Should you follow an alkaline diet if you have cancer?

Updated: Feb 21

A common question I am asked by my patients is whether there is any value in following an alkaline diet to help to fight cancer. In this article we will delve into what an alkaline diet looks like, why it is of interest for people with cancer, and explore the evidence for its value.



What is an alkaline diet?

The theory behind the alkaline diet is that you can influence the acidity level (pH) of your blood by modifying the way you eat and drink. Proponents of the diet suggest that eating a diet rich in so called acidic-forming foods, such as those from animal products, will produce an acidic (low) blood pH and this promotes ill health, including increasing the risk of cancer. Conversely, eating a diet high in alkaline-forming foods, such as fruit and vegetables, increases blood pH which is favourable and beneficial for health.


Why is the alkaline diet of interest in relation to cancer?

Some laboratory studies have demonstrated that cancer cells favour a highly acidic (low pH) environment. So, if we stop eating acidic foods and eat an alkaline diet, can we increase our blood pH and create an environment that stops cancer growing? Well, like in all situations that relate to the function of the body, the answer is not as simple as this.


Many of the studies looking and acidity and cancer cell multiplication have been performed in the laboratory and cannot be easily extrapolated into real life.


Our blood pH level is very tightly regulated at pH 7.4 and our bodies have several compensatory mechanisms, involving our kidneys and respiratory system, to maintain this level within a very narrow healthy range. Any excess acid load is excreted in the urine as a waste product and we naturally see changes in urinary pH levels, as the body maintains the correct pH balance. Of note, urine pH is not an indicator of blood pH. The only state in which blood pH is altered is during severe acidosis, when an individual is critically ill.


It is apparent, therefore, that our blood pH is not altered beyond its normal ranges by what we eat and drink and there is no robust scientific data establishing the benefit of following an alkaline diet for the prevention or treatment of cancer currently.


What about alkaline water?

Alkaline water is typically bottled water with an altered mineral content that makes it, well alkaline! Alkaline water can be very expensive and as described above, it will not change the pH of your blood, only your urine. If you enjoy the taste of alkaline water over other beverages, consume it to keep your hydration up by all means.


Could the alkaline diet be harmful?

There is no common consensus on the classification of foods as acid or alkaline. However, all so called “acidic foods” including meat, fish, eggs, dairy, sugar, and some grains are typically excluded when following an alkaline diet. Additionally, some fruits, vegetables, nuts, and seeds are also classed as acidic. The diet is therefore highly restrictive and very low in protein. Adequate protein intake is especially important for people undergoing cancer treatment. Furthermore, plant-based foods, particularly fruit, vegetables, wholegrains, pulses, nuts, and seeds are known to contain cancer-fighting properties and should make up the bulk of a healthy diet. Quality animal products (meat, poultry, eggs and dairy) can be included as part of a healthy, balanced diet and the only reason to exclude them is personal choice or dietary allergies or intolerances.


In summary, balanced nutrition is important to support healing, repair, bolster the immune system and manage the side effects of treatment. Food should also be a source of enjoyment and pleasure. Excluding the many helpful sources of nutrients when following an alkaline diet is not advisable given that such measures are more likely to be disadvantageous rather than beneficial in battling cancer.

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