A galactagogue is a substance that induces lactation. The most commonly cited galactagogues are herbal: fenugreek, brewer's yeast, blessed thistle, and alfalfa; others include anise, astragalus root, burdock, nettle, fennel, flax, soapwort, vervain, and marshmallow root. Clinical evidence for their efficacy is often lacking. According to the Talmud, the drinking of wine will increase the quantity and quality of breast milk. Galactagogue medications are also available, usually by medical prescription.