Disclaimer. This article is for information and knowledge purposes only. It is imperative that you get clearance and are monitored if you plan to undertake any form of diet therapy especially if you have Cancer or and Chronic Illness.

What is Methionine?

Methionine is an amino acid. Amino acids are the building blocks of protein. When we think of protein, we usually think of animal protein such as meat; however most foods contain varying amounts of protein and therefore, amino acids. Our digestive system must break protein down in order to utilise the amino acids. These amino acids are then absorbed into the bloodstream and go to our cells where they supply the nutrient.

Methionine is just one of the amino acids that make up protein. Methionine is a building block of protein that is necessary for cell growth.

There has been much research however, into how methionine can fuel the growth of cancer cells, therefore restricting methionine would make sense.

Why is restricting methionine so important in cancer therapy?

Cancer cells use Methionine as fuel

Cancer cells require dietary supply of methionine for survival and therefore, methionine restriction is a promising avenue for treatment. Restricting methionine by diet depletion, alone or in combination with certain chemotherapeutics, is a promising cancer therapy (3).

Diet and Cancer is one of the most confusing parts of the patient’s journey. The internet is saturated with advice about what diet a patient should be following after they are diagnosed with cancer. It is important to identify an ideal anticancer diet that targets metabolic pathways of cancer cells without affecting healthy tissues. Targeting metabolic pathways is a fancy way of saying ‘blocking the fuel supply to the cancer’.

Studies have shown that Cancer cells are methionine dependent compared to normal cells as they have an elevated requirement for methionine in order to proliferate. This dependence is termed ‘methionine addiction’.

Treatment Resistance

Over the course of standard cancer therapies such as chemotherapy, there is often a plateau that occurs with the cancers responsiveness. This phenomenon occurs because the cancer cells become good at becoming resistant to the therapy through different means such as using Drug Efflux Pumps and enhanced DNA repair.. It would be ideal to combine different modalities to then potentially optimise the effectiveness of chemotherapy/radiation. Without methionine, cancer cells are weakened and become much more susceptible to all forms of treatment. Implementing a methionine-restricted diet can be a very powerful addition to a cancer program.

Methionine Metabolism

Most patients will be familiar with the ‘Warburg Effect’. This is where a cancer cell uses/ferments glucose for energy. The excess use of methionine by cancer cells also has a name and this is called the ‘Hoffman Effect’(7). This term is not well known, but it is very important when it relates to cancer cell metabolism as it addresses the nutrition or ‘metabolic dependence’ of the cancer cell for methionine to fuel its growth.

Methionine Dependency of Cancer

Early studies of metabolism identified a strict metabolic requirement for the amino acid methionine in transformed cells (cancer cells). Methionine dependence is only found in cancer cells and not in normal, healthy cells.

Methionine Restriction with Chemotherapy using Cell-Cycle Arrest

 Normal dividing cells follow a typical cycle, their job is to grow, divide and then die. Cancer cells do not follow the normal cell cycle. Instead of dying, they multiply and continue to reproduce other abnormal cells.

The below diagram shows the major checkpoints for the cell cycle: