If It’s Good Enough For An Infant, It’s Good Enough For Me!
One argument you hear for the sufficiency of low-protein vegan diets, particularly raw food diets based around lower-protein fruits like bananas and dates, is that babies can go through their most rapid period of growth consuming only mother’s milk.
Mother’s milk is in the ballpark of 6% of calories from protein (it actually varies slightly over the course of breastfeeding). So because adult humans are growing much more slowly than infants, the reasoning goes, how could they require more than 6% of their calories from protein?
“Human breast milk is good enough for a breastfeeding six-month-old, so you’ll do just fine on 6% of your dietary calories or less coming from protein!” – Lots of raw food diet and vegan books
To be honest, I totally bought this argument until I started thinking about it a bit more, and did some research on just how many calories a baby burns relative to its tiny bodyweight.
Let’s use the Institute Of Medicine’s recommended dietary allowance (RDA) figure to break down the low-protein diet breast milk justification.
It Comes Down To Protein And Calorie Needs:
The protein RDA between birth and one year is 1.5 g/kg of bodyweight 1, and babies can hit this target on a diet of just breast milk, which is only 6% protein as a percentage of calories. How is that possible?
Babies are calorie-burning machines, at least relative to their size, since they need to fuel such quick growth.
A 9.7 pound female infant needs 438 calories per day, or 45 calories per pound 2
So what about an adult woman?
Let’s say she’s 30-years old, 5 foot, 4 inches tall, and 126-pounds. She needs to take in 2,000 calories a day if she’s moderately active, which works out to 15.8 calories per pound 3. Her protein RDA is .80 g/kg of bodyweight 4
Depending on how active she is, our 30-year-old needs around six times the total protein intake of the infant, but only around four to four and a half times more total calories.
So to hit the RDA of .80 g/kg on a diet with 6% of calories from protein, she’s have to consume not the 2,000 calories she needs to maintain her bodyweight at a moderate activity level, but 3,100 calories. So she’d be getting fatter trying to hit the 45.6 grams of protein RDA.
And if she wanted to hit the corrected RDA value discussed in my soon-to-be-released protein article – 1.2 g/kg – while sticking to 6% of calories from protein, she’d need to consume 4,650 calories.
So she’s got some options:
- Eat 6% of her calories from protein like an infant, but consume way too many calories trying to reach he protein target and get fat as a result.
- Eat 6% of her calories from protein and take in 2,000 calories per day and end up not thriving to the same degree that she could (more on this in my next protein article).
- Eat 6% of calories from protein, but become a vigorous athlete so she can burn all those extra calories off while eating a low protein diet.
- Eat the correct amount of calories to maintain her weight, but up her protein intake to 14-19% of calories, depending on activity level.
As you can see, the breast-milk protein justification falls apart when you look at it beyond the surface level.
Babies and adult humans are going through radically different phases of growth, so yes, they have different protein density needs.
Human breast milk is sufficient to sustain a rapid rate of growth – the quickest growth spurt humans ever go through. But that growth is burning through calories at a rate that humans never achieve again.
Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005). Link.↩