the 42-year-old mother-of-two tweeted a picture of her $ 29 grocery shop , which included eggs , vegetables , brown rice and black beans .
gwyneth is taking part in the new york city food bank challenge , which aims to raise awareness and funds for the city 's food banks .
the city 's weekly food stamp allowance is just $ 29 per person per week .
gwyneth 's healthy food choices have already come under fire from critics who claim they contain nowhere near enough calories for a whole week .