Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Vitamin B12

Vitamin B12 is a compound that is essential for proper brain functioning. This vitamin helps keep neurons [ For more on 'neurons' go here: http://www.braingle.com/mind/317.html ] healthy by maintaining the myelin sheath that protects the axons. Insufficient vitamin B12 can cause serious and permanent damage to the neurons, which can lead to memory loss, fatigue and slowed thinking.

Vitamin B12 is found in fish, meat, poultry, eggs, milk and fortified breakfast cereals. Vegetarians and vegans should be careful to make sure they are getting enough B12 as part of their diet, or via supplements.

Age, smoking and drinking are all factors that contribute to deficiencies in vitamin B12, however it is possible for a deficiency to occur because of a problem absorbing the vitamin through digestion. If this is the case, eating more B12 will not help; the individual will need to get monthly injections.
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For more mind exercises: http://www.braingle.com/mind/