Researchers from Ohio State University report that 1.66 teaspoons of safflower oil for 16 weeks were associated with a reduction in fasting blood sugar levels by between 11 and 19 points, and increases in HDL cholesterol of about 14 percent.
Writing in Clinical Nutrition, Prof Martha Belury are her co-workers noted that the levels of safflower oil intakes are consistent with recent dietary reference recommendations.
“Women in our study reported an average linoleic acid intake of 6.8 percent of total energy,” wrote the authors. “Adding linoleic acid consumed from the supplements, average intake increased to 9.8 percent of energy.
“The Dietary Reference Intake Report has set the acceptable macronutrient distribution range at 5 to 10 percent of energy from n-6 PUFA. Accordingly, subjects in our study were not consuming a sub-optimal amount of linoleic acid before supplementation, nor did supplementation increase linoleic acid consumption beyond what is recommended for a healthy diet,” they added.
Building on earlier data
The new paper builds on previous findings from a clinical trial with 55 obese and menopausal female diabetics, 35 of whom completed the study. The women received either safflower oil or CLA (conjugated linoleic acid) for 16 weeks, followed by a four-week washout period, and then a cross-over to the next 16-week supplementation period began.
Findings published in 2009 in the American Journal of Clinical Nutrition (doi: 10.3945/ajcn.2008.27371) indicated that CLA supplementation reduced body weight, BMI and total adipose mass without altering lean mass, while no changes to markers of inflammation and insulin resistance were observed.
On the other hand, the safflower oil phase did not affect total body fat readings, but improvements in the weight of trunk fat tissue were observed, as was an increase in muscle tissue, wrote the researchers in AJCN. Moreover, the safflower oil was associated with reduced fasting blood sugar levels.
The new findings, a result of secondary analysis of data collected from that clinical trial, indicated that, while safflower oil did not affect body fat or weight measures, it was associated with an increase in insulin sensitivity of about 2.7 percent, which represents an improvement. Insulin resistance, or lowered insulin sensitivity, is the hallmark of type-2 diabetes.
In addition, Belury are her co-workers recorded a 0.64 percent decrease in levels of a protein called HbA1C, a marker of long-term presence of excess glucose in the blood. C-reactive protein, a marker of inflammation, also decreased in the safflower oil group, with a 17.5 percent average decrease recorded.
Make room for omega-6?
"The health benefits of omega-3 PUFAs seem convincing,” said Belury, “but I think there's also a place for omega-6 PUFAs.
“We've known for a long time that polyunsaturated oils are very beneficial for cardiovascular disease prevention, and these data we are adding now show that these oils can also help with other aspects of metabolic syndrome, including even glycemic control," she added. "We suspect it could be through a mechanism that is not yet identified."
Belury added that the long-term effects of safflower oil from this study alone are unknown, before adding that she thought it possible to reduce the risk of cardiovascular problems by continuing supplementation.
Harry Rice, PhD, VP regulatory and scientific affairs at the omega-3 trade association Global Organization for EPA and DHA (GOED), told NutraIngredients-USA that, while he found the research "interesting" he considered the conclusion that 'Inclusion of a small amount of readily available and inexpensive safflower oil into the diet may have meaningful effects on clinically important risk factors in the management of diabetes and prevention of diabetes-related complications' to be a "stretch, not to mention a concern".
"First, this publication is based upon secondary analyses; therefore, the findings should be used to design future experiments, not draw conclusions," said Dr Rice.
"Second, given the ongoing, credible debate about the displacement of the long-chain omega-3 fatty acids, EPA and DHA, from the diet by omega-6 fatty acids (e.g. linoleic acid), the authors' conclusion could send the wrong message and have the unintended consequence of reducing long-chain omega-3 stores in a select group of people," he added.
Source: Clinical Nutrition
Published online ahead of print, doi: 10.1016/j.clnu.2011.01.001
“Time-dependent effects of safflower oil to improve glycemia, inflammation and blood lipids in obese, post-menopausal women with type 2 diabetes: A randomized, double-masked, crossover study “
Authors: M.L. Asp, A.L. Collene, L.E. Norris, R.M. Cole, M.B. Stout, S-Y. Tang, J.C. Hsu, M.A. Belury