What is whey?

You might have heard about “whey” from the nursery rhyme Little Miss Muffet who sat on a tuffet eating her curds and whey. Curds and whey are components of milk. The curds are casein; the whey is a fast-acting protein. Whey provides a source of energy for exercise as well as the raw materials to repair and build muscles. It is a rich source of branched-chain amino acids including leucine, valine and isoleucine. These amino acids are directly absorbed into the muscle without having to be metabolized in the liver.

How do we build muscle?

Protein (as amino acids) is required to build muscle. During exercise, muscle is broken down, signalling the body to build more muscle. However, it is the specific amino acid leucine that triggers muscle protein synthesis. Think of muscle protein synthesis like turning on a light. Leucine flicks the switch, while protein is the electricity that powers the light. Once leucine flicks the switch, this enhanced muscle protein building lasts for about 24 hours, providing there is enough protein available.

How much protein do I need in a day?

The current recommendations for protein intake range from 1.2-2 g/kg/day. Protein intake should be spread throughout the day with 20-30 g per meal. Older adults need higher amounts to stimulate muscle protein synthesis.

What are the best sources of protein for building muscle?

Studies show that after resistance exercise, eating milk-based protein rather than other sources of protein is more effective in building muscle and increasing strength. This is likely due to a combination of its high leucine content and greater solubility. The result is that leucine levels in the blood will rise faster, triggering muscle protein synthesis.

However, all high quality sources of protein, including the right combination of plant proteins, can build muscle.

How much leucine do I need in a day?

Experts recommend that we get 2-3 grams of leucine per day. You can easily get that from three servings of milk products. Whey protein-isolate supplements contain approximately 2.5 g of leucine per scoop.

Meat, eggs and soy protein all contain whey. If you are meeting your protein requirements, you are getting enough leucine. The issue with leucine and protein in general is not that we aren’t getting enough, but that we are not spreading it throughout the day. Getting more than 2-3 grams of leucine every day at isn’t as good for you as spreading it throughout the day.

Whenever possible, choose food first.Food gives a variety of nutrients and non-nutritive compounds that work together to promote your health.

AFCLA Members

Are you looking for practical nutrition tools for your clients? Log in to the AFLCA Members section of the website and order free resources today!  A great compliment to this article would be the postcard Are you a Protein Pro? 


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Lee Finell, RD

Registered Dietitian

Lee (MHSA, RD) is a registered dietitian and Program Manager at Dairy Farmers of Canada. She writes articles and develops programs and resources that help Albertans translate the science of nutrition into healthy food choices.

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