A review of the week’s plant-based nutrition news 10th October 2021
This week I cover papers on chronic pain, resistant hypertension, benefits of soya in people with type 2 diabetes, whole grains versus refined grains and an exciting new study in multiple sclerosis.
DIET AND CHRONIC PAIN: There is a growing interest in using lifestyle approaches, including diet, to support the management of chronic pain. Muscleskeletal pain, including back pain, is one of the leading causes of disability globally. Inflammation contributes to the generation of pain in a number of disorders. Given than some foods, particularly those typical of a Western-style diet, are associated with inflammation and others are anti-inflammatory, it makes sense to consider a dietary approach to managing pain. Regarding inflammation, researchers have developed the Dietary Inflammatory Index that classifies food based on their inflammatory potential. No surprise that whole plant foods are anti-inflammatory and processed and unprocessed meat, refined grains and sugar are amongst some of the most inflammatory foods.
The current study brings together available data on food and dietary patterns and the impact on pain. Forty-three studies reporting on 48 chronic pain groups receiving a whole food dietary intervention were included. These included elimination protocols (n=11), vegetarian/ vegan diets (n=11), single-food changes (n=11), calorie/macronutrient restriction (n=8), an omega-3 focus (n=5), and Mediterranean diets (n=2). The studies covered a range of conditions including including 13 studies on rheumatoid arthritis, 11 on fibromyalgia, 10 on osteoarthritis, seven on other musculoskeletal pain and two on neuropathic pain. The vegetarian, vegan and plant-based studies mainly covered rheumatoid arthritis, osteoarthritis, diabetic neuropathy and fibromyalgia. The duration of the interventions ranged from 2 weeks to 2 years, with an average of 18 weeks and included a median of 44 participants (range 1–389). A third of studies were from the USA and studies included more female than male participants.
There is quite a bit of detail presented within the paper. Overall, it was found that dietary interventions are effective at reducing pain. No single dietary approach stood out, but positive results were found for elimination diets, vegetarian/vegan and Mediterranean diet as being best. Overall, interventions that emphasised whole foods had better outcomes. Features in common of successful dietary approaches were an emphasis on diet quality, nutrient density and an associated weight loss.
The results are not really surprising give what we know about the inflammatory potential of foods. Whole plant foods, herbs and species have the highest concentration of antioxidant and anti-inflammatory compounds and are much lower in compounds that are associated with inflammation such as saturated fat, haem iron, advanced glycation end products, found in animal foods.
LIFESTYLE MODIFICATION AND RESISTANT HYPERTENSION: Randomised lifestyle medicine studies are rare, yet we know lifestyle approaches can address the root cause of many chronic conditions, including hypertension. A plant-based diet is as effective as medication and along side other healthy habits, should be the first line approach to managing high blood pressure (BP). Nevertheless, some people have hypertension that is very resistance to any treatment, including prescribed medications. The current study investigated the impact of a 4 months intensively supervised diet and exercise programme in 140 people with resistant hypertension, that is, a blood pressure >130/80 despite 3 medications. This was compared to a group that only received a one hour education session providing the same information on diet and exercise as the intervention group.
The intervention group received education from a nutritionist on the DASH (dietary approached to stop hypertension) diet, caloric and sodium restriction. (≤2300 mg/d) and underwent weekly 45-minute group counselling sessions delivered by a clinical psychologist that emphasised changes in the initiation of eating behaviour, individualised problem solving, and maintenance of long-term behaviour change. Participants also exercised at a cardiac rehabilitation facility 3 times per week for 30 to 45 minutes at a level of 70% to 85% of their initial heart rate reserve. It should be noted that the DASH diet is a plant-based diet that was designed in recognition of the fact that vegetarian diets were effective at maintaining a healthy blood pressure, but researchers thought that allowing some animal ‘foods’ would be more acceptable to people!
The results showed that both the intervention and the control group benefited in many of the measured parameters, but the intervention group benefited more. In the intervention group the reduction in BP was as much as that expected by anti-hypertensive medication and included reductions in both clinic and ambulatory BP (only clinic BP was reduced in control group). The systolic BP was lowered by a median of 12mmHg and 59% of the intervention group achieved a BP <130/80. Weight loss was 15.3lb in the intervention group compared to 8.5Ib in the control group. There were improvements in other markers of cardiovascular health including high-frequency heart rate variability and flow mediated dilatation that did not improve in the control group.
It turns out that the diet changes were not that radical in the intervention group or that different from the control group. For example, calorie intake dropped in both groups by around 200 calories and sodium intake by around 250mg. What did seem to be different between the groups was a a slightly higher fibre, vegetable, potassium and magnesium in the intervention group. The differences between the exercise parameters were much greater between groups. This study can’t distinguish between diet versus exercise benefits.
Overall, the study clearly demonstrates the power of lifestyle intervention even in established, difficult to treat conditions. The authors conclude ‘Lifestyle modification including adoption of the Dietary Approaches to Stop Hypertension diet with caloric restriction and reduced salt consumption and regular aerobic exercise can significantly lower blood pressure and improve cardiovascular disease biomarkers’.
SOYA AND CARDIOVASCULAR RISK FACTORS IN TYPE 2 DIABETES: Over the last 2 years, we have had some excellent papers on the benefits of including soya in the diet. Mainly thanks to Dr Mark Messina who really has done some incredible work. We now have enough evidence to conclusively state that minimally processed soya foods are a healthy addition to any diet pattern and should be encouraged. Any myths about adverse impacts are just that, myths that are unsubstantiated by the current body of human evidence.
This new systematic review and meta-analysis brings together 22 trials that investigate the impact of soya consumption in 867 participants with type 2 diabetes. The studies were conducted in a wide range of countries, including Canada, China, Iran, UK and USA. The doses of soya used in the interventions ranged from 17.8–69g/day.
The results showed that soya consumption reduced serum triglyceride levels, total and LDL-cholesterol and C-reactive protein (a marker of inflammation). People with dyslipidaemic benefited the most from adding soya to the diet. Soya reduced fasting blood glucose in those with elevated levels at baseline and in those people with a higher soya intakes of >30g/day. Soya was also able to reduce systolic blood pressure in those with hypertension (>135mmHg). Favourable effects were more apparent in studies that lasted longer than 8 weeks.
There are so many reasons to add soya to the diet, including swapping cow’s milk for soya milk. There is conclusive evidence that soya does not affect fertility nor does it adversely affect hormone health. However, there is good evidence that soya consumption can reduce the risk of heart disease and cancer and support good bone health. The doses used in the current study were quite small, given that a portion of soya is considered to be 80g.
WHOLE GRAINS IMPROVE CARDIOMETABOLIC HEALTH: Whole grains are defined as the intact, ground, cracked, or flaked fruit of the grain, that includes the endosperm, germ, and bran. In contrast, refined grains only contains the endosperm and thus much of the beneficial nutrients have been removed. Compared with refined grains, whole grains are higher in fibre, magnesium, vitamin E, potassium. There is also strong evidence to support the consumption of whole grains rather than refined grains for the reduction in risk of cardiovascular disease (CVD), cancer and type 2 diabetes.
This prospective study used data collected from the National Heart, Lung, and Blood Institute (NHLBI) Framingham Heart Study (FHS) Offspring Cohort. The FHS is a long-term, community-based population study, initiated in 1948, with the aim of studying determinants of CVD. In 1971, 5124 offspring of the original cohort were recruited into the Offspring cohort. Participants were assessed regularly with a medical history and physical examination and dietary assessment.
This analysis specifically examined the impact of consuming whole grains, after adjusting for other dietary and lifestyle factors. Whole grains included were barley, brown rice, brown rice flour, buckwheat groats, bulgur, cornmeal, corn flour, millet, oats, oat flour, rye, rye flour and whole wheat flour. Refined grains were refined cold ready-to-eat breakfast cereal (defined as containing <25% whole grain by weight), cooked breakfast cereal (not oatmeal), white bread, English muffins, bagels, muffins, biscuits, white rice, pasta, pancakes,waffles, crackers, and pizza.
The results showed that participants consuming the most whole grains (48g/day or 3 serving/day) compared to those consuming the least (<8g/day and 0.5 servings/day) had less of an increase in waist circumference (greater impact in females), fasting glucose, systolic blood pressure at every 4 year interval of assessment. Whole grains were also associated with increases in HDL cholesterol and lower triglycerides. The opposite was true for refined grain consumption.
The impact on waist circumference was independent of overall body mass index and over the 18 years follow up it amounted to a difference of 8cm in waist circumference. Prior studies have shown that a 1cm increase in waist circumference increased the risk of CVD by 2%. The authors conclude ‘Among middle- to older-age adults, replacing refined gains with whole grains may be an effective dietary modification to attenuate abdominal adiposity, dyslipidaemia, and hyperglycaemia over time, thereby reducing the risk of cardiometabolic diseases’.
There is such a wide variety of whole grains to choose from and variety is a key component of a healthy diet. Variety in the diet improves the range of nutrients obtained and also improves the health of the gut microbiome.
DIET QUALITY, MEAT AND MULTIPLE SCLEROSIS: Interest in the impact of diet on multiple sclerosis (MS) is growing. Given the chronic, progressive nature of this condition, patients have been exploring diet and lifestyle approaches without much support from the medical community for while. However, there is increasing acknowledgement that controlling body weight, inflammation, dyslipidaemia and improving the health of the gut microbiome through the adoption of healthy lifestyle habits may be an important management strategy. In addition, last week I covered the impact of a healthy diet, including fruits and vegetables, on mental health and well-being. When it comes to diet, there are two main dietary approaches. Both avoid the consumption of processed foods. The Wahls protocol is a more paleo-style diet emphasising organic, grass-fed meat plus lots of fibre-rich vegetables, whilst limiting starchy vegetables and whole grains. The Swank, overcoming MS and Mcdougall protocols are varying degrees of a plant-based diet, limiting saturated fat, meat and dairy whilst emphasising whole plant foods. This is a nice review of the current dietary approaches.
The current paper adds extremely useful evidence to the literature. It reports the findings of a prospective analysis of diet and disability, clinically significant fatigue, and depression risk in an international cohort of people with MS followed over a 2.5-year period. The analysis includes 1,346 participants, the majority of whom had relapsing-remitting MS (68%). Interestingly, around 40% of participants did not consume meat or dairy.
The results showed that the a higher quality diet with greater consumption of fruits, vegetables and fibre was associated with less disability, fatigue and depression. In addition, the consumption of meat was associated with a significantly increased risk of disability, with dairy also showing some association but not as strong.
There are plausible mechanisms for this finding, the main one being that a fibre-rich diet, low in meat improves the health of the gut microbiome and therefore would have benefits for restoring the immune system. The authors conclude ‘This suggests some promise for healthy and particularly high-fibre plant-based diets in altering the immune profile and thereby moderating clinical progression in MS’. Of course this type of study can not prove cause and effect but the results are compelling nonetheless. Prior results from this same study cohort, Health Outcomes and Lifestyle In a Sample of people with Multiple sclerosis (HOLISM), can be found here.
There are a number of anecdotal cases amongst the plant-based community, including our own group, of a plant-based diet improving if not halting the progression of MS. Dr Saray Stancic, now working at PCRM, has documented her remarkable story of healing from MS in the documentary Code Blue and her book What’s Missing From Medicine. It is great to see the medical literature catching up with these records of personal experience.