat and that cooking reduces it. Squeeze lemon over food just before serving rather than boiling it for long.
Dressings: lemon juice, extra virgin olive oil, salt and pepper make a simple dressing for salads, grains such as quinoa or bulgur, and grilled vegetables.
Fish: lemon is the classic partner for baked salmon and other fish.
Warm drinks: a slice of lemon in ginger tea with a little honey is a comforting drink in winter.
Zest: if you use the peel, choose unwaxed lemons and wash them well. The table above does not include the peel.
Storage: whole lemons keep for weeks in the fridge; a cut lemon is best used within a few days.

Who should be careful

Teeth. Healthdirect Australia lists citrus fruits such as lemons among acidic foods that can contribute to dental erosion. If you drink lemon water often, use a straw, rinse your mouth with plain water afterwards and wait at least 30 minutes before brushing, because enamel stays softer for a while after acid exposure.
Hereditary haemochromatosis. Because vitamin C increases iron absorption, the NIH notes that high vitamin C intake may be a concern for people with this iron-overload condition. Normal use of lemon as a seasoning is a very small amount, but discuss supplements and large daily amounts with your doctor.
Sensitive stomach. If sour or acidic foods trigger your heartburn or reflux, follow your own experience; MedlinePlus advises avoiding foods that cause your symptoms.

FAQ

How much vitamin C is in a lemon?

According to USDA data, 100 g of lemon flesh has 53 mg of vitamin C. A small lemon of 58 g gives about 31 mg and a larger one of 84 g about 45 mg; a single wedge gives under 4 mg.

Does lemon help you absorb iron?

Yes, for plant iron. The NIH states that vitamin C improves the absorption of non-haem iron, the type found in legumes, grains and leafy greens. Squeezing lemon over lentils, beans or spinach is an easy way to use this.

Does lemon water help with a cold?

Probably not much. Studies summarised by the NIH found that regular vitamin C supplements of at least 200 mg a day do not prevent colds in most people and only modestly shorten them. A slice of lemon has a few milligrams, but a warm drink can still be soothing.

Sources

USDA FoodData Central, SR Legacy: Lemons, raw, without peel (FDC ID 167746). fdc.nal.usda.gov
NIH Office of Dietary Supplements. Vitamin C: Fact Sheet for Health Professionals. ods.od.nih.gov
Healthdirect Australia. Dental erosion. healthdirect.gov.au
MedlinePlus. Gastroesophageal reflux disease. medlineplus.gov
Atkinson FS, Foster-Powell K, Brand-Miller JC. International Tables of Glycemic Index and Glycemic Load Values: 2008. Diabetes Care 2008;31(12):2281-2283. PMC
Lad U, Lad V. Food Guidelines for Basic Constitutional Types, from Ayurvedic Cooking for Self-Healing, 2nd ed. The Ayurvedic Institute. ayurveda.com

This page is for information only and is not medical or dietary advice.

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