This is part of an ongoing series I am starting called “Understanding Anorexia.” These posts (which I will continue to do every now and then going forward) will focus on different physiological, nutritional, and psychological aspects of anorexia nervosa (AN). Today we will be talking about zinc deficiency! This is a major topic to be aware of you are experiencing AN, have a history of AN, or work with people with AN.

Zinc deficiency is one of the most common micronutrient deficiencies in those with AN. Given that zinc is involved in so many key physiological processes, it is vital for eating disorder treatment and recovery to ensure that your zinc levels are in a good place. In this post, we are going to cover several topics related to zinc including:

• What is zinc and why is it important?
• What are good food sources of zinc?
• How are zinc deficiency and AN related?
• What can I do to improve my zinc levels?

Let’s dive in!

What is zinc and why is it important?

Zinc is one of the key trace minerals needed by our bodies for good health and proper functioning. There are two kinds of minerals – macro minerals and trace (or micro) minerals. Macro minerals (such as calcium, potassium, and sodium) are needed by the body in much larger quantities. In contrast, trace minerals (such as iron, zinc, and iodine) are needed in much smaller quantities, yet are also vital to bodily functioning. Zinc is the second most abundant trace mineral in the body, following iron.

Adequate levels of zinc are important for:

• Normal brain functioning, including serotonin metabolism and reducing anxiety/depression
• Immunity and wound healing
• Normal sense of taste and smell
• Stimulating normal food intake and regulating weight
• Hormonal production, growth, and sexual development
• Skin health

While this list is by no means conclusive, you can begin to see just how vital zinc is to a number of processes.

What are good dietary sources of zinc?

So, how do we get zinc in our diet? The best dietary sources of zinc are found in red meat and seafood (knocking it out of the ballpark are oysters of all foods!). Let’s check out a few more zinc-rich food sources:

The recommended dietary allowance, or RDA, for zinc is 8 mg per day for females ages 14-18 years and 9 mg per day for females ages 19+. For males ages 14+, the RDA for zinc is 11 mg/day. As you can see, a serving of beef (this is the data for 3 oz of chuck roast) gives you most of your recommended daily requirement for zinc, while a serving of cashews provides a smaller, but still significant, amount of zinc.

While we are talking about dietary sources of zinc, it’s also important to discuss the concept of “bioavailability.” Bioavailability refers to the amount of the nutrient consumed that is actually absorbed by the body. For example, it could say on a given food label that it contains “50% of your daily value for iron,” but there are a number of factors that affect how much of that “50%” is actually going to be absorbed by your body, meaning taken up into your bloodstream. A number of factors affect the bioavailability of a nutrient in a given food, including the food structure, the chemical form of the nutrient, interactions among different nutrients in the food, and the processing, preparation, or treatment of the food.

In terms of the bioavailability of zinc in certain foods, it is important to know that meat and seafood sources have the highest bioavailability of zinc due to certain compounds in these foods that enhance zinc absorption. In contrast, the zinc found in plant sources is less bioavailable due to the high content of phytates (the storage form of phosphate) in these foods, which acts to inhibit zinc absorption. Thus, it will likely be harder for those on vegetarian and vegan diets to obtain adequate levels of zinc from their diets – more on that later.

How are zinc deficiency and AN related? [Part 1: Why you may be more likely to be zinc-deficient]

First, let’s talk about a few reasons why someone with AN may be more likely to be zinc deficient. As mentioned previously, zinc is one of the most common micronutrient deficiencies among those with AN. One obvious reason why you may be zinc-deficient if you are experiencing AN is the simple fact of not eating enough food in general. What’s more, the zinc-rich food sources discussed above – predominantly meat and seafood – are commonly restricted or avoided altogether in those suffering from AN. In one study involving 45 AN patients, 96% of the patients avoided beef, and 75% of the patients avoided both beef and poultry. All of the patients in this study were zinc-deficient.

It’s common for people with AN to start avoiding meat years prior to the onset of the full-blown eating disorder. For some people, eating a vegetarian diet can be a “socially acceptable” way of hiding their unhealthy fear and relationship surrounding eating meat (while for others, of course, eating a vegetarian diet can be no problem).  I know for me, when I was experiencing AN, I pretty much stopped eating red meat entirely, and my zinc levels suffered tremendously as a consequence of this and of the malnutrition my body was experiencing more broadly.

Another factor to consider is that many women with AN are not getting their periods, and may be on the birth control pill in an effort to “solve” this problem. I didn’t have my period for over 6 years, and all of the conventional doctors I went to about this didn’t seem very concerned about it or interested in considering that it may be my eating/exercise habits that were causing this (when it seems to me like that was the obvious cause!). They simply suggested that I take the pill to “get my period back,” when in reality, that would have merely put a band-aid on the problem by inducing a fake period (as in, no ovulation or natural hormonal cycle would be involved in this “period.” Should I have done this and ever wanted to go off the pill to have kids my problem would have still been there. Not to mention the damage I was causing to my bones and body more broadly by not getting my period – the birth control pill would have done nothing to solve this either).  Tangent aside, research shows that hormonal contraceptives can alter the way our bodies process, absorb, and metabolize micronutrients, zinc included. This study showed that in the sample size studied, the women on hormonal oral contraceptives had significantly lower zinc levels (6.21% lower) compared to women with healthy, normal menstrual cycles who were not on oral contraceptives. The authors concluded that these changes in how the body processes zinc (resulting from taking oral contraceptives) “may alter the dietary zinc requirement” in these women.

All that to say, if you are experiencing AN or any form of malnutrition, restricting your meat/seafood intake, and/or on the birth control pill, you are likely at greater risk for zinc deficiency.

How are zinc deficiency and AN related? [Part 2: Cause or result?]

While it is clear (as previously mentioned) that the malnutrition of AN will likely lead to decreased serum zinc levels, it is also thought that zinc deficiency, prior to the onset of AN, may also contribute to the development of the eating disorder. In other words, an existing zinc deficiency may be one small piece of the puzzle leading to the development of AN (the etiology of which is a very complicated puzzle of biological, psychological, and environmental factors), and this deficiency will almost certainly be made worse with the onset of AN. (And in the case of normal zinc levels prior to the start of AN, zinc levels will also almost certainly be made worse with the onset of AN).

Due to zinc’s important neurological functions, zinc deficiency (independent of AN) is associated with depression, anxiety, ability to calm down from stress, and other mood disorders, which can be part of the psychological picture when it comes to developing AN. What’s more, this interesting study showed that rats fed a zinc-deficient diet developed anxious and anorexic-like behaviors (including reduced food intake) compared to rats on a zinc-adequate or zinc-supplemented diet.

I don’t know what my zinc levels were prior to the onset of the AN, but I wouldn’t be surprised if they had been lower than what is considered normal, given my anxious tendencies and quick spiral into AN. The same could be true for you if you are suffering from AN.

Given that zinc deficiency can perpetuate anxiety and food restriction compulsions, studies have also shown the importance of zinc supplementation in the treatment of AN. Zinc supplementation has shown promising results in helping to improve weight gain, food normalization, skin and hormonal abnormalities, and depression/anxiety symptoms in those with AN compared to those with AN who are not supplementing zinc.

What can I do to improve my zinc levels?

After reading this far, you now have a greater understanding of the importance of zinc, it’s connection to AN, and things to consider as to whether you may be at greater risk for a zinc deficiency. Here are a few tips I would recommend on the basis of all that I’ve shared above:

• If you have AN or another eating disorder, I would highly recommend getting your zinc levels checked. Hopefully you are working with an eating disorder-trained physician and/or dietitian who can help you in supplementing zinc properly to improve your levels if needed. As you continue to improve your relationship with food, eating more food and more variety of foods (including zinc-rich food sources), this will also help to improve your zinc levels. I would recommend testing zinc levels using an HTMA test if possible.  Note: it is important to also test and monitor your copper levels if dealing with a zinc deficiency and/or supplementing zinc. 
• If you eat a vegetarian or vegan diet, I would also recommend getting your zinc levels tested, as it is harder to maintain adequate zinc levels without eating meat and seafood regularly. If needed, you could consider working with a dietitian to supplement zinc properly and learn how to better enhance zinc absorption from the plant-based zinc sources you are consuming.
• For anyone else, it’s also not a bad idea to test your zinc levels! The typical American diet isn’t always the richest in micronutrients, and it may be challenging for some to maintain zinc levels in the proper range unless you are intentional about it. I know for me, I recently got my zinc levels in the normal range and then back-slided again once I stopped supplementing, even though I try to be intentional to incorporate zinc-rich food sources regularly. I could just be more genetically prone to zinc deficiency, so I am back to supplementing again for now and will test again in a few months.

Hopefully this post on AN and zinc deficiency was helpful for you. If you have any more questions on this topic, feel free to leave them in the comments!

References:

CL; SJCB. Zinc supplementation in the treatment of anorexia nervosa. Eating and weight disorders : EWD. https://pubmed.ncbi.nlm.nih.gov/11930982/. Accessed June 15, 2021.
Hermens DF, Simcock G, Dutton M, et al. Anorexia nervosa, zinc deficiency and the glutamate system: The ketamine option. Progress in neuro-psychopharmacology & biological psychiatry. https://www.ncbi.nlm.nih.gov/pubmed/32169564. Published July 13, 2020. Accessed June 15, 2021.
M; FSSFVF. Effect of contraceptive pill on the selenium and zinc status of healthy subjects. Contraception. https://pubmed.ncbi.nlm.nih.gov/19501214/. Accessed June 15, 2021.
Office of Dietary Supplements – Zinc. NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/. Accessed June 15, 2021.
Zinc status and meat avoidance in Anorexia Nervosa … https://www.researchgate.net/publication/271327154_Zinc_status_and_meat_avoidance_in_Anorexia_Nervosa. Accessed June 15, 2021.