I wrote a letter to Straits Times Forum for the first time on May 10 this year; it was followed by another letter two days later. I was trying to defend white rice from the accusation that it is more potent than sugary drinks in causing diabetes.
I never thought my first brush with mainstream media would have been defending white rice, a carbohydrate — the food group of which I eat little.
Let’s get something out of the way to facilitate a productive discussion — we are talking about the fundamental question of what causes diabetes. We are not talking about how and what you should eat to control your blood sugar if you are already diabetic — if you are, the healthcare industry has no shortage of advice and drugs to offer you, so let’s leave that aside for the time being. In addition, we are talking about type-2 diabetes, which accounts for more than 90% of all diabetics.
Straits Times published a follow-up article on May 12 to provide further explanations as to why white rice is targeted in the fight against diabetes. An FAQ was also published a day later to answer questions asked by Straits Times readers.
Therefore, after so much has been said, why do we still need a blog post on this subject? Well, because we owe it to our 400,000 diabetic sufferers in Singapore — there is always room for better understanding and clarity, and the information given so far, in my view, missed the mark. Diabetes is a horrible scourge that needs to be eradicated. In his declaration of war on diabetes, our health minister outlined that the first key prong will be “…to cut down on new diabetes cases.” For that, we need to understand better the likely causes of diabetes and, just as important, not dilute our focus and energy on the unlikely causes of diabetes.
So, let’s examine in detail why white rice is an unlikely cause of diabetes and the merits of the reasons given that it is. Oh, and why the accusation that it is worse than sugary drinks in causing diabetes is really questionable.
White Rice Consumption and Diabetes
If white rice consumption causes diabetes, we would expect a positive association with the amount of rice consumed and the prevalence of diabetes. To recap, here’s some data showing rice consumption patterns and diabetes prevalence for Singapore and China:
Source links: Prevalence, Consumption, Population
Source links: Prevalence, Consumption
Do you see the positive association?
Exactly. Neither do I.
Diabetes rates increased despite a significant drop in rice consumption.
In the follow-up Straits Times article, it was explained:
“… white rice is also a major culprit — largely because it is a staple, so more of it is eaten. Starchy white rice, it has been found, can overload Asian bodies with blood sugar and heighten their risk of diabetes…”
Of course we eat a lot of white rice, because it is our staple! But, we do not eat it as much as the Chinese — as the data above shows, they ate and still eat several times more than we do. Their more overloaded bodies should reflect much higher diabetes rates than ours, right? No, we are now essentially the same: 11.6% versus 11.3%.
For me, the most startling statistics, terrible as they are, are not the high prevalence rates that we see today, but the very low numbers in 1975 for Singapore and 1980 for China — they were very low despite the prodigious amounts of rice consumed, amounts that were even higher than today’s. What new food was introduced into our diet that caused this explosive growth of almost 500% to more than 1,000% in diabetes rates? If we can identify the causative agent and remove it from our diet, would we revert to the good old days of not too long ago?
So, can we agree there were little ill-effects in the past? Below are the counter-arguments given:
“In the pre-industrialisation era, there was a lot more physical exertion. Even in everyday life, people walked a lot more than today. Exercise is known to offset some of the ill-effects of unhealthy food.”
“People did not live as long in the past. In Singapore, for example, life expectancy at Independence in 1965 was only 65 years. Today, Singaporeans are living 20 years longer. This alone provides chronic diseases with a greater opportunity to surface. Among people 65 years and older, one in three is diabetic.”
Okay, there are many good reasons to be physically active. Do we walk less than our pre-industrial ancestors? Perhaps, though, we are likely to exercise more than they did — jogging gained popularity only from the 1970s. A survey shows that in 1992, 13.6% of Singaporeans claimed to exercise regularly (three days or more per week for at least 20 minutes each time) and this rose to 19% by 2010. Another 27% in 2010 also claimed to exercise occasionally — so, today we have a total of 47% that we can argue are somewhat physically active. Anyway, what is the connection to white rice here? Once we do less exercise, the full-blown ill-effects of our centuries-old staple food will show up in the explosive rise of diabetes numbers? I would argue that this is highly unlikely.
An aging population is certainly linked to a prevalence of chronic diseases — not just diabetes, but also hypertension, strokes, lipid disorders, asthma, chronic obstructive pulmonary disease, etc. If the increases were due solely to the effect of aging, we should see significant increases in the data for older populations with little change for younger populations:
Source links: 1975 (estimates derived from different age brackets), 2010 (prevalence data beyond 69 years not available)
Diabetes prevalence for the older population of 60-69 years did rise a significant 387% from 1975 to 2010. But rates for all other younger populations also rose significantly!
How much of the total absolute increase in diabetics is accounted for by the older populations?
Source links: Population, the rest as per Table 3. Prevalence estimate for 70+ assumed to be similar to 60-69 years. Population breakdown for 18-29 years not available so 20-29 years is used.
So, the older 60+ years accounted for 42.8% of the total increase from 1975 to 2010. Then, how do we explain the other 57.3% attributed to the younger populations? An international study of diabetes in nine Asian countries found that one in five adult patients developed diabetes before they were 40 years old, and the average age was 30!
Our longer life expectancy is definitely part of the story in the rise of diabetes for the older age groups. But again, just like exercise, there’s nothing in the data to implicate white rice as either the cause of diabetes or the reason for the explosive increase in diabetes over the past 35 years.
High Glycemic Index (GI) of white rice
A bowl of white rice is said to contain twice the carbohydrate content of a can of soft drink. Also, the GI for white rice is said to be higher than that of soft drinks — meaning it will raise your blood glucose level faster.
So, the GI for white rice is higher than sugar. So what? White rice has been a staple food consumed by many societies for hundreds, if not thousands of years, and our body can handle it very well with no ill-effects. The GI of white rice was not a problem before; why should it be a problem now?
Our diary calories: 1/3 from rice, but sugary drinks only 3.5%
Implicit in this argument is the conventional wisdom that all foods are the same. They can all be reduced to their energy content: a calorie from rice is similar to a calorie from sugar, or from fat, or from protein. All that matters is their caloric content. Therefore, unlike white rice, such drinks cannot be a problem, because only 3.5% of your daily caloric content comes from it.
But the biochemistry, and the consequences, of how our body deals with white rice and sugar are very different. Sugar is half glucose and half fructose. Unlike glucose, which can be broken down by virtually every cell in our body for energy, fructose can only be metabolized by our liver — and the entry of fructose into our liver kicks off a series of chemical processes that can lead to dangerous consequences, the most remarkable one being the buildup of fat in the liver, i.e. nonalcoholic fatty liver disease — similar to what can happen to your liver if you drink too much alcohol.
It can also:
- Elevate triglycerides
- Increase harmful LDL , the “bad” cholesterol
- Increase blood pressure
- Make tissues insulin-resistant, a precursor to diabetes
Yes, it can prime you to become diabetic.
How much sugar do we need to ingest before all these harmful effects kick in?
Well, we don’t really know. For a genetically susceptible population such as ours, is it possible that all it takes is 3.5% of our daily caloric intake from sugary drinks?
How many teaspoons of sugar are we talking about? The mean daily energy intake of an adult Singaporean in 2010 was 2624 kcal.
- 3.5% of 2624 = 92 kcal
- 1 teaspoon = 4g of sugar, and 1g of sugar = 4 kcal
Therefore 92 kcal = 23g of sugar = 5.8 teaspoons, only? Really?
This is less than a can of Coke with 35g of sugar, 8.7 teaspoons!
We have, in fact, some more details from our Health Promotion Board (HPB), where they put the average daily total sugar intake for Singaporeans to be at 11 teaspoons, with the top fifth hitting 18 teaspoons!
- Average = 11 teaspoons = 44g = 176 kcal = 6.7% of daily calories
- Top fifth = 18 teaspoons = 72g = 288 kcal = 11% of daily calories
Anyway, what does genetically susceptible mean? Does it mean that, compared to Caucasians, our risk of getting diabetes is higher when we take in sugar? If this is true, in order to win our war on diabetes, should we:
- Change our character, i.e. let go of our century-old habit of eating white rice, or
- Avoid eating sugar, or
- Conduct definitive studies on the role of sugar in our diabetes epidemic
I would argue that the totality of available evidence today points to (2) for personal action, and (3) for our best and brightest researchers.
Three studies were cited in defense of the attacks on white rice:
- White rice consumption and risk of type 2 diabetes: meta-analysis and systematic review. (Link here)
- Rice and noodle consumption is associated with insulin resistance and hyperglycaemia in an Asian population. (Link here)
- White Rice, Brown Rice, and Risk of Type 2 Diabetes in US Men and Women. (Link here)
The limitation of the first study was noted earlier in my letter to Straits Times. Namely, it was a study of association, not causation. Only white rice was studied, and there was no association analysis with any other food item, including sugar. Nothing in this paper points to white rice as the cause of diabetes. The observed association could very well be confounded by sugar consumption. That is, those that consumed more white rice, did they also consume more sugar?
What is the difference between association and causation? If we did a study to look at the association between body height and different sports, we will most likely find that many basketball players are taller than average. But, you will not conclude from this association that playing basketball will cause you to grow taller.
The second study was also a study of association, with no analysis of sugar consumption. No conclusion can be drawn that white rice, or noodles, causes diabetes.
The third study is also an association analysis and is more interesting. Here are some extracts of the results:
“Men and women who had high white rice intake were less likely to have European ancestry or to smoke and more likely to have a family history of diabetes.”
“…brown rice intake was not associated with ethnicity but with a more health-conscious lifestyle and dietary profile. For example, participants with higher brown rice intake were more physically active, leaner, less likely to smoke or have a family history of diabetes,”
So, the study was comparing a group of genetically susceptible people with family histories of diabetes with a group of health-conscious people who chose to eat brown rice!
The study claimed to carry out secondary analyses to repeat the associations among white participants and found similar results.
Ethnicity aside, imagine for a moment the characteristics of people who chose to eat brown rice.
Wouldn’t this group of motivated health enthusiasts also tend to eat less sugar?
Thanks for reading; I appreciate your comments and suggestions.