New Jersey Mayor Cory Booker closed his fourth day (Friday) of the food stamp challenge with difficulties and caffeine withdrawal, but still determined to finish out what he promised.

On day 4 of his SNAP challenge, Booker wrote on his LinkedIn blog post, "so far it has been the most difficult. I'm realizing more and more that my current daily food intake cannot continue at the same pace, and so my new focus is on smaller portions spread throughout the day."

Having an apple for breakfast and a can of seasoned chick peas for lunch, Booker's dinner consisted of broccoli, cauliflower, black beans, corn casserole and a sweet potato which he ate in small portions between 2 p.m. and 7 p.m.

"I've also finally hit the wall with caffeine withdrawal - I've had a terrible headache all day and have been feeling sluggish. I'm starting to think I need to put a little more thought into my caffeine addiction," Booker wrote in his post.

Using his Twitter as a way to speak to his supporters, Booker tweeted a pircture of an Apple Saturday morning, the start of his fifth day, indicating that's what he ate for breakfast, again.

Booker has been getting support for his food stamp challenge, which started on Dec. 4, living on only $30 for the week. he has been getting support from his now 1.3 million Twitter followers, some giving him advice about how to do the challenge successfully. However, the Newark mayor has run into critics, with some suggesting that he is misleading about the design of the program and how it's used, according to Huffington Post.

"It's not meant to be your only calorie intake source," said CNN's Christine Roman on Wednesday. "'Supplemental' is the key. The government designs it so this is on top of what little money you might have, food pantries, soup kitchens."

Booker responded by saying it was just "reality" that many Americans rely on food stamps to survive.

"There are many families -- and I talked to a group of security guard workers yesterday who make seven dollars and change, don't have health care benefits, so if they get sick, they have to either take days off of work and lose that money, or work through the sickness, who don't have retirement benefits, who find it hard at the end of the month to pay their rent, to buy their food, and are struggling," Booker said. "She may think its a supplemental program, but for many Americans who are working even, this is the difference between going deep into food insecurity, not being able to provide for their families, and having a bridge to stability."

Booker's food stamp challenge ends on Dec. 11. What do you think of it? Sound off below!