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Updated: Aug 30, 2023

Identifying nutrient deficiencies can be quite challenging. Some deficiencies can take months, even years to manifest clinically.

Calcium deficiency will get compensated through bone loss for decades before it finally manifests through osteoporosis, usually after age 50. Bloodwork for calcium will almost certainly remain normal as long as bones serve as an adequate calcium reserve. Inadequate calcium in the diet can go unnoticed and undiagnosed for decades. Other nutrient deficiencies, like B12, can take 3-6 months before they start manifesting mild and unsuspecting symptoms that get progressively worse. Some nutrient deficiencies, like iron, can cause symptoms rather quickly, even within weeks. We know that nutrient deficiencies are out there, yet they seem to take an inordinate amount of time to identify and treat. Why is this? Are there any specific blood tests that those adopting plant-based diets should consider?

Challenges In Identifying Nutrient Deficiencies

Many factors can make it difficult to quickly and efficiently identify nutrient deficiencies. These include, but aren’t limited to: their non-specific symptom presentation, the confounding and distracting variables, the step-wise approach of medical investigations and the cost-effectiveness considerations of working in a publicly funded healthcare system. It’s also quite important to note that many nutrient deficiencies aren’t easy to identify reliably, even with our modern blood testing methods.

Firstly, hindsight is 20/20, and once the deficiency is diagnosed, the cause becomes obvious retrospectively. Most people don’t come in to the doctor’s office suspecting they have zinc deficiency. They often present with non-specific symptoms, like fatigue or brain fog. Most symptoms don’t scream out clearcut diagnoses and often require a thorough history and physical examination to rule out more obvious causes. Doctors will usually start by ruling out common and dangerous causes of these symptoms. That being said, at the beginning stages of certain nutrient deficiencies, these conditions may lead to some symptoms, without leaving any other physical traces that could be detected during a medical check up. This makes nutrient deficiencies excessively difficult to diagnose during a routine history and medical examination at your physician’s office. We’re often seeing patients that are going through challenges in their lifestyle choices and in those that aren’t exercising, aren’t sleeping or in those who work long hours or live stress-filled lives, it’s always easier to blame fatigue on these factors than on nutrient deficiencies. As a medical doctor who has been in practice for almost 15 years, I order lots of bloodwork, and relatively speaking, I rarely find nutrient deficiencies as the primary explanation for the patient’s symptoms. My initial evaluation will usually consist of a thorough history taking and physical examination, and then many other confounding variables will influence my decision to investigate or not.

These confounding variables can include anything from medical conditions, mental health challenges and even poor lifestyle choices that could also explain the patient’s symptoms. As a doctor, it’s my responsibility to use my judgment and to investigate those who I think tests will reveal abnormalities. I wish I could snap my fingers and get a VIP blood panel for everyone who walks in the door, but this would be a highly inefficient way of practicing medicine, while overusing the finite resources we all share and wasting many patient’s time.

I 100% agree with universal access to health care, but that doesn’t mean our current healthcare system doesn’t have its challenges. The COVID-19 pandemic has really shone a light on this reality. At one point in New-Brunswick, only urgent blood tests were being done, simply because we didn’t have enough phlebotomists or lab technicians to manage the demand. Managing the finite resources of our healthcare system is not only the responsibility of the healthcare workers, but also of its consumers. Instead of blindly ordering blood work for anyone presenting with vague and non-specific symptoms, there are other ways we can increase the efficiency of the healthcare system in identifying nutrient deficiencies.

Zooming Out On Nutrient Deficiencies

High Risk Groups

Before ordering blood work to identify nutrient deficiencies, it’s important to identify if the person in question is in a high risk group. A thorough medical and dietary history will identify common conditions or medications that are frequently associated with specific deficiencies. This would include people who are pregnant or lactating, since we know that this increases the risks of iron deficiency. Other examples include those taking specific medications, like metformin for diabetes, or antacids, which are more likely to be associated with deficiencies in B12. Identifying risk factors like family history is also of utmost importance since conditions like celiac disease have a strong genetic predisposition and are frequently identified after diagnosing nutrient deficiencies like iron deficiency.

Restrictive Dietary Patterns

Identifying specific dietary patterns is also very important since we know that some are associated with specific nutrient deficiencies. B12 deficiency is more likely on a plant-based diet, while other deficiencies are seen on ketogenic diets, for example. A thorough dietary history can help identify those who would be at particular risk of specific deficiencies. This is where I’d want to identify specific food groups that some people could be avoiding for different reasons. Some people avoid animal products for ethical reasons, while some will avoid legumes for digestive issues. Since restricting specific food groups can be associated with specific nutrient deficiencies, it’s very important to identify this situation quickly in order to avoid unnecessary investigations or delays in diagnosis.

Specific Patterns Of Symptoms

It’s important to recognize that many nutrient deficiencies will cause non-specific symptoms. That being said, some symptoms can also be highly suggestive of specific nutrient shortfalls. Iron will often cause a cluster of suggestive symptoms that can range from fatigue to increased perceived exertion while doing physical activity, all the way to shortness of breath during activities of daily living. In this case, it’s important to be highly suspicious of possible iron deficiency and to rule it out with appropriate testing. Neurological symptoms, like ataxia (loss of balance) or paresthesias (tingling sensations) will often require testing of B vitamins, specifically B12. Patients need to have easy access to high quality information in order to educate themselves on the possible nutritional causes of their symptoms. This will improve the efficiency of medical consultations with their doctor and will help identify which investigations to focus on. Documents like the Nutritional Fact Sheets produced by the National Institutes Of Health (NIH) should be made readily and easily accessible to healthcare professionals and patients.

Zooming In On Nutrient Deficiencies

Many useful resources like food guides or smartphone applications can also assist in identifying possible nutrient deficiencies. Food guides can serve as checklists that can be used in order to identify specific food groups that are not well represented by one’s dietary pattern. I specifically enjoy using the Canadian Food Guide and Dr. Greger’s ”Daily Dozen” food checklist that can be printed, or downloaded as an app on your smartphone. This can help patients and healthcare professionals zoom in on specific nutrients of concern by singling out specific food groups that are being neglected. Food log apps, like Cronometer, can be useful in identifying nutrient deficiencies. Although they can help quantify nutrient consumption, they often won’t account for other factors, like medical conditions or medications that can affect nutrient absorption. It’s not what you eat, but what you absorb, and these tools do have certain limitations to consider. For example, they do not factor in the many variables that can affect nutrient absorption, like oxalates or phytates that can decrease nutrient bioavailability and absorption. So even though your smartphone app says you’ve consumed enough zinc, you may not have absorbed it all depending on the other nutrients that were consumed at the same time. One must be cautious to avoid being wrongfully reassured by these nutrient logs that have also been identified as possible triggers of disordered eating patterns.

Teamwork With Your Healthcare Provider

Due to their non-specific presentations and many other confounding variables, nutrient deficiencies can be difficult to identify. It’s useful to first look at the specific risk factors that could make specific deficiencies easier to identify, and this can be done with a thorough medical and dietary history. These could include a personal or family history of certain medical conditions. It could also include specific dietary patterns or restrictions of certain food groups for medical or ethical reasons. With access to high quality information, most patients can even start educating themselves in identifying these particular risk factors before consulting their medical professional. After a detailed history and medical examination, a stepwise approach to investigating possible deficiencies through blood work remains a minimally invasive and cost-effective way of quickly identifying deficiencies before they cause severe and irreversible symptoms. Nutrition is being increasingly recognized as a major determinant playing a crucial role in most of the common chronic diseases encountered today. In the search for optimal health, analyzing food logs and dietary patterns through food group checklists or smartphone apps will likely become the most cost-effective strategy used to identify nutrient deficiencies. This could help prevent unnecessary overuse of the finite healthcare resources we have in Canada, considering that most of these resources are already stretched to their breaking points by increasing rates of lifestyle induced chronic diseases. Unfortunately, most doctors like me are so overwhelmed by treating chronic disease that we find it very difficult to focus on prevention, where much of our efforts should go.

If you and your healthcare provider decide that blood testing could be useful in your specific situation, consider having a complete blood count, or CBC, done to look at white and red blood cells. A metabolic profile including blood sugar, lipids (or fats in the blood, including cholesterol and Apo-lipoprotein B), HbA1C (blood sugar average over the last 3 months) could be considered before and after your transition to a plant-based diet. Measurable improvements in your metabolic markers can be expected within 6-8 weeks, but 3 months seems to be a more reliable marker. Certain nutrients of concern, like iron markers and vitamins B12 and D are useful and more likely to be low. Other markers like minerals (zinc, calcium, etc.) are less useful since blood levels are often maintained within very narrow ranges at the expense of other tissues where it could be lacking. Other tests, including thyroid function, can be ordered after your physician conducts a careful history to determine if it’s necessary or not. The most important thing to remember is that tests aren’t perfect and if you suspect any specific nutrient deficiency, I’d suggest you consider logging in your food intake in an app like Cronometer. You’re much more likely to be able to determine if you could benefit from blood testing by having a clear picture in advance of certain nutrients that you might be lacking.

If you’re considering a transition towards a plant-based diets, then I assume you take health seriously. Any diet, if not well planned, can lead to nutrient deficiencies and plant-based diets are no different. Aim for a wide variety of foods from fruits, veggies, whole grains, legumes, nuts and seeds, and your health is very likely to improve. Consider blood tests before and after your transition to measure and monitor progress and also if you’re suspecting deficiencies. If well planned, metabolic improvement is almost guaranteed and deficiencies can be avoided!

Check out my website, where you can download my free recipe eBook, and subscribe if you’d like to join my email list and to receive updates about new blogs!

Look for me on the socials, @plantbased_dr_jules on Instagram and go like my Facebook Page, Plant-based Dr. Jules. If you’re looking for some fitness motivation and are curious to see what a plant-based athlete can accomplish, follow me, @maritimeninja, on my fitness account on Instagram or check out my fitness group on Facebook, called Maritime Ninja Warrior. I'm a two-time world championship qualified athlete and you can follow my fitness journey there! You can even access the resources section by becoming a member. It's free and there, you can download free resources like my plant-based recipe eBook!

You also check out my YouTube channel here for more tips and tricks on how to embark on a plant-based journey!

Thanks for reading!


Mogre V, Stevens FCJ, Aryee PA, Amalba A, Scherpbier AJJA. Why nutrition education is inadequate in the medical curriculum: a qualitative study of students' perspectives on barriers and strategies. BMC Med Educ. 2018;18(1):26. Published 2018 Feb 12. doi:10.1186/s12909-018-1130-5

Devries S, Willett W, Bonow RO. Nutrition Education in Medical School, Residency Training, and Practice. JAMA. 2019;321(14):1351-1352. doi:10.1001/jama.2019.1581

Craig WJ, Mangels AR, Fresán U, et al. The Safe and Effective Use of Plant-Based Diets with Guidelines for Health Professionals. Nutrients. 2021;13(11):4144. Published 2021 Nov 19. doi:10.3390/nu13114144

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2 comentarios

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I really want to be more plant based but my diet is so limited. My intention is to focus on what I can eat in hope have a strong enough immune system to at least enjoy the summer without having to live on Anti histamines.

Anyway, don’t…

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