Does a yoghurt a day keep diabetes away?

Even if this probably is a good news story, an initial caveat is justified. Establishing a causal link between consumption of an individual food product, like yoghurt, and a specific disease is fraught with challenges. It could be a statistical anomaly or covariant factors that were responsible for the effects but not possible to be eliminated during the statistical analysis. In this study, also the authors point out that to confirm the findings controlled studies would be necessary.

With this caveat out of the way, researchers from Harvard School of Public Health found that a high intake of yoghurt seemed to be associated with an 18% lower risk of developing type 2 diabetes. If true, it shows the benefit of having yoghurt as part of a healthy diet.

Facts about the disease

Type 2 diabetes is a chronic condition that occurs when the body doesn’t produce enough insulin, or the body’s cells develop resistance to insulin. The condition has a strong genetic background and is also often associated with modifiable lifestyle risk factors like an unhealthy diet and lack of exercise. Type 2 diabetes usually develops in middle age adults but is increasingly occurring in younger age groups. The Harvard researchers pointed out that about 366 million people are affected by type 2 diabetes worldwide and it is estimated that this will increase to 552 million people by 2030, which puts pressure on global healthcare systems.

The disease develops over a long period of time with a progressive insulin resistance. As insulin is increasingly ineffective at managing the blood glucose levels, the pancreas responds by producing greater and greater amounts of insulin wearing the insulin-producing cells out. By the time someone is diagnosed with type 2 diabetes, they have lost 50 – 70% of their insulin-producing cells. This means type 2 diabetes is a combination of insulin resistance and not enough insulin.

It might be possible to significantly slow or even halt the progression of the condition by increasing the amount of physical activity and adopting a healthier diet. And here yoghurt might be a part of a healthy diet.

Facts about the study

The Harvard researchers pooled the results of three large prospective cohort studies that have been following the medical history and lifestyle habits of health professionals in the USA for different purposes. At the beginning participants had been asked to complete a questionnaire to gather baseline information on diet, lifestyle and occurrence of chronic disease. Participants were followed up every two years for 16-30 years depending on cohort with a follow-up rate of more than 90 per cent.

In this particular analysis of the cohorts results, the researchers excluded participants with diabetes, cardiovascular disease or cancer at baseline as well as lack of response to the question on dairy consumption as this was the target for the analysis. This resulted in a coverage of almost 195,000 remaining participants aged between 25 to 75 years for the analysis.

Study benefits included the large sample size, high rates of follow up and repeated assessment of dietary and lifestyle factors.

What did they find?

Within the three cohorts 15,156 cases of type 2 diabetes were identified during the follow-up period. While adjusting for chronic disease risk factors such as age and BMI as well as dietary factors, the researchers found that total dairy consumption had no association with the risk of developing type 2 diabetes. They then looked at consumption of individual dairy products, such as skimmed milk, cheese, whole milk and yoghurt and found that high consumption of yoghurt was associated with a lower risk of developing type 2 diabetes.

To confirm their results the authors conducted a meta-analysis, incorporating their results with results from a few other published studies that also investigated the association between dairy products and type 2 diabetes. Overall they concluded that consumption of one 28g serving of yoghurt per day was associated with an 18% lower risk of type 2 diabetes.

So overall some good news.

What to think of the findings?

While an 18% improvement might not sound that much every bit helps. It is extremely rare to find any food that can have a major impact on a particular health condition. What comes to mind is vitamin C rich foods like oranges that can fully protect against scurvy, but not much else. An overall healthy diet is more important than individual food components and of course yoghurt can be part of that healthy diet.

There are other support for yoghurt consumption. In 1904, four years before he jointly won the Nobel Prize in Physiology or Medicine for his research in immunology, Professor Elie Metchnikoff gave a public lecture in Paris. He suggested that beneficial healthy bacteria could be cultivated in the gut by eating yoghurt or other types of sour milk. He had surveyed 36 countries and found that more people lived to the age of 100 in Bulgaria, a high yoghurt consuming country, than anywhere else.

Later research has shown that probiotic bacteria found in yoghurt improves fat profiles and antioxidant status in people with type 2 diabetes and suggest this could have a risk-lowering effect in developing the condition.

You be the final judge, but a little yogurt every day is probably not a bad thing!

Low-fat yoghurt anyone?

Low-fat yoghurt good for health claim researchers

Low-fat yoghurt good for health claim researchers

I’m a fan of low-fat Greek yoghurt so of course I had to take note when British researchers claim that eating 80 g/day can prevent the development of type 2 diabetes. They had selected 4,255 men and women for the study from a larger cohort of 25,000 involved in the EPIC-Norfolk study. This included 753 people who developed type 2 diabetes over 11 years of follow-up and 3,502 randomly selected people for comparison.

But hang on there, isn’t EPIC the European Prospective Investigation into Cancer and Nutrition? One of the type of epidemiological studies that I am very suspect of in relation to diet correlations. Well, yes but maybe this time they could be right.

Actually, they had abandoned the typical food frequency questionnaire (FFQ) that is commonly used to record food consumption and replaced it with a prospective 7-day food consumption diary. I think the FFQ is a joke and should not be used for serious food studies. Of course the diary method is a big step forward. Still it was used only once to capture food consumption during a single week and 11 years later they tried to link this ancient food pattern with the development of type 2 diabetes. A little suspect!

So what did they find?

According to the results, eating a normal portion of yoghurt could reduce the risk of developing diabetes by 28%, compared to eating very little or no yoghurt at all. Expanding that to any low-fat fermented dairy product, such as low-fat cheese, still cut the risk by 24%.

In public-health terms this would involve consuming 4.5 standard-size portions (125 g) per week of low-fat fermented dairy products, mainly yoghurt and unripened cheese such as cottage cheese and fromage frais.

The researchers also looked at diets containing cake, pudding, biscuits, or chips and concluded that eating yoghurt instead of such snacks resulted in a 47% lower risk for diabetes. No other food substitution resulted in a significant reduction in diabetes risk.

To be plausible there has to be a reasonable mechanism that can explain the results. In this case it could be due to promotion of the synthesis of menaquinone (vitamin K2), which has been linked to reduced rates of type 2 diabetes, or the actions of probiotic bacteria, which have been found to improve lipid profiles and antioxidant status in patients with type 2 diabetes.

Read the nutrient information panel

Be careful with the sugar content (Photo: Judy van der Velder)

Be careful with the sugar content (Photo: Judy van der Velder)

Before you jump on the low-fat-yoghurt bandwagon just a few reflections. The first relates to the cut-off level for fat used by the researchers. They considered products with less than 3.9% fat as low-fat. In Australia, full-fat yoghurt commonly contains 3.4% fat except for Greek and European style yoghurt. Also, if you read the ingredient list for low-fat yoghurt you will find that the fat is commonly replaced with sugar and the actual energy level might even be increased. So be a bit careful in the brand of yoghurt you go for.

But who am I to spoil the fun. The researchers were pleased to note that while other research looked at certain foods that raise health risks, such as consuming high amounts of added sugar, they were happy to report on foods, like yoghurt and low-fat fermented dairy products, that could be good for our health.

A good news story among all the doom and gloom.

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Madness in blaming acidogenic food

Here we go again, you do think that some myths proven wrong would disappear. But not so. This time it is a dubious epidemiological study (yes I know I have a bias against spurious epidemiological results) that is claiming a relationship between acidifying foods and diabetes without a believable mechanistic theory to explain the results.

Let’s start from the beginning to better understand why the researchers even thought about testing the influence of so called acid producing foods on the development of type 2 diabetes.

Body regulation of pH

The pH of different items (Illustration: Edward Stevens)

The pH of different items (Illustration: Edward Stevens)

In the early 20th century nutritionists coined the term acidic and alkaline diets describing a group of foods that was supposed to be able to affect the pH of bodily fluids like blood and urine. As I am sure you know acidity-alkalinity is expressed on a pH scale with 7 as neutral between the two. A pH of 0 is completely acidic, and a pH of 14 completely alkaline. Blood happens to be slightly alkaline, with pH maintained in a very close range of between 7.35 and 7.45. The theory of the alkaline diet proposed that eating certain foods would help maintain the body’s ideal pH balance to improve overall health. But we now know that the body maintains its pH balance regardless of diet. This is very important and thus precise regulatory mechanisms make sure there are no deviations.

But pH is not constant across the body. On the contrary, the stomach has a pH ranging from 1.35-3.5. It must be acidic to aid in digestion. Urine can also be acidic and this is the one area in which the diet may affect the pH level. The role of the diet and its influence on the acidity of urine has been studied for decades. Urine excretion is actually a clever way of balancing our overall body pH.

Diet will not influence blood pH

Next we should look at the purported acidic and alkaline diets. And this is not as easy as it sounds. You would think that the acid in foods like lemons, grapefruit and even tomatoes would cause the trouble, but this is not the case. Instead, it is claimed that meat, fish, poultry, dairy products, processed foods, white sugar, white flour, alcohol and caffeine produce acid in the body after they’ve been digested. On the contrary, the alkaline diet is mostly vegetarian. In addition to fresh vegetables and some fresh fruits, alkaline-promoting foods include soy products and some nuts, grains, and legumes.

There’s no doubt that replacing sausages and potato chips with fruits and vegetables is good for you. But this has nothing to do with the alkalinity of the diet, rather basic facts about nutrition and physiology. No matter what we eat, the pH of our blood is going to stay the same.

The term “alkaline diet” has been used by alternative medicine practitioners, with the proposal that such diets treat or prevent cancer, heart disease, low energy levels as well as other illnesses. These claims are not supported by medical evidence and make assumptions about how alkaline diets function, contrary to current understandings of human physiology. The “acid diet” has also been considered a risk factor for osteoporosis, though more recently, the available weight of scientific evidence does not support this hypothesis.

The new epidemiological results

Diet and diabetes studied in 10,000 women (Photo: The Advocacy Project)

Diet and diabetes studied in 60,000 women (Photo: The Advocacy Project)

Now researchers propose that an acidic diet may be associated with up to a 56% increased risk of type 2 diabetes. They followed more than 60,000 women over 14 years in order to assess whether dietary acid load impacted later risk of type 2 diabetes. At the beginning of the study the women had to complete a food frequency questionnaire. From the collected dietary data they calculated a potential renal acid load at that time and then followed the women for 14 years recording new cases of diabetes. Assuming that their diets stayed the same over that long time span, they concluded that dietary acid load 14 years ago was linked to increases in the incidence of type 2 diabetes.

While there have been recent improvements in recognising different variables that can affect acid excretion in urine, the level of detail needed to predict the urinary pH based on diet is still daunting. Precise calculations require very detailed knowledge of the nutritional components of every meal as well as the rate of absorption of nutrients, which can vary substantially from individual to individual, making effective estimation of potential renal acid load very difficult.

Although the research team attempted to adjust for confounding factors, there could be many other reasons for their findings. Intake of various macronutrients and food categories were very different across the diet groupings. The high acid group consumed the least magnesium and magnesium has previously been inversely linked to type 2 diabetes. The high acid group consumed the fewest vegetables. Although the evidence is somewhat unclear, vegetable intake is usually associated with a reduced risk of type 2 diabetes, particularly root vegetables and leafy greens. Coffee is one of those consumables that everyone knows is bad for you but which is actually linked to a number of health benefits, including a reduced risk of type 2 diabetes. The high acid group consumed the least coffee. We could go on and on.

The myth exposed

That diets high in acid producing elements will lead the body in general to become acidic and foster disease goes against “everything we know about the chemistry of the human body” and has been called a “myth” in a statement by the American Institute for Cancer Research. Unlike the pH level in the urine, a selectively alkaline diet has not been shown to cause a sustained change in blood pH levels, nor to provide the clinical benefits claimed by its proponents. Because of the body’s natural regulatory mechanisms, which do not require a special diet to work, eating an alkaline diet can, at most, change the blood pH minimally and transiently.

What you eat can have a profound affect on your health, but the acidity or alkalinity of foods is not important. As has been stated in another blog, eat your vegetables and fruits. Get your micronutrients and plant polyphenols. Drink your coffee. Try not to eat so much food that you gain weight and overload your cells’ ability to handle the energy. Exercise consistently and intelligently. And you will be fine without worrying about acid producing food.

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