Nutrient Depletions and Drug Action Phases

Maxine Fidler, MS, ND

Nutrient Depletions and Drug Action Phases

When we hear about nutrient depletions, what may first come to mind is inadequate intake. We don’t always consider medications, along with their beneficial effects, can result in unintended depletions of vitamins, minerals, amino acids, fatty acids, or other nutrients. Many available resources on drug-nutrient interactions focus on the effects of nutrients on a particular medication, such as why some medications can’t be taken with milk or grapefruit juice. Less often discussed are the effects of medications on nutrient status.

To understand how nutrient depletions can occur, we need to understand how drugs are processed. There are three phases of a drug’s action in the body.

Pharmaceutical Phase

First is the pharmaceutical phase, where the medication is ingested, and dissolves in the stomach so that it can be absorbed. In the pharmaceutical phase, stomach pH may affect how medications are dissolved. Medications may dissolve more slowly than expected at a high pH, while those with enteric coating may dissolve too quickly at a low pH.1,2
pH abnormalities can also affect the breakdown of nutrients at this stage.

Pharmacokinetic Phase

Next is the pharmacokinetic phase, which is how the drug is processed by the body. Pharmacokinetics can be understood as what the body does to the drug, including absorption (usually through the small intestine), distribution to body tissues (through circulation), metabolism (by the liver), and excretion (through urine or feces).3,4,5 

In the pharmacokinetics phase, there are many opportunities for nutritional depletions. Absorption may be affected, either through direct action on the intestinal lumen, inhibition of digestive enzymes, or inadequate availability of bile. Medications that increase intestinal motility affect digestion by decreasing the time allotted for absorption, limiting bioavailability.6,7,8 Nutrient depletion, once present, affect liver metabolism, which depends on adequate micronutrients.9


The last in the phases of drug actions is pharmacodynamics, which can be described as what the drug does to the body. This includes interactions with nutrients, food, and other drugs, any of which can also result in nutritional depletion. In the pharmacodynamics phase, medications can affect micronutrient status adjunct to their intended function. Some alter the body’s use of a nutrient, while others increase the body’s need for specific nutrients.10


Those at highest risk for nutrient depletion from medications include the elderly and those taking multiple medications. Age-related changes to the digestive tract increase risk for nutrient loss, such as increased gastric pH, decreased gastric emptying, decreased intestinal motility, decreased absorption in the small intestine, and decreased kidney and liver function.11,12  Others who are vulnerable include infants, adolescents, and users of alcohol or tobacco.13

Wondering how a specific medication might affect nutrient status? Access this
Drug Nutrient Interaction Checker to find out. Enter a drug name and then click interaction report.



  1. Lewis C et al. Journal Of The American Dietetic Association [serial online]. 1995;(3):309. 
  2. Leibovitch E et al. Geriatrics [serial online]. March 2004;59(3):19-33. 
  3. Murray J et al. Journal Of The American Dietetic Association [serial online]. 1991;(1):66. 
  4. Le J. Merck Manual. Clinical Pharmacology. 
  5. Le J. Drug Excretion - Clinical Pharmacology - Merck Manuals Professional Edition. 
  6. Leibovitch E et al. Geriatrics [serial online]. March 2004;59(3):19-33. 
  7. van der Heide F et al. Gastroenterology [serial online]. April 1, 2016;30(Diagnosis and Management of Malabsorption):213-224. 
  8. White R et al. Journal Of Human Nutrition & Dietetics [serial online]. April 2000;13(2):119-129. 
  9. Alonso-Aperte E et al. European Journal Of Clinical Nutrition [serial online]. March 2, 2000;54(3):S69. 
  10. Park B et al. Plos ONE [serial online]. June 27, 2016;11(6):1-12. 
  11. Abimbola FE. Overview of Pharmacodynamics.
  12. Langsjoen P et al. Biofactors [serial online]. December 2003;18(1-4):101. 
  13. Alonso-Aperte E et al. European Journal Of Clinical Nutrition [serial online]. March 2, 2000;54(3):S69. 


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