Grapefruits are large, tart and tangy fruits known primarily for their vitamin C content. Named for the way the fruit hangs in bunches (like grapes), the grapefruit is a nutritious member of the citrus family. The fruit, often mistaken for a pomelo, can be found with either white, pink, or red pulps – all with different levels of sweetness while offering very similar benefits. The best part? While grapefruits are normally in season from winter through early spring, you can experience the health benefits of grapefruit all year round. Here is what the fruit has to offer.

Nutrition content
A glass of chilled grapefruit juice, especially in winter, helps seriously boost your levels of vitamin C, which gives grapefruits a high place amongst various citrus fruits. It’s packed with the benefits derived from various nutrients and vitamins, including potassium and lycopene. Along with these, it also contains calcium, sugar and phosphorous. Grapefruits are high in fiber and low in calories, and they contain bioflavonoids and other plant chemicals that protect against serious diseases like cancer, heart disease, and the formation of tumors. Grapefruit juice is ranked among those highest in antioxidant activity. Seeing as grapefruits are rich in essential vitamins and minerals, there is no doubt that the fruit can provide numerous health benefits.

Grapefruits for weight loss, appetite control and metabolism improvement
The grapefruit diet is apparently not a myth. That's what a new study by the Nutrition and Metabolic Research Center at Scripps Clinic has confirmed. Researchers there found that the simple act of adding grapefruit and grapefruit juice to one's diet can result in weight loss. A 12-week study, led by Dr. Ken Fujioka, monitored weight and metabolic factors, such as insulin secretion, of the 100 men and women. On average, participants who ate half a grapefruit with each meal lost 3.6 pounds, while those who drank a serving of grapefruit juice three times a day lost 3.3 pounds. However, many patients in the study lost more than 10 pounds.

"For years people have talked about the grapefruit diet, and some even swear by it, but now, we have data that grapefruit helps weight loss," said Dr. Fujioka, principal researcher at the Nutrition and Metabolic Research Center at Scripps Clinic. "Our study participants maintained their daily eating habits and slightly enhanced their exercise routine; the only dietary change was the intake of Florida grapefruit and grapefruit juice." The study abstract concludes: “Although the mechanism of this weight loss is unknown it would appear reasonable to include grapefruit in a weight-reduction diet.”
Grapefruit works also as an excellent appetite suppressant as compared to many other substances and foods. It is said that smell of the grapefruit reduces the feeling of hunger, which is the reason why people often include grapefruit in their weight loss programs.

The high amounts of fiber contained in this fruit can also satisfy hunger and help people avoid the temptation to overeat, since it is a bulky food, and stimulates cholecystokinin to be released, a hormone that regulates digestive juices and acts as a hunger suppressant.
Last but not least, grapefruits boost metabolism: nootkatone, a very rare and important compound found within grapefruits, improves energy metabolism in the body activating the AMPK (protein kinase implicated in the control of metabolism). This results in higher endurance and energy, increased weight loss, and a reduction in the the chances of developing diabetes.

Grapefruits reduce heart disease risk
Further adding to the health benefits of grapefruit, some studies have also found that the fruit contains compounds responsible for boosting heart health and reducing heart disease risk. One study, published in the Journal of Agricultural and Food Chemistry, discovered compounds found in red and blond grapefruit were able to lower blood cholesterol levels in as little as one month. The research was performed on 57 patients who had had coronary bypass surgery.

Grapefruits repair DNA, protect against cancer, osteoarthritis and rheumatoid arthritis
After exposing cell cultures to naringenin, a flavonoid concentrated in grapefruit, researchers found that the compound helps DNA to repair by inducing two DNA-mending enzymes during the replication stage. The study was published in the Journal of Nutritional Biochemistry.

In addition to naringenin protecting DNA, vitamin C is essential for preventing free radical damage. The vitamin C content and phytonutrients found in grapefruit help to prevent a number of issues related to DNA damage and oxidative stress, including: osteoarthritis, rheumatoid arthritis, asthma, and cancer growth.
Finally, grapefruit juice has been shown to protect against colon cancer when consumed 3 times daily at 6 ounces for each serving. The research, presented at the 228th National Meeting of the American Chemical Society, found that grapefruit, along with isolated compounds found in grapefruit (apigenin, hesperidin, limonin, naringin, naringenin, and nobiletin), ignite the death of cancer cells and even increases production of healthy colon cells. This may be one of the most intriguing health benefits of grapefruit.

Grapefruits boost immune system, prevent colds
Along with containing high amounts of vitamin A, potassium, folate, and thiamin, grapefruits contain one of the most well known vitamins for boosting immunity and lessening the duration of colds or sickness – vitamin C. Vitamin C has been shown in numerous studies to lessen respiratory issues and prevent asthma. One study published in the journal Thorax found that consuming vitamin C-rich fruit reduced wheezing symptoms in children while also aiding asthma, chronic cough, shortness of breath, and even runny nose.

Grapefruits help control diabetes
Diabetic patients can safely eat grapefruit, because consuming grapefruit can reduce the level of starch in the body. If a patient is diabetic, intake of grapefruit can help them to regulate the flow of sugar in their body, effectively handling the disease. Recent studies have shown this beneficial relationship between diabetes and grapefruits to be due to the flavonoid content of grapefruits, along with a number of other healthy benefits from those compounds.

Grapefruits prevent kidney stones
A study published in the British Journal of Nutrition found that women drinking 1/2-1 liter of grapefruit, apple, or orange juice daily reduced their risk of developing kidney stones. The juices work to increase urinary pH and hasten the rate at which citric acid is excreted, which reduces the risk of calcium oxalate stones forming.

Grapefruits for liver cleansing and detoxification
Grapefruit contains numerous liver-cleansing agents. Among them are vitamin C, various antioxidants, and phytonutrients called limonoids that helps toxic compounds to excrete from the liver by making them more water soluble. The fruit also contains a flavonoid compound known as naringenin, as mentioned earlier, which causes the liver to burn fat rather than store it.

Grapefruits solve the problem of indigestion and acidity
Grapefruit is useful for solving the problem of indigestion. It is very light as compared to other foods and thus, acts immediately on indigestion by easing the heat and irritation caused in the stomach. It improves the flow of digestive juices, which eases the movement of the bowels and keeps your excretory system regulated. This is due to the presence of fiber and vegetative pulp in grapefruits, that adds bulk to the bowels and regulates your excretory schedule, and grapefruit extract is also often used in modern medicine for these same reasons.
Fresh grapefruit juice creates an alkaline reaction after digestion. The citric acid of the fruit is contained in the human body and thus, increases the effect of the alkalinity reaction after digestion.

Grapefruits help treat gum disease
According to a study published in the British Dental Journal, consuming 2 grapefruits each day for two weeks results in significantly less bleeding of the gums. Grapefruits were shown to drastically increase plasma vitamin C levels and help manage periodontal disease.

Grapefruits for skin health
The high amount of vitamin A in grapefruit endows it with powerful antioxidant properties to combat skin damage caused by oxidative stress. Moreover, grapefruit vitamin C content is essential for producing healthy collagen, a protein that keeps your complexion plump and smooth. Grapefruit helps maintain adequate moisture levels in the skin, protecting it from dryness, psoriasis, acne, and wrinkles.

Grapefruits fight insomnia
A simple glass of grapefruit juice, if drunk before going to bed, can promote healthy sleep and alleviate the irritating symptoms and repercussions of insomnia. This is due to the presence of tryptophan in grapefruits, the chemical we often associate with becoming sleepy after big meals. The levels of tryptophan in grapefruit juice lets us nod off peacefully to sleep.

Warning: many medications don’t mix with grapefruits: if you are taking medication, be sure to check with your doctor before eating grapefruit or drinking grapefruit juice, as many medications mix badly with the fruit. Certain chemicals in grapefruits, like naringin, and other less common compounds can negatively interact with various drugs and cause damage to your organ systems. Here is a list of medications that shouldn’t be taken with grapefruit juice.

Here is a delicious recipe, a "good" idea to take advantage of the benefits of grapefruit...

Citrus salad with grilled shrimp adobo

Ingredients
4 cloves garlic, minced
1 teaspoon ground cumin
1/2 cup fresh grapefruit juice
1/4 cup orange juice concentrate
2 tablespoons extra virgin olive oil
salt and freshly ground black pepper to taste
1 pound jumbo shrimp, peeled and de-veined (leave the tail sections intact)
4 oranges
4 grapefruits
5 cups washed, stemmed spinach leaves or mesclun
Directions:
Combine the ingredients for the marinade in a mortar and pestle or blender and puree until smooth. Correct the seasoning, adding salt and pepper to taste: the mixture should be highly seasoned. Combine the shrimp and 2/3 of the marinade in a non-reactive bowl and stir to mix. Cover the bowl with plastic wrap and marinate the shrimp for 30 minutes, turning occasionally.
Cut the rind (both the zest and white pith) off the oranges to expose the flesh. Make V-shaped cuts to remove the individual segments from the membranes, working over a bowl to catch the juices. Remove any seeds with a fork. Section the grapefruit the same way. Arrange the orange and grapefruit segments around the outside edge of a platter or 4 salad plates, alternating orange and grapefruit segments. Mound the spinach or mesclun in the center. - The recipe can be prepared ahead to this stage. - Preheat the barbecue grill or broiler to high. Grill or broil the shrimp until cooked, 1 to 2 minutes per side. Arrange the shrimp on top of the salad and spoon the reversed marinade over the greens. orange and grapefruit segments, and shrimp.
Makes 4 servings.