In our world, the cost of fruit keeps rising while bananas remain affordable. Originating about 4,000 years ago in Malaysia and today commercially grown in Costa Rica, Mexico, Ecuador, China, Thailand, and Brazil. (Read the History of Bananas here.) This crescent-shaped fruit is mostly yellow but often known for this color. They contain fiber, potassium, magnesium, as well as vitamins C and B6. Over the years, a number of different researchers have found the nutritional benefits of bananas.
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BANANAS MAY HELP PREVENT STROKES
A study published in 2002 followed 5,600 men and women older than 65 years for four to eight years. During this time, researchers recorded the amount of potassium that the participants consumed, the levels of potassium in their blood, their use of diuretics (medications for high blood pressure, heart failure, and kidney disease), and the number of strokes that the subjects experienced. The researchers found that the risk of stroke was highest among those who had low levels of serum potassium in the blood and low intake of foods, such as bananas, with higher levels of potassium. So, to help prevent strokes one must add the nutritional benefits of bananas to their daily diet.
A 2007 issue of Environmental Nutrition describes research conducted at the Harvard School of Public Health. Researchers reviewed the diets of more than 43,000 men and found that those with the highest intake of foods high in magnesium and potassium, like bananas, had a reduced risk of stroke. The article noted that, “The Food and Drug Administration now even permits bananas to be marketed with a health claim points to potassium’s link in the prevention of high blood pressure and stroke.”
RESEARCH IN ALZHEIMER’S DISEASE
A study published in 2005 in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association used data from the Baltimore Longitudinal Study of Aging to review the diets of 579 non-demented people age 60 and over. Over the next several years (the mean follow-up was 9.3 years), 57 people developed Alzheimer’s disease. The researchers determined that those who consumed at least the recommended dietary allowance of 400 micrograms of folate, a key in the nutritional benefits of bananas, had a 55 percent reduced risk for developing Alzheimer’s disease. In another study published in 2008 in the Journal of Food Science, researchers found that when they exposed nerve cells (neurons) to banana, orange, and apple extracts, the antioxidants, or specifically phenolic phytochemicals, in the fruit prevented oxidation.
Why is this important? There is a good deal of evidence that brains of people with Alzheimer’s are exposed to high levels of oxidative stress. This results in cellular dysfunctions that cause nerve degeneration. Thus, including more foods such as bananas in the diet may protect the brain from the ravages of diseases like Alzheimer’s. “These results suggest that fresh apples, bananas, and oranges in our daily diet, along with other fruits may protect neuron cells against oxidative stress-induced neurotoxicity and may play an important role in reducing the risk of neurodegenerative disorders such as Alzheimer’s disease.”
A University of California, San Francisco, study published in 2002 in The Journal of Clinical Endocrinology & Metabolism noted that the consumption of potassium-rich foods, such as bananas, in postmenopausal women helps prevent the loss of calcium from the bones. How does this work? Salt does not appear to have a similar effect on men or younger women. It is in postmenopausal women that the intake of excess amounts of salt increases the amount of bone minerals excreted in the urine.
In the study, 60 healthy postmenopausal women were placed on a low salt diet for three weeks. Measurements were taken of their excreted calcium, as well as bone protein and NTx (high levels indicate bone is being broken down or reabsorbed). After three weeks, the subjects were placed on a high salt diet. Half the women were given a potassium supplement; the other half received a placebo. The women remained on the high salt diet for four weeks.
The researchers found that the calcium loss in women taking potassium citrate decreased four percent. The placebo group had an increase of 33 percent. NTx excretion increased 7.5 percent in women on potassium citrate, while it increased 23 percent in women taking the placebo. The researchers note that, “Increased intake of dietary sources of potassium alkaline salts, namely fruit and vegetables, may be beneficial for postmenopausal women at risk. Especially those at risk for osteoporosis, particularly those consuming a diet generous in sodium chloride.”
A study conducted in Sydney, Australia, and published in 2007 in The American Journal of Clinical Nutrition evaluated how foods that are high on the glycemic index, such as bananas, may assist people dealing with insomnia. Foods like these increase the levels of the amino acid tryptophan in the blood; and, tryptophan is well-known to foster drowsiness. People who ate higher glycemic foods about four hours before going to bed required only nine minutes to fall asleep; people who ate lower glycemic foods needed 17.5 minutes to fall asleep.
When the high glycemic diet was given one hour before bedtime no such dramatic difference occurred. But, the study only included 12 healthy men between the ages of 18 and 35. The high glycemic diets will likely lead to excess weight gain and diabetes. So, they are not a good choice for those who are already overweight or at higher risk for diabetes.
MOOD AND COGNITION
In a Dutch study, published in 2002 in Brain, Behavior, and Immunity, researchers examined what happens to mood and cognition when the body’s levels of tryptophan (which, as previously noted, is found in bananas) are depleted. The subjects consisted of 27 volunteers . Of these, 16 had an immediate relative dealing with major depression. When researchers lowered the level of tryptophan in the bodies of the volunteers, they had problems with memory. In addition, half of the subjects with a family history of depression felt depressed. Opposingly, nine percent of those without a family history of depression reported feeling depressed. These findings should be of special interest to those who have a family history of depression. Also important to those who have low levels of tryptophan in their bodies,. These symptoms may be the caused by a number of factors such as dieting and undergoing immunotherapy for cancer.
Ina Swedish study published in 2005 in the International Journal of Cancer, researchers obtained dietary information on a group of 61,000 women between the ages of 40 and 76 for 13.4 years. During this time, 122 women developed renal cell carcinoma. The researchers found that certain fruits and vegetables, such as bananas, offered protection against renal cell carcinoma. The most common form of kidney cancer. People who ate bananas four to six times per week had about half the risk of developing this type of cancer as people who did not eat bananas. Some epidemiologists contend that anti-cancer properties of bananas are a result of their high amounts of potassium.
A study conducted by researchers in London, which was published in 2007 in the European Respiratory Journal, investigated whether wheezing was less common in children with higher consumption of fruits such as bananas. Using a questionnaire, the researchers surveyed 2,640 children between the ages of five and ten years. The researchers found that children who ate bananas one or more times per day were less likely to wheeze.
Bananas, and other foods such as honeydew and zucchini, contain proteins in their pollen that are similar to ragweed pollen. People who react to ragweed pollen may also react to eating these foods. Particularly during the ragweed season that begins in August and ends with the first fall frost. Still, for most people, bananas should be a wonderful, cost-effective part of the diet. They are recommended to be eaten frequently.