1 December 2018


While plant-based diets are recommended to reduce the risk of heart disease, some are associated with a higher risk of heart disease, according to a study published in the Journal of the American College of Cardiology.
Plant-based diet
The Harvard researchers created three versions of a plant-based diet: an overall plant-based diet which emphasized the consumption of all plant foods and reduced (but did not eliminate) animal food intake; a healthful plant-based diet that emphasized the intake of healthy plant foods such as whole grains, fruits and vegetables; and a less healthy plant-based diet which emphasized consumption of refined grain products, fries, white bread, sugar-sweetened beverages etc.

“When we examined the associations of the three food categories with heart disease risk, we found that healthy plant foods were associated with lower risk, whereas less healthy plant foods and animal foods were associated with higher risk,” said Ambika Satija, the study's lead author. “It's apparent that there is a wide variation in the nutritional quality of plant foods, making it crucial to take into consideration the quality of foods in a plant-based diet.”

The authors note limitations on their study: it’s observational and based on self-reported diet assessments. It’s very important to remind people that not all plant-based diets are created equal, but we have a couple of quibbles about their lists. They did not look at the overall GI/GL of diets; and their selection of “less healthy” foods which includes the usual suspects leaves out alcohol (they say they adjusted for it), and adds in foods/beverages that current dietary guidelines recommend as good choices in moderation as part of a healthy eating pattern. In particular: 
  • Traditional staples (regular durum wheat pasta and white rice) – often combined with significant portions of vegetables and eaten worldwide by millions of people in healthy meals that are part of their cuisine; and 
  • 100% fruit juices – ½ cup or 125mL is regarded as equivalent to one serving of fruit in Dietary Guidelines. 
No wonder the punters are confused about what to eat – nutrition gurus aren’t consistent with dietary guidelines they help formulate.

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While a predominantly plant-based diet-rich in fruits, vegetables, nuts, legumes, and seeds with no (i.e., vegan) or few animal products has been linked to a significantly lower risk of developing type 2 diabetes, it’s not clear if it might also be linked to improved mood and wellbeing. To try and find out, researchers trawled through the available evidence. The studies involved a total of 433 people in their mid-50s, on average.
Vegan diet
A systematic critical analysis of the results showed that quality of life – both physical and emotional – improved only in those patients on a plant based/vegan diet. Similarly, depressive symptoms improved significantly only in these groups.

Nerve pain (neuropathy) eased in both the plant based and comparator diet groups, but more so in the former. And the loss of temperature control in the feet in those on the comparator diets suggests that eating predominantly plant-based foods may have slowed the progressive nerve damage associated with diabetes, say the researchers.

Average (HbA1c) and fasting blood glucose levels fell more sharply in those who cut out or ate very few animal products and these participants lost nearly twice as much weight: 5.23 kg vs 2.83 kg. The fall in blood fats (cholesterol and triglycerides) – a known risk factor for cardiovascular disease – was also greater in those on plant based/vegan diets.

In six of the studies, those following a plant based/vegan diet were able to cut down or discontinue the drugs they were taking for their diabetes and associated underlying conditions, such as high blood pressure. Overall, the results indicated that even though the plant-based diets were more difficult to follow, at least to begin with, participants stuck to them better than those in the other groups.

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A plant-based diet high in carbohydrates can reduce body weight and body fat and improve insulin function in overweight individuals, according to a study published in Nutrients.
Vegetarian diet
In the 16-week randomized clinical trial, researchers with the Physicians Committee for Responsible Medicine placed participants in either a plant-based, high-carbohydrate, low-fat diet group or asked them to maintain their current diet. The plant-based diet group avoided all animal products and added oils and limited fat intake to 20–30 grams per day. There were no limits on calories or carbohydrate intake. The control group maintained their current diets, which included meat and dairy products. Neither group altered their exercise routines. Total carbohydrate intake did not change in the control group, but increased significantly in the plant-based diet group, both as absolute intake and as a percentage of total calories. Participants in this group focused on whole, minimally-processed carbohydrates from fruits, vegetables, whole grains, and legumes.

At the end of the trial, body mass index, body weight, fat mass, visceral fat volume (fat around the organs), and insulin resistance decreased significantly in the plant-based diet group. There were no significant changes in the control group.

“Fad diets often lead people to fear carbohydrates. But the research continues to show that healthy carbohydrates -- from fruits, vegetables, beans, and whole grains -- are the healthiest fuel for our bodies,” says lead study author Hana Kahleova, M.D., Ph.D., director of clinical research for the Physicians Committee for Responsible Medicine.

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These GI results are from a randomized, crossover study that compared the effects of consuming bite-sized and pureed guava and papaya in 19 healthy participants (9 elderly and 10 young adults) recruited from the general public in Singapore. Glycemic index testing was carried out following the International Standard.

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A recent randomised crossover study conducted in China published in Nutrients demonstrated that medium or low GI dried fruit (dried apples, dried jujubes, dried apricots and raisins), did not raise blood glucose concentrations excessively when consumed as a substitute for a high GI carbohydrate-based food (rice).

Eleven healthy, young Chinese volunteers consumed the test meals in a randomised order on seventeen separate mornings with a one-week wash-out period between each test session. The test meals included: (1) dried fruits containing 50g available carbohydrates; (2) mixed meals consisting of dried fruits and rice each contributing 25 g available carbohydrates; (3) mixed meals consisting of dried fruits and rice each contributing 25 g available carbohydrates supplemented with 30g almonds. Taking the nutrient profile and antioxidants of dried fruits into account, the researchers say they may have the potential of being included into a blood-glucose-managing diet without altering the total carbohydrate intake.

Dried fruit GI values
Tip: Dried fruits generally have low GI values and are a great source of fibre, but the calorie count is much greater than for fresh fruit, so watch portion size. Dried fruit can be very more-ish!

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The kererū pigeon (Hemiphaga novaeseelandiae) was named Bird of The Year in New Zealand, winning the popular vote by a clear margin. This metallic green, grey and white native wood pigeon is renowned for its spectacular aerobatics, the ‘whoosh’ of its wings and its complete lack of self-discipline. Forest and Bird, who organise the annual competition, uses terms like “drunk” and “gluttonous” to describe it because it likes to gorge itself on rotten fruit on the forest floor. Some seasons, the abundance of fermented fruit can leave the pigeons so drunk they end up falling from the trees and having to be rescued.

kererū pigeon
Not a tall story says GI News editor, Philippa Sandall. “Growing up in New Zealand we had a bumper cropping Christmas plum tree in our garden that became jars and jars of jam (great for gifts). But, the tree was such a prolific producer, my mother couldn’t keep up the preserving and plums lay fermenting on the ground. One year we rescued a tipsy thrush who had seriously overindulged. It took him several hours to sober up in a cardboard box to keep him safe from the family cat.