Why be vegetarian - Part 3

Sue Radd

At the fifth International Congress on Vegetarian Nutrition (ICVN), held in March last year at Loma Linda University (California, USA), Professor Walter Willett, a Harvard University-based authority on nutritional epidemiology, presented perspectives on ageing and the impact food choices can have on it.

Ageing isn't just about looking in the mirror to see more wrinkles and greying hair. Speakers at the ICVN were clear that ageing isn't one thing-various changes occur within the body and the search is on to be able to manipulate these changes in a positive fashion.

Key changes that occur during ageing include the loss of lean mass (our muscles), development of insulin resistance, oxidative damage to macromolecules such as DNA, proteins and fats in the body, mitochondrial damage, glycation, telomere shortening resulting in cell death, hardening of the arteries and loss of brain function.

Diet and diabetes

Professor Willett said, "Insulin resistance is right at the root of the list of problems affecting our society, leading to metabolic syndrome-and these feed off each other. For example, as the duration of type 2 diabetes increases, there is a significant increase in the risk of dying from a heart attack-12 times higher than normal after having had diabetes for 25 years.

So how can what we choose to eat help avoid these problems? Many studies have shown that vegetarian diets postpone and reduce the risk of coronary heart disease and, in non-vegetarians, a healthy diet and lifestyle can help people avoid 82 per cent of the coronary heart diseases currently experienced in the world. Now it seems a vegetarian diet can help both those with diabetes and those at risk of developing it.

Plant-based diets work by providing more wholegrains, nuts, legumes, fruits and vegetables, which have been shown in population studies to be linked to a reduced level of insulin resistance. Professor Willett cited a randomised study on the Mediterranean diet, conducted over two years with patients who have insulin resistance. With the Mediterranean diet-one that is high in fruits, vegetables and multigrain products but low in meat products-50 out of the 90 patients experienced a resolution of the syndrome, compared with only 12 out of 90 in the control group.

A Harvard Nurses Health Study also found that 92 per cent of type 2 diabetes is preventable by simultaneously reducing five modifiable risk factors-quitting smoking, keeping your body mass index (BMI) below 25, engaging in moderate to vigorous exercise, keeping alcohol intake very low and having a diet score in the upper 40 per cent.

Ageing and antioxidants

The free-radical theory of ageing was first proposed 50 years ago, and various antioxidant nutrients and plant foods are thought to be important in all parts of the body. Thus, what's good for your eyes is good for your heart and also your brain. As the brain is less protected from oxidation than other parts of the body, it may need even more-or "supercharged"- antioxidant foods.

Dr James Joseph, research physiologist at the Jean Mayer USDA HNRCA Laboratory at Tufts University, presented his findings from studies conducted over several years on high-antioxidant value foods at the ICVN. Foods high in antioxidants include strawberries, blueberries and spinach. In tests conducted in the laboratory, he found that such colourful plant foods retard the onset of age-related declines in brain function and can improve memory.

Calorie restriction or calorie selection?

Dr Donald Ingram, professor and director of the Nutritional Neuroscience and Ageing Laboratory at Pennington Biomedical Research Centre in Louisiana (US), spoke about the challenge of slowing ageing and the possibilities of even "turning back the clock."

Dr Ingram reviewed the evidence that calorie restriction modulates ageing. Research in this field began in the 1930s with Professor Clive McKay at Cornell University, who first showed the lifespan of rats could be significantly extended by giving them less food to eat on a daily basis. While still ensuring people are consuming healthy food and obtaining enough nutrients from it, the message is to eat less to live longer.

The major features of calorie restriction include a reduced incidence and delayed onset of age-related diseases such as heart disease, cancer and diabetes, as well as improved immune function, reduced inflammation, increased stress resistance and better behavioural performance later in life. Several studies are currently being undertaken with humans, and early data shows a reduction in risk factors for these chronic diseases. However, a significant reduction in calories-for example by 30 per cent-is a tough treatment for extending life! Imagine if you were consuming 2100 calories (about 8800 kilojoules) per day-this would mean dropping your intake to 1400 calories (less than 6000 kilojoules) every day!

Dr Ingram posed the question of whether individuals should eat less generally and live longer or eat more specifically to live longer. Making better food choices and eating things with fewer calories, such as fruits and vegetables, could be beneficial in this respect.

Whole plant foods are best

The "blue" zones of the world where the greatest number of centenarians live-such as Okinawa, Sardinia, Costa Rica and even California among Seventh-day Adventists- all enjoy heavily plant-based diets, thought to be one of the main reasons for their exceptional longevity. Such diets are loaded with calorie-restriction mimetics-substances found in plant foods that literally mimic the effects of calorie restriction in the body.

In a session entitled "Food, not nutrients, is the fundamental unit of nutrition" at the ICVN, Dr David Jacobs from the University of Minnesota clearly illustrated that food synergy exists and the effect individuals can expect from whole plant foods is "more than parts of the food or an equivalent cocktail of compounds." It isn't that nutrients have no value but relying on nutrients alone may be fooling people. "Stop trying to make drugs out of this stuff-just eat the foods," he said.

Going nuts

It would have been inconceivable 20 years ago for nuts to be given the same "weighting" as fruits and vegetables in studies allocating dietary scores, Professor Joan Sabate from the School of Public Health at Loma Linda University told ICVN attendees. But today, nuts are known to be associated with positive health outcomes and are starting to be as "revered" as other high-profile plant foods. The first population-based study in the world relating the frequency of nut consumption to lowering heart attack risk was published in 1992 by Professor Sabate, and he presented additional data-published and unpublished-from the past six years.

Nuts protect against heart disease and anyone with cardiac risk factors or a family history should incorporate nuts and seeds into their daily diet. Six years ago, four large population studies showed increased nut intake reduced heart disease risks. The more often nuts were consumed, the stronger the protection. According to Professor Sabate, an 8.3 per cent reduction in heart disease is evident for each weekly serving of nuts.

He and his team at Loma Linda also recently pooled analysis data to examine the effect of nuts on serum lipids. They combined individual data from 25 dietary trials on nuts and found an overall total cholesterol decrease of five per cent.

Nuts also possibly lower the risk of diabetes in women, although it is unknown if they work the same way in men. The Nurses Health Study showed that peanut butter consumption on at least five days per week was linked with a 20 per cent reduced risk of diabetes.

And although nuts are feared by many dieters, they are not related to obesity, according to the latest information. Professor Sabate said new data shows no connection in men but in women, an inverse relationship exists, meaning those who eat nuts more frequently actually have lower BMIs.

In a nutshell, nuts are very good for you.

Environmental benefits of vegetarianism

One of the sessions that generated most interest at the ICVN focused on climate change and food production. Albert Einstein once said, "Nothing will benefit human health and increase chances for survival of life on earth as much as the evolution to a vegetarian diet." This statement is backed up by research conducted by Hal Marlow, professor in the Department of Environmental Health at Loma Linda University, who compared the environmental impacts of a vegetarian diet to a non-vegetarian diet.

Professor Marlow found significant differences in the use of water, pesticides and other markers of planetary health, according to the type of diet followed. Compared to their vegetarian counterparts, Adventist omnivores were estimated to use 810 additional litres of water per week. Modern agriculture is very water intensive-data was shown for  California, where one third of the water expended for irrigation goes to support the livestock industry. In terms of using less water by diet followed, Professor Marlow's study found in favour of vegetarians by a factor of three to one.

Worldwide, 2.5 million tons of pesticides are used annually. The World Health Organisation estimates 1 million pesticide poisonings occur each year, and it has been suggested pesticides may cause cancer and other negative health issues. With regard to pesticides, meat eaters were responsible for an extra four grams per week being applied to plants humans consume and those grown to feed animals for meat production.

Professor Marlow concluded his presentation by stating, "What you eat matters. We have a duty to take care of this planet."

Food choices and greenhouse gases

Dr Annika Carlsson-Kanyama, associate professor for the Energy and Environmental Security Group at the Royal Institute of Technology (Sweden), looked at the life cycle of various food products and how this affects greenhouse gas emissions. The life cycle process is complicated and involves consideration of greenhouse gas emissions at each stage of the food's life, including processing, transportation and storage considerations. To illustrate, Dr Carlsson-Kanyama gave an example of sushi consumed in Sweden. When you eat sushi there, its origin involves fishing outside Chile (to catch food for fish!), farming salmon in Norway, flying salmon to Taiwan to be processed, shipping sushi to Europe and finally selling it in Stockholm.

While carbon dioxide is the major greenhouse gas, Dr Carlsson-Kanyama also considered methane and nitrous oxide-methane is 25 times and nitrous oxide 285 times stronger than carbon dioxide. She calculated emissions of greenhouse gases for 22 food products. These ranged from 400 grams to 30 kilograms per kilogram of food product. Locally-produced vegetables were at the lowest end of the scale, while beef was the most climate-unfriendly item.

Foods creating the least amount of greenhouse gas emissions were mainly vegetarian, unprocessed and could be transported by boat if necessary. Processing foods or transporting them by aeroplane increases the emissions. Initiatives are starting to be seen in Europe, which will advise the public about the likely environmental impacts of various foods. For example, Tesco-the largest supermarket chain in the United Kingdom-will be putting a carbon label on all its 70,000 items sold.

Whichever way you look at it-by water or pesticide usage, or greenhouse gas emissions- the bottom line is that minimally processed plant foods sourced locally and plant-based diets composed of these foods are better for planetary health, as well as the health of its human population.

This is the third of a three-part series looking at aspects of vegetarianism. Visit the ICVN or Sue Radd's website for more information.

This has been a feature from Record, January 31, 2009