For getting good crop sweet potatoes should be harvested before frost kills the vines or soon thereafter. To give highest yields it need in 130-170 days from planting are needed. But “baby bakers” or smaller roots can be harvested up to a month earlier.
Roots continue to grow until frost affects the vines. However, an extremely hard frost can cause damage to roots near the surface.

Try to prevent chilling injury of roots when soil temperatures drop to 50°F or lower, as this can result in internal decay in storage. Direct sunlight for over an hour can sunburn the roots, so dig only those that can be picked up immediately.

The greatest danger from delayed digging of sweet potatoes harvest is in the effect wet soil has on the roots. Excessive moisture can prevent digging injuries from healing properly allowing decay of the roots.
Disease control continues through harvesting and storing of sweet potatoes.
Even a small wound can easily become infected with decay organisms. Take care during digging and handling to avoid skinning and bruising the roots.

If possible, line containers with rags or other soft material to avoid scratching the roots. Put healthy roots directly into clean storage containers at harvest. Although large amounts of soil clinging to roots during storage are not desirable, freshly-dug sweet potatoes are easily damaged during the washing process. Allow sweet potato roots to dry and cure before removing excess soil.

Free radicals are chemicals that damage cells and cell membranes and are associated with the development of conditions like atherosclerosis, diabetic heart disease, and colon cancer.
Since these nutrients are also anti-inflammatory, they benefit in reducing the severity of conditions where inflammation plays a role, such as asthma, osteoarthritis, and rheumatoid arthritis.
Mineral content of sweet potatoes is rather low.

But some varieties contain significantly level of calcium, iron and potassium.
Saying in short words sweet potatoes are for sure great benefit for your health

Depending on the cultivar and conditions, tuberous roots mature in two to nine months.
Although the leaves and shoots are also edible, the starchy tuberous roots are by far the most important product.

How to grow sweet potatoes

The sprouts, called slips, are what will be planted.
At least 2 weeks after the date of the last average frost, clip the slips from the potatoes with a scissors or knife.
Remember which end of the slip was attached to the potato: that end will go in the ground and become roots and more potatoes. Longer slips should be cut in 4” to 6” pieces.
Dig the potato bed to a depth of 8” to 10”. Sweet potatoes grow well in low fertility soil but the addition of compost will loosen the soil and make the roots easier to dig in the fall. A string from one end of the bed to the other will help to keep the row straight.

Plant the slips into the soil 12” apart. Water well after planting and keep watered until signs of growth are observed. The slips have leaves but no roots. So don’t be alarmed if they lose a few, or all, of their leaves. They will survive.

An alternative method is to use small bedding plant flats known as “six-packs” or small flower flats.
Fill the pot or flat with potting soil and plant the slips, one to a cell or pot. Allow 2 weeks for roots to grow, and then plant in prepared beds. This method requires more materials and work, but is much less of a shock to the slip.

While growing sweet potatoes there are almost no pest problems. But they do require weeding until the canopy forms.

One medium sweet potato contains almost twice the recommended daily allowance of vitamin A, 42 percent of the recommendation for vitamin C, four times the RDA for beta carotene, and, when eaten with the skin, sweet potatoes have more fiber than oatmeal.

At that it benefits with only about 130 to 160 calories.

Additionally a medium sweet potato contains:
Fat 0.39 g
Protein 2.15 g
Net Carbs 31.56 g
Dietary Fiber 3.9 g
Calcium 28.6 mg
Sodium 16.9 mg
Potassium 265.2 mg
Foliate 18.2 mcg
Vitamin C 29.51 mg
Vitamin A 26081.9 IU

Being rich in dietary fiber, sweet potato lowers the risk of constipation, diverticulosis and colon and rectal cancer.
Sweet potatoes have been found to helpful in minimizing the risk of heart disease, diabetes and obesity.