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Nutrition Through The Ages: Special Edition - Drug & Nutrient Interactions

Updated: May 24, 2023

By the time adults are 50 and 60 years old, 75% are taking prescription medications daily. By the time we reach 80 years of age, 90% of us are taking prescription medications. For many, it may be unclear exactly how the medications they take can impact the nutritive quality of the foods they eat AND they may be unaware how some foods can even alter the impact of the medication.

When a medication goes into your body, four things happen to it through normal body processes:

  • Absorption

  • Distribution

  • Metabolism

  • Excretion

Absorption

The first step, absorption, occurs for any oral medication you may take and begins in the mouth going all the way through the intestinal tract. Drug manufacturers can develop a variety of formulations to ensure absorption occurs in a predictable manner to ensure efficacy of the medication. Some dosage forms, such as orally disintegrating tablets, are formulated to be placed on the tongue and will dissolve while more common tablets and capsules are formulated to be swallowed whole, allowing your stomach pH to dissolve the medication to be absorbed from there. Absorption is a key area where we see many of the drug and nutrient interactions existing.



Certain vitamins and minerals require a low pH, meaning an acidic environment, to properly absorb into your bloodstream. The most common examples of this are iron, cobalamin (vitamin B12), ascorbic acid, calcium and magnesium. Whereas medications such as proton pump inhibitors (PPIs), increase the pH of the stomach to help relieve heartburn or the symptoms of gastroesophageal reflux disease (GERD), but this increase has the possibility of leading to nutrient deficiencies where a low pH is needed for absorption. This decrease in nutrient absorption can have long-term effects, such as bone fractures when not enough calcium is properly absorbed.


Similarly, some medications, when taken with nutrients, can inhibit the absorption of those nutrients because the two compounds bind each other up. This is the case when someone takes an antibiotic like tetracycline with calcium, magnesium, or iron supplements. Generally, antibiotics are taken for a short amount of time, and would not result in lasting effects, but those taking chronic antibiotics should be aware of these interactions to prevent vitamin related deficiencies.


Distribution

The next step all medications go through in the body is distribution. This is where the drug has been absorbed into the bloodstream, and is being circulated around to find its target of action. Along the way, it will inevitably go through your liver. The job of the liver is to filter out any toxins entering your body, including medications. One way it does this is to change the toxin to be inactive by altering its structure, and making it more water soluble so that it can be excreted in the urine.


Metabolism

While in the liver, we call this step Metabolism. Similar to how our bodies metabolize food to break down into nutrients, the liver is breaking down compounds to be excreted.

The liver is home to thousands of enzymes that have different targets to metabolize anything it can come in contact with, but there is one group of enzymes known as CYP that are the biggest players when it comes to food/drug interactions.

Many of you may have seen that you should avoid grapefruit with certain medications, and the reason is because of metabolism. One chemical component of grapefruit, along with other fruits and juices in this family, is known to inhibit one of these enzymes. By doing this, the medication that was supposed to be inactivated by the liver is now free to exert its effects, but at a higher rate than what was studied during dosing trials. Now, because the grapefruit is inhibiting the enzyme, you have too much medication in your system, anywhere from 1.5 to 15 times more than simply taken by itself, and are more likely to experience side effects or toxicity.


Another herbal supplement, St. John’s Wort, alternatively induces enzymes to be activated. The flip side of this property is now some medications will not work. Two reasons for this are that they:

  1. are being inactivated at a higher rate, or

  2. medications that rely on the liver to be activated will be over activated, again leading to potentially leading to more serious side effects or toxicity.

For these reasons, St. John’s Wort is not recommended by pharmacists, although this can be challenging to educate patients on as it is readily available over the counter for purchase.



Excretion

The final step is excretion. Here is where we can eliminate compounds through either urine or feces. The kidneys play an important role in vitamin, mineral, and water excretion and reabsorption. We have learned about drug-nutrient interactions most from patients with chronic kidney disease (CKD) and have found that sodium, potassium, magnesium, and B vitamins can all be impacted by a variety of medications that have targets within the kidneys.


Blood pressure medications, such as diuretics and ACE inhibitors can result in patients having too much or too little potassium in their blood. Since potassium is a key electrolyte associated with heart rhythm, this can be potentially detrimental to patients.

  • Sometimes, patients may be put on potassium supplements to help in the regulation of this key mineral.

  • Sodium is associated with hydration, and antidepressants and antipsychotics are known to decrease sodium levels, resulting in dehydration because the kidneys cannot reabsorb water as well.

  • Finally, B vitamins, particularly B1, can be overly excreted when patients are on diuretics, resulting in vitamin B deficiencies.

In the older adult population, studies have shown that polypharmacy, or taking more than five medications, is associated with a decrease in nutritional status. This can be multifactorial, some may be due to side effects reducing appetite and therefore leading to malnutrition, others could be associated with how medications work on the body as described above.

One particular trial found that over a three-year period, patients who were on ten or more medications (excessive polypharmacy) had a higher risk of being malnourished, greater difficulty in daily tasks, and greater impaired cognition when compared to non-polypharmacy patients. When it comes to nutritional status and medications in the older adult, a true analysis of risk and benefit is warranted.


As we age, disease states can take their toll on quality of life and mortality, and many medications have shown great benefit in preventing serious cardiovascular events and symptom control of chronic diseases. Proper follow up with primary care providers will help evaluate the benefits and risks of medications on a regular basis, catching any side effects or nutritional deficits early on in therapy, making the necessary changes in a “whole patient” approach. Your pharmacist is also a quick phone call away to help answer any questions you have about vitamins, supplements, over the counter medications, and how they may interact with your medications. Asking these key questions will help ensure you are getting the maximum benefit from your medications, while still maintaining a healthy lifestyle.


Author Bio

Melissa Dempsey, MA, PharmD is currently a Clinical Pharmacist working in both inpatient and outpatient pharmacy settings. She completed her PGY-1 Pharmacy Resident working in the ambulatory care setting at Cape Fear Valley Medical Center in Fayetteville, NC. Before becoming a pharmacist, she was a middle school science teacher in both Washington and North Carolina. Her love of science drew her to change career paths, and now enjoys teaching her patients about their chronic disease states, how their medications work, and goals of therapy. She also can be found working in your neighborhood retail pharmacy, helping patients choose over the counter medications, discussing patient care with physicians, administering vaccines and conducting medication reviews for patients in hopes of preventing polypharmacy.


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Resources

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5. D'Alessandro C, Benedetti A, Di Paolo A, Giannese D, Cupisti A. Interactions between Food and Drugs, and Nutritional Status in Renal Patients: A Narrative Review. Nutrients. 2022;14(1):212. Published 2022 Jan 4. doi:10.3390/nu14010212


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