Can You Eat Too Many Raisins?

It takes little more than water, time and sunshine to transform plump, juicy grapes into sweet, chewy raisins. That doesn't mean you would have found people downing them by the handful in ancient Rome, where the dried fruit was a precious commodity used to pay taxes, reward top athletes and “cure” old age. Although raisins are far more affordable and obtainable today, you'd still be wise to enjoy them as the Romans did - in moderation.

Serving Size

It takes slightly more than 4 pounds of fresh grapes to produce a pound of raisins, according to the book “Wellness Foods A to Z: An Indispensable Guide for Health-Conscious Food Lovers.” The fresh fruit loses about 80 percent of its water during the drying process, which is why raisins are significantly smaller - and far more nutrient-dense - than grapes. You'll get just over 100 calories from 1 cup of grapes, which is the standard size for a single serving of most fresh fruit. Given that grapes are roughly four times larger than raisins, it makes sense that 1/4 cup of raisins - which also supplies just over 100 calories - amounts to one serving of the dried fruit.

Packed With Fiber

A loosely packed 1/4-cup serving of seedless raisins - or right around 70 raisins, according to the U.S. Department of Agriculture - has about 108 calories, 1 gram of protein, 29 grams of carbohydrates and very little fat. It also provides 1.4 grams of fiber, or 6 percent of the recommended daily value. Because raisins contain equal amounts of soluble and insoluble fiber, they promote normal cholesterol levels as well as bowel regularity. A serving of raisins also supplies 8 percent and 4 percent of the daily values for potassium and iron, respectively. Potassium helps counteract the effects of sodium, iron keeps your cells oxygenated and both minerals are needed for normal muscle contraction.

No Sour Grapes

Raisins are the perfect example of why dried fruit is sometimes called “nature's candy” - nearly 80 percent of their calories come from simple sugars, according to the USDA. Although this does make them a good source of quick energy, it also means they're tasty enough to be tempting. It's not hard to eat two or more servings of raisins in one sitting, especially if you don't know what a 1/4-cup serving actually looks like. While you'd get close to 3 grams of fiber and 16 percent of the daily value for potassium from 1/2 cup of loosely packed raisins, you'd also be getting about 215 calories almost 60 grams of carbohydrates, most of which are simple sugars.

Sugar High

Eating too many raisins affects your blood sugar levels in two ways. Although fiber slows the process somewhat, simple carbohydrates generally raise your blood sugar more quickly than complex carbohydrates, the kind found in vegetables and whole grains. It's the total amount of carbohydrates you consume that determines how high your blood sugar levels go, however, which is why a large serving of raisins has a far greater effect on your blood sugar than a small one. Diabetics avoid high blood sugar levels by consuming fruit in portions that contain no more than 15 grams of carbohydrates. If you're diabetic or insulin-resistant, therefore, a serving of raisins is about half the standard amount, or just 2 tablespoons.