And That’s the Fruity Truth
Marc Gregory Yu, MD
For Filipinos living with diabetes, fruits are both a boon and a bane. On one hand, the overflowing abundance of fresh succulent produce in the country, courtesy of fertile soil and a balmy tropical climate, makes daily meal planning a walk in the park. On the other hand, it is also easy to be lured by an extra serving or two, resulting in the all-too-familiar horror stories of fasting sugar levels suddenly shooting up or HbA1c levels going haywire. The good news is that various bioactive components of several fruits have been studied as potential supplementary therapies to combat diabetes and obesity (This “fruity” approach is in fact well-established in other branches of medicine such as Chinese and Ayurvedic medicine).
Here are some locally available fruits with possible beneficial roles in diabetes:
1. Durian (Durio zibethinus)
The king of fruits may not possess the most pleasant smell among them, but it is widespread in Southeast Asia and has been studied for its anti-diabetic and anti-obesity potential. Every 100-gram portion of edible durian contains 64 grams of water, 27 grams of carbohydrates, 5 grams of lipids, 3 grams of fiber and 1.5 grams of protein. In a small study, durian positively influenced blood sugar balance in 10 diabetic patients by altering both insulin levels and insulin action in the participants. This effect was seen more in those who took durian as compared to those who either took other fruits (mango, pineapple, banana and rambutan) or did not take any fruit. Furthermore, the relatively high level of polyphenols in durian makes the fruit an excellent antioxidant.
2. Mangosteen (Garcina mangostana)
Widely available in both Southeast Asia and India, mangosteen is currently riding the waves of fame in the Philippines under a popular packaged household name. 100 grams of an edible mangosteen portion contain a whopping 80 grams of water, 18 grams of carbohydrates, and almost 2 grams of fiber. In a small study involving 40 participants who were given a proprietary mangosteen juice blend, reductions were seen in body mass index (BMI) and C-reactive protein, a pro-inflammatory chemical in the body. Although the study recommended further investigation on the exact dose needed to replicate the results, its findings were supported by other studies which demonstrated decreased expression of pro-inflammatory genes with mangosteen, as well as decreased production of white fat. Similar to durian, mangosteen is also rich in polyphenols, in addition to other reputed antioxidants such as xanthones, alpha-mangostin, and mangostanin. These substances and have all been shown to protect against the production of bad cholesterol (low density lipoprotein or LDL) in the body.
3. Jackfruit (Artocarpus heterophyllus)
Jackfruit is also widely distributed in both India and Southeast Asia. 100 grams of an edible jackfruit serving contain 73 grams of water, 24 grams of carbohydrates, 1.6 grams of fiber, 1.5 grams of protein, and almost 300 IU of Vitamin A. One study demonstrated improved blood sugar control in both healthy and diabetic patients who ate about 20 g/kg of jackfruit. Moreover, jackfruit has been shown to contain antioxidants such as flavonoids, stilbenoids, arylbenzofurons, and artocarpesin. Artocarpesin, in particular, suppressed low-grade inflammation in mouse white blood cells and rat brains – an important step in the prevention of diabetic complications. An interesting observation is the higher antioxidant capability of jackfruit seeds as compared to the edible portion.
4. Avocado (Persea americana)
Avocado, while available in the Philippines, is mostly native to the Americas. Every 100-gram edible portion contains around three-fourths water, 15 grams of lipids, 8.5 grams of carbohydrates, 6 grams of fiber, and 2 grams of protein. Data from a clinical study of 55 participants who were given 200 g/day of avocado for 6 weeks showed decreases in body weight, BMI, and body fat percentage, pointing to the possible role of avocado in regulating energy and body weight balance. Avocado is rich in monounsaturated fats (MUFA), which help improve cholesterol, triglyceride, and blood sugar levels. Finally, the antioxidant functions of the fruit are due to a substance called persenone A, which was shown to suppress inflammatory chemicals in mouse white blood cells.
5. Guava (Psidium guajava)
Compared to other fruits, studies on the antidiabetic effects of guava are more inconclusive. In a small trial of mice induced to develop diabetes, administration of 1 g/kg of guava juice reduced blood sugar levels, but this effect was not seen in a similar study on rabbits. Research on guava fruit peel extract also yielded ambiguous results. One study showed that the peel extract actually raised blood sugar levels in diabetic mice, while another study demonstrated the opposite (lower blood sugar and cholesterol levels). However, 10 mg/kg of guava extract reduced the accumulation of fat droplets in the liver cells of obese mice, signifying its possible benefit in fatty liver disease. Additional studies are needed to identify the fruit’s beneficial constituents.
6. Lychee (Litchi chinensis)
Lychee is not originally endemic to the Philippines, but has been introduced to the country and has since grown well in specific areas. 100 grams of edible lychee contain than 80% water, 16.5 grams carbohydrates and 1.3 grams of fiber. The feeding of lychee water extract decreased body weight, total cholesterol, fasting blood sugar, and triglyceride levels in rats. The fruit also suppressed tumor necrosis factor, a pro-inflammatory chemical, in the same rat models, and further exhibited preventive actions against the development of diabetesinduced cataract. A new lychee-derived polyphenol mixture called oligonol is currently being marketed as an antioxidant after demonstrating decreases in white fat among mice.
7. Persimmon (Diospyros digyna)
Like lychee, persimmon is also not endemic to the Philippines but has since been introduced from Japan and China. The major component of persimmon peel, proanthocyanidin, decreased blood sugar, cholesterol, triglyceride, and oxidative substance levels in both diabetic rats and diet-induced obese mice, with progressively greater effects at higher doses. Tanin, isolated from persimmon pulp, was demonstrated to possess antioxidant capabilities as well.
THE BOTTOM LINE
This list is not exhaustive. Many other fruits are currently undergoing evaluation for their beneficial effects as well. What remains the main limitation is the lack of large, defining studies with determination of optimal dosages for these fruits. Accessibility is another drawback, as not all of these fruits are endemic to or cultivated in many countries and thus remain “exotic” to the rest of the global community. It is important for both the scientific and agricultural communities in these respective countries to continue conducting research both on the utility and availability of these fruits in combating diabetes and its related disorders. No matter how promising their bio-defensive properties may seem, one can never have too much of a good thing – and it is still always best to eat fruits in moderation.
REFERENCE: Dewanjee et al. Food Chem Toxicol. 2009; Fang et al. J Agri Food Chem. 2008 Fernando etal. J Ethnopharmacol. 1991; Gu et al. Food Res Int. 2008; Kim et al. J Agri Food Chem. 2000; Oh et al. J Ethnopharmacol. 2005; Pieterse et al. Nutrition. 2005; Roongpisuthipong et al. Diab Res Clin Pract. 1991; Sakurai et al. Biosci, Biotech and Biochem. 2008; Toledo et al. Int J Food Sci Nutr. 2008; Udani et al. Nutr J. 2009.
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