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by Prof. Meenakshi Bhattacharjee, Rice University, Houston TX.
Raspberries belong to the rose (Rosaceae) family. Among U.S. consumers, raspberries are the third most popular berry and follow right after strawberries and blueberries. Known as nature’s candy, wild raspberries have been gathered for consumption by humans for thousands of years. With their rich color, sweet juicy taste and antioxidant power, it is no wonder raspberries remain one of the world’s most consumed berries. There are over 200 species of raspberries, all belonging to the scientific genus called Rubus. Fortunately, however, many of the raspberry species that are grown commercially can be placed into one of three basic groups: red, black, and purple raspberries. Each color berry has a unique composition of vitamins, minerals and antioxidants.
According to the USDA National Nutrient Database, one cup of raspberries (about 123 grams) contains 64 calories, 1.5 grams of protein, 0.8 grams of fat, and 15 grams of carbohydrate (including 8 grams of fiber and 5 grams of sugar). Eating one cup of raw raspberries will provide 54% of your vitamin C needs, 12% of vitamin K, 6% of folate, 5% of vitamin E, iron, and potassium, and 41% of manganese needs for the day as well as lesser amounts of thiamin, riboflavin, niacin, pantothenic acid, vitamin B-6, calcium, magnesium, phosphorus, zinc and copper. Raspberries contain the antioxidants alpha and beta-carotene, lutein, zeaxanthin, and choline. Raspberries are also a powerful source of polyphenols such as anthocyanin, flavonols and ellagitannins, which decrease oxidative damage from free radicals and have shown potential in animal and human studies for preventing or reducing risk of chronic diseases such as cancer and heart disease.
Health benefits of consuming raspberries
Many studies have suggested that increasing consumption of plant foods like raspberries decreases the risk of obesity, diabetes, heart disease and overall mortality while promoting a healthy complexion, increased energy, and overall lower weight.
Several animal studies have shown a positive correlation between intake of flavonoids in berries and memory improvement as well as decreasing the delay in cognitive ability related to aging.
A recent report in the American Journal of Clinical Nutrition associated the intake of flavonoid-rich foods like raspberries with a lower risk of death from cardiovascular disease and stated that even small amounts of flavonoid-rich foods may be beneficial. One flavonoid in particular, anthocyanins, have been shown to suppress inflammation that may lead to cardiovascular disease. The high polyphenol content in raspberries may also reduce the risk of cardiovascular disease by preventing platelet buildup and reducing blood pressure via anti-inflammatory mechanisms.
Aedin Cassidy, a nutrition professor at Norwich Medical School at the University of East Anglia in the United Kingdom, led an 18 year study with Harvard Public School of Health tracking 93,600 women aged 25 to 42. She states that their study was able to show “for the first time that a regular sustained intake of anthocyanins from berries can reduce the risk of a heart attack by 32% in young and middle-aged women.” The potassium in raspberries supports heart health as well. In one study, participants who consumed 4,069 mg of potassium per day had a 49% lower risk of death from ischemic heart disease compared with those who consumed less potassium (about 1,000 mg per day).
Given the rich antioxidant and anti-inflammatory phytonutrient mixture found in raspberries, it’s not surprising to see studies showing raspberry benefits in cancer prevention. Chronic excessive oxidative stress and chronic excessive inflammation can combine to trigger the development of cancer cells in a variety of human tissue. By providing a rich supply of antioxidants, raspberries can help lower risk of oxidative stress, and providing a rich supply of anti-inflammatory nutrients, raspberries can help lower the risk of excessive inflammation. When combined, these results mean decreased risk of cancer formation. In animal studies to date, the cancer types most closely examined in relationship to raspberry intake are cancers of the breast, cervix, colon, esophagus, and prostate. Anti-cancer benefits of raspberries have long been attributed to their antioxidant and anti-inflammatory phytonutrients. In animal studies involving breast, cervical, colon, esophageal, and prostate cancers, raspberry phytonutrients have been shown to play an important role in lowering oxidative stress, reducing inflammation, and thereby altering the development or reproduction of cancer cells. But new research in this area has shown that the anti-cancer benefits of raspberries may extend beyond their basic antioxidant and anti-inflammatory aspects. Phytonutrients in raspberries may also be able to change the signals that are sent to potential or existing cancer cells. In the case of existing cancer cells, phytonutrients like ellagitannins in raspberries may be able to decrease cancer cell numbers by sending signals that encourage the cancer cells to being a cycle of programmed cell death (apoptosis). In the case of potentially but not yet cancerous cells, phytonutrients in raspberries may be able to trigger signals that encourage the non-cancerous cells to remain non-cancerous The role of the a protein complex called nuclear factor kappa B (NFkB) is likely to be involved in this set of events.
Within this context of obesity and blood sugar regulation, another aspect of raspberry phytonutrients has captured the attention of researchers involving the ability of raspberry extracts to block activity of an enzyme called alpha-glucosidase. Alpha-glucosidase is a starch-digesting enzyme, and when it becomes active in the digestive tract, it increases the breakdown of starches into sugars. These sugars get absorbed up into the bloodstream and can cause excessively high levels of blood sugar following a meal. (This process is called postprandial hyperglycemia.) By blocking activity of alpha-glucosidase, raspberry extracts may make it possible for persons with type 2 diabetes (or obese persons experiencing problems with blood sugar regulation) to better manage their blood sugar levels. In obese persons with type 2 diabates, adiponectin is not produced in sufficient amounts or, if adequately produced, remains too inactive. This inadequacy of adiponectin in obese persons with type 2 diabetes is a key problem for regulation of their blood sugar and blood fats. By activating adiponectin, the tiliroside in raspberries can help improve insulin balance, blood sugar balance, and blood fat balance in obese persons with type 2 diabetes. In studies to date, there is no indication that raspberry tiliroside will stop weight gain or prevent fat accumulation. But it may be able to help prevent unwanted consequences of too much body fat and compromised regulation of blood sugar, blood insulin, and blood fats. Any plant food with skin has lots of fiber – and raspberries have lots of skin! Eating high-fiber foods help keep blood sugar stable. Studies have shown that type 1 diabetics who consume high-fiber diets have lower blood glucose levels and type 2 diabetics may have improved blood sugar, lipids and insulin levels.
Control of obesity:
One of the most fascinating new areas of raspberry research involves the potential for raspberries to improve management of obesity. Although this research is in its early stages, scientists now know that metabolism in our fat cells can be increased by phytonutrients found in raspberries, especially rheosmin (also called raspberry ketone). By increasing enzyme activity, oxygen consumption, and heat production in certain types of fat cells, raspberry phytonutrients like rheosmin may be able to decrease risk of obesity as well as risk of fatty liver. In addition to these benefits, rheosmin can decrease activity of a fat-digesting enzyme released by our pancreas called pancreatic lipase. This decrease in enzyme activity may result in less digestion and absorption of fat.
Digestion, detox and disease prevention
The fiber and water content in raspberries help to prevent constipation and maintain a healthy digestive tract. Adequate fiber promotes regularity, which is crucial for the daily excretion toxins through the bile and stool. Recent studies have shown that dietary fiber may play a role in regulating the immune system and inflammation, consequently decreasing the risk of inflammation-related conditions such as cardiovascular disease, diabetes, cancer, and obesity.
According to the Department of Internal Medicine and Nutritional Sciences Program of the University of Kentucky, high fiber intakes are associated with significantly lower risks for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases. Increased fiber intake has also been shown to lower blood pressure and cholesterol levels and enhances weight loss for obese individuals. Women should aim for about 25 grams of fiber per day, and men should aim for about 30 grams. One cup of raspberries provides 8 grams of fiber.
Easy on the eyes
Foods high in vitamin C like raspberries have been shown to help keep eyes healthy by providing protection against UV light damage. Raspberries also contain the antioxidant zeaxanthin, which filters out harmful blue light rays and is thought to play a protective role in eye health and possibly ward off damage from macular degeneration. A higher intake of this fruit (3 or more servings per day) has also been shown to decrease the risk of and progression of age-related macular degeneration.
How to incorporate more raspberries into your diet
Raspberries are available fresh, frozen, freeze-dried and in jellies, syrups and jams. Most raspberry jellies, spreads, juices and wine have added sugars, which tack on additional calories. When looking for jellies or jams, go for all-fruit spreads without the added sweeteners and fillers. Make sure to check the label of frozen and dried raspberries, which may also added sugars.
People who tend to eat at least 3 servings of berries per week see the most benefits. The best way to eat raspberries is fresh, right out of your hand (after washing of course)!
Here are some other tips to help increase your raspberry consumption:
Always keep a bag of frozen raspberries on hand for adding to smoothies and oatmeal
Forgo the syrupy sweetness of canned fruit cocktail and make your own fresh fruit cocktail with raspberries, pineapple, sliced peaches and strawberries
Add raspberries, grapes and walnuts to your chicken salad
Slice raspberries and add them to plain Greek yogurt with a drizzle of agave nectar and sliced almonds
Top whole grain waffles or pancakes with fresh raspberries or fold them into muffins and sweet breads
Blend raspberries in a food processor with a little water and use as a fresh syrup to top desserts or breakfast foods
Mix raspberries into a spinach salad with walnuts and goat cheese.
Possible health risks of consuming raspberries
The Environmental Working Group produces a list each year of fruits and vegetables with the highest levels of pesticide residue. Raspberries are number 27 on the list of produce that the EWG suggests that you buy in the organic version to ensure a lower risk of pesticide exposure. Of note, raspberries in supplement form are also being studied for their ability to help with weight loss and combat obesity. Research remains in the early stages, and there have been no human studies to date to prove the effectiveness of supplements like raspberry ketones and extracts, which often have stimulants like hoodia and caffeine added.
There is no doubt that incorporating low-calorie, high nutrient foods like raspberries in accordance with an overall healthy diet will support weight loss, but the ability of concentrated formulas in the form of a supplement to help with weight loss is uncertain at best.