Myths and Diet: Ask the Dietitian

Nourish - Article 04

We’ve all consulted Dr. Google at one time or another. Unfortunately, there is a lot of false, misleading and potentially harmful information on the internet, particularly on the subject of nutrition and cancer.
Despite what these articles may claim, there is no silver bullet to cure cancer. Before you venture into alternative diets, complementary therapies or nutritional supplements, we recommend that you evaluate their scientific basis and be aware of any potential for causing additional harm.

Five Common Diet Myths

“Sugar feeds cancer”

Fact: Cutting out refined or processed sugary foods, though good for your general health, will not kill cancer cells.

The misleading belief that sugar fuels the growth of cancer cells leads some people to avoid sugar and/or all carbohydrates altogether. Not only is this counter-productive for anyone struggling to maintain their weight while dealing with side effects of cancer and treatments, but the anxiety of trying to completely avoid all sugar (or ‘carbs’) can create unwanted stress.


If you are thinking about trying a low-carb or ketogenic diet, it would be well worth discussing this with a specialist cancer dietitian. They will help you weigh up the potential benefit versus risks, taking into account the latest evidence based for your specific tumour type and individual circumstances.

“Cutting out dairy can stop tumour growth”

Fact: There is little evidence to support the benefits of removing dairy from your diet.

Many people avoid dairy products because of the fear that they contain hormones which increase the risk of cancer or promote cancer growth. In the EU, cows, goats and sheep cannot be treated with growth enhancing hormones by law. Furthermore, there is no clear link between dairy-rich diets and cancer. The evidence actually suggests that low-fat dairy provides a protective role in the development of breast cancer. This could be due to properties including vitamin D, calcium, butyrate, conjugated linoleic acid and lactferrin. Dairy can therefore be a really great source of nutrition and is a particularly useful way of increasing energy and protein intake if you are losing weight or having difficulties with eating.

“Herbal remedies can cure cancer”

Fact: Sadly, this is simply not true. Although alternative or complementary therapies including some herbs, spices or remedies may help people cope with nausea and other side-effects of cancer and its treatments, none have so far been shown to be effective for treating cancer.

Some alternative therapies may actually be harmful or contraindicated during chemotherapy or other cancer treatments because they may interfere with how well the treatments work. This may also be true for some high dose vitamin supplements with antioxidant properties.

“The Alkaline diet can cure cancer”

Fact: There is no scientific basis to support the idea that an alkaline diet can either prevent or cure cancer.

The theory is that an acidic diet changes your body’s pH by causing your blood to become acidic. This in turn encourages cancer formation because of reports that cancer cells thrive in acidic environments.

This claim contradicts everything we know about the chemistry of the human body. The food you eat simply cannot can change the acidity or alkalinity (pH) of your blood. Certain foods may be able to change the pH of your urine or saliva (waste products) but your blood or body’s pH is tightly regulated by the kidneys and the lungs. It is not something which could be influenced by diet.

The idea that tumours thrive in acidic environments is based on laboratory studies done with cancer cells in petri dishes. They do not necessarily represent how tumours behave in the body.

Most importantly, an alkaline diet can be harmful due to being highly restrictive and low in protein (meat, dairy, pulses) which can contribute to malnutrition in people who are already at increased risk due to their disease and treatment side effects.

“Buying organic reduces the risk of cancer”

Fact: Pesticides and herbicides are only found in low doses in foods that we buy and there is currently no proof that these residues increase our risk of cancer.

While the dangers of pesticides and herbicides when used improperly or excessively are well-known, in the UK pesticide are rigorously tested and laws exist to ensure that all agricultural pesticides are used within a safe level. Vegetables and fruits may contain low levels of these chemicals, however, scientific evidence supports the overall health benefits and cancer-protective effects of eating vegetables and fruits.

How does Onko help?

We don’t believe in fad diets or gimmicks. Our dietitians assess your baseline nutritional status and agree weekly nutrition plans with you. We build nutrition plans based on the latest research and your individual needs, taking into account any food preferences, allergies or symptoms that may be affecting your eating.

If you have cancer and are about to undergo or are recovering from treatment, it is important you aim to sustain and improve your fitness and strength. This usually means getting adequate energy, protein, vitamins and minerals from a broad range of food sources.

If you are considering trying any new diet, high-dose antioxidant supplements, herbal or alternative remedies in conjunction with your cancer treatment you should discuss this with your oncologist or dietitian.

The recap

No single food is going to dramatically change your path to wellness; the secret is in getting a wide variety and a good balance.

Strict diets such as ketogenic diets can be restrictive and can actually increase symptoms such as constipation and nausea.

Furthermore, the anxiety of trying to completely avoid a particular food or food group can create unhelpful levels of stress.