White sweet potato
The same tuber without the colour. What you get is the starch and the fibre, and not the provitamin A.
Glycemic index
No separate reliable value for the white variety appears in the international tables. Reckon on the neighbourhood of the orange one, so mid-range, and lower if you let it cool first.
How to use it
As the starch on your plate. It is drier and less sweet than the orange one, so it suits savoury food and a stew better than the oven with cinnamon.
The best version
Firm, with no soft spots or sprouts. A tuber that feels light for its size has dried out.
How to prepare it
Boil it and then let it cool. Eaten cold, or reheated the next day, it gives you more resistant starch than straight out of the pan, and that is the reason to make it a day ahead.
What it does
What this tuber gives you is starch and fibre. When it was set against the orange kind in a trial in schoolchildren, it was the control group: the children on the orange tuber improved their vitamin A stores and the children on the white one did not.
Let cooked starch cool and part of it crystallises into resistant starch: it reaches your large intestine undigested and the bacteria there turn it into butyrate, the fuel your colon wall runs on. In a randomised trial in 42 older and 42 mid-age adults, butyrate in the stool rose in the older group on resistant starch, and Bifidobacteria increased in both groups.
Watch out
The rise in butyrate in that trial was small, and it came from a resistant starch out of a sachet rather than from a cooled tuber. How much yesterday’s plate gives you has not been worked out.
Do not pick it over the orange one if the pigment is what you are after. With no colour there is no provitamin A in it, and then you are eating a potato under another name.