Lager was born in West Superior, Wisconsin, the only child of Gustav Walfred Lager (a station engineer, who was born in Sweden) and Hilda Marie Erickson Lager (also born in Sweden).
On October 15, 1933, she founded a health food store named The House of Better Living at 1207 West Sixth St., Los Angeles, California.
Lager was notable for promoting soybean recipes.
[1] Her most well known book The Useful Soybean received positive reviews.
[2][3] In 2009 she was the subject of a biography, Mildred Lager: History of Her Work with Soyfoods and Natural Foods in Los Angeles (1900-1960).