A white, smooth-skinned yam with distinctive mucilaginous flesh when grated raw. Contains dioscorin (ACE-inhibitory blood pressure protein), allantoin (wound-healing and anti-inflammatory), and high mucilage content (dietary fiber that acts as a prebiotic). Unusual among yams for being safe to eat raw — a property that preserves heat-sensitive compounds that cooking destroys.
Available at Asian grocery stores nationwide (H Mart, 99 Ranch, Mitsuwa). Increasingly available at Whole Foods in metropolitan areas. The product is affordable and stores well in the refrigerator for 2 weeks.
Chinese yam's dioscorin protein has documented ACE-inhibitory activity — the same mechanism as pharmaceutical ACE inhibitor drugs (like lisinopril) but at food rather than pharmaceutical concentrations. A 2014 study (Molecules) found purified dioscorin reduced blood pressure in spontaneously hypertensive rats as effectively as captopril (a first-line ACE inhibitor). Allantoin (0.5mg/g in yam mucilage) accelerates wound healing by stimulating keratinocyte proliferation — relevant for Black Americans with elevated rates of diabetic foot ulcer and slow-healing wounds. The mucilage (glycans) from Chinese yam has been shown to selectively stimulate Lactobacillus and Bifidobacterium growth in human fecal microbiome studies. TCM clinical tradition uses shan yao to 'tonify the spleen and lung' — the functional correlate is digestive and immune support.
Peel (wear gloves — the raw skin contains calcium oxalate that irritates skin). Grate raw over rice (tororo gohan) — the mucilaginous texture is distinctive and acquired. Slice and stir-fry 3-4 minutes with sesame oil and soy sauce (Chinese preparation). Add to soups and hot pots. Boil and mash like potato. Available at Japanese, Chinese, and Korean grocery stores in most US cities. Available year-round — stores well.
Free, no account needed to ask.