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I have been lifting weights recently so protein and growth have been on my mind.

I was reading about the composition of human breast milk ( http://en.wikipedia.org/wiki/Human_breast_milk#Composition ). I was a bit surprised because it doesn't have as much protein as I thought it would since babies grow so fast during the breast-feeding stage. What implications might this have for an adult seeking to build muscle?

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Babies aren't adults. We're a carrying species, not a cache, therefore breast milk can be low in protein as we feed our children (very) often. – Efaitch Jul 26 2011 at 20:10

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Protein is but one building block. A simple explanation (not totally accurate, but gets the point across) is that protein "fills up the muscles". That is, a weightlifter doesn't really make new muscle cells (no one does), the protein just makes them bigger and stronger. A growing baby is actually making new cells (and quite rapidly), and the building blocks of cells (cell walls) are primarily saturated fat and cholesterol, which breast milk is quite rich in.

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 You've forgotton something. The simple explanation you propose completely ignores the fact that the main nutrient in milk is carbohydrates. Babies would not survive on fat, cholesterol and protein alone. Not even paleo babies. – thhq Jul 27 2011 at 0:33
Protein does not 'fill up the muscles', it IS the muscle about 90 grams out of 454, water/glucose/glycogen/fat/trace elements make up the rest of the 75% of 1lb of muscle that 'fill it'. – Bill1102inf Jan 17 2012 at 0:46
Did you miss the part where I said simple explanation and "not totally accurate". Sometimes you just need a simple model to get the basic idea. – miked Jan 17 2012 at 3:18
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Anthropologist John D. Speth has written a lot on the issue of protein. The protein needs for a fetus and an infant, and even gestating mother, are surprisingly low and higher levels of protein might even be toxic. Pregnant hunter-gatherer women generally eat low-protein diets. Goes to show that our association with protein and growth is not as neat as it seems. It als goes to show that life stage matters quite a bit in human nutritional needs.

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All pregnant women I know who consumed lots of animal products and plenty of protein remained pretty healthy. Babies were healthy as well. There were no signs of toxicity whatsoever. – aaa Jul 27 2011 at 2:56
an example of too high would mean a hunter-gatherer reliant mainly on lean game without a reliable source of fat or carbs. – Bread-Eating Beelzebub Jul 27 2011 at 3:19
and I sincerely doubt an American eating animal products would have similar problems since most eating products we eat have plenty of fat. I'd really worry about a low carb pregnant woman reliant mainly on chicken breast and fish. The negative effects would be mild though, perhaps a lower birth weight and perhaps a little bit a cognitive impairment, but scientists aren't sure how much. – Bread-Eating Beelzebub Jul 27 2011 at 3:23
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This is covered in Perfect Health Diet. Here is one article for you from the blog - http://perfecthealthdiet.com/?p=2712

This was, in part, their basis for 20% carbs, 15% protein, 65% fat. For adults they essentially double the protein and take half the carbs in breast milk as one way to "justify" their optimal levels. There were other aspects of their ratio justification in the book.

I have posted this before here on PH - I think most people overestimate their protein requirements. The answer your question is one does not need nearly as protein as conventional wisdom suggests. The old 1 g/lb bodybuilder mantra seems to die a hard death like the Diet-Heart Hypothesis.

EDIT - Page 9 in PHD covers this in "Human Breast Milk and the Adult Diet" section - "How will the optimal adult diet differ from an infant's? The brain is the body's primary consumer of carbs, and the brain accounts for 50% of calorie consumption in infants, but only 20%...in adults. Since adults require less than half the carbs that infants do, the optimal adult carb intake is likely about 20% of total calories rather than the 39% of infants. Starting from human like ratios (39%C, 54%F, 7%P), and changing half the carb calories to fat and protein, we get a ratio of 20% carb - 64% fat - 16% protein.

Other quotes from the book on Page 24

  • Except for some protein deficient vegans and misguided bodybuilders, almost everyone eats a healthy amount of protein
  • Only a few - very few! - protein calories can support rapid muscle growth. The protein content of muscle is 16.4%, so adding 26 pounds of muscle per year requires only 5 gms (20 calories) of protein per day [Aravind editoral - this one has me a bit vexed]
  • In the normal range of protein intake, controlled trials have not been able to detect any additional muscle gains from higher protein consumption

I am NOT vehemently asserting that PHD is the gospel, just giving you a relatively popular Paleo source for your consideration.

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This article has a great description of many of the details involved. One question I would have is what is the distinction between 'muscle-building' athletes and weight training athletes that have already built the majority of their muscle mass. The length of muscle building periods for adults are over-estimated, in my opinion. – Jesse Jul 27 2011 at 1:44
@Jesse - Good question. I don't know. I guess since both my Olympic dreams and Mr Olympia dreams have faded, I've stopped worrying about it. I do understand that for some people performance is an important consideration, but I'm an old fart that just needs to be strong enough to carry the groceries, my daughter, and laptop bag to work :-) – Aravind Jul 27 2011 at 1:56
there are a few raw vegan bodybuilders who have low-protein diets and big muscles – Bread-Eating Beelzebub Jul 27 2011 at 2:04
@Melissa - I agree. Given my dietary background, I have never been wasting away and am as strong as most of my meat eating friends when adjusted for height/weight. Perhaps there is some strong confirmation bias, but I'll own it! – Aravind Jul 27 2011 at 2:06
Meat is useful for reasons other than the pure amino acids. Creatine, carnosine, etc. If people put on muscle with more meat perhaps it is those nutrients and not total protein – Stabby Jul 27 2011 at 2:19
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Babies aren't simply small, scaled down versions of adults.

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It might be low in protien but babies still get around 2g protien/kg of bodyweight which also seems to work quite well for athletes.

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You're right, milk isn't a good idea. Babies develop primarily because of the hormones and fat in milk, not protein. Milk for adults is completely unnecessary and even damaging; stick to quality lean meat for your protein needs.

For more info on cutting out dairy: http://whole9life.com/2009/07/dairy-manifesto/

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I don't drink milk, but I eat a fair amount of dairy. If I want protein I eat cheese. – thhq Jul 26 2011 at 22:51
Or, even better, fatty meats... – Ambimorph Jul 27 2011 at 4:21

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