Many randomized controlled studies have been conducted and funded by the Almond Board of California to examine the consumption of almonds in relation to blood glucose control. Studies suggest that including almonds in a healthy diet may have benefits for people with type-2 diabetes (T2D) as well as for those with prediabetes (also called impaired glucose tolerance), who are at risk for their prediabetes developing into type 2 diabetes.
One recent studyii conducted in India showed that almonds had a positive impact on both blood sugar control and markers of heart health in adults with type-2 diabetes (T2D). Fifty Asian Indian adults with T2D and elevated cholesterol levels substituted 20% of their daily calories with whole, unroasted almonds as part of a well-balanced diet. They not only saw improvements in hemoglobin A1c (an indicator of longer-term blood sugar control), but in several cardiovascular risk factors linked to type 2 diabetes, including:
- Waist circumference: an indicator of health risk associated with excess fat around the waist
- Waist-to-height ratio: a measure of body fat distribution
- Total cholesterol: a measure of the amount of cholesterol in the blood
- Triglycerides: a form of fat in the blood that can raise risk for heart disease
- LDL-cholesterol: the harmful type of cholesterol that is a main source of cholesterol buildup and blockage in the arteries
- C-reactive protein: a marker of inflammation in the body
A randomized trial2 in 19 U.S. adults (including seven with T2D) reported a 30% reduction in postprandial glycemia in participants with T2D after eating a test meal containing one ounce (28 grams) of almonds compared to an almond-free test meal similar in calories, fat and available carbohydrate. The same researchers looked at the longer-term effects of almonds on glucose control in a small group of 13 adults with T2D. Participants consumed a daily one-ounce serving of almonds (five days per week for 12 weeks) or a cheese snack with the same number of calories. After 12 weeks, hemoglobin A1c in individuals with T2D was reduced by 4% from baseline in those in the almond group. The small study size is a limitation of this study. Larger studies will be useful in better understanding the impact of almonds on blood glucose in people with T2D.
A new study3 reported that eating almonds daily for 12 weeks reduced insulin resistance, improved pancreatic function, and helped control blood glucose levels in Asian Indian adults with overweight and obesity. The almond group achieved significant reductions in body weight, body mass index (BMI), and waist circumference over the intervention period and lowered their total cholesterol. Obesity is a risk factor of both type 2 diabetes and cardiovascular disease.
Researchers studied 352 male and female Asian Indian participants (ages 25- 65 years old) in this randomized control trial. BMI ranged from 23 kg/m2 and up. (Researchers used World Health Organization – Western Pacific Region BMI guidelines where > 23 kg/m2 corresponds to overweight and > 25 kg/m2 to obese.) Participants had central obesity, dyslipidemia (i.e., imbalance of blood lipids, such as cholesterol), family history of diabetes, normal blood pressure as well as hypertension, and they routinely consumed mid-morning snacks.
Participants in the almond treatment group experienced over 12 weeks:
- improvement in their beta cell function (the pancreas cells that make insulin)
- reduced insulin resistance and glucose
- lowered total cholesterol and triglycerides
- significant reductions in body weight, BMI, and waist circumference
A study limitation is that results may only generalize to Asian Indian adults with overweight and obesity.
Another 12-week study4 assessed the impact of almond consumption (~two ounces or 60g/day) in a cholesterol-lowering diet on short- and long-term glycemic control, blood lipids, endothelial function, oxidative stress and inflammation in 33 Chinese (Taiwanese) adults with T2D. Results showed that among patients with better-controlled blood glucose levels (baseline HbA1c ≤8%), the diet with almonds reduced HbA1c by 3% and fasting blood sugar levels by 5.9% compared to the control diet, suggesting that including almonds in a healthy diet might help further improve blood sugar control in T2D patients with HbA1c ≤8%. Serum cholesterol levels and biomarkers for inflammation and oxidative stress remained unchanged over the course of the study. As with the previous study, the relatively small sample size is a limitation, so larger studies will be useful in better understanding the impact of almonds on blood glucose in people with T2D.
Almonds and Prediabetes
Studies also suggest that as part of a healthy diet, almonds may have benefits for people with prediabetes. Finding dietary strategies to reverse prediabetes to normal blood sugar levels has been called “the holy grail of medicine.” Two recent research studies investigate how eating almonds in a small handful (about 20 g or .7 oz) before major meals can benefit blood sugar control.
One study5, conducted over three days, and the other6, over three months, demonstrated benefits to blood sugar control for Asian Indians with prediabetes and overweight/obesity. The three-month almond intervention broke new ground, reversing prediabetes, or glucose intolerance, to normal blood sugar levels in nearly one quarter (23.3%) of the people studied.
In the three-month study, participants were randomized into either the almond treatment group or into the control group, and both were provided with diet and exercise counseling as well as home-use glucometers to measure their glucose levels, which were recorded along with dietary intake and exercise.
Study measures included body weight; circumferences of waists, hips, and arms; and body fat estimates. Biochemical measures included insulin, blood sugar, hemoglobin A1c, C-peptide, glucagon, proinsulin, high sensitivity C-reactive protein, tumor necrosis factor alpha, and lipids.
Eating 20 g (0.7 oz) almonds ahead of breakfast, lunch, and dinner, for three months resulted in first-of-its kind statistically significant reductions for the treatment group in:
- body weight, body mass index, waist circumference, skinfold tests for shoulder and hip areas, as well as improved handgrip strength
- fasting glucose, postprandial insulin, hemoglobin A1c, proinsulin, total cholesterol, LDL-cholesterol, and very low-density lipoprotein with no changes in beneficial HDL-cholesterol
These substantial metabolic improvements led to nearly one quarter (23.3%) of the prediabetes study participants returning to normal blood glucose regulation. These findings are meaningful for global public health given the prevalence of diabetes, the troubling rates of progression from prediabetes to diabetes, and are specifically relevant to Asian Indians in India who are disproportionately impacted because of their greater tendency to progress from prediabetes to diabetes. Limitations include the relatively small sample size and limited period of intervention. Since the study included Asian Indians who had well-controlled prediabetes, the researchers cannot extrapolate the same impact of a premeal load of almonds in participants with type 2 diabetes.
In the three-day study, 60 Asian Indians were equally divided into one group that consumed a 20 g (0.7 oz) portion of almonds and the control group received no almonds and both groups were given an oral glucose tolerance test (OGTT). Using a continuous glucose monitoring system (CGMS), researchers compared the glycemic effects of preloading three meals a day with 20 g (0.7 oz) of almonds for three consecutive days in 60 participants, with the participants who received no preloading of almonds.
Researchers found that indicators for hyperglycemia, such as blood glucose, serum insulin, glucagon, and C-peptide (only OGTT results) were lower for the almond group versus the control group. There was an 18.05% decrease in post-prandial (or post-meal) blood glucose (PPBG) levels, indicating improved regulation of glycemic responses among the almond consumers.
Results from the CGMS showed statistically significant improvement in glucose variability over the first 24 hours in the almond group, indicating appropriate glucose control. Specifically, PPBG levels were lowered by 10.07% in the almond group compared to control. Treatment with premeal almond loading significantly improved several indicators that reflect daily glycemic control compared to the control group. Limitations include a limited period of intervention with a smaller sample size comprising people with prediabetes. Also, nutritional intervention studies can trigger behavioral changes in both groups as the participants are made aware of their risk during the recruitment process and were given dietary instruction prior to the study. Further research is needed to investigate the effects of almond preloading consumption on the same measures in different ethnicities and in individuals with type 2 diabetes and normal body weights to be able to provide broader recommendations.