Food and drink interactions with oral chemotherapy

Yes, some can. Food and drink affect oral chemotherapy in two main ways. First, a meal can change how much of a tablet is absorbed from the gut. For some medicines, food increases absorption so much that taking the tablet with a heavy meal could raise the dose in your body; for others, food reduces absorption so the treatment works less well; and for some, a meal protects the stomach and helps tolerance. This is why some tablets must be taken with food, some on an empty stomach, and some at a set time away from meals. Second, certain foods, drinks and supplements affect the liver enzymes that break medicines down, which can raise or lower the level of medicine in your blood.

The best-known example is grapefruit, including grapefruit juice, which blocks an enzyme that breaks down many medicines, including several targeted cancer tablets, and can raise their levels and side effects. Some related citrus fruits, such as pomelo and Seville oranges, may have a similar effect. Herbal products are another common and underestimated source of interactions. St John's wort can lower levels of many medicines. Turmeric supplements, green tea extracts, high-dose antioxidant supplements, ayurvedic and homeopathic products, and some traditional remedies may affect the liver, bleeding or the way chemotherapy works. Ordinary cooking amounts of spices such as turmeric are usually fine, but concentrated supplements are different. Alcohol can add to liver strain, nausea and dehydration. People are rarely warned about these interactions, so ask your pharmacist which apply to your specific tablets.

Normal meals are usually fine

For most people, a balanced diet is safe and helpful. The concern is specific foods, timing and supplements.

Consistency helps

Taking tablets in the same way relative to meals each day keeps medicine levels steady.

Supplements need checking

Tell your team about every vitamin, herbal and ayurvedic product, even if you think it is harmless.

It cannot tell you which interactions apply to your medicine. Interactions are specific to each drug, and a food that is a problem for one tablet may be completely safe with another. Your pharmacist can check your exact medicine against a proper interaction database.

It also cannot give a complete list of every food, herb or supplement that might interact. Research on many traditional and herbal products is limited, which is why the safest approach is to tell your team about everything you take and avoid starting new supplements without advice.

Traditional remedies

Families often suggest remedies to boost immunity or strength. Some may interact with treatment. Check before using them.

Fasting

Fasting can make timing with food difficult. Discuss plans with your team.

Tea and coffee

Ordinary amounts are usually fine, but some medicines have caffeine cautions. Ask if unsure.

Milk and antacids

Calcium and antacids can affect absorption of some medicines. Check timing with your pharmacist.

Tube feeding

Feeds can interact with some medicines. Get specific pharmacy advice.

Dietary changes

Big changes in diet, such as starting a detox or juice cleanse, can affect treatment. Ask first.

Cooking spices

Normal cooking amounts of spices are usually safe. Concentrated extracts are different.

Keep a list

Write down foods and supplements to avoid on your safety card.

How food changes absorption

When a tablet is swallowed, it dissolves in the stomach or intestine and the medicine passes through the gut wall into the bloodstream. Food changes this process in several ways. It slows stomach emptying, changes acidity, increases bile flow and alters blood flow to the gut. For medicines that dissolve better in fat or bile, a fatty meal can greatly increase the amount absorbed, sometimes enough to raise side effects. For medicines that need an acidic stomach or an empty gut, food can reduce absorption so that less medicine reaches the cancer. This is why the instructions for one tablet may say to take it with breakfast, while another must be taken an hour before food or a couple of hours after. Following the instruction consistently keeps medicine levels predictable from day to day.

Family meals and traditional diets

Many families prepare special foods, herbal drinks or strengthening mixtures for someone having cancer treatment, often with love and good intentions. Before adding anything new, such as concentrated turmeric drinks, herbal decoctions, wheatgrass, papaya leaf extracts or supplements bought for immunity, check with your team or pharmacist. Ordinary home-cooked meals with normal spices, dal, vegetables, rice or roti, curd and fruit are usually safe and helpful, as long as food timing instructions for the tablets are followed and food hygiene is good when counts are low.

What to do next

Ask your pharmacist whether your tablets should be taken with or without food and which foods, drinks or supplements to avoid, avoid grapefruit unless cleared, show your team every supplement you take, and call if you feel unwell after an interaction.