Michela Villa
Marta Vernero
INTRODUCTION
Banana not only is very delicious, but also has a lot of medical value. It is produced by a plant called Musa (probabilly from the name of the doctor who discovered it), a member of the Musaceae’s family plant; particularly edible bananas come from Musa Acuminata and Musa Blbisiana species.
This fruit is made of water (75%), carbohydrate (23%), proteins (1%), fatty acids (0,3%) and alimentar fiber (2,3%) and their proportions can change according to the grade of maturation and species. Moreover, pulp contains lots of vitamins such as vitamin A, B2, B1, C, PP, B6 (it promotes protein’s metabolism) and E, and it is full of minerals as calcium, phosphorus, iron and potassium. All these elements make it very helpful to regenerate skin, that is why it is believed to help maintaining a young appearance.
Bananas can also help us overcome or prevent a substantial number of illnesses and conditions, making it a must to add to our daily diet. In fact, a study carried out on 61.000 women, demonstrated that eating two or three bananas a week can cut the risk of kidney cancer to 50%.
An other advantage of bananas was tested in UK on a sample of two-hundred students who tried to eat 3 bananas a day (one for breakfast, one in the morning brake and one for lunch) and reported that they were able to be more concentrated on their studies and that their brains’ performances were highly improved.
However, most important and studied effects of bananas are:
- inhibition of hiv replication
- improving physical performances
- prevention from hypertension and stroke
- cure for depression
- antiacid action on stomach
- regulation of bowel’s motility
- cross reaction in allergies.
(Wikipedia)
BANANA AGAINST HIV
BanLec is a jacalin-related lectin isolated from the fruit of bananas, Musa acuminata. This lectin binds to high mannose carbohydrate structures, including those found on viruses containing glycosylated envelope proteins such as human immunodeficiency virus type-1 (HIV-1). University of Michigan Medical Center in USA led a trial to investigate the role of BanLec in inhibiting HIV replication.
The HIV-1 envelope protein gp120 contains 20–30 possible N-linked glycosylation sites. Because glycosylation is essential to the virus, it presents an attractive therapeutic target. The lectin termed BanLec, isolated from the ripened fruit of the banana (Musa acuminata cultivars) can recognize high mannose structures. Therefore, scientists hypothesized that BanLec might inhibit HIV-1 through binding of the glycosylated HIV-1 envelope protein, gp120. An enzyme-linked immunosorbent assay confirmed this teory. Furthermore, BanLec is able to block HIV-1 cellular entry, as indicated by the decreased levels of the strong-stop product of early reverse transcription seen in the presence of BanLec. The relative anti-HIV activity of BanLec compared favorably to other anti-HIV lectins (two anti-HIV drugs currently in clinical use). Based on these results, BanLec is a potential component for an anti-viral microbicide that could be used to prevent the sexual transmission of HIV-1.
Because glycosylation is not specific to HIV-1, lectins have the potential to inhibit the replication of a broad spectrum of viruses. Indeed, it has been shown that lectins can inhibit other enveloped viruses including Ebola, Marburg, influenza, severe acute respiratory syndrome coronavirus, and hepatitis C virus.
One potential benefit of the use of lectins as anti-HIV agents is their ability to target multiple different glycosylation sites on the virus, thus making it more difficult for resistance to develop. In support of this prediction, previous studies that determined the resistance profiles of HIV-1 treated with lectin showed that multiple mutations in the envelope sequence were needed for the development of resistance. Furthermore, different mutations in N-linked glycosylation sites are required for the development of resistance to different lectins. This suggests that the combinatorial or simultaneous use of multiple lectins can reduce the likelihood of failure of a lectin-based anti-viral therapy due to resistance.
A lectin isolated from bananas is a potent inhibitor of HIV replication, 2010.
BANANA AS AN ENERGY SOURCE DURING EXERCISE
A study of North Carolina Research Campus, Kannapolis (USA), compared the acute effect of ingesting bananas (BAN) versus a 6% carbohydrate drink (CHO) on 75-km cycling performance and postexercise inflammation, oxidative stress, and innate immune function using traditional and metabolomics-based profiling. Trained cyclists (N = 14) completed two 75-km cycling time trials (randomized, crossover) while ingesting BAN or CHO (0.2 g/kg carbohydrate every 15 min). Pre-, post-, and 1-h-post-exercise blood samples were analyzed for glucose, granulocyte and monocyte phagocytosis and oxidative burst activity, nine cytokines, F -isoprostanes, ferric reducing ability of plasma (FRAP), and metabolic profiles using gas chromatography-mass spectrometry.
Heavy exertion induces transient inflammation and oxidative stress, and wide ranging perturbations in the immune system. Various nutritional agents have been tested for their capacity to attenuate these indicators of physiologic stress while supporting exercise performance and recovery. Bananas are a cost effective energy source and used by endurance athletes because of the perception that they are a good source of carbohydrate and potassium.
In conclusion, in this randomized, crossover study, cyclists ingesting BAN or CHO at a rate of 0.2 g/kg carbohydrate every 15 min (and one 0.4 g/kg carbohydrate dose pre-exercise) were able to complete 75-km cycling trials with no differences in performance measures. Changes in blood glucose, inflammation, oxidative stress, and innate immune measures were also comparable between BAN and CHO 75-km cycling trials, and similar to what we have previously reported for carbohydrate-fed athletes. Shifts in serum metabolites following BAN and CHO 75-km cycling time trials were extensive, and indicated a similar pattern of increased liver glutathione production and fuel substrate utilization including glycolysis, lipolysis, and amino acid catabolism. FRAP was higher during BAN compared to CHO, but did not translate to diminished oxidative stress as measured with F -isoprostanes. Serum levels of free dopamine increased in BAN compared to CHO, but concentrations were small with no demonstrable cardiovascular effects. Indeed, after ingestion, an undetermined proportion of food dopamine is absorbed, with most rapidly conjugated by sulfate or glucuronide, blunting most of dopamine's biological activity. Moreover, dopamine cannot cross the blood-brain barrier, and thus does not contribute to mood improvement during exercise free form of dopamine constitutes less than 2% of total plasma dopamine. In general, ingestion of bananas before and during prolonged and intensive exercise is an effective strategy, both in terms of fuel substrate utilization and cost, for supporting performance.
Bananas as an energy source during exercise: a metabolomics approach, 2012
BANANA AND BLOOD PRESSURE
Bananas are one of the most rich-of-potassium fruits, and this is why it is able to decrease blood pressure and, therefore, protect from heart stroke.
A lot of studies (such as the ones led in Vanderbilt University School of Medicine and Harper Medical Communications of Nashville) can confirm this theory; indeed the researchers all agree that “to decrease sodium and increase potassium in our diet is probably the most urgent decision that people have to make for their cardiovascular health”. Indeed, a low potassium intake (below 40 meq/day) has been associated with an increased risk or exacerbation of hypertension and an increased risk of stroke; moreover an increased excretion of potassium can cause an important rise of blood pressure: each three unit higher urinary sodium-to-potassium ratio was associated with a 1.6/1.0 mmHg higher blood pressure. On the other hand an increased income of potassium has shown lower effects in reducing blood pressure in both normotensive and hypertensive patients.
A study was led on genetically engineered rats (called stroke-prone rats because they were likely to have heart attacks due to their new genetic conditions) whose incidence of stroke greatly declined when they were fed a diet rich in potassium. Because high blood pressure is the major risk factor for stroke, scientists suspected that the potassium was working to decrease the rats' blood pressure. This suspicion was ultimately shown to be true, and further research demonstrated that potassium has similar protective effects in humans.
But how is potassium able to decrease blood pressure? The mechanism leading to this association is still unclear, but some hypothesis have been made: one school of thought says that the action of potassium somehow makes blood vessels less sensitive to compounds, like hormones, that normally cause blood vessel contraction. Other researchers suggest that potassium actively produces blood vessel relaxation. Regardless of which theory is correct, both agree that relaxed blood vessels are the ultimate effect of potassium.
Consequently, for people who have hypertension, following an overall eating plan called DASH (Dietary Approaches to Stop Hypertension) may be useful for lowering blood pressure. The DASH diet is higher in potassium, magnesium, and calcium, and lower in total fat, saturated fat, and sodium than the typical American diet, and includes eating bananas to achieve the higher potassium intake.
(Association potassium-blood pressure)
(Association potassium-blood pressure)
(Mechanism of action of potassium)
BANANA AND HAPPINESS
A group called MIND, the largest mental health charity in England, did a study amongst people suffering from depression and found that many of them felt much better after simply eating a banana.
Bananas are rich in serotonin and tryptophan (its precursor). In fact, its peel turns from yellow to brown and even black due to the tryptophan transtormation into serotonin. Anyway, if ingested, this serotonin is destroyed in the stomach by the monoamine oxidase; in addition to that it couldn’t cross blood brain barrier, so it is clear that it could not be its serotonin content that makes us happy. On the contrary, the tryptophan is absorbed by the gastrointestinal tract and is able to cross blood brain barrier, therefore it is converted into serotonine that has a powerful effect on improving our mood and relaxing us.
(Wikipedia)
(Serotonin)
BANANA AS A SOURCE IN DEVELOPING COUNTRIES
Bananas are an ideal food for young children and families for many regions of the world, because of their sweetness, texture, portion size, familiarity, availability, convenience, versatility, and cost. For these reasons bananas can be a potential resource for alleviating some deficiencies in developing countries.
- IRON FORTIFICATION OF BANANA
Iron deficiency anemia is one of the serious ailments related to nutrition in the developing countries. Fruit and vegetable crops favor the bioavailability of iron. Wild bananas are rich of iron, furthermore is possible to create iron-fortified bananas. Iron-fortified bananas provide an effective means of controlling the iron deficiency; thus, they could be developed as a functional food to overcome the malnutrition-related iron deficiency.
- CAROTENOID-RICH BANANAS
Banana cultivars rich in provitamin A carotenoids may offer a potential food source for alleviating vitamin A deficiency, particularly in developing countries. Foods containing high levels of carotenoids have been shown to protect against chronic disease, including certain cancers, cardiovascular disease, and diabetes. Because the coloration of the edible flesh of the banana appears to be a good indicator of likely carotenoid content, it may be possible to develop a simple method for selecting carotenoid-rich banana cultivars in the community.
Iron fortification of banana by the expression of soybean ferritin, 2011
Carotenoid-rich bananas: a potential food source for alleviating vitamin A deficiency, 2003
LATEX-FRUIT SYNDROME
Banana does not only have positive effects: approximately 30-50% of individuals who are allergic to natural rubber latex (NRL) show an associated hypersensitivity to some plant-derived foods, especially freshly consumed fruits, such as banana. This association of latex allergy and allergy to plant-derived foods is called latex-fruit syndrome. An increasing number of plant sources, for example avocado, banana, chestnut and kiwi have been associated with this syndrome. The prevailing hypothesis is that allergen cross-reactivity is due to IgE antibodies that recognize structurally similar epitopes on different proteins that are phylogenetically closely related or represent evolutionarily conserved structures. In a study of Department of Pathophysiology of University of Vienna, several types of proteins have been identified to be involved in the latex-fruit syndrome. As banana is concerned, the proteins involved in this desease are Class I chitinases containing an N-terminal hevein-like domain that cross-reacts with hevein (Hev b 6.02), a major IgE-binding allergen for patients allergic to NRL. Although there is much information about the plant-derived foods and some data about the allergens involved in the latex-fruit syndrome, it is not always clear whether latex sensitization precedes or follows the onset of food allergy.
The latex-fruit syndrome, 2002
CONCLUSION
In conclusion, banana should be introduced in everyone’s diet especially in that of the ones who suffer from hypertension and make lot of sport. Anyway it would be wise to inform your doctor before radically change your diet introducing many bananas, as they could lead you to hyperkalaemia that may cause catastrophic effects.
