Your Child May Not Need as Much Protein as You Think
A scientist and mother takes a critical look at raising children without meat.
“Are you sure it’s okay for us to raise our kids vegetarian?”
Question posed to me by my better half.
When my husband and I were expecting our first child, we had lengthy discussions about whether or not to raise our children without meat. At the time, he was an omnivore and I was plant-based.
Seven years later, our three children are vegetarian, my husband is a pescatarian (plants plus dairy plus fish), and I am still decidedly plant-based.
Every so often, my husband jokingly “threatens” to start offering meat to our children if they slip on the growth charts. Thankfully, this has not been an issue. All our children are not only tall and solid but bursting with energy from dawn to dusk.
While this is certainly encouraging, we would be doing our children a disservice if we assumed that all is well based on these superficial criteria. Health problems that stem from nutritional deficiencies are not always obvious, and can take years to appear.
I decided that it was time to set aside my ethical and environmental motivations, put on my scientist hat, and dig into the research on protein needs.
Headlines
The task of reviewing the scientific literature on the protein needs of children was surprisingly manageable. Due to restrictions on doing direct experiments on children, there are relatively few large, direct studies of children’s protein needs.
Here are my top-level findings:
- Your child’s protein needs are shaped by their age, weight and calorie needs.
- You can easily calculate your child’s protein needs using a simple formula. The trick is using the right “Protein X Factor”. This is where the research comes in.
- Meeting your child’s protein needs is likely easier than you thought.
Let’s dig into these findings, and the science behind them.
First, a quick biology refresher:
Proteins are long chains of amino acids
Proteins are the building blocks of our bodies — they make up the bulk of your muscles, skin, hair, nails, and more.
Proteins are also wee workhorses that carry out the daily “work” inside your cells.
Read more about proteins here: Part 1 (What Are Proteins?) and Part 2 (A Protein’s Journey From Bite to Bicep).
Show Me the Data!
This table shows the estimated daily protein needs of three moderately active children: a 2-year-old girl (25 lbs), a 7-year-old boy (60 lbs) and a 12-year-old girl (90 lbs).
As you can see, there are two ways to describe protein needs. The first is using total grams of protein per day, and the other is using percent of calories coming from protein (relative to total calories from protein, fat, and carbs). Use whichever method you find easier to work with.
Introducing the Protein X Factor
The “Protein X Factor” (my term) is the magic number needed to calculate protein needs. It tells you how many grams of protein you need per pound (or kilogram) of weight and reflects the body’s need for proteins to fuel tissue growth and repair. It varies with age and stage of life, as well as physical activity and health status.
The Protein X Factor is highest for babies and women who are in the second half of their pregnancy. Children have a higher “Protein X Factor” than adults due to their growth-related needs — a child would have greater protein needs than an adult of the same size.
Most studies of protein needs are designed to find out what this number is for a given population and circumstance. There are several different technical approaches, each with their own strengths and weaknesses. None are perfect. The key is understanding the limitations of your chosen method(s).
In my calculations above, I used a Protein X Factor of 0.70 grams per pound to calculate the protein needs of for three hypothetical children. I explain my choice of number in my Gory Details Appendix.
Crunching the Numbers
To calculate YOUR child’s daily protein needs in grams, try this formula using your child’s weight:
This calculation shows how I estimated that my 25 pound toddlers need 18 grams of protein per day:
- 25 lbs x 0.70 g/lb = 18 grams
- Use your child’s weight times a Protein X Factor of 0.70 if weight is in pounds or 1.55 if weight is in kilograms.
To calculate YOUR child’s needs as a percent (%) of daily calories, try this formula using your child’s weight and calories:
Building on the calculation above showing a daily need of 18 grams of protein:
Step 1: 18 grams protein x 4 calories/gram = 72 calories
- Four calories is the amount of energy in one gram of protein.
Step 2: 72 calories / 1000 calories = 0.08 = 8% of calories
- For your child’s calories needs, see Gory Details Appendix (Source: Health.gov)
Reality Check
You may be surprised at how low your child’s protein needs are, but my examples are actually much higher (30–50% more) than the national guidelines in the United States and Canada (which are based on roughly 0.50 grams per pound). There is a good chance that my numbers are overly generous, but I’m erring on the side of caution and explain my reasons in my Gory Details Appendix.
Note: When comparing recommendations, be sure that you are making an apples-to-apples comparison(e.g. total daily grams vs grams per kg or grams per lb).
If you are still skeptical, let’s see what mother nature has to say:
Mother Nature’s Baby Food
Mother nature’s baby food provides a great benchmark for what babies (and toddlers) thrive on, and informs the needs of children as well (who grow less rapidly than babies).
Spoiler alert: Breast milk is not particularly high in protein.
A 1-cup serving of breast milk has 172 calories yet only 3 grams of protein (12 calories)! This translates to 8% of calories — the same as my science-based guideline for toddlers.
Note that children need a higher percent of calories from protein than toddlers (my estimates are 11%-13% versus 8%). This is because toddlers not only need a lot of protein, but also tons of calories. I weigh nearly five times more than my toddlers, but eat only twice as much.
Note: A cup of cow milk or soy milk has more than twice as many grams of protein as a cup of breast milk. It’s not clear that more is better.
What’s the Answer?
So…
Are my vegetarian children meeting their protein needs?
We know what ‘enough’ looks like; we just need to look at our sources to see how they measure up. I’ve done this for my kids using both metrics — grams and percentage — and am happy to declare that the answer is YES! I feel even better knowing that I set a higher bar than the national guidelines.
Using grams, I learned that my twin girls are getting all the protein they need from 2 cups of soy milk per day and a serving of oatmeal. No need to worry about the rest of their food! For my seven-year-old, the key is steering him away from “empty calories” in processed foods. Provided he is filling up on whole grains, nuts, beans, and dairy, he is in good shape.
I urge you to also consider the percentage protein method. Although it may seem unnecessarily complicated, it can actually make things easier, and save you from having to keep a running tally of grams.
Start by getting to know the protein percentages of your commonly consumed foods, ‘binning’ them into above-target, below-target, or on-target. Throughout the day, balance ‘below-target’ foods with ‘above-target’ foods. The average over a few days is what matters most, so you can balance an off day with a higher protein day.
My upcoming article will take a look a common whole foods and where they fall in terms of percentage protein.
Your Turn
To answer the question for your family, start with the simple needs calculations above, then educate yourself about the protein content in your family’s diet. The easiest way to get started is to read labels on some of your commonly consumed foods. It can take some time to get to know what’s in your food, but it’s an investment worth making.
For a more comprehensive look at plant and animal sources of protein, check out my companion articles (more links coming soon) .
Spoiler alert: It’s easy to hit your protein goals on a whole-foods diet — but difficult to achieve on a fast food or pastry diet.
Future Directions
While I feel confident that my children’s protein needs are being met by their vegetarian diet, I still owe it to them to do the same research for other key nutrients such as iron, calcium, and vitamin B12.
Furthermore, meeting your overall protein needs is just one layer of the picture of protein needs. We also have specific needs for each of the nine essential amino acids. I have already asked how my diet stacks up in this regard, but have yet to do this for my children.
See Busting the Myth of Incomplete Plant-Based Proteins
One of my biggest takeaways from this little research expedition is that children are not simply mini-adults. Their needs are unique and evolving. For some nutrients, it may suffice to simply scale down your own diet, while for others, this may not be the case. I feel strongly that it is worth educating ourselves so that we leave nothing to chance.
Follow me as I research health, fitness and nutrition issues for myself and my family at https://fueledbyscience.com
Limitations and Caveats
I’ve focused on the amount of protein that children need to meet their basic needs for maintenance, growth, and routine activity. Needs vary depending on a number of factors including: extreme athletics; certain diseases, recovery from surgery, calorie restriction.
Protein needs can also vary significantly between individuals (for example, based on amount of lean muscle mass) and are impossible to predict exactly. Science will give us averages — and a sense of the range of variation.
Disclaimer: These findings should not be seen as medical advice. They are simply my personal guidelines based on my review of the scientific literature.
Appendix: Gory Details
My process for developing my personal protein needs guidelines:
Step 1: Take a critical look at the recommendations from key groups of expert scientists.
Both the World Health Organization and the Institute of Medicine published reports on nutritional requirements. These were the basis for the nutritional guidelines in Canada and the United States. The Protein X Factor in these reports gradually decreases from around 0.5 in toddlers to around 0.40 for teens (in grams of protein per pound of weight). See my References section for links.
I learned from these reports that the national recommendations for children are largely based on studies in adults, with additional allowances to support predicted growth. On the plus side, the adult studies were based on a fairly large body of work, using an approached called the Nitrogen Balance method. This method was chosen because it is the most commonly used approach and provides a large dataset to work with. It’s worth noting that this method is thought to potentially underestimate protein requirements. No method of estimating protein needs is perfect, we simply need to understand the limitations of whatever method we choose.
Step 2: Search the scientific literature for other relevant studies.
My conclusions were heavily influenced by one additional study. I wouldn’t normally put so much stock in a single (small) study but did in this case because I wanted to err on the side of being generous with my recommendations for children of all ages. Furthermore, the actual data in the study looked quite “tight” (internally consistent).
It was a small study of 7 healthy children (ages 6–11) that used a different method, called Indicator Amino Acid Oxidation or IAAO for short. This method is thought to be more accurate than the Nitrogen Balance method, but it is more challenging to apply. As a result, there are very few studies, and the studies tend to be small.
This study found a Protein X Factor of 0.70 (grams per pound) — considerably higher than the number in the national guidelines described above. I applied this number in all three of my examples.
Step 3: Reality Check
I looked for other ways to ask the same question. I turned to Mother Nature’s Baby Food (breast milk) as a benchmark and was greatly reassured by the fact I am recommending a protein intake higher than that of breast milk!
References
- Breast milk nutritional information
- Institute of Medicine report — based on Nitrogen Balance method (plus estimated deposition needs in the case of children)
- World Health Organization report — based on Nitrogen Balance method
- Small study of protein needs in children — based on Indicator Amino Acid (IAOO) method
- Children’s Calorie Needs (Source: Health.gov)
- [a] Sedentary means a lifestyle that includes only the physical activity of independent living.
- [b] Moderately Active means a lifestyle that includes physical activity equivalent to walking about 1.5 to 3 miles per day at 3 to 4 miles per hour, in addition to the activities of independent living.
- [c] Active means a lifestyle that includes physical activity equivalent to walking more than 3 miles per day at 3 to 4 miles per hour, in addition to the activities of independent living.
