Colin Kaepernick just can’t seem to stay out of the news these days. The nation rose in outrage in the wake of his decision to sit during the national anthem, and two San Francisco 49er fans recently stepped up to let Kaepernick know how they felt about his decision to go vegan. 

“I’ve been a 49er fan since I’ve been born. I can’t believe you’re a vegan now. That hurts my livestock-producing family,” 7-year-old Taylor Rohrig said. Rohrig and her 11-year-old brother Tucker together wrote and produced the video message, which has since been seen by more than 50,000 people on Facebook alone. 

Read, “Really, Colin Kaepernick? Young pig farmer speaks out”

Now others in the sports world are asking if Kaepernick has been hurt by his vegan diet. After all, it wasn’t that long ago the quarterback shared an Instagram photo with a picture of steak, eggs and fruit and added, “This is lunch..... I don't eat vegetables[.] They make you weak!"

Kaepernick apparently went vegan nine months ago, and fans and analysts alike have started to notice his loss of muscle mass. As ProFootballTalk said in an article here, Kaepernick once was so muscular his then-coach worried his muscles could impact his throwing motion.

Now he looks just plain skinny.

Kaepernick vehemently denies that he's lost body mass due to his diet. San Francisco coach Chip Kelly suggests it was Kaepernick’s injuries, which include a torn ligament in his throwing hand’s thumb, a bone bruise and cracked cartilage, that have kept him from the weight room.

That may be partially true. There are vegan athletes playing in the National Football League, including former Chicago Bears defensive lineman David Carter. However, Carter admits to having lost 40 pounds after switching to the new diet before gradually getting back up to 300 pounds. Retired tight end Tony Gonzalez had a similar response to a vegan diet. Like Carter (and potentially Kaepernick), Gonzalez lost too much weight with a vegan diet to maintain his strength and weight and had to re-incorporate meat into his diet to gain back some of that strength.

Kaepernick could also  be struggling with a B12 deficiency, which is a relatively common occurrence among vegans and vegetarians.

An adult's recommended dietary allowance for B12 is 2.4 micrograms, and meat just so happens to be the top source for B12. Pork is no exception -- One 3.5 ounce serving contains between 0.66 micrograms (pork chops) to 1.23 micrograms (bacon) of B12. Beef also is an impressive source for B12.

While there are non-animal sources of B12, the University of Maryland Medical Center (UMMC) reports the amount of the vitamin varies and non-animal sources are not considered to be reliable sources of B12.  The UMMC also found that people absorb B12 from meat more easily than from plant sources.