Foster, who has 32 total touchdowns in three NFL seasons, made the announcement on Twitter last week.
"Officially a vegan now. We'll see how this goes. But week one down. So far, so good. Feels wonderful," the 6-foot-1, 229-pound running back said of giving up any form of animal products.
News of Foster's diet decision caused a social media uproar.
"People feel so strong about meat and milk. I wish they felt this strong about peace," the two-time Pro Bowler wrote shortly after his original tweet.
Since taking hold of the Texans' starting job in 2010, Foster has run for 2,840 yards on 605 carries (4.7 yards per carry) and caught 119 passes for 1,221 yards. Undrafted out of Tennessee four years ago, he signed a five-year, $43.5 million contract with Houston in March.