When I tell patients they suffer from either diabetes or « borderline » diabetes, they all reply the same thing: « how could I have diabetes, I don’t eat lots of sugar or desserts ». Little do they know, type 2 diabetes, although it does manifest as high blood sugar, is caused by insulin resistance, not by eating carbs.
There is one important nuance. Once in an insulin resistant state, blood sugar will potentially spike after a high carbohydrate meal. Of course this will depend on the amount and type of carbohydrate, a complex topic that I’ve broken down here. This is merely a manifestation of insulin resistance, not the cause. To understand how high carb plant-based diets can actually prevent and even reverse type 2 diabetes, it’s important to discuss the science and mechanisms behind the claims.
What Is Diabetes?
Diabetes is a devastating disease characterized by elevated blood sugar (glucose). This condition, when severe or prolonged, leads to complications that are highly likely to lead to disability, loss of quality of life or even premature death. Acute elevations in blood glucose, if high enough, will lead to the 3 P’s: polydipsia (extreme thirst), polyphagia (extreme hunger) and polyuria (frequent urination). Extremely high levels of blood glucose might cause more severe symptoms like blurred vision, dizziness, fainting or even altered mental status and coma if left untreated. If blood sugar levels are only moderately elevated, they may not give obvious symptoms over the short term. Long term elevations in glucose are almost certain to lead to toxic changes in blood vessels. When these changes occur in small blood vessels, we call them microvascular complications and these include numbness or pain/burning in hands and feet, called neuropathy. Altered sensations in feet can lead to altered biomechanics while walking, which can cause corn, callouses and ulcers that have trouble healing. Diabetes is the leading cause of toe or foot amputations. Microvascular complications affecting the kidneys are called nephropathy and are a leading cause of kidney failure requiring dialysis. This same condition tends to affect similar types of blood vessels in the eye’s retina, where it is called retinopathy, a world wide leading cause of blindness. High blood glucose is not only toxic for small blood vessels, but for larger ones as well. Macrovascular complications include heart attacks, strokes, vascular claudication and erectile dysfunction (which is a combination of micro and macrovascular disease). All that to say that diabetes can spell disaster when blood glucose remains too high, or moderately high for too long. Most deaths are directly related to the above mentioned complications which severely impact quality of life and life expectancy. Since many of these complications take years to develop, most people don’t see any urgency in improving their modifiable lifestyle risks. It’s not a matter of if diabetics will get these complications, but a matter of when. Most end up not changing at all, and will rely on a life sentence of drugs and injections to keep their blood sugar for spiking out of control. Medications do a great job of controlling the elevated blood sugar, but do not address the root cause of the disease: insulin resistance.
Insulin Resistance
Insulin is an energy storage hormone produced by cells in our pancreas. It’s secretion is stimulated by our consumption of carbohydrate rich foods, as well as fatty acids and animo acids (the building blocks of protein). Insulin will then enter over bloodstream, and via complex biochemical processes that are beyond the scope of this article, they’ll help us store the energy we eat by helping glucose’s entry into liver and muscle cells. Insulin also helps store fatty acids in our fat stores and helps us synthesize new protein from amino acids. When blood sugar rises after eating, insulin gets released. When blood sugar gets too low, insulin secretion is suppressed.
In type 1 diabetes, the pancreatic cells that produce insulin get damaged and insulin production stops. These patients require exogenous insulin through injections to survive. In type 2 diabetes, the pancreatic cells remain functional and insulin does get produced. Insulin does knock on cellular doors, hoping it can escort glucose in cells to get used or stored. The issue isn‘t insulin, but the door itself. With a dysfunctional door that stays closed, insulin keeps rising in an attempt to knock on the door louder and louder until someone opens it. Why doesn’t the door open even with high levels of insulin banging on it? That’s the hallmark of type 2 diabetes. In insulin resistance, there is sufficient insulin, but the door it’s supposed to open simply doesn’t. In an overweight or obese patient suffering from insulin resistance, fat accumulates inside their cells (intramyocellular lipids) and crowds the cell to an extent where insulin can’t open the door. Medications don’t treat the cause, which is insulin resistance, they simply help your body lower your blood sugar through other mechanisms. If you remove the medications, insulin resistance is still there and the diabetes returns.
To reverse insulin resistance, the goal should be to decrease intramyocellular lipids. This is best achieved by aiming for an ideal body weight, eating a diet high in whole plant foods, by reducing animal and processed foods that are associated with insulin resistance, and by having a healthy microbiome which seems to impact blood sugar control and diabetes development.
Mechanistic Considerations
As stated earlier, insulin resistance is a major contributor to elevated glucose and increasing insulin sensitivity will help avoid diabetes or even manage or reverse it in those already diagnosed. Low fat vegan diets decrease deposition of intracellular lipids as well as help achieve a healthy body weight, and both of these improve insulin sensitivity. We even have some evidence that plant-based diets actually improve beta-cell function. Plant-based diets, due to their high fiber and water content as well as their lower fat content, provide less calorie dense meals. Studies have also suggested that plant-based diets increase meal associated thermogenesis, meaning they actually increase post-prandial metabolism. All of these factors act together to decrease body weight, insulin resistance as well as to improve hypertension and cholesterol which are associated to the cardiovascular complications seen in diabetics.
Why Diabetes Is Dangerous
Diabetes is estimated to contribute to 1 in 9 deaths in adults aged 20 to 79 years old and about half of diabetes deaths occur in people under the age of 60. Half of deaths in diabetics are caused by cardiovascular disease and since cardiovascular disease is associated with hypertension and cholesterol, both proven to be significantly decreased through plant-based diets, consideration should be given to adopting this dietary pattern. Considering the high likelihood of micro and macrovascular complications which can greatly affect quality of life and life expectancy, it is of great importance that we do all we can to educate patients on how to prevent and reverse this serious disease. Since cardiovascular disease is the main killer of diabetics, you’ll be happy to read that besides improving diabetes control, plant-based diets also help improve almost every single risk factor associated with cardiovascular complications seen in diabetic patients. Plant-based diets, besides lowering blood sugar, also improve every other measurable metabolic parameter, including blood pressure, cholesterol, weight, waist circumference and BMI.
Preventing Diabetes
The best way to not worry about diabetic complications ruining your life is to not get the disease in the first place. The data very clearly proves that adopting a plant-forward dietary pattern is the best way to avoid ever having to deal with type 2 diabetes. People look surprised when I recommend a plant-based diet to treat and prevent diabetes. How could a diet with over 50% of calories coming from carbs possibly help avoid diabetes?
Here’s quick look at the powerful data we have on the protective properties of plant-based diets and diabetes.
The Data
Although I’d love to list the overwhelming number of significantly powered studies that show the insane benefits of plant-based eating when it comes to diabetes prevention, I assume this isn’t everyone’s cup of tea, so I’ll refrain and list the most important ones in the references section at the bottom of this article.
High quality evidence shows to what extent plant-forward diets can help prevent diabetes. A study by Tonstad et al. in 2019 showed that the more plants you eat, the lower your risk of developing diabetes will be. A systematic review and meta-analysis of 3 cohorts totaling over 150000 participants showed an almost 50% reduction in diabetes incidence when comparing a healthy plant-based diet to an unhealthy one. I know I won’t blow any minds by stating that healthy diets prevent diabetes, but plant-based diets seem to have that special something that even health conscious omnivorous diets don’t have.
Treating Diabetes With Meds
Modern medical advancements and pharmaceuticals are one of the main reasons our populations aren’t sicker than we currently already are, considering the obesogenic environment we live in. Although they do lower blood glucose, they don’t reduce insulin resistance, which is not addressing the root cause. If medications really worked, we wouldn’t need refills on them. Even if many patients would rather swallow pills than change their lifestyle, I do make sure to evaluate readiness to change. Many people are still highly motivated to change, and in many with very high blood sugar, I still regularly prescribe medications when indicated and try to motivate them to change their diet and lifestyle so we can remove some meds once their blood glucose is at a safe level. When adopting a plant-based diet for diabetes reversal, aim for minimally processed foods, keep vegetable oils really low, and in those looking to lose weight, use calorie dense plant foods in moderation (like nuts, seeds and their butters, as well as oils and avocados).
Treating Diabetes With Diet
The goal of treating diabetes with diet should be to address the root cause: insulin resistance. That being said, in certain scenarios where blood sugars are extremely high, rapid blood glucose improvements are warranted and can be achieved through medications and with rapid dietary interventions.
Dietary interventions aimed at weight loss are likely to lower insulin resistance and maintaining a calorie deficit is likely to confer benefits in blood sugar control. We have many diets that are capable of causing rapid weight loss and improvements in metabolic parameters, although the sustainability of these dietary patterns can be called into question, as well as their long term safety. For example, keto dieting is a way to quickly lose weight and is often associated with improved blood sugar averages in diabetics, but it has also been shown to lead to micronutrient deficiencies, cholesterol increase and increases the risk of cardiovascular disease, the top killer of diabetics. Achieving a short term improvement in blood sugar isn’t worth increasing cardiovascular mortality over the long term. Many other diets have the same effect of short term glucose control in exchange for long term increases in mortality.
The diets that have accumulated significantly powered data showing long term improvement in diabetes control include the Mediterranean diet, the DASH diet, the Portfolio diet, the vegetarian diet and the low fat vegan diet. Keep in mind that all of these diets favor increasing the amount of whole plants, while decreasing the amounts of animal and processed foods and are all considered to be plant-based diets. Remember that the term « plant-based » is an umbrella term, including plant-forward diets like flexitarianism, vegetarianism, veganism and other diets that have a plant-predominant characteristic.
Diabetes And Specific Food Groups
If subscribing to a specific dietary pattern isn’t attractive to you, you’ll be happy to hear that eating specific types of foods have also been shown to help reduce diabetes incidence in those that don’t yet have the disease, and also improve control in those already diagnosed. As illustrated in the graph above, a diet high in legumes is associated with better blood sugar control. Eating fruits and veggies, contrary to what many believe, also improve blood sugar control, as well as eating nuts and whole grains. Put all of these protective foods together you have a whole food plant-based diet!
The Data
The data included adequately powered RCTs as well as huge systematic reviews and meta-analysis, with some including over 26000 patients with follow-ups ranging from 74 weeks, to 8 and 12 years. These studies frequently compare participants on plant-based diets with those on control diets, which even included the diet recommended by the American Diabetes Association. They consistently showed that measures of diabetic control, as well as other metabolic parameters, were significantly lower in groups adopting a plant-based pattern of eating. One study (a SRMA of over 280 participants over 3 weeks) also showed that simply replacing 35% of protein coming from animals with plant-based protein led to a significant reduction in blood sugar and insulin.
I could list innumerable studies that all say the same thing: plant-based diets improve basically every single measurable parameter linked to diabetes control, morbidity and mortality. Even considering that plant-based diets are high-carb diets, those who regularly read my blogs already understand that not all carbs are bad. If you have carb-phobia, consider reading my recent blog post about carbs not being the enemy here.
Choosing A Study From The Literature
After I entered my study search terms into PUBMED, I began to search for studies that were adequately powered and that were well designed to show the benefits of plant-based diets in term of diabetes prevention or management. I found a 2018 study by Chen et al., that looked at over 6000 patients with an average age of 62. They looked at older adults from 3 sub-cohorts of the Rotterdam Study (RS), a prospective population-based cohort in the Netherlands. The researchers aimed to investigate whether level of adherence to a diet high in plant-based foods and low in animal-based foods is associated with insulin resistance, prediabetes, and type 2 diabetes. They used a continuous plant-based dietary index and collected dietary intake data with a questionnaire at baseline. Average follow-up was 2-4 years. They measured glucose and insulin levels to then calculate insulin resistance. What they found was that a diet higher in plant-based foods and lower in animal-based foods was associated with lower insulin resistance, and a lower risk of prediabetes and type 2 diabetes, suggesting a protective role of a more plant-based opposed to a more animal-based diet in the development of type 2 diabetes. The number of participants and long follow-up were strengths of this study as was the reliable measurements of glucose and insulin. Calculating a plant-based dietary index helps measure differences between different intake of plant and animal based foods. This study showed that higher adherence to an overall plant-based diet is associated with lower longitudinal insulin resistance, and lower risk of prediabetes and type 2 diabetes, indicating a protective role of diets high in plant-based foods and low in animal-based foods.
My Diabetes Plant-Based Prescription
Plant-Based diets have proven their worth when looking at diabetes prevention and treatment. It’ll take lots of education to reassure patients skeptic of plant-based diets and the fact that they are high carb diets. Carbs are still feared by many and even healthcare practitioners still have lots to learn about dietary interventions proven to prevent and treat diabetes. Plant-based diets are still misunderstood by those unaware of the data since this dietary pattern isn’t yet part of medical school programs or nutrition course curriculums. It’ll take years before the new data gets incorporated into medical guidelines, but that doesn’t mean you have to wait to adopt it. Plant-based diets are associated to lower rates of multiple chronic diseases, including cardiovascular disease, cancer, allergic and auto-immune conditions. Now you can add diabetes prevention and treatment to the list.
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