In the discussion threads below, Jeff Novick expresses two concerns with nutritional yeast: (a) high calorie density, and (b) IGF-1. The latter concern is expressed in discussion threads from 2008-2009 time frame below where the relationship between Total Protein and IGF-1 levels, and the relationship between "protein bio-availability" and IGF-1 levels is being discussed. This discussion is fascinating and suggests that lower protein percentages may be favorable for cancer prevention. In addition, we should perhaps avoid "food processing techniques that make plant protein more bio-available than found in nature". Does anybody have more insights to share in this regard? What do we know in 2023? Thank you!

Articles by Jeff Novic:

• (2017) Nutritional Yeast, B12, Protein, IGF-1 and more… Excerpt:

  Nutritional yeast is often used by vegans and vegetarians because it is thought to be a good source of B vitamins and protein and some think of it as a good source of B12. As you mentioned, it is also often used as a cheese substitute in some recipes. Some people even use it in a shaker as a Parmesan cheese substitute. However, I am not a fan of nutritional yeast, I don't use it myself and don't recommend it. It's calorie density is 1700 cal/lb, virtually the same as sugar. If you find it useful in some recipes, use it sparingly as a condiment as you would sugar.

• (2011) Nutritional Yeast and B12. In this article, Jeff Novick quotes Dr Jack Norris from this article:

  B12 is light sensitive. Nutritional yeast is likely to be exposed to the light because it is often stored in clear bins or plastic bags.

  We know of one vegan who thought he was getting B12 from nutritional yeast yet developed B12 deficiency symptoms that resolved upon taking a B12 supplement.

• (2008) Nutritional Yeast, Protein and IGF: a fascinating discussion centered around this research paper by Luigi Fontana et al (2008) titled "Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans". Jeff Novick shares snippets from a private conversation:

  We have tested IGF-1 about every 3 months since 2003. We test it along with the IGF binding proteins 1, 2 and 3, insulin, T3 and the VAP test.

  We wanted to see how total protein fared against the above battery of tests as well as individual protein concentrates including whey, brewers yeast, soy protein isolate, nonfat yogurt, kefir. and a mixture of individual amino acids. The results were frightening -- each one of these substances sent IGF-1 significantly higher -- independent of total calorie intake.

  The goal was to customize our CR diet to produce IGF-1 in the lower third of the reference range and to get IGFBP1, which is an indicator of SIRT1 activity, glucagon activity, etc., at the high end of the reference range.

  This is consistent with the downregulation of energy availability and of anabolic activity that is shown in long-lived CR animals.

  I have found, however, that protein absorbability makes a greater difference in IGF-I (and the binding proteins) than total protein, if the protein is from vegetables and grains, beans (this does not mean concentrates), and fruits.

• (2008) Brewers Yeast vs Nutritional Yeast. Jeff Novick says:

  Brewers yeast, which is different than Nutritional yeast, is often sold as a supplement usually as a rich source of B vitamins. Sometimes it is promoted to help with immunity, cholesterol levels, diabetes and weight loss but there is really little evidence to support this.

  If you were to follow the dietary guidelines and principles recommended here, you will get in all your nutrients in the proper forms and in the proper balance. The only exception if you were a strict vegan is B12. While these yeasts are often promoted as a good source of B12, they are not considered a reliable source of B12.

• (2013) Negative Impact From Eating Too Much Nutritional Yeast?