Dr Coy on sugar metabolism and COVID-19

In 2021 Dr Coy gave an interview setting out his view of the relationship between blood glucose and the severity of COVID-19. It is published here in full as a record of his thinking. This summary sets out the argument first.

Dr Coy’s case rests on a single biochemical step. A virus has no metabolism of its own. To replicate, it uses the machinery of the cell it has infected, and the genetic material it needs to copy is built from ribose. Ribose is made from glucose. His philosophy, based on his research, is that the supply of glucose to the host cell sets a limit on how readily the virus can be copied.

He then adds a second mechanism, which is the part he finds most interesting. Research published in 2020 reported that SARS-CoV-2 infects monocytes and macrophages and switches their metabolism from combustion to fermentation, so those immune cells come to rely heavily on glucose. That is the Warburg effect, the same metabolic switch he has spent his career studying in tumour cells, appearing in immune cells during a viral infection. For him this is evidence that the pathway is a general feature of mammalian biology rather than something peculiar to cancer.

From these two points he draws his dietary conclusion: that what matters is not sweetness but the height of the blood glucose curve, that starch counts as much as sugar, and that sugars metabolised by other routes, particularly galactose, behave differently. He also argues that the first few days after infection are the decisive window.

These are his conclusions, drawn from the research available to him in 2021. They have not been tested in clinical trials, and he says so himself in the interview below.

Based on an interview Dr Coy gave in 2021. His words have been lightly edited for clarity; it is published here as a record of his position at the time. It is his own view. It is not medical advice, and nothing in it should be used to make decisions about treating an infection. If you are unwell, contact your doctor or NHS 111.

Conducted by VITALISSIMO, powered by GU, 2021. With Dr Johannes Coy, author of The New Anti-Cancer Diet and Fit with Sugar.

– DR COY: Yes. Shortly after the start of the SARS-CoV-2 outbreak in Wuhan, doctors there determined, and published studies proving, that high blood glucose levels lead to severe forms of COVID-19 and indicated that high blood glucose levels should be avoided in patients with the disease. Numerous studies have since confirmed the harmful role of high blood glucose as a trigger for severe forms of COVID-19. A recently published study showed that it is the decisive factor and even younger people with none of the other typical coexisting illnesses can suffer from severe forms.

– DR COY: Yes. It has been shown that viral proliferation is directly connected to the amount of glucose in the blood. But the type of sugar determines whether viral proliferation is facilitated or not.

– DR COY:The sugar glucose is very easily converted into ribose, another sugar. As ribose is needed as a building block for the replication of the SARS-CoV-2 virus, and all other viruses, the conversion of glucose into ribose is the decisive step in virus replication. So reducing the amount of glucose in your diet limits the conversion of glucose into ribose, so that fewer building blocks are available for viral replication.

– DR COY: Yes. Not only does glucose promote viral replication, it also leads the immune system to overreact, meaning that immune cells migrate to the lungs and cause massive damage. The SARS-CoV-2 virus infects certain immune cells, monocytes and macrophages, and alters their metabolism, replacing the usual combustion metabolism with a sugar fermentation metabolism so that the immune cells then only use glucose as fuel. This leads to a massive increase in sugar intake in these immune cells. Radioactively labelled glucose has also been used to make lung damage visible in COVID-19 patients, as this method using radioactive sugar is particularly effective.

Does sugar make COVID-19 worse? Yes, says Dr Johannes Coy.

–DR COY: Ingesting as little sugar as possible as soon as you know you have been infected, or at the latest when you start getting symptoms. And doing so radically, at least for the next four days, because the first days will decide the extent to which the virus proliferates and the immune system reacts. I believe a diet high in fats is the right approach, with as few carbohydrates as possible to avoid raising the blood glucose level.

– DR COY: Yes, galactose, a component of lactose. Lactic acid bacteria split lactose into its components, glucose and galactose, and then ferment just the glucose into lactic acid. Galactose then remains as a valuable sugar in fermented milk products such as kefir and buttermilk. I believe a keto diet, in other words one that is high in fats and low in carbohydrates, with added galactose, is a sound approach.

A keto diet, in other words one that is high in fats and low in carbohydrates, with added galactose, is the best protection against severe forms of COVID-19.

–DR COY: Galactose is a form of sugar that doesn’t supply cells with energy when it is metabolised by fermentation. Instead, it must be metabolised in the combustion engines of the cells, the mitochondria, so that the cells can release its energy. Galactose therefore triggers combustion in the cell.

-DR COY: Studies have shown that, in overweight people, galactose starts to mobilise fats while the person is still eating and triggers the fat-burning process.

-DR COY: Yes, because you don’t need to avoid carbohydrates completely. You just have to choose the ones that keep blood glucose levels stable. I believe the ideal diet is low in white sugar and starch, and uses natural sugars like galactose and tagatose to keep blood glucose levels stable. Physical movement is the ideal addition.

-DR COY: Yes, a study was recently published in one of the most renowned medical journals showing that high blood glucose levels are directly associated with the occurrence of, and death from, cardiovascular diseases. Earlier studies showed that high blood glucose levels are connected with memory loss, Alzheimer’s and cancer.

 For vegetarians, there are also lupin beans, which are a good low-carb, high-fibre source of protein, nuts, seeds and berries.

-DR COY: All green vegetables, particularly all types of cabbage and root vegetables such as Jerusalem artichokes, parsnips and salsify, which are carbohydrates that do not increase blood glucose levels, are suitable. Oily fish, alpine cheeses, eggs, butter and cream are excellent, as are fermented milk products such as kefir and buttermilk, which contain the useful sugar galactose. For vegetarians, there are also lupin beans, which are a good low-carb, high-fibre source of protein, nuts, seeds and berries. You can also eat pulses such as kidney beans and soya beans, but not too much.

-DR COY: For both COVID-19 and cancer, it is often assumed that diet does not play a particularly important role in the progression of the disease. This has already started to change to some extent for cancer. In some hospitals in the USA, a keto diet or fasting is recommended before chemo or radiotherapy in order to reduce the amount of glucose in the patient’s body. We’ve not been aware of the metabolic changes caused by the SARS-CoV-2 virus and the huge importance of sugar metabolism for the existence of severe forms for as long, so it will probably take some time for this important knowledge to be applied in clinical practice.

This interview records Dr Coy’s own view as given in 2021. It is not medical advice. If you are unwell, or have questions about your own health, contact your doctor or NHS 111.