Lysine in Plant-Based Diets For Kids

There is concern about lysine in plant-based diets. Some recommend that plant-based eaters consume at least three servings of lysine-rich plants daily such as beans to prevent deficiency. But is this really necessary? What about kids who dislike beans? This post includes everything you need to know about lysine in plants.

Got a toddler who won’t touch a bean? You may be worried about their protein or amino acid intake, specifically, the amino acid lysine.

Some people claim that plant-based diets may be deficient in lysine because it tends to be lower in plant-based diets and is found mainly in legumes, which – let’s be honest – aren’t always kid’s favorite food!

Here’s what to know about meeting lysine needs on a predominantly or exclusively plant-based diet. 

THE INCOMPLETE PROTEIN MYTH

One of the most common misperceptions about plant foods is that they lack one or more of the nine essential amino acids that our bodies need to grow and properly function.

However, this is the evidence-based truth: all whole plant foods contain all nine essential amino acids we need, including lysine. That’s right, even broccoli contains lysine. With this being said, lysine is the least abundant essential amino acid found in plant foods, which is why predominantly and exclusively plant-based individuals may have been advised to focus on their intake. 

But is lysine really that hard to come by? How much lysine do kids need? And what are the richest plant sources of lysine for kids? We’re covering all of these questions and more in this post.

WHAT IS LYSINE?

Lysine is an amino acid, a building block of protein. While some amino acids can be synthesized by the body, nine amino acids cannot and we refer to these as essential or indispensable amino acids. For this reason, we must get essential amino acids, like lysine, through our diet or supplements. 

Lysine has several important functions in the body. It plays a role in:

• Tissue growth and repair
• Production of collagen, the most abundant protein in the body
• Absorption of calcium, iron, and zinc
• Synthesis of carnitine, a compound that transports fatty acids into cells to be used for energy

WHY ARE PEOPLE CONCERNED ABOUT LYSINE?

The concern about lysine has to do with it being a “limiting amino acid” in a plant-based diet.

The term “limiting amino acid” refers to the essential amino acid found in the lowest amount in a food item, relative to the body’s requirements. When we don’t consume adequate amounts of limiting amino acids, like lysine, through our diet, protein synthesis is restricted. In other words, when the limiting amino acid no longer remains, the synthesis of proteins that require that amino acid will stop.

LIMITING AMINO ACIDS

Four essential amino acids that may be limited in the diet include lysine and threonine in cereal grains, methionine in legumes, and tryptophan in corn. Because many cultural dietary patterns rely heavily on grains, there is concern that individuals who don’t consume sufficient quantities of lysine-rich foods like legumes are not getting enough lysine. However, these countries often face challenges such as malnutrition, related to deficiencies in total protein intake. In developed countries, like the United States, protein deficiency is rare.

WHAT FOODS CONTAIN LYSINE?

Lysine is found in all whole foods that contain protein. The highest concentration is in animal foods, followed by legumes and grain-based foods. 

On average, animal foods contain approximately 85 mg of lysine per gram of protein while legumes and cereals contain about 65 mg and 29 mg of lysine per gram of protein, respectively. To put this into context, 3 ounces of chicken has approximately 23 grams of protein and 1,955 mg of lysine, 1 cup of lentils has 18 grams of protein and 1,170 mg of lysine, and 1 cup of white rice has 4 grams of protein and 116 mg of lysine.

While animal foods are the primary source of lysine, plant foods like tofu, tempeh, beans, lentils, nuts, seeds, and quinoa are also good sources of lysine.

PLANT-BASED SOURCES OF LYSINE

Food (Toddler Serving Size)	Lysine (mg)
Oats, 1/4 cup uncooked	125
Whole Wheat Bread, 1 slice	50
Whole Wheat Pasta, 1/3 cup cooked	50
Whole Wheat Crackers, ½ cup	50
Whole Wheat Tortilla, 1 8-inch tortilla	125
Quinoa, 1/3 cup cooked	150
Black Beans, 1/4 cup cooked	250
Tofu, 2 ounces	375
Soy milk, 8 ounces	475
Chia seeds, 1 teaspoon	25
Hemp seeds, 1 teaspoon	125
Pumpkin Seeds, 1 tablespoon	100
Almond Butter, 1 tablespoon	93
Peanut Butter, 1 tablespoon	63
Broccoli, 1/4 cup cooked	4

 

HOW MUCH LYSINE DO KIDS NEED?

The recommended daily amount of lysine for children is:

• 7-12 months: 89 mg/kg body weight/day
• 1-3 years old: 58 mg/kg body weight/day
• 4-8 years old: 46 mg/kg body weight/day
• Girls 9-13 years old: 43 mg/kg body weight/day
• Boys 9-13 years old: 46 mg/kg body weight/day
• Girls 14-18 years old: 40 mg/kg body weight/day
• Girls 14-18 years old: 43 mg/kg body weight/day

LYSINE CONTENT IN THREE TYPICAL PLANT-BASED TODDLER DIETS

To determine if plant-based children are getting enough lysine in a typical diet, we created three sample menus and calculated the lysine content, then compared it to the recommended amount of lysine. We tried to keep the menus as similar as possible with the exception of the legumes.

We used Cronometer to analyze the menus and nutritional data was taken from the Nutrition Coordinating Center Food & Nutrient Database (NCCDB) curated by The University of Minnesota.

For this exercise, we used an average 2-year-old, weighing ~26 pounds (~11.8 kg). The daily lysine recommendation for this toddler would be approximately 684 mg of lysine. 

We analyzed three sample menus for this hypothetical child:

• Menu 1 did not contain beans or legumes.
• Menu 2 included 2 servings of soy milk (legume) but did not contain beans.
• Menu 3 included 2 servings of soy milk and 1 serving of beans.

Sample Menus for a 1-3-Year-Old

Menu 1: No Legumes

Breakfast:

¼ cup oats (uncooked)

1 tablespoon hemp seeds

½ cup strawberries

Snack:

1 cup oat milk

1 apple

Lunch:

2 slices of whole wheat bread

1 tablespoon of peanut butter

1 banana

5 carrot sticks

Snack:

1 cup of oat milk

½ cup of wheat crackers

¼ cup of blueberries

Dinner:

⅓ cup of whole wheat pasta

¼ cup of marinara sauce

¼ cup broccoli

Total = 1123 kcal, 36.8 g protein, 1250 mg lysine

 

Menu 2: No Beans with Soy Milk

Breakfast:

¼ cup oats (uncooked)

1 tablespoon hemp seeds

½ cup mixed berries (strawberries)

Snack:

1 cup soy milk (fortified)

1 apple (small)

Lunch:

2 slices of whole wheat bread (medium slice)

1 tablespoon of peanut butter (unsalted)

1 banana (small)

5 carrot sticks (5 slices)

Snack:

1 cup of soy milk

½ cup of wheat crackers

¼ cup of blueberries

Dinner:

⅓ cup of whole wheat pasta (cooked)

¼ cup of marinara sauce

¼ cup broccoli (cooked, whole pieces)

Total = 1,101 kcal, 43.1 g protein, 1750 mg lysine

 

Menu 3: 1 Serving of Beans with Soy Milk

Breakfast:

¼ cup oats (uncooked)

1 tablespoon hemp seeds

½ cup mixed berries

Snack:

1 cup soy milk

1 apple

Lunch:

2 slices of whole wheat bread

2 tablespoons of peanut butter

1 banana

5 carrot sticks

Snack:

1 cup of soy milk

½ cup of wheat crackers

¼ cup of blueberries

Dinner:

1 whole wheat tortilla

¼ cup refried beans (vegetarian)

¼ cup broccoli

Total = 1,183 kcal, 50.4 g protein, 2100 mg lysine

What did we find?

All three menus (even the one excluding lysine-rich legumes) exceeded both the recommendation for lysine and protein. 

The first menu lacked legumes (which contain greater concentrations of lysine compared to grains), yet provided about 1.25 grams or 1250 milligrams of lysine, nearly double the requirement for this child. The second menu did not include beans but did include soy milk (technically in the legume category). It provided approximately 1.75 grams or 1,750 grams of lysine. The final menu contained 2 servings of legumes and soy milk, a common recommendation for plant-based children, and provided about 2.1 grams or 2,100 mg of lysine, more than three times the daily requirement for this child. 

After comparing the amount of lysine provided by each menu to the 684 mg daily lysine recommendation for 2-year-old weighing ~26 pounds, it’s clear that lysine needs are not only met but exceeded with all the menus, even the first menu which does not include legumes. 

Therefore, even if your little one won’t touch a bean, they will be getting more than enough lysine as long as they are eating enough food and a variety of protein-rich foods.

PBJ’S RECOMMENDATIONS

If you didn’t read the entire blog post, that’s okay! Here’s what you need to know:

• Lysine is an essential amino acid that must be obtained through the diet. 
• Animal foods like meat, eggs, and dairy products are the highest sources of lysine. 
• Lysine-rich plants include beans, lentils, soy products, quinoa, nuts, and seeds
• All foods containing protein also contain lysine
• Despite being less plentiful in plant foods, predominantly and exclusively plant-based eaters are able to meet (and likely exceed) lysine requirements as long as calorie and protein intake is sufficient

We love beans – and we hope your child does too! They’re an awesome source of protein, fiber, and minerals for kids and adults. But if you can’t get your kid to eat a legume, it’s ok. As long as your child is eating enough food throughout the day, including protein-rich plant foods such as whole grains, legumes, nuts, and seeds, you don’t have to obsess about “lysine-rich plants!”

Chime-in: Were you concerned about lysine in plant-based diets for kids before reading this post? 

If you found this post helpful, we think you should read these too:

• Everything You Need To Know About Plant-Based Protein
• Meal Planning for Toddlers
• Meal Prep Ideas for Busy Families
• 5 Myths About Plant-Based Diets for Kids

*Thank you to our dietetic intern Sydney Navid for writing and researching this post. Sydney is currently a master’s student in dietetics at Columbia University. You can follow Sydney for great recipes and nutrition information on her Instagram channel: @sydneynavid.