Review of the plant-based nutrition and lifestyle medicine news May 2024
I was spoilt for choice this month as there have been some superb papers. I link to ones that I haven’t been able to discuss at the end. I cover genetics vs lifestyle, plant-based diets for cardiovascular disease and cancer, harms of animal-based low-carb diets, ultra-processed foods and dietary factors in multiple sclerosis.
GENETIC VERSUS LIFESTYLE FACTORS: We are always asked how modifiable lifestyle factors impact genetic predisposition to certain conditions. This paper is the first to investigate the joint association of genetic risk and lifestyle factors with human lifespan.
The study analysed data from participants in the UK Biobank study. 353, 742 adults were divided into three groups based on a polygenetic risk score for lifespan: favourable (23.1%), intermediate (55.6%), and unfavourable (21.3%). Lifestyle factors were used to create a healthy lifestyle score. This included no current smoking, moderate alcohol consumption, regular physical activity, healthy body shape, adequate sleep duration, and a healthy diet. Participants were categorised into favourable, intermediate, and unfavourable lifestyles. Of note, a healthy diet was defined as the following: Fruits: ≥ 3 servings/day, Vegetables: ≥ 3 servings/day, Fish: ≥2 times/week, Processed meats: ≤ 1 times/week, Unprocessed red meats: ≤ 2 times/week, Whole grains: ≥ 3 servings/day, Refined grains: ≤2 servings/day.
Over a median follow-up of 12.86 years, there were 24, 239 deaths. The results showed that genetic risk and lifestyle scores were independently associated with lifespan. A high genetic risk resulted in a 21% increased risk of death compared with a low genetic risk and this was independent of lifestyle factors. An unfavourable lifestyle was associated with an approximately 78% increased risk of death compared with a favourable lifestyle within and across genetic risk categories. When assessing both genetic risk and lifestyle scores, those with a genetic propensity for a short lifespan and an unfavourable lifestyle had 104% higher rates of death. In contrast, individuals with a genetic propensity for a short lifespan but a favourable lifestyle had 54% lower rates of death than those with a genetic propensity for a short lifespan and an unfavourable lifestyle. The life expectancy at 40 years was 52.5 years for participants with a genetic propensity for long lifespan and a favourable lifestyle and was 45.8 years for participants with a genetic propensity for short lifespan and an unfavourable lifestyle with a mean difference of 6.7 years in lifespan. Among individuals with a genetic propensity for short lifespan, those with a favourable lifestyle would have 5.2 years longer of lifespan than those with an unfavourable lifestyle.
So what do all these figures mean? The authors state ‘Adherence to healthy lifestyles could largely attenuate the genetic risk of shorter lifespan or premature death’. Overall, the genetic risk of a shorter lifespan or premature death might be offset by a favourable lifestyle by approximately 62% adding around 5 years to life.
These results speak to the common refrain ‘Genetics load the gun but lifestyle pulls the trigger’.
GAINS IN LIFE EXPECTANCY (LE) FROM DIETARY MODIFICATION: This study also assesses the impact of lifestyle on LE but models’ dietary modification alone rather than all lifestyle factors. Specifically, the study aimed to estimate the increase in LE resulting from the transition from typical national dietary patterns to longevity-optimising dietary changes, more feasible dietary modifications, or optimised vegan dietary changes in China, France, Germany, Iran, Norway, the United Kingdom, and the United States.
The authors used data from their previous study which modelled the impact of a healthy diet on LE. A longevity diet was defined as one that is higher intake than a typical diet in whole grains, legumes, fish, fruits, vegetables, and includes a handful of nuts, while reducing red and processed meats, sugar-sweetened beverages, and refined grain. Shifting to such a diet at any age was shown to result in a longer lifespan with the earlier the change the greater the number of years added. At age 20 years, shifting to a longevity diet is expected to result in an extra decade of healthy life. The greatest gains were seen for those consuming more legumes, whole grains and nuts and the least red and processed meat. The authors have created this Food for Healthy Life calculator that can be used to assess the impact of various foods on lifestyle expectancy.
The current study modelled the impact of shifting from the typical diet of the seven countries listed to either a longevity diet as defined in their original study, a feasible diet (halfway between Western and longevity diets) and a fully vegan diet. The results showed that shifting from the typical country-based diet to a longevity diet at the age of 40 years increased LE by 6.2 to 9.7 years and shifting to a vegan diet increased LE by 5.2 to 8.7 years. Shifting to a feasible diet resulted in an increased LE of 2–4 years. Once again, consuming more legumes, whole grains and nuts and least red and processed meat resulted in the greatest gains. The slightly greater LE of the longevity diet was as a result of including fish, however the authors note that a vegan diet has benefits that go beyond just individual health. A vegan diet has considerable benefits for planetary health and the animals and also reduces food costs. Including fish in the diet, significantly increases the cost of food shopping and of course the fishing industry is hugely unsustainable.
For me this study is reassuring as it confirms that an optimised vegan diet has significant longevity benefits compared to the current commonly consumed diet patterns in seven high- and middle-income countries. There is only a small difference in longevity compared to the longevity diet that includes fish that may well be negated by the other positive impacts of a vegan diet.
PLANT-BASED DIETS FOR CARDIOVASCULAR HEALTH AND CANCER: The plant-based and vegan community are sometimes guilty of suggesting that a vegan or plant-based diet is a cure all for all chronic conditions. We should be careful not to over-exaggerate the available data because this detracts from the fact that we have pretty of robust data demonstrating the power of a plant-based diet for preventing our top killers — cardiovascular diseases (CVD) and cancer.
This huge study brings together all the available data on the impact of vegetarian and vegan diets, termed here as animal-free and animal-products free diets, on the risk factors associated with the development of cardiometabolic diseases, cancer and their related mortalities. The analysis included 49 studies spanning two decades of research from 1st January 2000 to 31st June 2023. It found that vegetarian and vegan diets (compared to omnivorous diets) are significantly associated with a better lipid profile (lower total and LDL-cholesterol), glycaemic control (lower fasting glucose and HbA1C), body weight/BMI, inflammation (lower C-reactive protein), and lower risk of ischaemic heart disease (15–40% reduction in risk) and cancer (13–20% risk reductions). For cancer risk there is inconsistency in the data with regards cancer types, but there is a more consistent association with lower rates of gastrointestinal cancer for those consuming a meat-free diet. A vegetarian diet is also associated with lower mortality from CVDs, both ischaemic heart disease and stroke (12–29% reduction). There were no studies assessing CVD and cancer mortality in vegans. The impact on HDL-cholesterol and triglycerides, systolic and diastolic blood pressure levels remain variable. Vegetarian but not vegan diets also reduce ApoB levels. No difference in the risk of developing gestational diabetes and hypertension were reported in pregnant women following vegetarian diets.
Overall, this study demonstrates the consistency of data supporting the benefits of animal-free diets on cardiovascular risk factors, cardiovascular diseases and cancer. There are more studies conducted in vegetarians than vegans. Diet quality is key when considering the impact of meat-free diets and this might account for some of the variation in results between studies. The authors do warn that there was heterogeneity in the quality of studies included in the analysis and hence we need to be cautious about the interpretation.
LOW-CARB HIGH-FAT DIETS (LCHF) AND CARDIOVASCULAR DISEASE: With all the available data supporting a shift to a plant-based diet for better cardiovascular health, it remains a mystery why LCHF diets are still so popular.
This study investigated the association between a LCHF dietary pattern with blood lipid levels and incident major adverse cardiovascular events (MACE — unstable angina, myocardial infarction, ischaemic stroke, peripheral arterial disease, and coronary and carotid revascularisation). The study used data from the UK Biobank cohort with participants followed for 12 years. Participants completed a validated self-administered, web-based 24-hour dietary recall. A LCHF diet was defined as reporting <100 g of carbohydrates per day and/or <25% total daily energy from carbohydrates and >45% total daily energy from fat (n=2,034). Individuals not meeting these criteria were classified as consuming a standard diet (SD — n=8,136). Diet was reassessed during follow-up as well. Blood samples were analysed for lipids and ketones. Participants were also tested and categorised as having or not having a high low-density-lipoprotein cholesterol (LDL-C) polygenic risk score (PRS) for familial hypercholesterolaemia-causing variants.
The results showed that the LCHF diet group had higher levels of LDL-cholesterol (LDL-C), non–high-density lipoprotein cholesterol, and apolipoprotein B. Also, a greater proportion of the LCHF group had hypercholesterolaemia relative to the SD group as per LDL-C and apolipoprotein B criteria. Where data were available, the LCHF group also showed higher levels of ketone bodies. Individuals reporting an LCHF diet were 2.18 times more likely to have a MACE than participants reporting a SD after adjusting for race/ethnicity, income, education, and CVD risk factors (diabetes, body mass index, hypertension and smoking). Individuals reporting a LCHF diet with LDL-C levels ≥5 mmol/L (equivalent to ≥193.4 mg/dL) had the greatest risk of atherosclerotic cardiovascular disease (6.68 times risk).
Regarding genetic background, individuals with a high PRS reporting an LCHF diet demonstrated the highest LDL-C levels and the greatest proportion of individuals with hypercholesterolemia (32.3%). A significant interaction was reported between dietary pattern and PRS that confirmed individuals reporting an LCHF diet with a high PRS had higher LDL-C levels compared to participants with a non-high PRS.
Overall, these data confirm that a LCHF diet increases blood cholesterol and the risk of cardiovascular diseases. The impact is worse for those at higher genetic risk for hypercholesterolaemia. However, it was noted there was individual variability in response to a LCHF diet, so not all people eating this way had an elevated cholesterol level.
These results really should put animal-based LCHF diets into the history books. When we know that plant-based diets reduce the risk of developing high cholesterol levels and CVDs, why would we consume an animal-based LCHF diet. Please do not listen to those that tell you a high blood cholesterol does not matter. It does, and it significantly increases the risk of CVD. The concerns around cholesterol levels being too low and increasing the risk of haemorrhagic stroke have been discounted so the lower your LDL-cholesterol level the better for overall health. There may be benefits for some people in lowering carbohydrate intake when consuming a plant-based diet. Here the fat is from plant sources and hence mainly unsaturated and beneficial for blood lipid levels.
PLANT-BASED DIETS AND PROSTATE CANCER: There are a number of studies demonstrating the benefits of plant-based diets (PBD) for men’s health, especially when it comes to prostate cancer risk. I have summarised the available data in this article.
This study is useful as it specifically assesses the impact of a PBD as defined by the plant-based dietary index on progression of prostate cancer once a diagnosis is made.
The study included 2062 men from the US enrolled in the Cancer of the Prostate Strategic Urologic Research Endeavor study with biopsy-proven non-metastatic prostate cancer. Diet was assessed at a median of 31.3 month after the diagnosis of prostate cancer and participants were followed for a median of 6.5 years after the dietary assessment.
The results showed that participants most adherence to an overall PBD had a 47% reduction in risk of cancer progression compared to those that were least adherent. Restricting the overall analysis to a healthy PBD did not seem to have an impact, however for those with the most more aggressive type of prostate cancer, adherence to a healthy PBD reduced the risk of progression by 55%.
The authors conclude ‘higher intake of plant foods after prostate cancer diagnosis was associated with lower risk of cancer progression. These findings suggest nutritional assessment and counselling may be recommended to patients with prostate cancer to help establish healthy dietary practices and support well-being and overall health’.
It is interesting to note that even those described as eating a healthy PBD were only consuming 1.1 portions of whole grains, 2.1 portions of fruit, 3.8 portions of vegetables, 0.4 portions of nuts per day and 0.1 portion of legumes per day. This is hardly what we would describe a healthy PBD. They were however eating half the amount of meat, dairy and eggs compared to those least adherent to a plant-based diet. The authors state that they did not assess the impact of an unhealthy PBD as this would not be recommended for improving health. This shows that any shift any from animal-source foods and increase in plant food consumption will benefit those with prostate cancer.
DIETARY FACTORS AFTER A DIAGNOSIS OF COLORECTAL CANCER (CRC): Along with the paper above on prostate cancer, this new analysis on CRC adds to the literature on the role of PBDs for improving outcomes after a diagnosis of cancer. The latest review on the topic suggests that PBDs may be beneficial but better quality evidence is still needed.
The current analysis come from the Global Cancer Update Programme and hence is robust and trustworthy. The analysis included 5 randomised controlled studies and 35 observational studies (30,242 cases, over 8700 all-cause and 2100 colorectal cancer deaths, 3700 progression, recurrence, or disease-free events) on post-diagnosis dietary factors, supplement use and colorectal cancer survival outcomes. Meta-analyses were conducted for: whole grains, nuts/peanuts, red and processed meat, dairy products, sugary drinks, artificially sweetened beverages, coffee, alcohol, dietary glycaemic load/index, insulin load/index, marine omega-3. polyunsaturated fatty acids, supplemental calcium, circulating 25-hydroxyvitamin D (25[OH]D) and all-cause mortality. In addition, analyses of alcohol, supplemental calcium, circulating 25(OH)D and colorectal cancer-specific mortality and for circulating 25(OH)D and recurrence/disease-free survival were conducted.
The results showed that the evidence remains limited in this field of study. However, overall the analysis suggested that consuming a healthy diet pattern defined as high intakes of fruits and vegetables, whole grains, nuts and legumes, and low intakes of red and processed meat, was associated with improved overall survival after colorectal cancer diagnosis. Food items associated with better prognosis included whole grains and coffee and with worse prognosis were sugar-sweetened beverages.
The authors conclusions are cautious but for me there is no downside in recommending a healthy plant-based or plant-predominant diet for people living with or beyond a cancer diagnosis. The benefits for cardiometabolic health alone are sufficient to make this recommendation and there is likely benefit for reducing the risk of developing a second cancer.
ULTRA-PROCESSED FOODS (UPF) AND MORTALITY: This large analysis adds to the growing amount of data on the health harms of UPF consumption. However, the mainstream narrative often lacks nuance. Not all UPFs are created equal and therefore each food or item should be assessed on its own merit based on its nutrient profile. For example, a plant-based milk alternative is considered a UPF, but it adds useful nutrients to a PBD and there is no evidence to suggest any associated harm.
This analysis is useful as it considers different subgroups of UPF consumption in over 100,000 participants of the Nurses’ Health Study and the Health Professionals Follow-up Study. During the more than 30 years of follow-up there were 30, 188 deaths of women and 18, 005 deaths of men. The results showed that UPF consumption had a small increase in mortality (4–9%) but from causes other than cardiovascular disease and cancer. In addition, it was meat/poultry/seafood based ready-to-eat products that showed the strongest and most consistent associations with mortality. However, this association was attenuated after adjusting for diet quality, using the Alternate Healthy Eating Index. Thus the authors conclude that ‘dietary quality has a predominant influence on long term health, whereas the additional effect of food processing is likely to be limited’.
The current narrative around UPFs is alarmist and is pushing people away from eating foods such as whole grain breads and cereals that can promote better health. Most of the available data shows that the biggest contributors to poor health come from the consumption of processed meat, sugar-sweetened beverages and cakes/fried foods/desserts. A large analysis published in 2023 confirmed these findings but also analysed the impact of plant-based meat and dairy alternatives and did not find a negative impact on health.
The narrative around UFPs is being used to negative frame a plant-based or vegan diet. To learn more, have a listen to this excellent podcast episode from In a Nutshell. Jenny Chapman, who is being interviewed, has written the report called Processing The Discourse Over Plant-Based Meat — a must read.
DIET FACTORS AND MULTIPLE SCLEROSIS: There is growing interest in the role of diet and lifestyle approaches for improving outcomes for people living with MS. I recently wrote about the impact of health habits and I have previously dedicated a news review to the topic of diet and MS, which included our publication of two case histories.
We have learnt a lot on the topic of diet and lifestyle for MS from the HOLISM study and this is the latest analysis from the longitudinal cohort. The study reports specifically on the impact of dietary factors on fatigue and disability in 839 participants living with MS. The mean age of the participants was 46 years and duration of MS was 7–12 years. In addition to assessing diet quality using the Diet History Questionnaire, specific questions were asked about the consumption of meat and dairy (including capturing information on those that did not consume meat and dairy), omega-3 fats from fish, fish oil or flaxseed oil and use of vitamin D supplementation.
The analysis found that a higher quality diet, consumption of omega-3 fats, vitamin D supplementation and avoidance of meat and dairy consumption were all associated with a reduced risk of progression and lower rates of fatigue and disability.
Diet and lifestyle modification is slowly but surely becoming a key part of management of MS. This has been spearheaded by the international charity, Overcoming MS. Their dietary recommendations are in line with the evidence supporting a plant-based diet with additional omega-3 fats from fish, fish oils or high strength flaxseed oil and vitamin D supplementation. They also pay attention to all pillars of lifestyle medicine.
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Addition papers that did not make it into this weeks review but useful to know about: Protein intake and sleep quality; Flavonoid intake and risk of type 2 diabetes; Advancing Lifestyle Medicine in New York City’s Public Health Care System.
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