Understanding cancer
Cancer and its treatments, whether surgery, chemotherapy, radiation, immunotherapy or targeted therapy, often change how you eat. Nausea, mouth sores, taste changes, diarrhea and fatigue can make meals hard, and many people lose weight and muscle without meaning to, which can make treatment harder to tolerate.
A dietitian works alongside your oncology team to keep you nourished through treatment, to sort reliable advice from the many diet claims made about cancer and, after treatment, to help you rebuild strength and eat in ways linked to a lower risk of recurrence.
How a dietitian helps with cancer
Screening for weight and muscle loss early, before it affects your treatment.
Practical plans for side effects: nausea, mouth sores, taste and smell changes, diarrhea, constipation and feeling full quickly.
Enough energy and protein during treatment, food first, with oral nutrition supplements when your appetite is low.
Reviewing supplements and herbal products for interactions with chemotherapy, radiation or targeted therapy.
After treatment: rebuilding strength, managing lasting effects and long-term eating habits.
What the evidence says
ESPEN guidelines recommend screening every person with cancer for malnutrition and starting nutrition support early, rather than waiting for major weight loss.
During treatment, protein needs are usually above 1 g per kg of body weight a day, and often up to 1.5 g.
There is no evidence that sugar makes tumours grow faster, and very restrictive diets can cause harmful weight and muscle loss during treatment.
After treatment, the American Cancer Society recommends a pattern rich in vegetables, fruit, whole grains and legumes, with little red and processed meat, sugary drinks and alcohol.
Your nutrition care
Nutrition care for cancer starts with a full assessment: your medical history, current medications, recent lab results, weight history and the way you actually eat. From there your Registered Dietitian builds a plan around your diagnosis, your treatment goals and the foods you like, and adjusts it at each follow-up as your results come in.
We see patients in person at our Ottawa and Gatineau clinics and by secure video across Ontario and Quebec, so you can keep appointments between medical visits without travelling. With your consent, we share the plan with your physician or specialist team so everyone is working from the same numbers.
Not sure where to start? Book a free initial consultation. We will go over your situation, answer your questions and tell you honestly whether nutrition therapy is likely to help.
Book NowQuestions about nutrition care for cancer
What should I eat during chemotherapy or radiation?
The priority is keeping your weight and muscle, which means enough energy and protein. That often looks like small, frequent meals, protein-rich snacks and nutrition supplements when your appetite is low. Your dietitian adapts the plan to side effects such as nausea, taste changes, mouth sores or diarrhea as they come up.
Does sugar feed cancer?
All cells, healthy ones included, use glucose, and eating sugar does not make tumours grow faster. Very restrictive diets meant to starve cancer can cause weight and muscle loss that weakens you during treatment. Limiting added sugar is still a sensible habit for overall health.
Are antioxidant or herbal supplements safe during treatment?
Some are not. High-dose antioxidants, St. John's wort, green tea extract and other herbal products can interact with chemotherapy, radiation or targeted therapy. Bring a list of everything you take, and your dietitian will review it with your oncology team.
Can a dietitian help after treatment ends?
Yes. Survivorship care focuses on rebuilding strength, managing lasting side effects, reaching a healthy weight and eating in ways associated with a lower risk of recurrence: more vegetables, fruit, whole grains and fibre, and less processed meat and alcohol.
Can I see a dietitian for cancer online?
Yes. We offer secure video appointments across Ontario and Quebec, as well as in-person visits at our Ottawa and Gatineau clinics. Online visits include the same assessment, plan and follow-ups.
Sources and guidelines
This page is general information, not individual advice. Your dietitian sets your own targets.