Nutrition, vitamins, supplements can all help with muscle growth. While muscle growth depends on exercise, and a very specific type of exercise that challenges the fastest-twitch muscle fibers, the process can be greatly enhanced with eating quality protein, and making sure that you also eat the right vitamins that will ensure conversion of amino acids into heavier muscle fiber bulk.
After a heavy workout, an excellent fuel for your exhausted muscles is whey protein. The best to be be found is made from the milk of grass fed cows. Since you could be ingesting a large amount of this supplement, I think it is worth it to avoid the pesticides, herbicides, drugs and lab-made hormones found in the milk of the average dairy cow. An additional bonus to this is the fact the omega 6 oil/omega 3 oil balance is vastly superior in the grass-fed cow milk.
If you are exercising to build muscle while on a weight loss diet, choose a protein powder mix with a sweetener like Xylitol or Stevia Leaf Extract, so you can avoid adding calories.
Some additional supplements necessary for muscle growth are the B vitamins B6, B12, and Folic Acid. Once you digest protein, your blood will have a substantial amount of the amino acid homocysteine. Homocysteine is not good for your blood and will irritate your arteries and promote blood clots. However, if you have the correct amounts of B6, B12, and Folic Acid present, the homocysteine is converted into the amino acids that build muscle fiber bulk.
Your muscles do not increase in the number of muscle fibers that they have, but the muscle fibers will get bigger.
The advantage of increasing muscle mass, especially as you age, is that muscles burn calories just to maintain. This will help keep your weight gain down as you get older. It decreases your insulin resistance too. The most impressive account about this that I have read to date is in the book “Slow Burn” by Frederick Hahn with Eades and Eades. A medical doctor describes how he REVERSED Type II Diabetes with the specific exercises and proper nutrition.