Yams

Yams are grown for food; growing them specifically for feed is seldom economical. Surplus tubers offer pet food makers a starch source. For flour, processors cut and dry the moist tubers before milling them.^2,3,6,9

1. 01 // Source Cultivated tubers Food yam tubers are harvested with substantial water and starch in their flesh.
2. 02 // Process Washed and chipped In a documented flour method, processors wash the tubers and cut them into chips.
3. 03 // Process Dried and milled The chips are dried to remove water, then ground into flour that stores more easily.
4. 04 // Output Yam flour The dry flour provides starch for the recipe; a label saying yams alone does not disclose the form used.

1. 01

   Supplies cooked starch

   Water yam is mostly starch on a dry basis. Cooked starch supplies dietary energy, though the cited dog digestibility trial tested lentil pasta rather than yam.^1,2

2. 02

   Helps form kibble

   Starch thickens during extrusion and helps a kibble hold its shape. Yam flour offers that function, but its performance in dog food has not been tested here.^1,3

3. 03

   Uses surplus crop

   Growing yam just for feed seldom pays. Surplus food tubers give manufacturers another starch option when local supply and price make sense.⁶

How much A tested inclusion rate for true yam in dog food was not found; ingredient lists report weight order, not recipe percentages.⁹

1. Brands say

   Yams supply useful energy in kibble

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   An analysis of 16 water yam varieties found 60.3 to 74.4% starch on a dry basis. Dogs digested cooked starch well in a lentil pasta trial, but that trial did not test yam.^1,2

2. Brands say

   Yam fiber supports a dog's digestion

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   The 16 water yam varieties contained 4.1 to 11% total dietary fiber. A brand promotes yam fiber, but the cited dog trial fed lentil pasta, so it cannot show a digestive benefit from yam.^1,2,10

3. Brands say

   Yam antioxidants protect dogs from damage

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   A flour study measured antioxidant activity after treating purple yam with different soaking solutions. It was a laboratory assay, not a dog feeding trial, and says nothing about protection from yam in finished kibble.^5,10

4. Critics say

   Yams are just empty filler

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   The 16-variety analysis measured substantial starch, which supplies energy and serves a recipe function. Yam is not a meaningful protein source, but calling its main contribution empty ignores that starch.^1,2