Orange-fleshed sweet potatoes may be one of nature's unsurpassed sources of beta-carotene. Several recent studies have shown the superior ability of sweet potatoes to raise our blood levels of vitamin A. This benefit may be particularly true for children. In several studies from Africa, sweet potatoes were found to contain between 100-1,600 micrograms (RAE) of vitamin A in every 3.5 ounces-enough, on average, to meet 35% of all vitamin A needs, and in many cases enough to meet over 90% of vitamin A needs (from this single food alone).
Sweet potatoes contain high levels of antioxidant nutrients, anti-inflammatory nutrients, and blood sugar-regulating nutrients. They are packed with vitamins A (in the form of beta-carotene) , B6 (pyridoxine), and C. They have plenty of manganese, copper, potassium, iron and dietary fiber, together with complex carbohydrates. But sweet potatoes are low in calories and fat-free.
Despite its name, sweet potatoes help to stabilize blood sugar levels and to lower insulin resistance. Diabetics should eat more sweet potatoes.
Sweet potatoes are not always orange-fleshed on the inside but can also be a spectacular purple color. Sometimes it's impossible to tell from the skin of sweet potato just how rich in purple tones its inside will be. That's because scientists have now identified the exact genes in sweet potatoes (IbMYB1 and IbMYB2) that get activated to produce the purple anthocyanin pigments responsible for the rich purple tones of the flesh. The purple-fleshed sweet potato anthocyanins-primarily peonidins and cyanidins-have important antioxidant properties and anti-inflammatory properties. Particularly when passing through our digestive tract, they may be able to lower the potential health risk posed by heavy metals and oxygen radicals.
Yet beta-carotene only begins to tell the story of sweet potato antioxidants. Particularly in purple-fleshed sweet potato, antioxidant anthocyanin pigments are abundant. Cyanidins and peonidins are concentrated in the starchy core of part of purple-fleshed sweet potatoes, and these antioxidant nutrients may be even more concentrated in the flesh than in the skin. That's sweet potatoes have genes (IbMYB1 and IbMYB2) that are specialized for the production of anthocyanin pigments in the fleshy part of the tuber. Ordinary, we have to rely on the skins of foods for this same level of anthocyanin antioxidants. But not in the case of sweet potatoes! Extracts from the highly pigmented and colorful purple-fleshed and purple-skinned sweet potatoes have been shown in research studies to increased the activity of two key antioxidant enzymes-copper/zinc superoxide dismutase (Cu/Zn-SOD) and catalase (CAT).
Recent research has shown that particularly when passing through our digestive tract, sweet potato cyanidins and peonidins and other color-related phytonutrients may be able to lower the potential health risk posed by heavy metals and oxygen radicals. That risk reduction is important not only for individuals at risk of digestive tract problems like irritable bowel syndrome or ulcerative colitis but for all persons wanting to reduce the potential risk posed by heavy metal residues (like mercury or cadmium or arsenic) in their diet.
Storage proteins in sweet potato also have important antioxidant properties. These storage proteins-called sporamins-get produced by sweet potato plants whenever the plants are subjected to physical damage. Their ability to help the plants heal from this damage is significantly related to their role as antioxidants. Especially when sweet potato is being digested inside of our gastrointestinal tract, we may get some of these same antioxidant benefits.
Anti-Inflammatory Nutrients in Sweet Potato
Anthocyanin and other color-related pigments in sweet potato are equally valuable for their anti-inflammatory health benefits. In the case of inflammation, scientists understand even more about the amazing properties of this tuber. In animal studies, activation of nuclear factor-kappa B (NF-κB); activation of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2); and formation of malondialdehyde (MDA) have all be shown to get reduced following consumption of either sweet potato or its color-containing extracts. Since each of these events can play a key role in the development of unwanted inflammation, their reduction by sweet potato phytonutrients marks a clear role for this food in inflammation-related health problems. In animal studies, reduced inflammation following sweet potato consumption has been shown in brain tissue and nerve tissue throughout the body.
What's equally fascinating about color-related sweet potato phytonutrients is their impact on fibrinogen. Fibrinogen is one of the key glycoproteins in the body that is required for successful blood clotting. With the help of a coagulation factor called thrombin, fibronogen gets converted into fibrin during the blood clotting process. Balanced amounts of fibrinogen, thrombin and fibrin are a key part of the body's health and its ability to close off wounds and stop loss of blood. However, excess amounts of these clotting-related molecules may sometimes pose a health risk. For example, excess presence of fibrinogen and fibrin can trigger unwanted secretion of pro-inflammatory molecules (including cytokines and chemokines). In animal studies, too much fibrin in the central nervous system has been associated with breakdown of the myelin sheath that surrounds the nerves and allows them to conduct electrical signals properly. If fibrin excess can trigger unwanted inflammation in nerve tissue and increase breakdown of the myelin wrapping the nerve cells (a process that is usually referred to as demyelination), health problems like multiple sclerosis (in which there is breakdown of the myelin nerve sheath) may be lessened through reduction of excess fibrinogen and/or fibrin. In preliminary animal studies, intake of sweet potato color extracts have been shown to accomplish exactly those results: reduction of inflammation, and simultaneous reduction of fibronogen levels. We look forward to exciting new research in this area of sweet potato's anti-inflammatory benefits.
Recent research has shown that extracts from sweet potatoes can significantly increase blood levels of adiponectin in persons with type 2 diabetes. Adiponectin is a protein hormone produced by our fat cells, and it serves as an important modifier of insulin metabolism. Persons with poorly-regulated insulin metabolism and insulin insensitivity tend to have lower levels of adiponectin, and persons with healthier insulin metabolism tend to have higher levels. While more research on much larger groups of individuals to further evaluate and confirm these blood sugar regulating benefits, this area of health research is an especially exciting one for anyone who loves sweet potatoes.
Take note of the purple-fleshed sweet potatoes. These purple sweet potatoes are purple in color due to the presence of a powerful antioxidant called anthocyanin.
Antioxidants are present in fruits and vegetables, and they help prevent diseases relating to cardiovascular problems and cancer. They also strengthen the immune system, are anti-inflammatory, and keep bones and skin healthy. The most powerful antioxidants are called phytochemicals, and the two very potent of these chemical compounds are beta-carotene and anthocyanin. Anthocyanins are flavenoid compounds which produce the purplish pigmentation in the purple sweet potatoes.
Two strands of anthocyanin, called cyanidin and peonidin, are powerful antioxidants which slow down the growth of cancerous cells, and are used to treat colon cancer. Research has shown that cyanidins and peonidins when passing through the digestive tract, may be able to reduce damage caused by heavy metals and oxygen radicals.
Sweet potatoes have storage proteins called sporamins which help the potatoes to heal its damaged parts. These are also antioxidants which are beneficial to our gastrointestinal tract. Another lesser known nutrient group of the sweet potatoes are the resin glycosides, which have antibacterial and antifungal properties.
How to eat sweet potatoes ?
The best healthy method to eat sweet potatoes is by steaming them whole with the skin intact. They should be ready for consumption within 7 minutes of steaming. As the skin also contains rich nutrients, you can also eat it with the flesh. If you don't want to eat the skin, it can be easily peeled off after the sweet potatoes are cooked.
By the way, the leaves of the sweet potatoes are also edible. They are nutritious and delicious. We usually stir fry them with dried prawns and chillies.