A common piece of dietary advice for people with diabetes — and for anyone, really — is to reduce consumption of refined and processed grains, and to focus on whole grains instead. Whole grains tend to contain more fiber and other important nutrients, including minerals. At least in some cases, the higher fiber content in whole grains may slow down the process of digesting and absorbing the starches in them — potentially leading to smaller spikes in blood glucose levels.
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But especially give the conflicting messages about how grains affect your blood glucose levels — some people see no difference between white and whole-wheat bread, for example — you may wonder if it’s actually important to reach for whole grains. A new analysis shows that at least when it comes to white bread, the risks associated with refined grains are clear: a greater likelihood of cardiovascular disease and death.
Clear disease risk from refined grains
The analysis, published in the journal BMJ, compared the intake of various grains with rates of cardiovascular disease and death among 137,130 participants in 21 countries. Participants completed detailed food frequency questionnaires and were followed for an average of 9.5 years. None of the participants had cardiovascular disease at the beginning of the study.
During the follow-up period, 9.2% of participants experienced at least one of the outcomes researchers were looking at — a non-fatal heart attack or stroke, heart failure or death from cardiovascular causes. Researchers compared these outcomes with participants’ self-reported grain intake, and grouped participants into different categories based on their average daily intake of refined grains. Those in the highest category for refined grain consumption — consuming at least 350 grams, or about 7 servings, each day — were at higher risk than for a range of poor outcomes than those in the lowest category, who consumed less than 50 grams each day. They were 27% more likely to die from all causes, and 33% more likely to experience a major cardiovascular event such as a heart attack or stroke. They also tended to have higher systolic blood pressure — the “top number” representing your blood pressure during heartbeats.
But notably, there was no increased risk of cardiovascular disease or death associated with consuming whole grains or white rice. This calculation was based on the estimated dry weight of grain products, and included both products made from whole-grain flour and less processed cooked, unground grains. In North America, Europe, South America and the Middle East, the main source of whole grains was whole wheat-bread. People in the highest category of refined grain consumption mostly ate white bread, as opposed to other forms of refined grains.
Based on these results. it appears that even when the main grain-based food most people eat is bread made from wheat, the choice of whole-wheat or white bread is important and closely tied to health outcomes.
Is less refined always better?
One important finding from the study is that a higher intake of white rice — technically a refined gran, since its outer bran layer has been removed — wasn’t tied to any of the poor health outcomes the researchers looked at. This was true both in Asian countries where rice intake was highest, and in other countries.
This result suggests that consuming the whole version of a grain — without any part removed — may be more important for some grains, such as wheat. There wasn’t enough data on brown rice consumption in this study to draw any conclusions about different health outcomes from consuming white versus brown rice.
The links between grain intake and health outcomes didn’t change when the researchers controlled for participants’ intake of sodium or saturated fat. So at least when it comes to these two nutrients — which are tied to a higher risk for cardiovascular disease when consumed in excess — it looks like there wasn’t anything skewing the results. For example, if participants who ate more white bread also ate more butter, there would be a concern that butter was actually responsible for the higher risk of cardiovascular disease seen in people who eat white bread (due to the saturated fat found in butter).
So with the possible exception of white rice, the message of this study is clear — less refined grains are linked to a lower risk of cardiovascular events and death.