Vegetarian Diets and the Risk of Diabetes

A September 2018 review 1 looked at whether the dramatic worldwide increase in cases of type 2 diabetes (T2DM – type 2 diabetes mellitus) could be slowed down if individuals made simple dietary changes rather than seeking solutions through medication.

Summary

The reviewers note that vegetarian diets are inversely associated with risk of developing diabetes, and this is independent of the positive association of meat consumption with diabetes development.

Range of diets

Vegetarian diets range* from:

  • vegan (no animal products)
  • lacto-ovo-vegetarian (no animal meat, but consumes milk and eggs)
  • pesco-vegetarian (consumes fish)
  • semi-vegetarian/flexitarian (occasional meat consumption)

*N.B. This review does not look at WFPB or non-SOS WFPB diets.

The most important aspects of any of these types of diets is the emphasis on:

  • whole grains
  • fruits and vegetables
  • legumes
  • nuts
  • reduction of saturated and trans fats

Problem – what problem?

Oh there’s a big problem, alright. Diabetes has now reached epidemic levels, with an estimated 451 million cases worldwide in 2017 – a number that is predicted 2 to increase to 693 million by 2045.

Where’s the evidence?

About 90% of diabetes diagnoses are type 2 (T2DM) – all of these appear to be lifestyle-related 3 . Additionally, the lifestyle factor most linked to improvements in protection against, treatment of and cure for is diet – with the take-home facts being that animal foods encourage whist plant foods discourage T2DM 4 .

As countries develop a more Westernised diet (also known as the SAD or Standard American Diet), the rates of diabetes within those countries increases 3 .

Omnivores vs Vegetarians

A diet differing from the typical Westernised diet is a vegetarian one. The results of changing to a vegetarian diet is clear. For instance, research 3 shows that vegetarians in the US have a lower prevalence of diabetes than omnivores (that is, those who consume both plant and animal foods, although much more of the latter than the former foods in the case of modern Westernised diets). Other research 5 6 7 8 9 backs up the proposition that a vegetarian diet is significantly better for the prevention and treatment of diabetes than an omnivore diet.

To the heart of the matter

People with diabetes have a 2–4 times greater risk of suffering from CVD (cardio-vascular disease) 10 . Even those who just adhered to a lacto-ovo-vegetarian diet have been shown 11 to have significantly decreased CVD risk factors, specifically blood pressure, serum cholesterol, and blood glucose levels than those adhering to an omnivorous diet.

Another 2013 study 12 examined ischaemic heart disease risk of vegetarians versus non-vegetarians in a large British sample of 44,561 individuals. They found that vegetarians had a lower BMI, non-HDL cholesterol, and systolic blood pressure than the non-vegetarians.

Other risks with diabetes

When looking at other diabetes risk factors and comorbidities, a 2015 study 13 found that those adhering to a vegan diet supplemented with vitamin B12 had a significantly larger decrease in neuropathic pain 14 than the control group receiving just B12 supplementation.

A 1988 study 15 examined patients who had diabetic neuropathy 16 and renal failure who followed a vegan diet for 12 months found significant improvements in the following:

  • creatinine clearance 17
  • urine protein levels
  • cholesterol levels
  • blood glucose levels

Is it too late for me?

Okay, if you’ve eaten a vegetarian diet from childhood, you are less likely to have developed diabetes; but what if you’ve been stuffing in the eggs and bacon, doughnuts and cream cakes for most of your life – is it too late? Another 2018 study 18 found that adopting a vegetarian diet later on in life can greatly reduce diabetes risk, showing the benefits of using a vegetarian diet in an intervention. Other research studies 19 20 21 show the same positive results of dietary changes later in life.

Medication vs diet

There’s also evidence 22 23 24 25 supporting the suggestion that adopting a vegetarian diet is more effective than at improving diabetes symptoms than traditional medication. Of course, packing in smoking and getting lots of exercise are also significantly important lifestyle factors that can prevent and treat diabetes.

Physical and mental benefits

A 2013 study 26 looked at the psychological effects of adopting a vegetarian diet. The investigators assessed the following:

  • quality of life
  • eating behaviour
  • depressive symptoms

They divided diabetic subjects into vegetarian and non-vegetarian groups and found an increase in quality of life and decrease in depressive symptoms in the vegetarian group. Regarding dietary restraint, the vegetarian group was was able to show an increased ability to resist the ‘temptation’ to eat more food and more unhealthy food than the non-vegetarian group. This study showed that adopting a vegetarian diet has both physical and psychological benefits for T2DM patients.

Not all vegetarian diets are equal

Some vegetarians live on processed foods, crisps, chips and sweets. Some hate all vegetables (except fried white potatoes!) while others eat largely whole plant foods.

To examine the differences in type 2 diabetes risk of vegetarians who consume an unhealthy diet (characterised by refined grains, starchy foods, added sugars, low fruits and vegetables) or healthy diet (characterised by whole grains, fruits, vegetable, legumes), a 2016 review 27 categorised the latter as hPDI (a Healthful Plant-Based Diet) and uPDI (an Unhealthy Plant-Based Diet Index) in order to distinguish between healthy and unhealthy plant foods being eaten.

Thus, hPDI assigned positive scores to:

  • whole grains
  • fruits
  • vegetables
  • nuts
  • vegetable oils
  • tea and coffee

and reverse scores to:

  • fruit juices
  • sweetened beverages
  • refined grains
  • potatoes (white)
  • sweets
  • desserts
  • animal foods

The uPDI used the opposite approach.

The results were pretty clear: PDI and hPDI were inversely associated with T2DM, and the uPDI was positively associated with T2DM. This shows the benefit of following a vegetarian diet that is high in whole grains, vegetables, fruits, nuts, and legumes in preventing T2DM.

Study conclusions

The researchers in this September 2018 review 1 drew the following conclusions:

  • the role of all types of vegetarian diets in the prevention and treatment of diabetes is well established
  • clinicians and healthcare providers should feel confident in recommending a vegetarian diet to their patients who have pre-diabetes or T2DM
  • the type of foods that should be consumed while following this diet is critical to achieve the therapeutic effects
  • a vegetarian diet that is high in unhealthy foods such as refined grains, saturated fats, and added sugars is positively associated with T2DM
  • a vegetarian diet that is high in healthy foods such as whole grains, fruits, vegetables, nuts, legumes, and unsaturated fats is negatively associated with T2DM

Final thoughts

It’s pretty obvious to all reasonable people who’ve done even a bit of research that a significant solution to diabetes (prevention, management and cure) lies in simple dietary changes (as well as dropping the tobacco and picking up the weights instead).

However, while this review does look at different manifestations of vegetarian diets, it does not cover in detail how much more effective a completely WFPB (ideally a non-SOS WFPB) diet is when compared with the rest of the vegetarian offerings. Naturally, it hints at this through its mention of the above-mentioned 2016 review 27

If you look online or go to a vegetarian/vegan restaurant and look at what often goes into their recipes you will soon understand what I’m getting at. A quick glance at the menus of one vegan restaurant 28 local to me reveals the potentially unhealthy ingredients and cooking methods that can be both plant-based and unhealthy at the same time – ‘double fried chips and a pot of garlic mayo‘ and ‘Sticky Toffee Pudding served with a caramel glaze‘ will only offer limited assistance, if any, to diabetic customers looking for the healthy alternative to bangers and mash!

Of course, as evidenced in this review, going plant-based rather than relying on pharmaceuticals is a move in the right direction – but for the greatest protection against diabetes, a non-SOS WFPD has been shown repeatedly in additional research studies 29 30 to trump the more watered-down veggie versions.

References

  1. Vegetarian Diets and the Risk of Diabetes. Olfert MD, Wattick RA. Curr Diab Rep. 2018 Sep 18;18(11):101. doi: 10.1007/s11892-018-1070-9. Review. [↩] [↩]
  2. Cho N, Shaw J, Karuranga S, et al. IDF Diabetes Atlas: global
    estimates of diabetes prevalence for 2017 and projections for 2045. Diabetes Res Clin Pract. 2018;138:271–81. [↩]
  3. Trapp CB, Barnard ND. Usefulness of vegetarian and vegan diets for treating type 2 diabetes. Curr Diab Rep. 2010;10:152–8. [↩] [↩] [↩]
  4. McEvoy CT, Temple N, Woodside JV. Vegetarian diets, low-meat diets and health: a review. Public Health Nutr. 2012;15(12):2287–94. [↩]
  5. Snowdon DA, Phillips RL. Does a vegetarian diet reduce the occurrence of diabetes? Am J Public Health. 1985;75(5):507–12. [↩]
  6. Vang A, Singh PN, Lee JW, Haddad EH, Brinegar CH. Meats, processed meats, obesity, weight gain and occurrence of diabetes among adults: findings from adventist health studies. Ann Nutr Metab. 2008;52(2):96–104. [↩]
  7. Fung TT, Schulze M, Manson JE, Willett WC, Hu FB. Dietary patterns, meat intake, and the risk of type 2 diabetes in women. Arch Intern Med. 2004;164(20):2235–40. [↩]
  8. Barnard ND, Katcher HI, Jenkins DJ, Cohen J, Turner-McGrievy. Vegetarian and vegan diets in type 2 diabetes management. Nutr Rev. 2009;67(5):255–63. [↩]
  9. Chen Z, Zuurmond MG, van der Schaft N, Nano J, Wijnhoven HAH, Ikram MA, et al. Plant versus animal based diets and insulin resistance, prediabetes and type 2 diabetes: the Rotterdam Study. Eur J Epidemiol. 2018. [↩]
  10. Yokoyama Y, Barnard ND, Levin SM, Watanabe M. Vegetarian diets and glycemic control in diabetes: a systematic review and meta-analysis. Cardiovasc Diagn Ther. 2014;4(5):373–82. [↩]
  11. Slavícek J, Kittnar O, Fraser GE, et al. Lifestyle decreases risk factors for cardiovascular diseases. Cent Eur J Public Health. 2008;16(4):161–4. [↩]
  12. Crowe FL, Appleby PN, Travis RC, Key TJ. Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians: results from the ePIC-Oxford cohort study. Am J Clin Nutr. 2013;97(3):597–603. [↩]
  13. Bunner AE, Wells CL, Gonzales J, Agarwal U, Bayat E, Barnard ND. A dietary intervention for chronic diabetic neuropathy pain: a randomized controlled pilot study. Nutr Diabetes. 2015;5(5):e158. [↩]
  14. What is neuropathic pain? Wikipedia. [↩]
  15. Barsotti G, Navalesi R, Giampietro O, et al. Effects of a vegetarian, supplemented diet on renal function, proteinuria, and glucose metabolism in patients with ‘overt’ diabetic nephropathy and renal insufficiency. Contrib Nephrol. 1988;65:87–94. [↩]
  16. What is diabetic neuropathy? Mayo Clinic. [↩]
  17. What is creatinine and creatinine clearance? WedMD [↩]
  18. Chiu THT, Pan W-H, Lin M-N, Lin C-L. Vegetarian diet, change in dietary patterns, and diabetes risk: a prospective study. Nutr Diabetes. 2018;8:12. [↩]
  19. Nicholson AS, Sklar M, Barnard ND, Gore S, Sullivan R, Browning S. Toward improved management of NIDDM: a randomized, controlled, pilot intervention using a lowfat, vegetarian diet. Prev Med. 1999;29:87–91. [↩]
  20. Turner-McGrievy GM, Barnard ND, Scialli AR. A two-year randomized weight loss trial comparing a vegan diet to a more moderate low-fat diet. Obesity (SilverSpring). 2007;15:2276–81. [↩]
  21. Kahleova H, Matoulek M, Malinska H, et al. Vegetarian diet improves insulin resistance and oxidative stress markers more than conventional diet in subjects with type 2 diabetes. Diabet Med. 2010;28:549–59. [↩]
  22. Anderson JW, Ward K. High-carbohydrate, high-fiber diets for insulin-treated men with diabetes mellitus. Am J Clin Nutr. 1979;32(11):2312–21. [↩]
  23. Barnard RJ, Jung T, Inkeles SB. Diet and exercise in the treatment of NIDDM. The need for early emphasis. Diabetes Care. 1994;17: 1469–72. [↩]
  24. Barnard ND, Cohen J, Jenkins DJ, et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care. 2006;29(8):1777–83. [↩]
  25. Tonstad S, Butler T, Yan R, Fraser GE. Type of vegetarian diet, body weight, and prevalence of type 2 diabetes. Diabetes Care. 2009;32(5):791–6. [↩]
  26. Kahleova H, Hrachovinova T, Hill M, Pelikanova T. Vegetarian diet in type 2 diabetes – improvement in quality of life, mood and eating behaviour. Diabet Med. 2013;30(1):127–9. [↩]
  27. Satija A, Bhupathiraju SN, Rimm EB, et al. Plant-based dietary patterns and incidence of type 2 diabetes in US men and women: results from three prospective cohort studies. PLoS Med. 2016;13(6):e1002039. [↩] [↩]
  28. The Green Room [↩]
  29. Current Diabetes Treatment – Practice or Malpractice? [↩]
  30. Plant-based Diets & Diabetes [↩]