Many people seeking to follow a healthier diet reduce their meat and dairy consumption, whether or not they choose an entirely vegetarian or vegan diet. As soy products are often used as substitutes for both meat and dairy, we’ll also look at the evidence about their suitability for people diagnosed with cancer.

The general advice for people diagnosed with cancer is to follow a healthy, balanced diet. The NHS has produced its ‘Eatwell’ guide to show what this includes and in what proportions. You can find the Eatwell guide here.

As you can see, the NHS recommends that two thirds of our diets should consist of fruits, vegetables and starchy foods such as potatoes and grains, with the rest made up of dairy and/or dairy alternatives, proteins and a small amount of healthy fats such as unsaturated oils and spreads. Therefore, most of the food types that they recommend are plant-based and the others can come from both animal and non-animal sources.

A healthy diet as set out in the Eatwell guide will usually provide the nutrients that you need, including vitamins and minerals, without the need to take supplements. If you’re eliminating meat, fish or other animal products from your diet, it may take a little more planning to make sure that you’re getting the nutrition that you need. For example, meat is a good source of iron, but it is also possible to get the iron you need from foods such as eggs, green leafy vegetables such as broccoli and kale and pulses such as peas, lentils and beans. Milk and dairy products contain calcium, but other sources include fortified plant ‘milks,’ almonds and bread. You can find more information about getting the nutrients that you need from a vegetarian or vegan diet here.

Two specialist oncology dietitians gave a presentation for us, in which they recommended aiming to meet your nutritional needs through diet. You can view this presentation here.

Although a well-balanced, healthy vegetarian or vegan diet can provide most of the nutrients you need without supplements, there are some situations where they might be recommended. In particular, it may be advisable to take supplements of vitamins D and B12.

The body makes vitamin D when the skin is exposed to sunlight, and it’s difficult to get enough from food alone. The Department of Health recommends that you consider taking a vitamin D supplement during autumn and winter, and at other times of the year as well if you aren’t often outdoors or if you wear clothes that cover up most of your skin when you’re outside. Find out more about this here.

Vitamin B12 is only available naturally from animal sources. Vegetarians who eat dairy products and eggs usually get enough from these sources, but vegans will need to make sure that they eat plant-based foods fortified with vitamin B12 or take a supplement. You can find more information about vitamin B12 on the Vegan Society’s website here.

Information on other important minerals such as Iodine and Selenium, which are unlikely to be found in vegan diets can be found here.

If you’re pregnant or have a health issue such as a vitamin or mineral deficiency or difficulty in absorbing nutrients from your food, you may also be advised to take a supplement. If you’re thinking of using supplements, it’s important to discuss this with your team first to make sure that they’re safe for you.

As we mentioned above, soy is a popular substitution for many animal products, as it can be made into products similar to meat items such as sausages and sandwich slices and dairy products such as milk, yogurt and custard. However, some media reports have suggested that soy can increase the risk of certain cancers or not be suitable for people with cancer.

These concerns arise from the fact that soybeans contain isoflavones, which are often defined as phytoestrogens (chemicals found in plants similar to oestrogen). As some ovarian and breast cancers are driven by oestrogen, we are sometimes asked whether consuming products that contain isoflavones is safe for those diagnosed with these cancers.

The evidence currently is that there are health benefits to consuming soy in its various forms, and that eating moderate amounts of soy is safe, including for those diagnosed with cancer. It can also help to alleviate hot flushes associated with surgical menopause.

Although there are similarities between isoflavones and oestrogen, they don’t behave in the same way in the body and their effect is much weaker. The studies that suggested a possible connection between soy and oestrogen-driven cancers were carried out in laboratories or on animals using higher doses of isoflavones than are found naturally in soy.

Specialist cancer dietitian Rachel White wrote about soy in the Ovacome Magazine Autumn/Winter edition in 2018 (pages 10-11). You can also read more about soy as part of a healthy diet, including for people with cancer here.

You can also read more about meat, fish and dairy products and cancer here.

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If you have any questions or need any further information please contact our support service team on 0800 008 7054 or email [email protected]

Reviewed by Rhia Saggu, Specialist Dietitian at Imperial College Healthcare NHS Trust

V.1.2. Last reviewed November 2022, due for review November 2025

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