Sweet potatoes and yams are often considered to be healthy foods because of their low fat content and rich vitamin content. However, that doesn't mean the two vegetables are without flaws. Depending on your nutritional goals, you may find that sweet potatoes and yams don't have a place in your diet, as some of the nutritional characteristics others cite as benefits may be detrimental for your diet.
High in Carbohydrates
While sweet potatoes and yams can be beneficial for fueling athletic activity because they are rich in carbohydrates, this can be a drawback in some cases. Yams are higher in carbohydrates, with a 100-gram yam providing 27 grams and an 100 grams sweet potato providing 21 grams, but both are inappropriate for low-carbohydrate diets. According to research from the February 2006 edition of "Archives of Internal Medicine," low-carbohydrate diets can promote quicker weight loss than low-fat diets, so yams and sweet potatoes may be detrimental for dieting.
Low in Protein
While yams and sweet potatoes are rich in carbohydrates, they are very low in protein. A 100-gram yam provides just 1.5 grams, while a 100-gram sweet potato offers 2 grams. Protein is essential for building and maintaining your body's tissues, and research suggests that increasing your protein intake may aid in dieting. A study from the July 2005 issue of "The American Journal of Clinical Nutrition" found that a high-protein diet improved fat loss and helped suppress appetite.
Low in Fat
Sweet potatoes and yams contain virtually no fat. While this can be helpful if you're following a low-fat diet, it can also be a major drawback. Fat promotes satiety, ensures proper growth and development and helps your body absorb vitamins, so consuming too many sweet potatoes and yams at the expense of fat-containing foods can be detrimental.
Low in Iron
Sweet potatoes and yams are both very low in iron. Iron is an essential nutrient that helps ensure proper cell growth and is essential for the delivery of oxygen to your cells. If you don't consume enough iron, you can experience fatigue and a compromised immune system.
Lack of Vitamin D
Yams and sweet potatoes are devoid of vitamin D, which is important because it supports your body's absorption of calcium. Your body needs calcium to maintain the strength of your bones and teeth, and chronic deficiency of vitamin D may increase your risk of osteoporosis. Additionally, research from the March 2011 edition of "Hormone and Metabolic Research" indicates that vitamin D intake promotes higher testosterone levels. Testosterone is an important hormone that helps maintain bone density and sex drive, builds muscle mass, promotes sperm and red blood cell production and helps ward off body fat.
Lack of Vitamin B12
While yams and sweet potatoes offer a number of vitamins, neither offers any vitamin B-12. This vitamin is essential because it helps form DNA and red blood cells. Failure to consume enough vitamin B-12 can also result in anemia, a condition in which your body doesn't produce enough red blood cells.