Why regular intake of grapefruit prevents diabetes, heart problems
Why regular intake of grapefruit prevents diabetes, heart problems
By Sade Oguntola
IN the last 10 years, grapefruit has been a pharmacologist’s nightmare, given its popularity and potential for interaction with many medications used in the treatment of many diseases. However, it is now emerging that apart from drug interactions, which have largely been attributed to some of its chemical constituents, its regular intake could play more important roles in the prevention of diabetes and cardiovascular diseases.
Researchers in a new study that tried to unravel the “mystery” of this ancient fruit, found it to be a functional food that can promote good health in individuals as well as support the management and prevention of diabetes and diseases of the heart and blood vessels.
Grapefruit is popular worldwide, not only because of its taste and nutritive value, but it is also considered to be a functional food that promotes good health.
Scientific claims of medicinal properties of grapefruit have led to increased worldwide consumption and a wide variety of bioactive compounds in grapefruit are being studied by scientists.
For instance, they have found that the relative abundance of the chemical substances in this fruit varies according to the variety, geographical location, time of harvesting and the method of processing the grapefruit.
Nonetheless, the most abundant are the flavonoids, which also accounts for its bitter taste.
Other chemical constituents identified in grapefruit include limonoid aglycones, glucosides, furanocoumarins, Vitamin C, folic acid, carotenoids, pectin and potassium.
However, grapefruit–drug interactions have been known for nearly a decade now, but unlike drug–drug interactions, food–drug interactions are difficult to legislate. Hence, nothing has been done to address the dangers that patients often expose themselves to while taking grapefruit with prescribed medications such as those for hypertension (calcium channel blockers), heart problems and high blood cholesterol levels (statins).
In fact, medicines for heart and blood vessel problems constitute more than 50 per cent of the close to 40 or more drugs so far known to interact with grapefruit, and the list is growing.
Nevertheless the degree of interaction of grapefruit-drug appears to be independent of whether the grapefruit was taken alongside with the drug. Even after few hours of taking grapefruit, the reaction can still occur.
Although grapefruit–drug interactions have been documented in over 225 publications in the scientific literature, involving more than 25 drugs, most of the information available on this in biomedical literature is largely built on speculations from in laboratory experiments and a few clinical(human) studies. Only a few clinical cases have been documented on grapefruit juice–drug interactions, perhaps because many such cases go unreported.
Unfortunately, some people, including the elderly are particularly vulnerable to grapefruit-induced drug interactions, since they are often on multiple medications, and they experience diminished drug disposition capacity.
Traditionally, grapefruit–drug interactions have been viewed in terms of enhancement of unwanted adverse effects. Nonetheless, positive aspects of grapefruit-induced drug interactions would be related to a potential reduction in costs incurred on reduced treatment regimens of different ailments such as diabetes.
For instance, Peter M.O Owira in collaboration with John Ojewole at the Department of Pharmacology, School of Pharmacy and Pharmacology, Faculty of Health Sciences, University of KwaZulu-Natal, Durban, South Africa, observed that the metformin-like effects of grapefruit juice supports the regulation of blood glucose.
This was a 2010 study carried out in rats and published in the Cardiovascular Journal of Africa.
Clearly, the clinical implications of this finding is significant, given that phenformin, another diabetes drug similar to metformin had to be withdrawn from the market when 50 per cent of the patients who took it died due to lactic acidosis.
One side effect of taking Metformin is lactic acidosis, and for this reason some diabetics should not take Metformin unless specifically advised to do so by their medical doctor. These include diabetics with kidney problems, liver problems and heart problems.
Although Metformin has been proven in clinical trials to lower glucose levels in people suffering from type 2 diabetes, in some cases the drug can lead to a buildup of lactic acid in the blood, which is referred to as lactic acidosis. This side effect is rare, affecting about one in every 30,000 Metformin patients. However, although uncommon, lactic acidosis amongst diabetics can be fatal.
Nonetheless, grapefruit has been part of many diets since the 1930 as an anti-obesity ingredient. A recent study reported that consumption of whole grapefruit or grapefruit juice is associated with significant weight loss and improved insulin resistance in patients with the metabolic syndrome, compared to placebo.
Metabolic syndrome is a group of conditions such as high blood pressure, high blood sugar and blood cholesterol, which put people at risk for heart disease and diabetes. Not all doctors agree on the definition or cause of metabolic syndrome. The cause might be insulin resistance. Insulin is a hormone your body produces to help you turn sugar from food into energy for your body. If you are insulin resistant, too much sugar builds up in your blood, setting the stage for disease.
Why regular intake of grapefruit defends people from diabetes, heart problems Nonetheless, the researchers wrote, “consumption of grapefruit may, therefore, have beneficial effects in patients with type 2 diabetes mellitus and other degenerative diseases, which may scientifically justify the age-old tradition of dietary supplementation with grapefruit.
“Grapefruit consumption has been associated with decreased fasting blood glucose and insulin levels, and total blood cholesterol level, low-density lipoprotein and triglyceride levels. So much attention has been paid to grapefruit–drug interactions that, to date, the role of grapefruit in prevention of the development of the metabolic syndrome, despite decades of advocacy, is not fully understood.”
Dietary flavonoids like naringin and hesperidin that are present in grapefruit have been identified as anti-diabetic and may reduce the risk of age-related chronic diseases. According to them, combined treatment with naringin and vitamin C has been demonstrated to ameliorate diabetes under laboratory conditions.
That flavonoids present in citrus fruits like grapefruits have a promising compounds against cardiovascular diseases is a dream becoming reality. Epidemiological studies are unanimous that increased dietary intake of flavonoids has been associated with reduced risk of ischaemic stroke and heart disease by improving blood circulation, preventing blood clotting and production of LDL, the bad cholesterol.
Certainly, attention has now shifted to investigating the how these flavonoids are able to protect against cardiovascular diseases such as heart disease and diabetes. No doubt, with the coming years, basic and clinical research on the heart and diseases that affect it would focus more on grapefruit and its flavonoids and/or their chemical derivatives.
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