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Although our knowledge of SARS-CoV-2 coronavirus (and COVID-19, the disease it causes) epidemiology is still uncertain in many areas, one of the strongest associations to emerge thus far is the link between diabetes mellitus and severe COVID-19 infection.

Some have suggested that the COVID-19 pandemic presents an opportunity to improve the care of diabetes patients. Here, we review what is known about the relationship between diabetes and COVID-19, and what individuals can do from a non-pharmaceutical approach to improve their diabetes management.

Diabetes—in a nutshell 

Diabetes mellitus is a condition characterized by elevated blood glucose and impaired insulin secretion or functioning. It has been called “the epidemic of the 21st century.”

Type 2 diabetes is often called “adult-onset” diabetes and involves reduced insulin secretion as well as insulin resistance, meaning that the cells become less responsive to the effects of insulin.

Type 1 diabetes is an autoimmune disorder that typically begins in childhood, where the pancreatic beta cells responsible for insulin production are destroyed. As a result, the patient can no longer produce their own insulin and must inject insulin.

The diabetes-COVID relationship 

Many reports have now emerged showing that patients who have diabetes are vulnerable to a more severe course of COVID-19. It has been suggested that the underlying metabolic perturbations (disturbances) present in diabetes cause an impaired immune response and exaggerated inflammation when infected with the coronavirus.

An early study found that “patients with diabetes presented with higher inflammatory serum markers, including lactate dehydrogenase (LDH), C-reactive protein (CRP), ferritin, D‑dimer, lower lymphocyte counts, and more pronounced computer tomography (CT) imaging pathologies indicating more severe overall and particularly lung involvement.”

In particular, elevated D-dimer indicates a state of increased clotting hypercoagulability and is especially linked with risk of death from COVID-19.

A large Chinese study of 1,099 COVID patients found that diabetic patients with COVID-19 were more likely to need intensive care compared to nondiabetic COVID patients. A total of 22 percent of ICU COVID patients were diabetic, compared to only 10 percent of non-ICU COVID patients.

Furthermore, there was a 3.6-fold higher rate of diabetes among COVID patients who required ICU and mechanical ventilation, or who died.

In analyses of 2,003 Chinese and Italian case fatalities, the prevalence of diabetes among COVID patients who died was twice that found in surviving COVID patients.

Another Italian study of 3,988 ICU patients found that type 2 diabetes was associated with an 18 percent increased risk of dying from COVID.

A study in Wuhan, China, found that among 605 nondiabetic COVID patients, having an elevated fasting blood glucose (≥7.0 mmol/L) upon admission to hospital was significantly associated with risk of death within 28 days.

A fasting glucose of 7.0 mmol/L or more is diagnostic for diabetes, while 6.1 mmol/L or more is defined as pre-diabetes (<5.6 mmol/L is considered normal). In this study, a fasting glucose of 7.0 or more was associated with 2.3-fold increased risk of death within 28 days, while fasting glucose of even 6.0 or higher was associated with a higher rate of complications during hospitalization.

This study suggests that optimal glucose control may be important for all individuals, including those without a diagnosis of diabetes, when it comes to mitigating COVID risk and/or severity.

Animal studies of viral infection suggest why this is so: elevated blood glucose levels facilitate local viral replication in the lungs and inhibit the antiviral immune response.

At this time, there are no good data distinguishing the effects of type 1 diabetes versus type 2 diabetes on COVID morbidity and mortality, although one publication did suggest there was no evidence of an increased COVID hospitalization rate among type 1 diabetics in Belgium during the first three months of the pandemic.

Improving diabetes 

Based on the data so far, it seems reasonable that better glycemic control may translate into mitigation of COVID morbidity and mortality. It should be noted that more research is still needed in this area and that diabetes management is not a replacement for following public health measures for COVID prevention. With that being said, the most crucial lifestyle factors for management of diabetes are weight loss, diet, and exercise.

Diet 

Adopting a diet high in green and coloured vegetables and lower in refined carbohydrates, with moderate amounts of lean protein and healthy fats such as nuts, olive oil, and fish mimics the Mediterranean dietary pattern, which has consistently yielded benefits in the areas of diabetes and heart disease.

Exercise 

Regular exercise five times weekly for up to an hour improves insulin sensitivity and promotes weight loss.

Stress management 

Stress management is also an important consideration, especially given that many of our unhealthy behaviours are an adaptation to life stress, contributing to a vicious cycle. Stress hormones such as cortisol and epinephrine increase blood glucose, and cortisol inhibits weight loss.

The vitamin D link 

In addition to better diabetes management, there is also emerging evidence of a link between vitamin D deficiency (<50 nmol/L serum 25(OH)D levels) and COVID infection.

One study reported a higher rate of vitamin D deficiency among ICU COVID patients compared to non-ICU COVID patients: only 19 percent of ICU patients had serum 25(OH)D levels greater than 50 nmol/L compared to 39 percent of non-ICU patients.

In another study of 499 patients, predicted COVID-19 rates in the vitamin D-deficient group were 21.6 percent versus 12.2 percent in the vitamin D-sufficient group. Since diabetics have a higher rate of vitamin D deficiency, optimizing vitamin D levels is another strategy that could help reduce risk in patients with diabetes. Vitamin D levels should be at least 75 nmol/L.

Natural health products (NHPs) can help 

NHPs with evidence for blood glucose regulation in patients with diabetes include

• vitamin D
• berberine
• alpha-lipoic acid
• chromium
• inositol
• curcumin

Other NHPs with additional benefits on secondary targets such as cardiovascular health and inflammation include

• fish-derived omega-3 fatty acids eicosapentanoic acid (EPA) and docosahexanoic acid (DHA)
• probiotics

Consult a licensed naturopathic doctor to determine which NHPs may be most suitable for you.