Thursday, December 3, 2009

Healthy food: Prunes

Prunes' Unique Antioxidant Phytonutrients

The fresh version (plums) and the dried version (prunes) of the plant scientifically known as Prunus domestica have been the subject of repeated health research for their high content of unique phytonutrients called neochlorogenic and chlorogenic acid. These substances found in prunes and plums are classified as phenols, and their function as antioxidants has been well documented. These damage-preventing substances are particularly effective in neutralizing a particularly dangerous oxygen radical called superoxide anion radical, and they have also been shown to help prevent oxygen-based damage to fats. Since our cell membranes, brain cells and molecules such as cholesterol are largely composed of fats, preventing free radical damage to fats is no small benefit.

Beta-Carotene for Even More Antioxidant Protection

Prunes' ability to deter oxygen-related damage to our cells is also related to their beta-carotene content. Prunes emerged from our food ranking system as a good source of vitamin A (in the form of beta-carotene)-just a quarter-cup of prunes will give you 16.9% of the daily value for vitamin A. Beta-carotene acts as a fat-soluble antioxidant,eliminating free radicals that would otherwise cause a lot of damage to our cells and cell membranes. Only after cholesterol has been oxidized by free radicals does it pose a threat to artery walls. The build-up of cholesterol in the artery walls forms plaques that can either grow so large they block blood flow or rupture, releasing a clot that can impede the flow of blood, and triggering a heart attack or stroke. Free radicals can also damage cellular DNA, causing mutations which, if serious enough, can result in the formation of cancerous cells. In addition, by causing damage, free radicals contribute to inflammation, which is one way the body clears out cells or other substances that have been damaged. In this way, free radicals increase the severity of a number of different conditions. This is why beta-carotene, which shuts down free radicals, has been shown in studies to be helpful for the prevention of a variety of diseases, including atherosclerosis, diabetic heart disease, and colon cancer, and why it has also been found useful for reducing the severity of inflammatory conditions like asthma, osteoarthritis, and rheumatoid arthritis.

Potassium for Cardiovascular Health

Prunes are a good source of potassium, providing 9.0% of the daily value for this mineral in a quarter-cup. Potassium is an essential mineral for maintaining normal blood pressure and heart function. Since a quarter cup of prunes contains a whopping 316.6 mg of potassium and only 1.7 mg of sodium, those diced dried prunes on top of your breakfast cereal may help to prevent high blood pressure and protect against atherosclerosis.

The effectiveness of potassium-rich foods like prunes in lowering blood pressure has been demonstrated by a number of studies. For example, researchers tracked over 40,000 American male health professionals over four years to determine the effects of diet on blood pressure. Men who ate diets higher in potassium-rich foods, as well as foods high in magnesium and cereal fiber, had a substantially reduced risk of stroke.

In addition to these cardiovascular benefits, the potassium found in prunes may also help to promote bone health. Potassium may counteract the increased urinary calcium loss caused by the high-salt diets typical of most Americans, thus helping to prevent bones from thinning out at a fast rate.

Prunes are widely known as a good source of dietary fiber, a reputation that was confirmed in our ranking system in which prunes were found to supply 12.1% of the daily value for fiber in just a quarter-cup. The health benefits provided by prunes' fiber are substantial:

Normalizing Blood Sugar Levels and Helping with Weight Loss

Prunes' soluble fiber helps normalize blood sugar levels by slowing the rate at which food leaves the stomach and by delaying the absorption of glucose (the form in which sugar is transported in the blood) following a meal. Soluble fiber also increases insulin sensitivity and can therefore play a helpful role in the prevention and treatment of type 2 diabetes. And, prunes' soluble fiber promotes a sense of satisfied fullness after a meal by slowing the rate at which food leaves the stomach, so prunes can also help prevent overeating and weight gain.

Prunes' Fiber for Regularity, Lower Cholesterol, & Intestinal Protection

Prunes are well known for their ability to prevent constipation. In addition to providing bulk and decreasing the transit time of fecal matter, thus decreasing the risk of colon cancer and hemorrhoids, prunes' insoluble fiber also provides food for the "friendly" bacteria in the large intestine. When these helpful bacteria ferment prunes' insoluble fiber, they produce a short-chain fatty acid called butyric acid, which serves as the primary fuel for the cells of the large intestine and helps maintain a healthy colon. These helpful bacteria also create two other short-chain fatty acids, propionic and acetic acid, which are used as fuel by the cells of the liver and muscles.

The propionic acid produced from prunes' insoluble fiber may also be partly responsible for the cholesterol-lowering properties of fiber. In animal studies, propionic acid has been shown to inhibit HMG-CoA reductase, an enzyme involved in the production of cholesterol by the liver. By lowering the activity of this enzyme, propionic acid helps lower blood cholesterol levels.

In addition, prunes' soluble fibers help to lower cholesterol by binding to bile acids and removing them from the body via the feces. Bile acids are compounds used to digest fat that are manufactured by the liver from cholesterol. When they are excreted along with prunes' fiber, the liver must manufacture new bile acids and uses up more cholesterol, thus lowering the amount of cholesterol in circulation. Soluble fiber may also reduce the amount of cholesterol manufactured by the liver.
A study published in the Archives of Internal Medicine confirms that eating high fiber foods, such as prunes, helps prevent heart disease. Almost 10,000 American adults participated in this study and were followed for 19 years. People eating the most fiber, 21 grams per day, had 12% less coronary heart disease (CHD) and 11% less cardiovascular disease (CVD) compared to those eating the least, 5 grams daily. Those eating the most water-soluble dietary fiber fared even better with a 15% reduction in risk of CHD and a 10% risk reduction in CVD.

Lastly, the insoluble fiber provided by prunes feed friendly bacteria in the digestive tract, which helps to maintain larger populations of friendly bacteria. In addition to producing the helpful short-chain fatty acids described above, friendly bacteria play an important protective role by crowding out pathogenic (disease-causing) bacteria and preventing them from surviving in the intestinal tract.

Fruit and Cereal Fiber Protective against Postmenopausal Breast Cancer

Results of a prospective study involving 51,823 postmenopausal women for an average of 8.3 years showed a 34% reduction in breast cancer risk for those consuming the most fruit fiber compared to those consuming the least. In addition, in the subgroup of women who had ever used hormone replacement, those consuming the most fiber, especially cereal fiber, had a 50% reduction in their risk of breast cancer compared to those consuming the least. Int J Cancer. 2008 Jan 15;122(2):403-12.

Fruits richest in fiber include apples, dates, figs, pears and prunes. When choosing a high fiber cereal, look for whole grain cereals as they supply the most bran (a mere 1/3rd cup of bran contains about 14 grams of fiber).

Iron Absorption

The ability of plum and prune to increase absorption of iron into the body has also been documented in published research. The ability of plum and prune to make iron more available may be related to the vitamin C content of this fruit.

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