What you rarely hear, and why it matters.
With or without a cancer diagnosis, nutrient deficiency is a hidden epidemic in the United States. It’s estimated that more than 90% of Americans don’t get enough of at least one essential nutrient from their diet. That’s why I wanted to address it in a three-part series, because chances are, many of my readers are in this boat.
Today, I’m specifically addressing cancer. The odds are striking: about 39% of us will develop cancer in our lifetime. Beyond the disease itself, treatment places significant nutritional demands on the body, and those demands continue well into recovery. People can and do live well with cancer, and nutrition is an important part of that picture. Yet it’s often the part that gets the least attention.
Vomiting, diarrhea, mouth sores, appetite changes, and intestinal damage can interfere with the body’s ability to take in, absorb, and retain the nutrients it needs. At the same time, tissue repair, inflammation, and muscle breakdown can increase nutritional demands.
Understanding how this happens helps explain why some people experience profound fatigue, weakness, weight loss, digestive problems, and delayed recovery during and after treatment.
Vomiting: More Than Losing Fluids
Repeated vomiting drains the body of water and electrolytes like sodium, chloride, and potassium. That can lead to dehydration, dizziness, muscle weakness, fatigue, and, in some cases, irregular heart rhythms.
Thiamin, or vitamin B1, deserves special attention. It helps turn carbohydrates into usable cellular energy, and the body stores only a small amount. When vomiting is prolonged and eating becomes difficult, stores can become depleted, which potentially affect the nervous system.
Magnesium may also become a concern when poor intake occurs alongside gastrointestinal losses or treatment-related kidney losses.
Diarrhea: Losing Minerals Through the Intestines
Diarrhea can rapidly increase losses of water, sodium, and potassium. It can also throw off the body’s natural acid balance. When it’s prolonged or severe, magnesium and zinc can be depleted, too. Zinc is important for immune function and tissue repair, so ongoing losses stack up when someone is already eating less.
When Eating Becomes Difficult
Treatment-related inflammation of the mouth and digestive tract can make eating painful. Mouth sores, nausea, changes in taste and smell, and feeling full quickly can all add to the challenge. Even someone who knows how important good nutrition is may struggle to eat enough.
Protein and calories often fall short first. Protein supplies the amino acids needed to rebuild damaged tissue. As the variety of food shrinks, other nutrients follow, including vitamin C, which supports collagen and healing; folate, which helps the body make new cells; and zinc. When this goes on for days or weeks, the gap between what the body needs and what it receives keeps growing.
Intestinal Damage: When Eating Does Not Guarantee Absorption
The intestinal lining is responsible for absorbing nutrients from food. When treatment damages it, the body can struggle to absorb iron, folate, vitamin B12, protein, and energy, depending on where and how severely the gut is affected.
Fat absorption can suffer, too. That affects vitamins A, D, E, and K, which need fat to be absorbed. These vitamins have distinct roles: vitamin A supports vision and epithelial tissues; vitamin D helps regulate calcium balance and bone health; vitamin E protects cell membranes; and vitamin K supports normal blood clotting.
Kidney Damage: A Less Obvious Route to Mineral Depletion
Some cancer treatments affect the kidneys’ ability to hold on to minerals. Cisplatin, a common chemotherapy drug, can cause magnesium to be lost through the urine, and potassium and phosphate losses can follow.
Magnesium is required for hundreds of enzymatic reactions, including those involved in energy production. Potassium is essential for normal muscle and nerve function. Phosphate is needed for cellular energy, bone mineralization, and numerous metabolic processes.
When these minerals become depleted, symptoms can include weakness, cramps, fatigue, and, in more serious cases, cardiac or neurological disturbances. These losses cannot always be corrected through food alone. Significant depletion may require targeted replacement and monitoring.
Anemia: Nutrient Deficiency Is Only One Possible Cause
Fatigue during cancer treatment is often attributed to the cancer or treatment itself, but nutrition may play a role. Iron is needed to make hemoglobin, which carries oxygen in red blood cells, and vitamin B12 and folate help red blood cells form normally. Low intake, poor absorption, or an existing deficiency can all make anemia worse.
However, cancer treatment can also suppress bone marrow and reduce blood cell production directly. Understanding the cause is important. Iron supplementation, for example, will not correct anemia caused solely by reduced bone marrow production.
Muscle Loss and the Nutrients Needed for Repair
One of the most important nutritional concerns during cancer treatment is the loss of lean tissue. When protein and calorie intake fall, the body may break down muscle to obtain energy and amino acids. Inflammation can speed this up.
Protein supplies the building blocks for muscle, enzymes, and immune proteins. Adequate calories matter because dietary protein should not have to serve primarily as an energy source.
Muscle loss can affect strength, mobility, and the ability to maintain normal daily activities. It may also prolong nutritional recovery.
Is Your Body Getting What It Needs to Recover?
During and after cancer treatment, knowing what to eat is only part of the picture. You also need to understand what your body may be losing, where absorption may be compromised, and which nutritional needs deserve closer attention.
Persistent fatigue, digestive problems, muscle loss, and difficulty recovering can have multiple causes, including nutritional deficiencies that may go unrecognized. Identifying the underlying issues is an important first step toward building a more targeted nutrition strategy.
If this sounds familiar, a nutrition plan built around your body and your treatment can make a real difference. Every situation is different, which is why I don’t believe in one-size-fits-all advice. I’ve walked alongside many clients through cancer treatment and recovery, including those living with a terminal diagnosis, and I’ve seen how the right nutrition can help them feel stronger and more like themselves. If that’s where you are, I’d love to talk. I offer a free 15-minute discovery call, and even if I’m not the right fit, I’ll help point you in the right direction.
From a Dear Client
“I was going through cancer treatments when I started talking to Angie about health and what I could do to support my very sick body. Three years after cancer, she is literally a lifesaver.” ~ Jenna
