Walter Willett World Nutrition Talk
Nutrition, February 19, 2020
These notes from Prof Willett's presentation at the EAT Stockholm Food Forum give holistic guidelines on what to eat for global well-being
- Identify dietary patterns that provide optimal health and well-being to the worlds population
- Recognising the dual burden of over and under nutrition
- To take into account environmental sustainability - look at Green House Gas (GHG) production, water and land use, maintain biodiversity and prevent antibiotic resistance.
Walter wanted to focus on the chronic disease link to nutrition. From the Global burden on health analysis statistics coronary heart disease (CHD) is the number one cause of death around the world. The incidence of diabetes (a great indicator of the metabolic state of the worlds population) has doubled in the last 20 years world wide.
Diabetes is the precursor to many other conditions. The worrying aspect of these trends is there is the possibility that they could continue to double. In the USA 50-70% of all American Indians have diabetes so there is no reason why this can't happen in many other parts of the world with present trends.
Types of studies of evaluating DIET and HEALTH
4 Randomised trial - controls confounding but costly and adherence to diet over many years is difficult.
Most of what we know about diet and it's link to health is taken from a combination of cohort and feeding studies. Examples of large cohort studies by Harvard are the Nurses Health study started in 1976 (121,700 subjects), health professionals follow up study started in 1986 (52,000 subjects), and the nurses health study II started in 1989 with 116,000 subjects. These are some of the most detailed studies on diet and health - gathering data about diet every 2 years and controlling for smoking and physical activity.
There are now several dozen large cohort studies being conducted around the world adding further information about diet and health. The most unhealthy component of total kcal in the typical western diet is "unhealthy" carbohydrates" (highly processed with sugar and fat added). Looking at types of dietary fat and the risk of CHD, trans fat is by far the worst (80% change in CHD compared to less than 20% change with saturated fat BUT monounsaturated and polyunsaturated fat were correlated with a LOWER risk of CHD)
In terms of dietary protein sources our choices have major implications for the environment as well as health Replacing red meat with other sources of protein is one of the strongest protections of risk for CHD. It was also shown to protect against type 2 diabetes then swap red meat for beans, lentils, and complex whole grains (this is also better for the planet)
Carbohydrate quality is extremely important in relation to health as carbs are the major source of kcal in almost every diet around the world. The quality can be assessed with looking at 2 dimensions of carbohydrates. Quality is improved with more fibre and with a lower glycemic load (slower conversion into sugar). So if you have a high glycemic load and low fibre (more refined grain for example) this will increase the risk of type 2 diabetes.
If you are lean and active then you can metabolise carbohydrates with less insulin. If you have a higher BMI then you respond with poor metabolic efficiency to carbohydrates. The same diet will effect people in different ways according to BMI.
Fruit and vegetable intake has been shown to be very beneficial for health especially with CHD.
The ecological footprint of dairy production is VERY large (GHG emission, land and water use) even when produced as efficiently as possible. There is no relationship between milk consumption and bone health. In fact many high dairy consuming countries have the worst fracture risk (eg Sweden, USA, and New Zealand). It is also falsely thought that growing children need to consume dairy for bone development - in fact for women there is NO benefit and for men in may actually INCREASE the risk for fractures later in life.
GLOBAL healthy diet can be defined by 4 primary elements
- Proteins mainly from plant based sources - legumes, nuts, seeds, and fish, modest amounts of poultry and dairy. Red meat very sparingly at most and processed meat AVOIDED.
- Healthy fats from unsaturated sources rather than saturated plus look at Omega 3 (algae, chia seeds, walnuts) - PLANT (avocados, nuts, seeds, cacao etc) rather than ANIMAL derived.
- Whole grains and minimal amounts of refined grains and sugar.
- GENEROUS and varied intake of fruits and vegetables
When looking at effect on our planet then we need to be getting our majority of kcal from plant sources over animal sources. Fortunately a healthy diet for us aligns with what is beneficial and sustainable for the planet. The highest emissions for GHG's are lamb, beef, and milk production, and the lowest are lentils, beans, and tofu (an exception is chicken BUT I am not promoting this as large amounts of antibiotics are required for industrial chicken raising)
A healthy diet has less red meat, less dairy, and less processed grain which has less environmental impacts. It is also important to look at crop acreage needed to produce food - the vast majority of crop land to grow cereal grains, wheat, and soy is then feed to animals. Growing animals for food is EXTREMELY INEFFICIENT and also not needed as part of a healthy diet.
-We need to stem our population growth to help with sustainability.
Walter Willett Talk at the EAT forum..........