A review of the week’s plant-based nutrition news 17th July 2022
This week my review is dedicated to type 2 diabetes, a condition that is of rising global concern, yet the vast majority of cases could be prevented or reversed.
DIETARY PROTEIN AND RISK OF TYPE 2 DIABETES: Protein is a much discussed and revered nutrient, with animal sources of protein still considered superior by some. Yet when considering health outcomes, replacing animal protein with plant sources of protein consistently improves health outcomes. It is no different for type 2 diabetes (T2D). Thus calls have been made by the medical and science community to modernise the definition of protein quality.
This study analysed the impact of dietary protein on the risk of T2D in two large prospective cohorts, the Women’s Health Initiative (WHI — 108,681 postmenopausal women) and the UK Biobank study (34,616 adults). Participants in the WHI were followed for a median of 15.8 years, during which time there were 15,842 cases of T2D diagnosed. Animal protein consumption was associated with an increased risk of T2D with those consuming the most having a 31% increased risk compared to those consuming the least. In contrast, plant protein consumption reduced the risk of T2D by 18%. Red meat, processed meat, poultry, and eggs were all associated with an increased risk of T2D. Findings from the UK biobank study were very similar. Replacing 5% of energy from animal protein with plant protein was associated with a 21% decrease in risk of T2D and plant protein consumption was associated with lower levels of inflammation. However, it should be noted that the association between animal protein and T2D risk was less significant when the results were adjusted for body mass index, suggesting that animal foods increase the risk of T2D predominantly by leading to increased weight. The authors conclude ‘substituting plant protein for animal protein may decrease T2D risk mainly by reducing obesity-related inflammation’.
These results are consistent with prior data. Analyses from the Adventist Health Studies and the EPIC-Oxford study demonstrate that meat-free diets significantly reduce the risk of type 2 diabetes, in part due to the association with a lower body weight.
DIETARY PATTERNS AND RISK OF TYPE 2 DIABETES: It tends to be best to assess the impact of dietary patterns rather than individual foods and nutrients on the risk of chronic disease. However, all healthy diet patterns share in common an emphasis on the consumption of minimally processed, whole plant foods. This remains true when it comes to T2D.
This study reports finding from the UK Biobank and included 120,343 participants followed for 8.4 years. During this time, 2,878 participants developed T2D. The results showed that a diet pattern high in chocolate, confectionary and butter (and other animal spreads) and low in fibre, fruits and vegetables was responsible for almost 50% of the risk of developing T2D. This type of diet was associated with excess consumption of calories, sugar and saturated fat, all known risk factors for T2D. The increased risk was only partly attenuated when controlling for body weight, suggesting that other mechanisms, in addition to adiposity, are at play. Interestingly, a high consumption of free sugar per se if not associated with an excess consumption of calories or saturated fat was not significantly associated with an increased risk of T2D. This led the authors to conclude that free sugar consumption is less of a concern for T2D risk than saturated fat intake.
It is clear that a diet pattern centred around whole plant foods can not only significantly reduce the risk of T2D but is the best way of putting diabetes into remission. On a side note, it is worth remembering the higher and earlier risk of T2D in people of South Asian origin, which is despite the high prevalence of vegetarianism. This emphasises the importance of diet quality rather than just the removal of animal foods. Here is an excellent interview with the principle investigators of the MASALA study in the US published in JAMA, outlining the elevated incidence of cardiometabolic risk factors and conditions in South Asians and associations with diet and lifestyle factors.
VEGETABLE CONSUMPTION AND RISK OF TYPE 2 DIABETES: Vegetable consumption seems key for prevention of T2D. In this study of 1485 participants from Greece followed for 10 years, those who consumed 4 or more servings (>400g) of vegetables per day had a 58% lower risk of T2D compared to those who ate <4 portions a day, with benefits greater in women than men (71% vs 44% lower T2D risk). Higher intakes of cruciferous vegetables, leafy vegetables, red/orange/yellow vegetables, allium family and legumes were particularly associated with a reduced risk. This risk reduction was independent of any other dietary factors. Higher vegetables intake was also associated with lower triglyceride levels.
There are many potential reasons for these findings, including higher consumption of fibre, exposure to protective phytochemicals such as organosulphur compounds found in the allium family, sulphorophane from cruciferous vegetables and carotenoids in the red/orange/yellow vegetables. Bioactive compounds in vegetables promote a healthier gut microbiome, which is important for glucose regulation and promotion of insulin sensitivity. This level of vegetable consumption is achievable and inline with all healthy eating guidelines.
DIABETES RISK AFTER A CANCER DIAGNOSIS: We have data demonstrating that not only does a diagnosis of T2D increase the risk of cancer, but there is also an elevated risk of T2D after a cancer diagnosis.
This study included 51, 353 participants from Denmark with a diagnosis of cancer and compared the risk of diabetes to individuals without cancer. The results showed that there was an increased risk of T2D for all cancers (9% overall increased risk), with the strongest associations for pancreatic, central nervous system (brain), uterine, lung, breast and urinary tract cancers. Interestingly, melanoma and haematological cancers were associated with a lower risk of T2D. Patients with cancer who developed T2D also had a 21% risk of all-cause mortality compared to patients without T2D. The authors conclude ‘Our data illustrate the need for increased focus on the development of T2D in cancer survivors’.
HEALTHY LIFESTYLES, CANCER AND CARDIOMETABOLIC DISEASE: A reminder of this important study from 2021 that provides actionable evidence for prevention of cardiometabolic disease, including T2D, in people with cancer.
This paper reports finding from the UK biobank study and examines the impact of a healthy lifestyle on the risk for cardiovascular disease (CVD) and T2D before and after the onset of cancer. Two sub-groups were included. A cancer-free cohort of 397,136 individuals in the general population and a cancer-prevalent cohort of 35,564 individuals with cancer. All participants were aged 40 to 70 years, free of CVD and T2D at recruitment and then followed for median of 14 years. The healthy lifestyle index (HLI) was made up of 5 cardiometabolic disease–related healthy behaviours (smoking status, physical activity, diet, alcohol consumption, and sleep duration). If participants met the criteria for each healthy habit they received a score of 1 and if not a score of 0, so a maximum score of 5 could be obtained. A healthy diet was high in fruits, vegetables, whole grains, refined grains, fish and low in unprocessed meat and processed meat.
In the cancer-free cohort 40,097 individuals (10.1%) developed cancer during follow-up. Each 1-point increment in HLI was associated with an 8% lower risk of developing cancer. A 1-point increment in HLI was also significantly associated with a 10% lower risk for developing CVD in patients diagnosed with cancer and a 12% lower risk in those free of cancer. Each additional healthy lifestyle factor had a 17%-26% reduction in risk of death during follow up, with smoking having the strongest negative impact. A 1-point increment in HLI was also associated with a 19% reduction in risk of T2D and a 16% reduction in T2D following a cancer diagnosis.
In the cancer cohort, cancer survivors with 5 healthy lifestyle factors had a 44% reduction in the risk of developing CVD and 38% reduction in the risk of T2D. A 1-point increment in HLI was associated with risk reductions of 10% and 13% in developing CVD and T2D, respectively.
Overall the finding confirm the importance of healthy lifestyle habits for prevention of cancer, CVD and T2D and also the benefits of these healthy habits after a diagnosis of cancer when the risk of chronic conditions is even higher.
DIETARY INTERVENTIONS FOR TYPE 2 DIABETES REMISSION: Remission should be the aim of diet and lifestyle interventions for people living with T2D. There are several dietary approaches that can lead to remission, defined as HbA1c <6.5% for at least 3 months with no surgery, devices, or active pharmacologic therapy for the specific purpose of lowering blood glucose. This new expert consensus statement has reviewed all the evidence on dietary interventions and come up with a recommendation for the optimal dietary approach taking into account short and long-term impacts on health outcomes, plus adherence and sustainability. The authors concluded that, ‘Diet as a primary intervention was considered most effective when emphasising whole, plant-based foods including whole grains, vegetable, legumes, fruits, nuts and seeds, with minimal consumption of meat and other animal products’. It is well worth reading the full document, which is open access.
Read my updated summary on the role of plant-based diets in prevention and treatment of type 2 diabetes here.