Low Glycemic Diet Improves Cardiometabolic Health

Note: While the main study we will discuss here is looking at people with diabetes, other studies are finding that low glycemic diets are associated with lower heart disease risk in the general population, including people without diabetes (1).

A 2021 study published in the BMJ (British Medical Journal) carried out an analysis of high quality studies on low-glycemic diets (diets which lead to less spikes in blood sugar) and found improvement in markers of heart health and metabolic health in diabetic patients. Heart health and metabolic health are closely related, and are usually referred to collectively as “cardiometabolic health”. In total, 29 studies that together included over 1500 participants were looked at to investigate trends in their findings. All of these studies were randomized clinical control trials, which are generally accepted to be the gold standard in research (2).

Consistent findings were reductions LDL cholesterol, systolic blood pressure, triglycerides, bodyweight, and body mass index (BMI, which is the ratio of weight to height), A1c (marker of average blood sugar over 3 months), fasting blood sugar levels, and a primary marker of inflammation know as CRP (2). When excessively elevated, these things are associated with worse cardiometabolic health.

Years before this study was done, studies looking into this topic were being carried out. In fact, in 2013, a scientific summit was held in Italy comprised of international experts on carbohydrate research, and they decided together that it was important to teach the public what low-glycemic means, and how minding this way of eating can help to improve and maintain health (3). Let’s take a look at what what “low-glycemic” means.

The word “glycemic” relates to glucose, the type of sugar that circulates in the blood and that cells use as energy. For example, “glycemia” is the level of sugar in your blood. A low-glycemic meal is a meal that leads to only small to moderate elevations in blood sugar. The term “low-glycemic” includes 2 main factors: glycemic index, and glycemic load. Glycemic index (GI) is a measure of how much a given amount of food causes blood sugar to rise after eating, and glycemic load takes into account both the glycemic index, as well as the amount of carbohydrate (in grams) contained in a volume of food.

Example: an apple is low on the glycemic index, and has a low glycemic load. However, if 8 apples are eaten in a sitting, the glycemic load becomes high.

There are lists that show the glycemic indexes and glycemic loads of different foods, but here are the main things you need to know without having to consult such a list. The group of foods that tends to cause blood sugar elevations after eating is called carbohydrate, a term that generally refers to foods containing mostly starch, sugar, and sometimes fiber. Fiber is not absorbed by the body for energy, so it is does not cause blood sugar elevations. This is a key point: while there are exceptions, the trend is that low- and medium-glycemic carbohydrates tend to contain some fiber, and are often non-processed. These are foods such as vegetables, beans, fruit, and whole grains. The lowest glycemic foods from this group are called non-starchy vegetables, and they include broccoli, cauliflower, Brussels sprouts, lettuce and other leafy greens, asparagus, beets, yellow squash, zucchini, onion, tomato, cucumber, green beans, and a few other less-commonly eaten veggies. High-glycemic carbohydrates tend to be low in fiber, highly processed, and contain refined flours and added sugars.

rotein-rich foods, such as fish, seafood, chicken, eggs, etc., are usually listed as zero or close to it on glycemic charts. This is also true for foods that are predominantly fat; foods such as nuts, olive oil, avocado, and others.

Taken together, this means that a plate with low to medium glycemic carbohydrate component, some protein, and some healthy fat will generally cause a relatively low-glycemic response (aka blood sugar response). Remember that glycemic load takes into account both the glycemic index, as well as the amount of carbohydrate (starch or sugar; we don’t count fiber) in the given food. In other word, the amount of starch and/or sugar that you eat affects the glycemic effect of the meal. This means that eating a large dinner plate piled high with only whole-grain brown rice, red beans, and 2 whole grain rolls would push the meal into the high-glycemic range, because the glycemic load would be so high. Rather, if the goal is to eat a lower glycemic meal, the red beans and rice might take up 1/4 to 1/3 of the plate, and you would also have some roasted chicken, and a non-starchy vegetable perhaps roasted in a bit of olive oil to add healthy fats to the meal.

Feel free to reach out with questions. We appreciate you taking the time to read this, and wish you health and happiness.

Jordan Smith, RD, LDN

Sources:

1. Jenkins DJA, et al; PURE Study Investigators. Glycemic Index, Glycemic Load, and Cardiovascular Disease and Mortality. N Engl J Med. 2021 Apr 8;384(14):1312-1322. doi: 10.1056/NEJMoa2007123. Epub 2021 Feb 24. PMID: 33626252.

2. Chiavaroli L, Lee D, Ahmed A, Cheung A, Khan T A, Blanco S et al. Effect of low glycaemic index or load dietary patterns on glycaemic control and cardiometabolic risk factors in diabetes: systematic review and meta-analysis of randomised controlled trials BMJ 2021; 374 :n1651 doi:10.1136/bmj.n1651

3. Augustin LSA, et al. Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC). Nutr Metab Cardiovasc Dis. 2015 Sep;25(9):795-815. doi: 10.1016/j.numecd.2015.05.005. Epub 2015 May 16. PMID: 26160327.