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What’s with the lemon-water hype?

If you've spent any significant amount of time perusing popular diet websites, chances are you’ve seen articles about the many benefits of lemon juice, or as frequently consumed, lemon water. In recent years, lemon water has gone from a simple taste preference to a health trend thanks to a variety of personalities, celebrity doctors, and popular diets.

Lemons are fruits and fruits are generally healthy, but some of the claims about lemon water make it appear downright miraculous. In this article, we’ll examine eight of those claims.

The Claims

Claim 1: Lemon water detoxifies the body

Detoxification claims are fraught with misunderstandings about human physiology, and even when a mechanism of action is plausible, its applicability to diets and supplements is seldom backed by any solid evidence.

Yes, nutrients and other bioactive agents in foods can affect detoxification enzymes in the liver. In rodents, both sulforaphane (plentiful in many cruciferous vegetables)^[1] and limonene (a prominent molecule in lemons) seem to have this effect.^[2] But the degree to which attainable dosages of limonene and other components of lemons can help a human liver detoxify a human body is still uncertain, and so are the greater health implications.

Verdict: It isn’t clear if lemon water will detoxify your body, and if it does, to what degree. At most, we can say there’s a plausible mechanism through which lemon water might help your liver detoxify your body.

Claim 2: Lemon water perks you up

Lemon water feels refreshing. But does it actually, physiologically, perk you up? Or is the refreshing feeling simply due to lemon water’s taste and aura of healthfulness?

A recurring claim is that the citrate in lemon contains a large number of negative ions, and that negative ions can counterbalance an excess of positive ions in our environment. This excess is blamed (mostly by sellers of devices that produce negative ions) for various ills, including tiredness and bad mood.

In placebo-controlled human studies, depression was the only mood parameter that saw a statistically significant improvement from negative-ion exposure. Poor study quality and the possibility of research bias, however, limit our confidence in the benefit.^[3] And of course, even if inhaling negative ions can help people with depression and lemons contain some negative ions, it doesn’t follow that drinking lemon water will benefit your mood. Inhaling lemon oil might,^[4][5] but the evidence is weak, and even if the benefit is real, once again there is no telling if it transfers to drinking lemon water.

One way in which lemon water could potentially affect mood is if it remedies a vitamin C deficiency. Severe vitamin C deficiency, also known as scurvy, comes with severe emotional disturbances, and lemons were once a prophylactic for sailors on long voyages.

Some preliminary evidence suggests that vitamin C can improve the mood of people with low levels of vitamin C, even if they don’t have scurvy.^[6][7][8][9] But though lemon water contains vitamin C, so do many foods you should be eating. Moreover, lemon juice is very bitter, so you might have a hard time drinking enough to obtain a notable amount of vitamin C.

Verdict: There is no direct evidence that lemon water can benefit your mood or your energy levels. All such claims are based on less-than-plausible extrapolations from studies on vitamin C, lemon-oil aromatherapy, and air ionizers.

Claim 3: Lemon water aids digestion

Secreted from the gallbladder into the small intestine, bile acids play a role in gut motility and facilitate the absorption of fatty acids and fat-soluble vitamins. But although lemon juice seems to increase bile-acid secretion,^[10] the effect on digestion is unclear. When you eat fatty foods, your gallbladder releases an appropriate amount of bile acids; should it fail to do so, the problem probably isn’t one lemon juice can remedy.

A related claim, also without human studies to back it up, is that the citric acid in lemon juice can improve your digestion by supplementing your stomach acid; but there again, unless you suffer from hypochlorhydria, you can trust the parietal cells in your stomach to produce an appropriate amount of acid. And if you do suffer from hypochlorhydria (i.e., if you can’t produce enough stomach acid), then you should see your doctor, rather than testing your luck with lemon juice.

It is true, though, that acidic foods may reduce the rate of gastric emptying,^[11] which could result, not in better digestion per se, but in better absorption of micronutrients and slower absorption of carbohydrates.^[12] However, the actual effects of lemon juice on nutrient absorption and glycemia after meals haven’t been specifically researched.

Finally, there are claims that lemon water contains fiber. It doesn’t, to any noticeable degree. Lemons contain fiber, yes, but unless you eat an entire lemon, peel included, you won’t get a notable amount of fiber from it, and there are better sources.

Verdict: It’s plausible that lemon juice could slow gastric emptying and thus reduce postprandial glucose while improving nutrient absorption, but at this time there is little evidence that lemon water aids in digestion.

Claim 4: Lemon water protects from acidic diets

This perennial subject has led to a fair bit of controversy. The basic idea is that, by making the blood too acidic, the standard American diet promotes a variety of diseases, notably cancer, diabetes, osteoporosis, and cardiovascular disease; but that, fortunately, various foods can bring your blood’s pH back into balance.

Having a blood pH that is too high (too alkaline) or too low (too acidic), can indeed be harmful, even lethal; but except in case of severe disease (cancer, ketoacidosis, liver failure, severe poisoning …), your blood pH is tightly regulated to a healthy range by your body’s built-in buffering system.^[13]

Could variations within this narrow range be relevant to health? Some people think so. They believe that leaning toward the lower end of the normal range is undesirable.^[14] The evidence is weak, however, since testing the hypothesis involves either diets high in fruits and vegetables or supplementation with essential minerals — two interventions that could easily affect health in ways unrelated to changing the blood’s pH. Moreover, a diet designed to heavily favor alkaline minerals only led to an increase in blood pH of 0.014, though it increased urine pH by 1.02.^[15]

There doesn’t seem to be any research on the effects of lemon juice on blood pH, but in a study with a single volunteer, 50 ml of lemon juice raised urine pH from 6.7 ± 0.1 to 6.9 ± 0.1.^[16] If the previously mentioned study is any indication, the increase in blood pH would be inconsequential.

Finally, if the goal is to alkalize the blood, or the whole body, one can wonder: Why lemon juice? Yes, lemon, though acidic, produces alkaline metabolites in your body and so has a negative potential renal acid load (PRAL); but lemon juice’s PRAL of -2.5 isn’t especially low among fruits. Raisins, notably, have a PRAL of -21.^[17]

Verdict: Not only does your body maintain your blood pH within a strict range, but even within that range, lemon water isn’t likely to have any meaningful effect.

Claim 5: Lemon water promotes weight loss

It isn’t rare for people to lose weight on “detoxification” diets that include lemon water. On these diets, people attempt to detoxify their bodies by eating little (or fasting entirely) and drinking lemon water often mixed with other ingredients. People can lose weight fast on such flash diets, but for the first couple of days that weight will be water rather than fat, and afterward the weight loss (from fat and muscle) can easily be attributed to the caloric deficit.

But wait, why would drinking lemon water lead to a loss of water weight?

Answer: It doesn’t. What causes the water loss is carbohydrate deprivation. To store one gram of glycogen in your liver and muscles, your body binds it to three grams of water, on average. If your body isn’t getting enough carbs, your glycogen stores get depleted in one or two days — a sudden weight loss of several pounds.^[18] Once you resume eating normally, however, the glycogen and water come rushing back.

And talking about water: there’s indeed some evidence that older adults (but not younger adults) eat less if they drink water before their meals.^{[19][20][21][22][23]} Can lemon water coax you into drinking more water? It might, if you enjoy the taste, but even if you do, you might unconsciously reduce your intake of regular water to compensate.

Finally, some experimental research in mice suggests that phytochemicals in lemon peels increase beta-oxidation of fatty acids and prevent obesity,^[24] but whether this translates to a notable effect of lemon juice in humans is anybody’s guess.

Though not studied as a weight-loss agent, a lemon-water cocktail with carbonated water and a non-caloric sweetener could serve as a low-calorie replacement for fruit juices or sugary sodas. You can easily mix such a cocktail yourself.

Verdict: Lemon water has no unique, proven weight-loss benefit, but it may help you lose weight if it coaxes you into drinking more water (if you’re an older adult, drinking water before meals can result in your eating less).

Claim 6: Lemon water fights cancer and CVD

Lemons contain many phytochemicals that may affect the processes involved in cancer and cardiovascular disease (CVD). It is tempting to leap from mechanistic evidence to disease prevention, but most often, mechanistically promising compounds prove disappointing in human studies, as was the case with vitamin C for CVD.^[25]

Moreover, even when a compound shows promise in human studies, the benefits might not extend to the foods containing that compound. For instance, an RCT reported that 500 mg of hesperidin per day could lower blood pressure and reduce inflammatory risk factors for heart disease,^[26] but since 100 ml of lemon juice contains, on average, only 20.5 mg of hesperidin,^[27] it isn’t surprising that another RCT reported that 1 tablespoon of lemon juice (≈15 ml) didn’t affect lipids or blood pressure.^[28] A higher dose of lemon juice might be beneficial, but how much higher? We don’t know.

Similarly, any plant food contains phytochemicals that can positively influence processes in various cancer cells, and lemons are no exception.^[29][30][31] But there again, RCTs on relevant clinical endpoints are needed to ascertain the effects of a given dosage of a given phytochemical or food.

Verdict: Lemon water doesn’t contain enough lemon to have any plausible prophylactic or curative effect.

Claim 7: Lemon water prevents colds

This claim is based mostly on lemon’s vitamin C content. The problem is, vitamin C doesn’t reduce the frequency of colds. Vitamin C can reduce the duration of colds, but only when supplemented consistently (i.e., not just after falling sick) in doses that are simply too high to obtain from lemons without getting a perpetual sour face.^[32]

Other chemicals in lemon, however, may positively influence the immune system. A rat study found that limonene could improve the ability of phagocytes to do their job,^[33] and lemons contain other chemicals that could conceivably help, such as hesperidin.^[34]

Verdict: There is some animal evidence that some chemicals in lemon can help fight colds, but we don’t know if those benefits extend to humans, and if they do, if high enough doses can be reached by drinking lemon water.

Claim 8: Lemon water helps against kidney stones

Lemons contain a substantial amount of citric acid, as far as fruits go.^[35] By combining with calcium in the kidneys, citrate (a derivative of citric acid) can prevent the formation and reduce the growth of both calcium oxalate and calcium phosphate. If your urine is low in citrate (a condition known as hypocitraturia), you are at risk of developing kidney stones.^[36]

Supplementation with potassium citrate is likely effective in the prevention and treatment of calcium-oxalate stones,^[37] and 85 ml of lemon juice was shown to increase urinary citrate as much as a clinical dose of potassium citrate.^[38] The minimum effective dose for prevention is unknown, and lemon juice hasn’t been evaluated with regard to stone size or clinical symptoms, but the rationale is there, at least.

Verdict: Due to their citric-acid content, lemons should help in preventing the formation and reducing the growth of kidney stones. This effect hasn’t been explicitly tested, though, unlike the effect of potassium-citrate supplementation.

Does lemon water have any negative effects?

Besides the fact that a large amount of lemon juice can be jarring to the palate, one concern is worth mentioning: the erosion of tooth enamel. The acidic nature of lemon juice may soften the enamel of your teeth, leading to their erosion.^[39][40] At the very least, you should avoid brushing your teeth soon after drinking lemon water. Chewing sugar-free gum could be a good idea, on the other hand, since doing so helps neutralize plaque acidity (probably by increasing salivation).^[41]

Verdict: The only known negative effect of lemon water is its erosive effect on tooth enamel.

Lemons are just fruits, and fruits are healthy

Like any other fruit, lemon has a unique phytochemical profile.^[42] It also distinguishes itself by its acidity, high citrate content, and low sugar content. The amount of micronutrients you’ll get from a tolerable amount of lemon juice is small, however, and too many health claims are based on studies testing high-dose phytochemicals found only in small amounts in lemons.

Yet those phytochemicals are there, and together, and in conjunction with the phytochemicals in other plant foods, they make lemons a valuable option in healthy diets. Although there isn’t a lot of research on the health effects of lemons, lemon juice (preferably with the pulp) may be worth including in your diet simply to increase the diversity of potentially beneficial phytochemicals you consume.

Lemon juice won’t contribute substantially to your micronutrient intake, but it also doesn’t contain very many Calories. In summary, lemons are generally healthy, as are most fruits. Lemon juice contains small amounts of beneficials micronutrients and phytochemicals, but it’s unclear if, among all fruits, lemons are uniquely valuable.