Sweet potatoes are root vegetables that are popularly consumed as a carb-heavy food. They are an excellent source of vitamins, minerals, and antioxidants like beta-carotene. However, sweet potatoes contain only modest amounts of protein. This article examines whether sweet potatoes can be considered a good protein source, especially compared to other plant and animal-based foods.
How much protein do sweet potatoes contain?
The protein content of sweet potatoes is low compared to other vegetables. A medium baked sweet potato (114 grams) contains about 2 grams of protein (1).
This equates to around 4% of the daily value (DV) for protein. Other starchy root vegetables like russet potatoes and yams have a similar protein content.
In contrast, the same serving size of broccoli contains 2.6 grams of protein, kidney beans have 5.7 grams, and chickpeas 8.9 grams of protein (2,3,4).
Therefore, sweet potatoes have relatively little protein compared to some other plant foods. However, they contain more protein than low-protein fruits like apples, oranges, and bananas.
Protein quality in sweet potatoes
Not only is the quantity of protein important, but also the quality. The quality is determined by the amino acid composition and digestibility.
Sweet potatoes contain moderate scores for protein digestibility and quality. The protein digestibility-corrected amino acid score (PDCAAS) of sweet potato protein is between 55–77% (5).
For comparison, other foods like soy protein, eggs, and beef have scores over 90%, while wheat has a score of 45% (6). The essential amino acid content of sweet potato protein is somewhat lacking compared to animal proteins.
However, sweet potatoes contain useful amounts of lysine and tryptophan, which are amino acids often low in other plant foods like grains (5).
Overall, despite containing relatively low protein content, the quality of sweet potato protein is moderate and comparable to some other plant proteins.
Protein content of different sweet potato types
There are many different varieties of sweet potatoes, which vary slightly in their nutrient profiles.
Some studies have analyzed the protein content of yellow, orange, purple, and white-fleshed sweet potato cultivars (5, 7).
On average, protein accounts for between 3–8% of the dry weight of sweet potato roots. However, protein content can range from 1–12% depending on the specific cultivar.
In general, protein content follows this order from highest to lowest:
– Purple sweet potatoes
– Yellow sweet potatoes
– Orange sweet potatoes
– White sweet potatoes
For instance, the Beauregard orange sweet potato contains 2.1 grams of protein per 100 grams. Whereas the Stokes Purple cultivar packs 4.2 grams of protein (5).
So if your goal is to get as much protein from sweet potatoes as possible, purple-fleshed varieties are your best bet.
How sweet potatoes compare to other protein sources
Although sweet potatoes contain small amounts of decent quality protein, the protein content is low compared to most other foods.
Here is how the protein in a medium baked sweet potato compares (1):
– 2 grams sweet potato protein
– 26 grams chicken breast protein
– 25 grams tofu protein
– 10 grams Greek yogurt protein
– 8 grams chickpea protein
– 5 grams kidney bean protein
– 3 grams egg protein (1 large egg)
Clearly, sweet potatoes are a poor source of protein compared to high-protein animal foods like poultry, beef, eggs, and dairy products.
Beans, lentils, edamame, and soy foods like tofu also pack substantially more protein per serving than sweet potatoes.
However, sweet potatoes do contain small amounts of protein that can contribute to your daily needs.
Health benefits of sweet potato protein
Here are some of the key benefits associated with the protein found in sweet potatoes:
– **Vegetable protein source** – As a plant source of protein, sweet potatoes may appeal to vegetarians and vegans looking to increase protein intake from non-meat sources. Eating a variety of plant proteins is healthy.
– **Gluten-free** – The protein in sweet potatoes does not contain gluten. This makes sweet potatoes an option for people who cannot tolerate gluten.
– **May enhance satiety** – Protein increases satiety compared to fat and carbs. The protein in sweet potatoes may therefore help enhance feelings of fullness after a meal (8).
– **Provides lysine** – Sweet potatoes contain more lysine, an essential amino acid, than many grains and beans. This makes their protein more complete (5).
– **Antioxidant benefits** – Compounds like anthocyanins found alongside the protein in purple sweet potatoes have antioxidant activities (9).
Therefore, getting a bit of protein from sweet potatoes offers some advantages. However, sweet potatoes are still considered a starchy vegetable rather than a significant protein source.
Can you eat too much protein from sweet potatoes?
It’s extremely difficult to get excessive protein from sweet potatoes.
Adults should aim for at least 0.8 grams of protein per kilogram of body weight daily, which equates to around 56 grams for a 70 kg (154 lb) person (10).
To reach this amount from sweet potatoes alone, you would need to eat around 28 medium baked sweet potatoes in a day. This would provide over 8000 calories and 330 grams of carbs, mostly starch.
Clearly, overdosing on protein from sweet potatoes is not a practical concern given their low protein density. Eating enough sweet potatoes to satisfy your daily protein requirements would lead to excessive calorie and carb intake.
Maximizing protein from sweet potatoes
Here are some tips to get the most protein from sweet potatoes:
– Choose purple sweet potatoes when possible, as they are highest in protein.
– Consume the skin for extra protein and nutrition. Baked sweet potato with skin contains an extra 0.5 grams protein vs. flesh alone.
– Pair sweet potatoes with legumes like chickpeas or lentils to balance amino acids and increase protein intake.
– Add sweet potatoes to high protein foods like yogurt, eggs, and chicken to make a complete protein meal.
– Use sweet potatoes to make protein-boosted pancakes, oatmeal, or desserts by adding Greek yogurt, milk, or protein powder.
– Try sweet potato protein powder or bars made from dehydrated purple sweet potatoes.
Sweet potato protein supplements
Due to their relatively high protein content, some purple and orange sweet potato varieties are dried and ground into powders for use in protein supplements and bars.
Compared to the whole root, sweet potato protein powder is more concentrated in protein. Some commercial sweet potato protein powders provide around 13 grams of protein per two tablespoon (28 gram) serving.
However, not all sweet potato protein supplements are created equal. Many use added milk or soy protein rather than sweet potato as the main protein source.
Check the ingredients list for the first or main ingredient. It should be dried sweet potato powder rather than a generic “plant protein blend”. As with any protein supplement, quality can vary considerably by brand.
Sweet potato protein powders can be used to boost the protein content of smoothies, baked goods, oatmeal, and desserts like protein puddings. They provide a non-soy, non-dairy alternative to common protein powders like whey and casein.
Should sweet potatoes be eaten for protein?
Sweet potatoes are an inherently poor source of protein compared to beans, dairy foods, eggs, meat, fish, and poultry. Their protein content and quality does not compare favorably.
However, sweet potatoes do provide small amounts of decent quality protein that can contribute to your daily needs, especially if consuming a plant-based diet.
Certain types of sweet potatoes like purple and yellow varieties contain more protein than the more common orange-fleshed sweet potatoes. Their soluble fiber may also enhance the digestion and utilization of protein from other foods eaten in the same meal.
In summary, sweet potatoes are primarily a good source of carbs and various vitamins and minerals. They should be viewed as a complementary source of plant protein rather than a significant provider. Sweet potatoes alone cannot meet protein needs.
Include sweet potatoes as part of a balanced diet containing a variety of lean proteins from both plant and animal sources. This will ensure you meet your protein requirements for optimal health.
Conclusion
Sweet potatoes contain only modest amounts of protein, providing around 2 grams per medium baked potato. This equates to just 4% of the daily value for protein.
Although sweet potato protein is moderately digestible and high in certain amino acids like lysine, it does not compare favorably in quality or quantity to most other protein-rich foods.
You would need to eat a very large amount of sweet potatoes to meet your protein RDA, which would lead to excessive calorie and carb consumption.
However, the protein in sweet potatoes, especially purple varieties, offers some benefits as part of a plant-based, gluten-free, or antioxidant-rich diet. The protein can contribute to daily needs and complement other dietary protein sources.
In conclusion, sweet potatoes are not a significant source of protein compared to beans, dairy, eggs, meat, poultry, and fish. But they can provide small amounts to help meet your needs as part of an overall balanced diet.
