Blood Testing Is the Gold Standard Assessment for Nutrient Status. Here’s Why.

An optimal nutritional status is a determinant factor for health and well-being. As a major, modifiable and powerful element to promote health and improve quality of life, health professionals have historically assessed nutritional status as part of routine health checks. 

Because the foundation of good physical health is a good nutritional status, understanding it is a crucial piece of the puzzle. For dietitians and doctors, this information allows them to give you the most personalized recommendations. For you, the individual, this information can empower your understanding of your own health and help you make informed decisions so you can take action. 

There have been numerous traditional methods of nutritional assessment and a few that are up-and-coming, but only one method stands above the rest in this crowded space: blood nutrient testing. 

When it comes to nutritional assessments, you have a lot of choices. Blood testing is the best method.
When it comes to nutritional assessments, you have a lot of choices.

Many traditional methods of nutritional assessment are time-intensive and prone to inaccuracy

Clinical assessment 

In clinical settings, a number of approaches have been traditionally used to assess nutritional status. Typically, the first step involves the collection of anthropometric data, like your height, weight, and other body measures. Height and weight are used to calculate your body mass index (BMI). BMI is employed at a population level as a tool to correlate the risk of certain diseases with weight. It can be useful when put into a bigger context, but BMI alone is not a very good predictor of nutritional status. This is because it is dependent only on height and weight, and does not take into account differences in body fat based on age, sex, and physical activity. For this reason, it can overestimate fat mass (adiposity) in some cases while underestimating it in others [1]. 

Dietary assessment 

Another way of assessing nutrient status is based on the recording and evaluation of food intake through 24-hour dietary recalls or food frequency questionnaires (FFQ). In a 24-hour dietary recall, you are asked to recall and report all foods and beverages consumed over the preceding 24 hours, while an FFQ assesses the frequency with which certain foods and food groups are eaten within a certain period of time. While the FFQ and a repeated 24-hour recall are acceptable tools for assessing nutritional status in large population studies [2,3], they are error-prone since they rely on memory alone. This can lead to an over or underestimation of portion sizes and intake of specific food groups. 

Additionally, there is great variability in terms of nutrient content within the same food type, due to factors like soil composition, sunlight exposure of the food, methods of harvesting and shelf-life of the food. And even assuming uniformity of the food source, the individual variability in nutrient absorption, which can be affected by many different factors, is not considered.  Ultimately, these methods don’t provide the level of accuracy needed to truly derive individual nutrient levels. 

Biochemical assessment 

In hospital settings, a biomarker that has been long used to assess nutrient status was serum albumin: thought to be a good indicator of malnutrition, further research has shown that it is not a reliable marker of nutritional status, mainly because its levels are strongly affected by inflammation or infection [4,5]. 

The science is still too young for two up-and-coming methods of nutritional assessment

So, outside clinical settings, what options are out there that can help you find out your nutritional status? In recent years, DNA and microbiome testing have emerged into the spotlight with the promise of developing standards of care based on personalized nutrition. 

blood testing is better testing method than microbiome and DNA for nutrient evaluation

DNA Testing 

Nutrigenetics is the study of how individual genetic variability affects nutrient metabolism and health outcomes [6]. Genetic variability influences the way people process nutrients like vitamin D, omega-3 fatty acids, dietary cholesterol, folate, choline, lactose, starch, and caffeine among others [7]. Differential responses to nutrient metabolism can eventually have an effect on the individual’s health and risk of developing certain diseases. 

The relationship between nutrient metabolism and genetic variations among individuals is incredibly complex and research is still in its infancy. What is known is that identifying a specific variation in your genome will not automatically translate into a certain health outcome as there are many factors at play. Ultimately, think of your nutrition-related genetics as what could happen over the course of your lifetime, not what’s happening right now

For this reason, in order to get the full picture, genetic information must be paired with information on what’s actually going on in your body currently, such as blood data. Due to the early stage of research in this area and the fact that genetic information cannot be used as a stand-alone nutrition assessment, DNA is not the ideal assessment method. 

Microbiome Analysis 

Microbiome testing is another recently popular approach when it comes to personalized nutrition. The microbiota, or the community of organisms living in your gut, plays a key role in your health. Gut microbes are responsible for the fermentation of non-digestible fiber and the production of beneficial short-chain fatty acids [8]. Additionally, they are able to produce vitamins (like B12, B6, B5, niacin, biotin tetrahydrofolate, and vitamin K) that humans do not have the ability to synthesize [9]. Testing your microbiota can give some interesting information on the types of bacteria populating your gut, but the research is not there yet to support personalized recommendations that go beyond the generic “eat more fiber”. Research does not currently support microbiome analysis as a form of nutritional assessment.

Blood testing - 
All the above-mentioned tools are a great add-on when you aim to better understand your health, but they just tell part of the story. 

To get the bigger picture, the most reliable way to assess your nutrient status is to search for the specific nutrients where they act: inside the body.

Blood nutrient testing: the gold standard nutritional assessment 

Blood testing is the gold standard for nutrient assessment and doctors and dietitians’ first choice. This is because of its superior accuracy compared to other non-analytical approaches. In the majority of cases, the blood levels of a specific nutrient reflect its true stores in the body. 

Additionally, while overt deficiencies can give clear symptoms, which allows for prompt intervention, more often, subclinical deficiencies aren’t spotted right away unless you dig deeper. In the case of vitamin B12, for instance, mild deficiency can cause tiredness [10]. This is a very generic symptom that taken alone is not very informative, but can easily be explained by a blood test. With today’s state of the art analytical tools, it’s possible to safely and accurately measure micronutrients at the nanomolar level. 

Blood testing - 
When blood is drawn for analysis, it is separated into a fluid component and a cellular component. Depending on whether blood is allowed to clot or an anticoagulant like heparin or EDTA is added to prevent clotting, the fluid component is called serum or plasma, respectively. Both serum and plasma can be used for accurate micronutrient analysis, but a few differences still exist. While serum is more stable once separated, plasma is more representative of circulating blood [11]. The cellular component of the blood can also prove very useful in determining certain nutrient levels like omega-3 fatty acids EPA and DHA, for example. This medium provides more reliable results when measured in red blood cells compared to plasma, because of the greater stability of the fatty acid composition over time [12].

The next time you desire to know more about your body, your health, and your nutrient needs, turn inward for the answers—your blood holds the key


  1. World Health Organization. (2019, October 16). Body mass index – BMI. Retrieved October 16, 2019, from
  2. Food and Agriculture Organization of the United States. (n.d.). Dietary assessment a resource guide to method selection and application in low resource settings. Retrieved from
  3. Steinemann, N., Grize, L., Ziesemer, K., Kauf, P., Probst-Hensch, N., & Brombach, C. (2017). Relative validation of a food frequency questionnaire to estimate food intake in an adult population. Food & Nutrition Research, 61(1), 1305193.
  4. Chojnowska, E. (1996). Serum albumin concentration is not a marker of nutritional status. BMJ, 313(7051), 230–230.
  5. Forse, R. A., & Shizgal, H. M. (1980). Serum Albumin and Nutritional Status. Journal of Parenteral and Enteral Nutrition, 4(5), 450–454.
  6. Camp, K. M., & Trujillo, E. (2014). Position of the Academy of Nutrition and Dietetics: Nutritional Genomics. Journal of the Academy of Nutrition and Dietetics, 114(2), 299–312.
  7. Kanter, M., & Desrosiers, A. (2019). Personalized Wellness Past and Future. Nutrition Today, 54(4), 174–181.
  8. Morrison, D. J., & Preston, T. (2016). Formation of short chain fatty acids by the gut microbiota and their impact on human metabolism. Gut Microbes, 7(3), 189–200.
  9. Kau, A. L., Ahern, P. P., Griffin, N. W., Goodman, A. L., & Gordon, J. I. (2011). Human nutrition, the gut microbiome and the immune system. Nature, 474(7351), 327–336.
  10. Hunt, A., Harrington, D., & Robinson, S. (2014). Vitamin B12 deficiency. BMJ, 349, g5226.
  11. Miles, R. R., Roberts, R. F., Putnam, A. R., & Roberts, W. L. (2004). Comparison of serum and heparinized plasma samples for measurement of chemistry analytes. Clinical Chemistry, 50(9), 1704–1706.
  12. Cao, J., Schwichtenberg, K. A., Hanson, N. Q., & Tsai, M. Y. (2006). Incorporation and Clearance of Omega-3 Fatty Acids in Erythrocyte Membranes and Plasma Phospholipids. Clinical Chemistry, 52(12), 2265–2272.

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