We have recently had a number of conversations about fruit and sugars, particularly glucose spikes caused by eating fruit and carbohydrates. Like other developed cities, tech-savvy Singapore has its fair share of residents, non-diabetics, using a CGM (continuous glucose monitor) to measure their blood glucose. Sometimes misinterpreting the data, even sometimes fearing fruit.
Should we be afraid of eating - enjoying - fruit? What do scientific studies themselves say on fruit, sugars and health? Many studies on this subject focus on the people most at risk from raised levels of glucose, those with diabetes or pre-diabetes. So we will start from there, reviewing the evidence, before we address the primary topic of this article: should non-diabetics be concerned? We also share the research on the currently much discussed topic of glucose spikes and eating foods in a specific order.
As ever, please talk to your doctor, or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle; especially if you are under treatment. We provide links to the quoted studies at bottom of page.
What do Studies on Fruit Consumption and Blood Glucose Show?
A meta-analysis of 19 randomised controlled trials showed "that fruit consumption significantly reduced fasting blood glucose concentrations but had no significant effect on Hb1Ac concentrations in people with diabetes. We speculate that because the monosaccharides in fruits are mainly fructose-based, have a low blood glucose response, and are slow to absorb, the metabolism of fruit does not require the participation of insulin, and can be quickly cleared and transferred after reaching the liver. Another possible reason may be that some of the included fruits have anti-diabetic effects to some extent.
Although the dry fruit had an increased sugar content compared with fresh fruit due to water loss, a subgroup analysis suggested that both dried and fresh fruit reduced blood glucose concentrations, and dried fruit has the characteristics of a long shelf-life and good transportability compared with fresh fruit." Y Ren et al, 2023
Another meta-analysis by Halvorsen et al, 2021, stated that "In this systematic review and meta-analysis of 23 cohort studies we found that high vs. low intakes of fruit and vegetables combined and fruit were associated with a 7% reduction in risk of type 2 diabetes.
There was suggestive evidence that intakes of apples, blueberries, grapefruit, grapes and raisins were associated with reduced type 2 diabetes risk, while positive associations were observed for intakes of fruit drinks, fruit juice, cantaloupe, potatoes, and some subtypes of cruciferous vegetables.
Diets high in fruit and vegetables may be important for the prevention of type 2 diabetes and it may be important to emphasize specific subtypes to reduce risk."
Ines Ellouze et al, 2023"We conclude that when and where possible, diabetic individuals should consume fresh, and in some cases, dried fruit rather than juices, pulps, pomaces, and other fruit-derived products. It is also important for these individuals to take into account the quantity of fruit and fruit products consumed on any given day. It is easier to consume the calorically dense fruit products like juice in higher volumes than their fresh whole food forms, which leads to a higher daily total energy intake." Interestingly, the study also details the effects of specific fruits.
When studying a Singaporean Asian population and the effect of temperate, subtropical and tropical fruit consumption on risk of type 2 diabetes, Alperet et al (2017), concluded the following:
"our findings suggest that the association between fruit consumption and type 2 diabetes mellitus (T2DM) risk differs by the type of fruit. The high consumption of tropical or higher-GI fruit, such as bananas, is associated with higher T2DM risk in men, whereas the high consumption of temperate fruit, such as apples, is associated with lower T2DM risk in women. Differences in associations may be partly explained by variations in glycemic index (GI) values in the different types of individual fruit but could also reflect the differences in phytochemical contents between types of fruit. Furthermore, choosing lower-GI whole fruit, grapes, or tangerines instead of juice is associated with lower T2DM risk.
Our findings support recommendations to promote the consumption of specific types of whole fruit, especially fruit with lower or moderate GI indexes such as apples and grapes, instead of juice as a public health strategy for reducing T2DM risk."
To note, on the fruit categories themselves:
"Temperate fruit included apples, pears, apricots and peaches, grapes, and persimmon. Subtropical fruit included oranges and tangerines. Tropical fruit included bananas, papayas, mangos, pineapple, watermelon, honeydew melon, and cantaloupe.
Lower–glycemic index fruit included apricots and peaches, apples, oranges, pears, and persimmon. Moderate–glycemic index fruit included tangerines, mango, papaya, and grapes. Higher–glycemic index fruit included bananas, honeydew melon, pineapple, cantaloupe, and watermelon."
A genetic study (Xu Jia et al, 2021) researching the risk of diabetes for those with a predisposition to diabetes showed that enjoying fresh fruit led to better health outcomes:"the present study provided evidence for interactions between fruit intakes and genetic predisposition of type 2 diabetes (T2D) with the risk of diabetes and related glucose metabolic traits in a Chinese community-based population.
Dietary fresh fruit intakes alleviate the association of the T2D-genetic risk score with the risk of diabetes and the increment in fasting plasma glucose, 2-hour plasma glucose and HbA1c levels. Also, the association between fresh fruit intake with a lower risk of diabetes and decrement of plasma glucose were more prominent in higher T2D-genetic risk score."
And for a mixed diabetic and non-diabetic population, does fruit support or harm health? A 2022 study following 80,000 people found the following:
"In conclusion, higher fruit intake frequency and amount were associated with lower incidence of Type 2 Diabetes in Chinese adults over 40 years old. The most prominent risk reduction of diabetes was in subjects consuming whole fresh fruit at least 7 times/week. Each 300 g/day higher fruit intake was associated with an 8.2% lower risk of diabetes, and each 100 g/day higher fruit intake was similarly associated with 2.8% lower risk of diabetes. The negative linear association between fruit intake and incident diabetes was markedly in normal glucose tolerance (NGT) population, while not significant in prediabetes. These findings emphasize the importance and effect of dietary whole fresh fruit, at least more than 7 times/week especially in NGT population, in diabetes prevention." Li et al, 2022
Food Order and Glucose Spikes
For the population without diabetes (or pre-diabetes) a current trend in online media is a discussion, verging on fear, around glucose spikes when eating food. Notably, none of the above studies touch on what order fruit is consumed with other items, simply the benefits from enjoying fruit as a regular and wholesome part of one's diet.
'Spike' is a potentially frightening name for an entirely normal biological response to consuming carbohydrates. For most of the population, this sudden increase and decline in glucose - shown as a sharp peak when measuring and visualising blood glucose data - is entirely normal and healthy. This is how the body is meant to react. When the increase in blood sugar does not return to normal (within say 2 hours), this indicates a potential problem as the sugar struggles to be cleared from the blood.
Consuming vegetables and proteins before carbs bluntens the spike, potentially useful for those that have pre-diabetes or type 2 diabetes, but not necessary for those in good health. So what does the evidence show when it comes to health outcomes? Not the fact that we can expect to see spikes after eating but rather, how is health affected?
In 2023 a 16 week randomised controlled trial by Shukla et al set out to investigate the effect of changing the order that food is eaten on health. In the study of pre-diabetic and healthy participants they found that contrary to their hypothesis, food order - irrespective whether the participants ate vegetables, carbs or protein first in the meal - made no meaningful difference over time. Glucose tolerance was unchanged in both groups after 16 weeks. Changes in weight, HbA1c were also similar between the groups. They did however find that those who ate their vegetables first ended up eating more vegetables.
Fruit and Weight Management
A systematic review of 41 randomised controlled trials, Guyenet et al (2019), found the following:
"The primary outcome of this review is the impact of whole, fresh fruit consumption on measures of adiposity including body weight, as measured by randomised controlled trials (RCTs). Overall, these RCTs suggest that increasing intake of whole, fresh fruit promotes weight maintenance or modest weight loss over periods of 3–24 weeks. High intakes of whole, fresh fruit in people with obesity may promote some degree of weight loss."
In Summary
The natural sugars in fresh fruit, bound with fibre and polyphenol anti-oxidants, are processed differently by the body compared to added sugars in processed foods. However, excessive intake of fruit juices or dried fruits, which are higher in concentrated sugars, may have a different effect on blood sugar levels. When looking at the totality of evidence, eating fresh fruit does not increase the risk of diabetes. Research suggests that consuming whole fruits, particularly those high in fibre like berries, apples and oranges may help reduce the risk of type 2 diabetes. Moderation and managing caloric intake is key.
Don't fear fruit, embrace it as part of a balanced diet.
Those with diabetes need to manage their diets and total sugar intake. Fruit can still be enjoyed in moderation, and your doctor can advise what might suit your specific circumstances best. The rest of us do not need to be concerned about fruit. And if after seeing the evidence you are still concerned about fruit and glucose spikes, enjoy some nuts and seeds (say walnuts, almonds, sunflower or pumpkin seeds) with your fruit. Healthy fats, satiating protein, additional polyphenols and micronutrients all support better health outcomes. What happens if you blend fruit, consumed as a smoothie? We review the evidence here.
And what else can fruit do? Make you happy! A 2024 study from Singapore (Li et al) showed that study participants who consumed at least three servings of fruit per day, compared to those who ate less than one serving, had a 21% lower risk of age-related depression. This can be accomplished by having one to two servings of fruit after each meal.
Improving health is about finding motivation, prioritising self-care and taking action. If you want to take effective and targeted steps that fit into your unique lifestyle, The Whole Health Practice is here to help. Whether you want to improve eating practices, beat chronic illness or enhance your overall well-being, our consultations and programs deliver results that are tailored to your needs.
Stay Healthy,
Alastair
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Related Studies and Resources
SingHealth Diabetes and Food: Top Tips on Fibre, Fruit and More.
Diabetes UK - fruit consumption, read more here.
Li H, Sheng LT, Jin A, Pan A, Koh WP. Association between consumption of fruits and vegetables in midlife and depressive symptoms in late life: the Singapore Chinese Health Study. J Nutr Health Aging. 2024 Jun;28(6):100275. doi: 10.1016/j.jnha.2024.100275. Epub 2024 May 28. PMID: 38810515.
Ellouze, I.; Akhavan, N.; Singar, S.; Dawkins, K.; Nagpal, R.; Arjmandi, B. The Relationship of Fruits and Fruit-Products Consumption with Glucose Homeostasis and Diabetes: A Comprehensive Update on the Current Clinical Literature. Dietetics 2023, 2, 237-266. https://doi.org/10.3390/dietetics2030018
Shukla AP, Karan A, Hootman KC, Graves M, Steller I, Abel B, Giannita A, Tils J, Hayashi L, O'Connor M, Casper AJ, D'Angelo D, Aronne LJ. A Randomized Controlled Pilot Study of the Food Order Behavioral Intervention in Prediabetes. Nutrients. 2023 Oct 20;15(20):4452. doi: 10.3390/nu15204452. PMID: 37892527; PMCID: PMC10610476.
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Chen Y, Qie X, Quan W, Zeng M, Qin F, Chen J, Adhikari B, He Z. Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication? Crit Rev Food Sci Nutr. 2023;63(20):4288-4324. doi: 10.1080/10408398.2021.2000932. Epub 2021 Nov 18. PMID: 34792409.
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Jia X, Xuan L, Dai H, Zhu W, Deng C, Wang T, Li M, Zhao Z, Xu Y, Lu J, Bi Y, Wang W, Chen Y, Xu M, Ning G. Fruit intake, genetic risk and type 2 diabetes: a population-based gene-diet interaction analysis. Eur J Nutr. 2021 Aug;60(5):2769-2779. doi: 10.1007/s00394-020-02449-0. Epub 2021 Jan 5. PMID: 33399975; PMCID: PMC8275558.
Halvorsen RE, Elvestad M, Molin M, Aune D. Fruit and vegetable consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of prospective studies. BMJ Nutr Prev Health. 2021 Jul 2;4(2):519-531. doi: 10.1136/bmjnph-2020-000218. PMID: 35028521; PMCID: PMC8718861.
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Other
Wang DD, Li Y, Bhupathiraju SN, Rosner BA, Sun Q, Giovannucci EL, Rimm EB, Manson JE, Willett WC, Stampfer MJ, Hu FB. Fruit and Vegetable Intake and Mortality: Results From 2 Prospective Cohort Studies of US Men and Women and a Meta-Analysis of 26 Cohort Studies. Circulation. 2021 Apr 27;143(17):1642-1654. doi: 10.1161/CIRCULATIONAHA.120.048996. Epub 2021 Mar 1. PMID: 33641343; PMCID: PMC8084888.
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