Eating an Apple Every Day: What Does the Science Say About Its Health Benefits?
The proverb "an apple a day keeps the doctor away" goes back well over a century, and it has lasted for a reason. Apples are not a cure-all, but the research on them is richer than many people expect. Studies have linked regular apple eating to better cholesterol levels, a lower risk of type 2 diabetes, better digestive health and better lung function.
Most of that evidence comes from observational studies, which show associations rather than proof of cause and effect. This article explains what each study found, how far its results can be trusted, and what that means for your diet.
Nutritional Benefits of Apples: What's Actually in Them
A medium apple with the skin on (about 182 g) provides roughly 95 calories, 4.4 g of fibre and around 8 mg of vitamin C, or about 9% of the Daily Value, according to USDA Food data Central. It is about 85% water, contains almost no fat or sodium, and gets its sugar mainly from fructose.
Much of an apple's fibre and many of its antioxidants, including polyphenols such as quercetin, are concentrated in the skin. That is why nutritionists usually recommend eating apples unpeeled. If you're curious about the role of fruit in a balanced diet, see our guide to fruit and diet.
Apples and Heart Health: What the Evidence Shows
The strongest direct evidence for apples and cholesterol comes from a randomised trial at Florida State University. It was presented at the Experimental Biology 2011 meeting, partly funded by the USDA, and later published in the Journal of the Academy of Nutrition and Dietetics (Chai et al., 2012). The trial enrolled 160 postmenopausal women aged 45 to 65. One group ate 75 g of dried apple a day for a year, while the other ate dried plums (prunes).
Women in the apple group saw their LDL ("bad") cholesterol fall by about 23% after six months and their HDL ("good") cholesterol rise by about 4%. They did not gain weight despite eating roughly 240 extra calories a day. The prune group improved less.
The researchers suggest that the pectin in apples may be partly responsible. Pectin is a soluble fibre that can bind to cholesterol-rich bile acids in the digestive tract so that they are excreted rather than reabsorbed. This is a plausible mechanism, not a proven one.
The trial was relatively small, involved only postmenopausal women and was partly funded by the USDA, so the results should not be assumed to apply to everyone. If you're interested in other foods that support heart health, browse our heart health articles.
Apples, Blood Sugar and Type 2 Diabetes
Apples have a relatively low glycaemic index, meaning they raise blood sugar more slowly than many other carbohydrate foods. Their fibre is thought to contribute to this.
Large cohort studies have also linked apple eating to a lower risk of type 2 diabetes. A 2017 meta-analysis in Food & Function pooled five prospective cohort studies. It found that people who ate the most apples and pears had an 18% lower risk of type 2 diabetes than those who ate the least.
Similarly, a 2013 study in The BMJ from the Harvard T.H. Chan School of Public Health followed 187,382 people across three cohorts. It found that three servings a week of apples and pears was associated with a 7% lower risk of type 2 diabetes. Blueberries and grapes showed stronger associations. Fruit juice was linked to a higher risk.
These are associations, not proof. People who eat more whole fruit tend to differ from other people in many ways, including exercise, smoking and overall diet. The BMJ study also found no link between a fruit's glycaemic index and diabetes risk, so the glycaemic index may not explain the findings.
Apples and Digestive Health
The fibre in apples includes both insoluble fibre, which adds bulk and supports regular bowel movements, and soluble fibre such as pectin. Gut bacteria ferment pectin, which is one reason it is often described as supporting a healthy gut microbiome. Fibre also helps you feel full, which is why apples are a popular low-calorie snack for people managing their weight.
Apples and Lung Health
Some of the less publicised research on apples concerns the lungs. The findings come from observational studies and show associations only.
A study published in Thorax in 2000 followed 2,512 middle-aged men in Caerphilly, Wales. After adjusting for smoking, body mass index, social class, exercise and energy intake, men who ate five or more apples a week had lung function (FEV1) about 138 mL higher than men who ate none. The study did not find that apple intake slowed the decline in lung function over time.
A later study, published in the European Respiratory Journal in 2017 (Garcia-Larsen et al.), followed 680 adults for ten years. Higher intakes of apples, bananas and tomatoes were associated with a slower decline in lung function in former smokers. After the researchers corrected for multiple comparisons, only the tomato finding remained statistically significant. The apple result should therefore be treated as suggestive.
Research on asthma points the same way. A 2001 case-control study of adults in London (Shaheen et al., American Journal of Respiratory and Critical Care Medicine) found that people who ate more apples were less likely to have asthma. A 2006 study in Thorax (Patel et al.) reported a lower risk of asthma, by about a third, among the highest apple eaters. Case-control studies rely on people's recall of their past diets, and neither study shows that apples prevent asthma.
Notes of Caution: What the Research Can and Cannot Tell Us
Most of the research on apples and health is observational. Observational studies can show that two things go together, but not that one causes the other. People who eat more apples may also exercise more, smoke less or eat better overall. Researchers adjust for these factors, but they cannot remove them entirely.
The cholesterol trial used dried apple in a fixed daily dose. Fresh apples may well have similar effects, but that has not been tested in the same way, so we cannot say how much a daily fresh apple would change your cholesterol.
Apples are part of a healthy diet, but they cannot make up for other unhealthy habits. People with an allergy to apples, including oral allergy syndrome (which is often linked to birch pollen allergy), should speak to a doctor or allergist before eating them. This article is general information, not medical advice.
Frequently Asked Questions About Apples and Health
Is it better to eat the skin of an apple?
Yes, in most cases. Peeling an apple removes a large share of its fibre and most of its polyphenols, which are concentrated in the skin.
How many apples a day is healthy?
There is no official recommended number of apples. For most people, one or two a day is a reasonable amount as part of a varied diet that includes other fruit and vegetables.
Can apples really help lower cholesterol?
There is some evidence that they can. The main trial found a clear drop in LDL cholesterol, but it used 75 g of dried apple a day, studied postmenopausal women only, and was fairly small. More research is needed before we can say that fresh apples have the same effect in the general population.
Do apples affect blood sugar levels?
Apples have a relatively low glycaemic index, and studies have linked eating them to a lower risk of type 2 diabetes. These are associations and do not prove that apples prevent diabetes. People managing diabetes should follow the advice of their healthcare team.
The Bottom Line on Apples and Health
The evidence for apples is better than many claims about "superfoods", but it is not conclusive. There is one randomised trial showing improved cholesterol, and several large observational studies linking apples to a lower risk of type 2 diabetes and to better lung function. None of this makes apples a wonder food. They are an easy, inexpensive and well-studied addition to a healthy diet. If you're looking for nutrition-focused posts about other foods and health, browse the rest of our nutrition articles.
References
- Chai SC, et al. Daily apple versus dried plum: impact on cardiovascular disease risk factors in postmenopausal women. Journal of the Academy of Nutrition and Dietetics, 2012.
- Guo XF, Yang B, Tang J, Jiang JJ, Li D. Apple and pear consumption and type 2 diabetes mellitus risk: a meta-analysis of prospective cohort studies. Food & Function, 2017;8(3):927-934. Link
- Muraki I, et al. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ, 2013;347:f5001. Link
- Butland BK, Fehily AM, Elwood PC. Diet, lung function, and lung function decline in a cohort of 2512 middle aged men. Thorax, 2000;55(2):102-108. Link
- Garcia-Larsen V, et al. Dietary antioxidants and 10-year lung function decline in adults from the ECRHS survey. European Respiratory Journal, 2017.
- Shaheen SO, Sterne JAC, Thompson RL, Songhurst CE, Margetts BM. Dietary antioxidants and asthma in adults: population-based case-control study. American Journal of Respiratory and Critical Care Medicine, 2001;164(10):1823-1828. Link
- Patel BD, Welch AA, Bingham SA, et al. Dietary antioxidants and asthma in adults. Thorax, 2006;61:388-393.
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