Protein levels in mother's milk
Here are some links to info about protein levels in human milk:
From http://www.dsiegel.com/wiwd/diet/protein.html:
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Take the Protein Challenge
Remember how your mom told you you need to get your protein every day? Where did your mom get her training in nutrition? Same place my mom did: from TV. If it's on TV, it must be real. But if something doesn't add up, check your assumptions. There isn't a documented case of protein deficiency in this country that isn't associated with a calorie deficiency. In other words, if you're absorbing enough calories, you are getting enough protein. This isn't strictly true. If you got all your calories from white sugar, you'd be missing some amino acids. If you got all your calories from Crisco, you'd be missing some amino acids. But if you got all your calories from pretzels, you'd come up with scurvy before you showed any signs of protein deficiency.
To prove this, I will pay you $20 for every documented case of protein-only deficiency (in the presence of 1400 calories or more absorbed daily) you can find in this country. This is your chance to get rich. Get out there and scour the medical literature so you can fill my mailbox with documented cases. I have my checkbook ready.
The Grim History
The funny thing about the protein myth is that the doctors are the last to get it. Every single doctor in this country agrees that babies grow healthy and strong with a diet that consists of only 6% protein. In fact, every doctor in this country agrees that 6% is too much, because babies need to be protected against malabsorption and different needs, so 6% actually exceeds any particular child's requirements. There is absolutely no argument on this issue. Why? Because that's how much protein is in mother's milk. Always has been. Always will be.
From http://www.earthsave.bc.ca/materials.../wa_dairy.html :
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What About Protein?
Nature tells us that baby humans are best served with the modest level of 5% protein found in their mother's milk. Babies grow more rapidly than at any other period in their lives. Their protein needs are, therefore, at a maximum. The biological reality is that we humans need very little protein in our diets.
Many people have come to believe that animal protein is of higher quality than plant protein, and that good health is dependant upon getting enough animal protein in one's diet. Fortunately, this isn't the case. Our biological needs for protein are as easily met by plant foods as they are by animal foods.
A varied diet that adquately meets the calorie needs of a person will also meet her or his protein needs. The widespread belief that it is necessary to carefully combine various plant foods to insure one's protein needs are adequately met is unfounded. People, including some world class athletes, who choose to eat no animal protein whatsoever enjoy excellent health without concern
People, including some world class athletes, who choose to eat no animal protein whatsoever enjoy excellent health without concern for combining proteins. If you want to insure that your diet is top-notch, eat a variety of fruits, vegetables, grains, legumes, nuts and seeds, and forget about protein.
From http://www.arthritis-back-knee-pain-...teinneeds.html (This link also contains an interesting table showing the relationship between growth rate in various animals and protein levels in their diet.)
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Our protein needs are highest when we are growing the fastest. This fact is a “no-brainer”. It is well established that mother's milk is the ideal food for baby. No other food is needed for the first year. Logic would tell you that if we looked at the percentage of protein in mother's milk at various stages of growth it would give us a clue as to our real needs.
Mother’s milk during the first week contains 2.38% protein. A lot is happening in the human baby’s body that first week. It only makes sense that it would require a lot of protein.
During the next month, the percentage of protein in mother milk drops to about 1.79% Though the child is still growing it is not growing as fast and does not need as much protein.
Well before the third month, the protein level in mothers milk is down to 1.49% This level of protein will maintain continuous growth without any supplements.
By six months the protein level of mother milk is down to 1.07% By this time most babies are getting some kind of supplemental feeding. However if left on mother milk only they will maintain healthy growth without additional supplementation.
From http://www.living-foods.com/rawgourmet/newsnov99.htm
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Most of us have been raised with the notion that a lot of protein is good for us. The meat and dairy industries depend on that attitude. But, ponder this for a moment: What is the most perfect food for a human being when it needs it most, as a newborn infant? You guessed it- it is mother’s milk. There is no other time in the life of a person when growth will be so dramatic. The infant will triple or quadruple in size in its first year and needs more protein to grow on than at any other time in its entire life span. And just how much protein is in mothers milk? The answer may surprise you. The amount of protein in mothers milk is 2.5 to 3.5 per cent.* Compare that to the amount of protein in cow milk at 30 per cent*. A baby cow needs to gain hundreds of pounds of mass in its first year, while it’s relatively small brain does not need to grow very much, quite obviously different than the needs of a human baby.
From http://www.ivu.org/congress/euro97/mother.html :
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Characteristics of mammals include their love for their young, which is determined by brain development, and suckling of them. Feeding with milk from another species, treated to make it closer to that of the correct species, leads to dangerous counterindications. Human milk contains 1.2% protein, minus 0.3% non-proteic nitrogen, which leaves 0.9%. Of course the amount absorbed by the body is lower than this. Cow's milk contains 4 times as much protein; rabbit's milk, 10 times as much.
Re: Protein levels in mother's milk
Here's another study, quoted at medscape.com:
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Major nutrients. Lactose, 5.5-6.0g/dL, is the most constant nutrient in human milk (Table I). Its concentration in breast milk is not affected by maternal nutrition.
Proteins amount to about 0.9g/dL in mature milk.[12]Recent studies comparing the impact of nutrition on lactation in industrialized and developing countries suggest that neither maternal diet nor body composition affects milk protein level.[1] However, limited data from earlier studies seem to indicate that short-term, high-protein diets can increase the protein and nonprotein nitrogen content of human milk,[13] while limiting maternal food intake can lead to lower milk protein levels.[13-15]
Why can't just all these studies agree with each other? :)
Re: Protein levels in mother's milk
There are two measures of protein that seem to be commonly used:
Percentage by total mass - so 0.9g/dL is approximately 0.9% protein by mass (1 dL of water weighs 100g, milk would be slightly more or less than this, but close enough).
Percentage as a proportion of total calories. Protein is 4 kcal per g. Breast milk averages 75kcal per dL. So that would be 100*(0.9 x 4)/75 which is 4.8% of total calories.
That's likely to be where the big differences occur.
The US seem to use the second method. It's how come broccoli gets labelled a high protein food by some people.
