Vegetables generally do not provide sufficient vitamin B12, with the exception of fermented soy products like tempeh, which may contain some B12 due to bacterial synthesis. Seaweed and spirulina are also mentioned as non-animal sources, but their B12 content is typically inadequate for health needs. The human body can store B12 for several years, but a long-term vegan diet without supplementation raises concerns about potential deficiencies. While gut microflora may contribute to B12 levels, regular intake is recommended, such as weekly supplementation or consumption of yeast extract products like Marmite or Vegemite. Increased B12 intake can benefit those engaged in physical activities by enhancing energy levels and reducing muscle fatigue.