Safflower Oil May Reduce Risk for Diabetes Complications
Laurie Barclay, MD
March 29, 2011 — Supplementation with 8 g safflower (SAF) oil daily improved glycemia, inflammation, and blood lipids in obese, postmenopausal women with type 2 diabetes, according to the results of a randomized, double-masked, crossover study reported online March 21 in Clinical Nutrition.
“The women in the study didn’t replace what was in their diet with [SAF] oil. They added it to what they were already doing,” senior author Martha A. Belury, PhD, RD, professor of human nutrition at Ohio State University in Columbus, said in a news release. “And that says to me that certain people need a little more of this type of good fat — particularly when they’re obese women who already have diabetes.
“I believe these findings suggest that people consciously make sure they get a serving of healthy oil in their diets each day — maybe an oil and vinegar dressing on a salad, or some oil for cooking. And this recommendation can be extended to everyone.”
Because the metabolic effects of dietary fat quality in people with type 2 diabetes are incompletely understood, the investigators aimed to assess the effects of conjugated linoleic acid (CLA) and SAF oils on glycemia, blood lipids, and inflammation. Their hypothesis was that dietary oils would improve glycemia, lipids, and inflammatory markers in a time-dependent way that follows the accumulation of LA and CLA isomers in the serum of participants using dietary oil supplementation.
“The message from this study could be misinterpreted by the general population,” Anoop Misra, MD, director and head of the Department of Diabetes, Obesity, and Metabolic Diseases at Fortis Hospital, New Delhi, India, told Medscape Medical News when asked for independent comment. “It is suggested that patients can eat whatever they are eating and follow their existing, often unhealthy lifestyle, but can protect themselves from diabetes and diabetes-related complications just by including 8 g [SAF] oil in the diet.”
Of 55 postmenopausal, obese women with type 2 diabetes who were enrolled in this study, 35 completed the trial and received 8 g (about 1 2/3 teaspoons) CLA followed by SAF daily for 16 weeks each or vice versa; regardless of order (ie, CLA or SAF first), there was a 4-week wash-out period between treatments. To identify the earliest time that a significant effect was detected, the investigators used a multiple testing procedure with predetermined steps analysis. Insulin sensitivity was estimated with the quantitative insulin sensitivity check index (QUICKI) equation, using fasting serum glucose and insulin concentrations.
CLA had no apparent effect on measured metabolic outcomes. During SAF supplementation, HbA1c decreased (−0.64 ± 0.18%; P = .0007); C-reactive protein decreased (−13.6 ± 8.2 mg/L; P = .0472), and QUICKI increased (0.0077 ± 0.0035; P = .0146) The minimum time to observed effect was 16 weeks after treatment. High-density lipoprotein cholesterol also increased with SAF supplementation (0.12 ± 0.05 mmol/L; P = .0228), with an effect detected at 12 weeks.
Among women supplemented with CLA or SAF, 4 weeks was the minimum time to detect an increase of c9t11-CLA, t10c12-CLA, and LA, respectively, in serum.
“The health benefits of omega-3 [polyunsaturated fatty acids (PUFAs)] seem convincing, but I think there’s also a place for omega-6 PUFAs,” Dr. Belury said. “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. We suspect it could be through a mechanism that is not yet identified.”
Is LA or Another Component of SAF Responsible for Improved Metabolic Measures?
On the basis of these findings, the investigators concluded that 8 g SAF daily improved glycemia, inflammation, and blood lipids, suggesting that “small changes in dietary fat quality may augment diabetes treatments to improve risk factors for diabetes-related complications.”
“We don’t know the long-term effects of [SAF] oil from this study alone, but I certainly think it’s possible that the risk for cardiovascular problems could be significantly decreased in this high-risk group if supplementation were continued,” Dr. Belury said. “A small change in eating behavior to alter the fatty acid content of the diet might improve metabolic measures in people already consuming what is considered to be an adequate amount of dietary [LA]. What is needed in our diet is PUFAs to help with cardiovascular disease — the number 1 killer of men and women in this country.”
Limitations of the study noted by Dr. Misra include the small sample size and an unclear basis of the selected dosage (8 g) of SAF.
“The major limitation of the study is that diet and exercise have not been assessed,” said Dr. Misra, who is also chairman of the National Diabetes, Obesity and Cholesterol Foundation and director of Diabetes and Metabolic Diseases, Diabetes Foundation of India. “Complete fatty acid profile of the patients should have been assessed. It is important to assess complete fatty acid intake, along with other nutrients, to evaluate health risk.”
In terms of additional research, Dr. Misra recommended a 4-group study with a larger sample size, and with basic diet and exercise counseling given to all participants. The 4 groups would be CLA, SAF oil, any other oil containing high LA content, and a combination of oils giving an n6/n3 ratio between 5 and 10, or alternatively, omega-3 supplementation.
“As has already been pointed out by the study authors, it cannot be concluded from this study whether it is LA or other components of SAF that are inducing biological effects,” Dr. Misra said. “A comprehensive study focusing on diet and exercise, along with the supplementations mentioned above, should be planned before concluding positively about the beneficial effect of SAF.”
The Ohio Agricultural Research and Development Center, the National Center for Research Resources, the Clinical Research Center at Ohio State, and the National Institutes of Health supported this study, along with an unrestricted gift from the Cognis Corp, which also provided the supplements. The study authors and Dr. Misra have disclosed no relevant financial relationships.
Clin Nutr. Published online March 21, 2011.
Medscape Medical News © 2011 WebMD, LLC
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