Preventing Diabetes

Hello and welcome to Nutrition Facts – the podcast that brings you the latest in evidence-based nutrition research.  I’m your host Dr. Michael Greger.

I’m often asked what my opinion is about one food or another.  I know what people are asking, but you know, I’m not interested in opinions.  I’m not interested in beliefs.  I’m interested in the science.  What does the best available balance of evidence published in the peer-reviewed medical literature show right now?  That’s why I wrote my book, “How Not to Die” and why I created my nonprofit site NutritionFacts.org and, now, this podcast.

Today we’re going to talk about diabetes and how to help prevent and manage it. 

Prediabetes is a disease in and of itself, associated with early damage to the eyes, kidneys, and heart.  The explosion of type 2 diabetes in children is a result of our epidemic of childhood obesity.  A plant-based diet, however, may help, given that veggie kids grow up to not only be taller, but thinner.  Here’s more of the story. 

Prediabetes is not just a high-risk state for the development of diabetes, prediabetes can be a disease in itself.  People with prediabetes may already have damage to their eyes, kidneys, blood vessels, and heart.

Evidence from numerous studies suggests that the chronic complications of type 2 diabetes start to develop during the prediabetic state.  So, by the time we have prediabetes, it may already be too late to prevent organ damage, so best to prevent prediabetes in the first place, and the earlier the better.

Thirty years ago, virtually all diabetes in young individuals was thought to be autoimmune type 1 diabetes.  But, since the mid-90s, we started seeing increasing type 2 diabetes among our youth, particularly in the United States.  Indeed, the term adult-onset diabetes has now been scrapped and replaced with “type 2” because children as young as eight are now developing the disease and the effects can be devastating.  A fifteen-year follow-up of children diagnosed with type 2 diabetes found an alarming rate in young adults of blindness, amputation, kidney failure, and death in young adulthood.

Why the dramatic rise in childhood diabetes?  Because of the dramatic rise in childhood obesity.  During the past 30 years, the number of children diagnosed as being overweight has increased more than 100%.  Once an obese child reaches 6, they’re likely to stay that way and, even if they don’t, being overweight in our youth predicts adult disease and death, regardless of adult body weight, even if we lose it.

Being an overweight teen may predict disease risk 55 years later–twice the risk of dying from heart attack, more cancer, gout, arthritis.  In fact, being overweight as a teen was a more powerful predictor of these risks than being overweight in adulthood.  This underscores the importance of focusing on preventing childhood obesity.

So, how do we do it?  From the official American Academy of Pediatrics Clinical Practice Guidelines, the problem appears to be kids eating too much fat and added sugars, and not eating enough fruits and vegetables.

Doctors, at every occasion beginning soon after a child’s birth, should endeavor to give sound advice regarding nutrition and growth so that obesity and its complications may be curtailed.  What might sound advice sound like?

Well, the chair of the nutrition department at Loma Linda University published a paper suggesting not eating meat at all might be an effective strategy.  Population studies have consistently shown that vegetarians are thinner than comparable non-vegetarians.  This is from the largest such study to date.

A body mass index of over 30 is considered obese, 25 to 30 overweight, and under 25 ideal weight.  The non-vegetarians were up at 28.8, the average meat eater in the U.S. is significantly overweight.  As one gets more and more plant-based, the average BMI drops, but even the average vegetarian in the U.S. is overweight.  The only dietary group that was, on average, ideal weight, were those eating strictly plant-based.  So that comes out to be about a 33-pound difference between the vegans and the meat eaters.

Vegetarian children grow up not only thinner, but taller.  Vegetarian kids grow to be about an inch taller than other kids.  Apparently, meat intake is somehow negatively associated with height.

I can just hear the Dairy Council now saying it’s because of all the milk the veggie kids must be drinking.  No.  The veg kids consumed significantly less dairy and much lower animal protein intake overall.

Meat intake is apparently associated with growing wider, though.  In school-aged children, the consumption of animal foods (meat, dairy, or eggs) is associated with an increased risk of overweight, whereas plant-based equivalents like veggie burgers, veggie dogs, veggie cold cuts were not, and whole plant foods like grains, beans, and nuts were found to be protective.

This may be because plant-based diets are low in energy density and high in starch, fiber, and water, which may increase feelings of fullness and resting energy expenditure, meaning resting metabolic rate.  Eating plant-based appears to boost metabolism; so, we just kind of burn more calories at rest, even, you know, when you’re sleeping.  However, we’re not sure how much of the benefits are due to increased consumption of plant foods versus the decreased consumption of meat.

Either way, plant-based diets should be encouraged and promoted for optimal health.  Local, national, and international food policies are warranted to support social marketing messages and to reduce the social, cultural, economic, and political forces that make it difficult to promote such diets.

For example, although the advice to consume a plant-based diet is sound, questions arise regarding the relative high price of produce.  Yes, we can reduce the burden of childhood obesity, prevent the further spread of the disease, but we need to ensure that plant foods are affordable and accessible to children of all income levels.

Fruits and vegetables may not fit on the Dollar Menu, but our kids are worth it.  Getting diabetes in childhood cuts nearly 20 years off their life. Who among us wouldn’t go to the ends of the Earth to enable our kids to live 20 years longer?

Why do some drug-based strategies shorten the lives of diabetics and some diet-based strategies fail to decrease diabetes deaths?  Here are some answers.

People with type 2 diabetes are at elevated risk for a number of serious health problems, including heart disease, premature death, blindness, kidney failure, amputations, fractures, frailty, depression, and cognitive decline.  And, the higher people’s blood sugars are, the more heart attacks and strokes they have, the shorter their lifespans, and the higher their risk of complications like blindness and kidney failure.  So, a study was designed in which 10,000 diabetics were randomized into an intensive blood sugar lowering intervention, where they put people on 1, 2, 3, 4, or 5 different classes of drugs, with or without insulin, to drive blood sugars down into the normal range.  Of course, you’re not treating the underlying cause, not actually treating the actual disease, but, you know, by lowering one of the effects of the disease, these high blood sugars, by any means necessary, the hope was to prevent some of the devastating complications.  How’d they do?

The intensive blood sugar lowering with drugs increased mortality.  After reviewing mortality trends, they concluded that the harm associated with the increased rate of death outweighed any potential benefits and they stopped the study prematurely for safety reasons.  They were successful in bringing people’s blood sugars down, but in trying to push people’s hemoglobin A1c under 6, they ended up pushing people six feet under, perhaps due to the adverse effects of the very drugs used to treat the disease.

Even just injected insulin itself may promote cancer, obesity, atherosclerosis, worsen diabetic retinopathy, and accelerate aging.  Insulin therapy may promote inflammation in the lining of our arteries, which may explain the results of this trial and other trials like it that showed the same thing–no reduction in the so-called macrovascular complications, heart attacks, and strokes, with intensive blood sugar lowering.  However, intensive therapy was associated with a 21% reduction in the development of microvascular complications like kidney dysfunction.

But any such benefits should be weighed against the increased risk of dying, increased weight gain, increased risk of severe hypoglycemia in intensively-treated patients.  So, trying to normalize people’s blood sugars with drugs may not be such a good idea. 

It should be noted, though, that these trials relied virtually exclusively on drugs and did not include any serious effort at diet and lifestyle change.

A 2013 paper in the New England Journal of Medicine found that an intensive lifestyle intervention focusing on weight loss did not reduce the rate of cardiovascular events like heart attacks in overweight or obese adults with type 2 diabetes; it did not increase their risk of death, but it did not seem to decrease it.  In fact, the trial was just stopped after about ten years on the basis of futility.  I mean, they lost weight, but they weren’t dying any less and that’s what we see across the board in these types of lifestyle interventions.  It’s good that the dietary intervention wasn’t killing anyone, but why wasn’t it actually helping people live longer?

Because they didn’t actually put them on a healthier diet; they just put them on a smaller diet, a calorie restricted diet, meaning essentially the same lousy diet, but just in smaller portions.  If we eat less and exercise more, we can lose weight, get more physically fit, slimmer and have better blood sugar control, but if our diets continue to be so unheart-healthy that our bad LDL cholesterol doesn’t improve, then we’re not going to be unclogging our arteries.  Whereas, individuals following healthier diets may experience improved reductions in blood sugar, body weight, and cardiovascular risk.  Yes, by eating a smaller quantity of food, without changing quality, we can lose weight, but the point of a lifestyle intervention is not to just fit people into skinnier caskets.

We’ve known for decades that plant-based diets are associated with lower diabetes risk.  But how low does one have to optimally go on animal product and junk food consumption?

Decades ago, we started to get the first inklings that a plant-based diet may be protective against diabetes.  Studies going back a half century found that those eating meat one or more days a week had significantly higher rates of diabetes and the more frequently meat was eaten, the more frequent the disease–and this is after controlling for weight.  Even at the same weight, those eating plant-based had but a fraction of the diabetes rates and, if anything, vegetarians should have had more diabetes just because they appear to live so much longer so have more time to develop these kinds of chronic diseases–but no–apparently lower rates of death and disease.

Fast forward 50 years to the Adventist-2 study, looking at 89,000 people and we see a stepwise drop in the rates of diabetes as one eats more and more plant-based, down to a 78% lower prevalence among those eating strictly plant-based.  Protection building incrementally as one moved from eating meat, to eating less meat, to just fish, to no meat, and then to no eggs or dairy either.

We see the same thing with another leading killer, high blood pressure.  The greater the proportion of plant foods, the lower the rates of hypertension and the same with excess body fat.  The only dietary group not, on average, overweight were those eating diets composed exclusively of plant foods but, again, this same incremental drop with fewer and fewer animal products.  This suggests that it’s not black and white, not all or nothing; any steps we can make towards eating healthier may accrue significant benefits.

Followed over time, vegetarian diets were associated with a substantially lower incidence of diabetes–fewer new cases–indicating the potential of these diets to stem the current diabetes epidemic.

What about eating a really healthy diet with just a little meat? Or is it better to eat none at all?  Well, we have new insight this year from Taiwan.  Asian diets, in general, tend to be lower in meat and higher in plant foods compared to Western diets, but whether a diet completely avoiding meat and fish would further extend the protective benefit of a plant-based diet wasn’t known, until now.

Traditionally, Asian populations have had low rates of diabetes, but a diabetes epidemic has since emerged and appears to coincide with increased meat, animal protein, and animal fat consumption, but the Westernization of Asian diets also brought along a lot of fast food and junk. So, these researchers at the national university didn’t want to just compare those eating vegetarian to typical meat eaters, but compared Buddhist vegetarians to Buddhist non-vegetarians eating traditional Asian diets.  Even the omnivores were eating a predominantly plant-based diet, consuming little meat and fish, with the women eating the equivalent of about a single serving a week and men eating a serving every few days. That’s just 8% of the meat intake in the U.S., 3% for the women.  The question:  Is it better to eat 3% or 0%?

Again, both groups were eating healthy–zero soda consumption, for example, in any group.  Despite the similarities in their diet, and after controlling for weight, family history, exercise, and smoking, the men eating vegetarian had just half the rates of diabetes, and the vegetarian women just a quarter of the rates.  So, even in a population consuming a really plant-based diet with little meat and fish, true vegetarians who completely avoided animal flesh while eating more healthy plant foods, had lower odds for prediabetes and diabetes after accounting for other risk factors. They wanted to break it up into vegan versus ovo-lacto like in the Adventist-2 study, but there were no cases at all of diabetes found within the vegan group.

Here’s a small step you can take – with some lasting impact.  A daily tablespoon of ground flaxseeds for a month appears to improve fasting blood sugars, triglycerides, cholesterol, and hemoglobin A1c levels in diabetics.   Here’s the research.

Drug companies are hoping to capitalize on the fact that the consumption of certain plants appears to lower the risk of diabetes by isolating the active components for use and sale as pharmacological agents. Though not as profitable, why not just eat the plants?

One plant in particular that’s now been tested is flax.  We’ve known for twenty years that having ground flaxseeds in your stomach can blunt the blood sugar spike from a meal, but it’s never been tested in diabetics, until now.

“An open-label study on the effect of flaxseed powder…supplementation in the management of diabetes…” A tablespoon of ground flaxseeds every day for a month and, compared to the control group, a significant drop in fasting blood sugars, triglycerides, and cholesterol, as well as the most important thing, a drop in A1c level.  This was just after a month; though if one’s sugars are already well-controlled, there may be no additional benefit.

No weight gain was reported in people adding a quarter cup of ground flax a day to their diets for three months.  In fact, the flax group ended up with a slimmer waist than the flaxseed oil or control group.  Even up to nearly a half cup a day—more than I’d recommend—still no significant weight gain, though this was only after a month.

How does flax help control diabetes?  Well, flaxseed consumption may improve insulin sensitivity in people with glucose intolerance.  About after 12 weeks of flax, there was a small, but significant, drop in insulin resistance—perhaps related to the drop in oxidant stress, given the antioxidant qualities of flaxseed phytonutrients.

Now, this was a small, unblinded study.  It’s hard to come up with a convincing fake flaxseed placebo.  So, look, if this was some drug they were testing, I’d never prescribe it, based on this one study, but it isn’t a drug; it’s just flaxseeds.  There’s just good side effects.  So, even if this study was a fluke or fraud, flaxseeds have other benefits.  So, even in the worst case scenario, I’d still end up benefiting my patients not quite, you know, ready or able to reverse their diabetes completely with a completely plant-based diet.

Thanks for listening to this episode of Nutrition Facts.  To see any graphs charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page.  There, you’ll find all the videos I highlighted with links to all the sources cited.

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Thanks for listening to Nutrition Facts.  I’m Dr. Michael Greger.