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Doctor teaching children about healthy balanced meals

You Are What You Eat, and What You Don’t

By James Greenblatt, M.D.+

“You are what you eat” is an old adage that most have heard throughout their life- starting in childhood. It’s a simple saying, and fundamentally common sense. 


However, there is a flip side: you are also influenced by what you don't eat. Recent studies show that our health depends just as much by what is on our plates as by what is missing from them, especially as food quality declines. This is particularly important to consider for children's physical, mental, and emotional development.


Redefining Essential


When it comes to human nutrition, “essential” means essential.


Over the course of evolution, the human body has developed the capacity to manufacture many nutrients that it needs to function properly. Vitamin D, for example, can be synthesized in our skin upon exposure to sunlight.


There are many nutrients, however, that the body requires to function optimally but cannot manufacture on its own. These are the “essentials,” and include vitamin C, vitamin B12, essential fatty acids, and minerals such as magnesium and zinc, among others.


And when it comes to mental health, “essential” assumes even greater significance, as many nutrients are required by the brain for optimal function. This is critical as we consider dietary habits alongside trends in worsening youth mental health. 


Nourished Minds & Neurodevelopment 


The single most energetically demanding organ in the body is the brain. Weighing around 1.2 kilograms (3 pounds), the brain accounts for a staggering 25% of the body’s total metabolic expenditures.1


And the brain’s need for nutrients is at an all-time high during adolescence—a stage of development characterized by rapid, profound changes. Unfortunately, adolescence is often the time when individuals have poor eating habits. Additionally, children in their mid-teens are often exposed to social or lifestyle changes that can negatively impact their emotion, thinking or overall behavior.Human health is not a fixed quantity. It falls along a continuum that is influenced by factors such as genetics, the environment, social history, and more. While we cannot discount the potential impacts of these factors on youth mental health, we also should not discount the potential role of nutrition.


Nutrition is one of the most significant determinants of brain development and function. It also happens to be one of the most easily corrected. 


Mother and son enjoying a mandarin orange in the kitchen and smiling.


Applied Nutrition for the Modern Era


In reality, making good choices for our children involves encouraging the consumption of nutrient-rich foods. It means educating our kids about nutrition, and how investments in health made now can yield long-term benefits. It also means considering the necessity of nutritional supplements. 


Due to a number of factors, ranging from climate change to nonregenerative agricultural practices, the nutritional content of many natural foods is declining.3 Furthermore, common food preparation techniques can dramatically reduce the vitamin and mineral content of food. Nearly 100% of vitamin C, for example, is lost through boiling.4


In addition to bridging the widening gap between what food can provide and what the body requires, supplements can help to ensure that children and teens will satisfy the vast nutritional demands of their growing bodies and brains. If you feel your child may need a supplement, consult their health care provider.


A properly nourished brain can lay a foundation for lifelong well-being. It is also why I strongly believe that we should remember the importance of what we both do—and don’t—consume. 



Ask The Expert 


What essential nutrients are children and teens most likely to be deficient in?


I have found that the nutritional status in children and teens is generally influenced by their dietary intake. 


For example:


  • Over consumption of sugar almost always increases the need for B vitamins.
  • Vegetarian diets, or those low in animal products, are usually low in zinc or B12. Animal products are the richest and most available source of the mineral.
  • Excess consumption of soft drinks, among other causes, depletes magnesium. The phosphoric acid found in soft drinks binds free magnesium making it difficult for the body to absorb.5


What roles do B Vitamins play in health?


Every single metabolic pathway of the human body relies, to some degree, on B vitamins. They help with energy production, red blood cell formation, and neurotransmitter synthesis, including the production of serotonin and dopamine. 


Together, the B vitamins act synergistically to support overall health through diverse pathways. It is for this reason that B vitamins, are a cornerstone of my nutritional approach to mental wellness. 


What are some common signs of low magnesium?


Accurately assessing a person’s magnesium status can sometimes be tricky. Magnesium is primarily found inside the cells of the body. Accordingly, blood levels do not accurately reflect tissue stores.6


Even without testing, supplementation is recommended in a majority of cases due to magnesium’s far-reaching benefits and safety profile (when dosed appropriately), as well as the widespread prevalence of magnesium deficiency.


How does zinc support the absorption of other essential nutrients?


Zinc is required to produce stomach acid as well as the activation of many digestive enzymes—both of which are necessary for the proper breakdown and absorption of food and nutrients in the digestive tract.


This is also why zinc deficiency can act as a positive feedback loop. When zinc levels are low, poor digestion can lead to other nutrient deficiencies and worsen zinc status even further.


How can I know if my child has any nutritional deficiencies?


Many nutritional deficiencies present with symptoms that may be misdiagnosed and are easily confused or overlooked. Still other children with nutritional deficits may have no overt signs or symptoms in the early stages. It’s also worth recognizing that each individual has unique nutritional requirements. 


The key to identify deficiencies in most cases is simply this: laboratory testing can help to identify adolescents who may not be meeting their nutritional requirements.


Meet Our Expert 


Photo of James M. Greenblatt


A pioneer in the field of integrative medicine, James M. Greenblatt, MD, has treated patients since 1988. After receiving his medical degree and completing his psychiatry residency at George Washington University, Dr. Greenblatt completed a fellowship in child and adolescent psychiatry at Johns Hopkins Medical School. Dr. Greenblatt currently serves as the Chief Medical Officer at Walden Behavioral Care in Waltham, MA and serves as an Assistant Clinical Professor of Psychiatry at Tufts University School of Medicine and Dartmouth College Geisel School of Medicine.  


An acknowledged integrative medicine expert, educator, and author, Dr. Greenblatt has lectured internationally on the scientific evidence for nutritional interventions in psychiatry and mental illness. Through three decades of practice and research, Dr. Greenblatt is a leading contributor to helping physicians and patients understand the role of personalized medicine for mental illness. To learn more about the author, please visit 



+Our Medical Consultants are retained advisors to Pure Encapsulations.  




1.Camandola S, Mattson MP. Brain metabolism in health, aging, and neurodegeneration. EMBO J. 2017;36(11);1474-1492.

2.Kessler RC, Angermeyer M, Anthony JC, et al. Lifetime prevalence and age-of-onset distributions of mental disorders in the World Health Organization’s World Mental Health Survey Initiative. World Psychiatry. 2007;6(3):168-176.

3.Colino S. Fruits and vegetables are less nutritious than they used to be. National Geographic. Published May 3, 2022. 

4.Lee S, Choi Y, Jeong HS, Lee J, Sung J. Effect of different cooking methods on the content of vitamins and true retention in selected vegetables. Food Sci Biotechnol. 2017;27(2):333-342.

5.Gropper SA & Smith JL. Advanced nutrition and human metabolism (6th ed.). Belmont, CA: Wadsworth/Cengage Learning; 2013.

6.Ismail Y, Ismail AA, Ismail AA. The underestimated problem of using serum magnesium measurements to exclude magnesium deficiency in adults; a health warning is needed for "normal" results. Clin Chem Lab Med. 2010;48(3):323-327