According to the United States Department of Agriculture, there are 109 calories in a 3-oz. serving of tuna in water. Tuna in oil provides slightly higher calories at 158 calories per 3-oz. serving. Both varieties are considered moderate calorie choices, according to the Food and Drug Administration, making up only 5 to 8 percent of a 2,000-calorie diet.
Fat
Tuna packed in water provides 2.5 g of fat per serving, while tuna packed in oil provides 6.8 g of fat. The oil used in packed tuna contributes about 4 g of fat, 1 of which is saturated fat. It also contains about 2.5 g each of polyunsaturated and monounsaturated fats.
Carbohydrates
Tuna is considered a carbohydrate-free food. Both tuna packed in oil and tuna packed in water are free of sugars, fiber, and all other carbohydrates. Carbohydrates are important sources of energy and are needed for the body to function properly. Be sure to include sources of carbohydrates at meals to stay healthy. Foods rich in carbohydrates include fruits and whole grains.
Protein
A 3-oz. serving of tuna, whether packed in oil or water, provides about 20 g of protein. The protein found in tuna is considered to be a complete source of protein. The Centers for Disease Control and Prevention states that complete proteins are proteins that provide all of the essential amino acids needed for your body to function properly. While protein needs vary depending on age, gender, and activity level, the recommended daily protein intake is approximately 46 to 56 g per day for men and women over 19 years of age. This means that a serving of tuna can meet nearly half of your daily protein intake needs.
