In the United States, the typical meal contains a protein source, a vegetable dish and a high-carbohydrate side dish, usually rice, potatoes or pasta. Making this as nutritious as possible means considering the array of nutrients in your meal. According to Clemson University, more than 70 percent of the white rice sold in the United States is enriched with extra folic acid, thiamine, niacin and iron, making it nutritious enough to rival potatoes in several areas, but potatoes are more nutrient-rich than rice overall.

Calories, Fat and Protein

If you are trying to lose weight by keeping track of your intake of calories and fat, either rice or potatoes could be helpful. Both are nearly fat free, with less than a gram of fat per serving. They are also similar in caloric content. A cup of plain white rice has 242 calories and brown rice contains 216. A medium baked potato falls between them with 230 calories. Rice, with 5 grams of protein per cup, has slightly more protein than a potato, with 3 grams.

Fiber

The majority of nutrients are in the potato, rather than the skin, as many believe, but the skin helps retain the nutrients in the potato and adds fiber content. Brown rice, which is unmilled with the hull removed, is a whole-grain food that provides 4 grams of fiber per cup, while the same serving size of white rice only has 1 gram of fiber. A medium baked potato gives you about 3 grams of fiber if you eat the skin and 2 grams if you do not. If you are trying to increase your fiber intake, baked potatoes and brown rice are better choices than mashed potatoes and white rice.

Vitamins

A cup of rice provides a third of your recommended daily intake for vitamin B-6, which helps your body make healthy red blood cells and amino acids. It also gives you 10 percent of your niacin and trace amounts of thiamine and riboflavin and 180 micrograms of folate. A potato gives you half your daily value of vitamin B-6, 45 percent of the vitamin C you need daily and small amounts of thiamine, riboflavin and folate.

Minerals

Because potatoes are grown underground, they offer a rich store of minerals that surpasses the mineral content of rice. Although rice has three times more iron than a baked potato, a potato provides five times the amount of calcium in a cup of white rice, twice the phosphorous and 14 times the potassium, rivaling potassium-rich foods such as bananas, spinach and broccoli. Rice and potatoes contain about the same amount of zinc and magnesium per serving.

Glycemic Index

The glycemic index of a food is the measure of how likely it is to raise your blood glucose levels. A lower glycemic index indicates a safer food for diabetics. This number varies greatly depending on the type of potato or rice you eat. According to Harvard University Medical Center, a medium-sized white potato has a glycemic index of 50, while a russet potato has a glycemic index of 85. White rice and brown rice fall between these figures, with glycemic indexes of 64 and 55.

Considerations