New Soybean Oil Health Claim Based on Solid Body of Evidence

Editor’s Note: The new soybean oil health claim was allowed in response to a petition submitted by Bunge Limited and is available on the FDA website. A letter of enforcement discretion from the FDA authorizing the new claim is also available on that site. 

By Guy Johnson, PhD

The U.S. Food and Drug Administration (FDA) vouched for the heart-health benefits of soybean oil in 2017 by acknowledging that there is sufficient “supportive scientific evidence” to authorize a new Qualified Health Claim (QHC) for soybean oil and certain foods made from it. Exact wording of the new claim reads:

“Supportive but not conclusive scientific evidence suggests that eating about 1 ½ tablespoons (20.5 grams) daily of soybean oil, which contains unsaturated fat, may reduce the risk of coronary heart disease. To achieve this possible benefit, soybean oil is to replace saturated fat and not increase the total number of calories you eat in a day. One serving of this product contains [x] grams of soybean oil.”

Foods eligible for the new claim

Soybean oil, including soybean oil that is sold as “vegetable oil,” is eligible to make the claim.  The claim also applies to soybean oil-containing dressings for salads, margarines and other spreads as well as other products, as long as they contain at least five grams of soybean oil per Reference Amount Customarily Consumed (RACC) and meet certain other restrictions for saturated fat, cholesterol, sodium and minimum nutrient content.

The rationale for allowing eligible soybean oil-containing foods to make the claim if they contain five grams per RACC is to give consumers the flexibility to incorporate the minimum effective amount of soybean oil (about 1 ½ tablespoons or 20.5 grams per day) into a typical eating pattern of three meals per day, plus a snack.

Scientific basis

The petition to the FDA cited 160 publications including controlled intervention studies, observational studies, review papers and meta-analyses as evidence that soybean oil has the potential to reduce the risk of coronary heart disease (CHD). This evidence fell into several categories: 

Soybean oil has a favorable fatty acid distribution which is low in saturated fatty acids (SFA) (~15%), moderate in monounsaturated (MUFA) (~23%) and high in polyunsaturated (PUFA) (~57%) fatty acids. Approximately 12% of the PUFAs in soybean oil (~7% of total fatty acids) are in the form of omega-3 fatty acids (mostly α-linolenic acid [ALA]). This fatty acid distribution makes soybean oil unique because it is a PUFA-dominant oil that is a meaningful source of omega-3 fatty acids; but has only about the same SFA content as olive oil.

The high PUFA content of soybean oil may be particularly important. The petition cited evidence from several controlled intervention studies1-5 that showed including omega-6 PUFAs (primarily from soybean oil) in the diet of human subjects reduced the incidence of CHD in experiments that lasted between two and eight years. These experiments did not meet the rigor that FDA requires for the authorization of health claims, but they are unique in that very few experiments have been conducted among humans that measured the effect of long-term dietary fatty acid modification on the actual incidence of CHD. These experiments are one of the reasons why public health authorities, including the American Heart Association6 and dietary guidance including the 2015-2020 Dietary Guidelines for Americans have, concluded there is somewhat stronger evidence for the cardioprotective effects of dietary PUFA compared to MUFAs. 

The petition also presented emerging evidence to suggest that ALA reduces the risk of CHD in its own right, and therefore contributes uniquely to the cardioprotective properties of soybean oil. Although firm conclusions could not be drawn,7 meta-analyses of observational studies were cited that concluded the intake of ALA is inversely associated with the incidence of CHD.8,9  In addition, a meta-analysis of 14 intervention studies reported beneficial effects of this fatty acid on plasma fibrinogen and fasting blood glucose concentrations.10

Soybean oil also contains non-fatty acid components including vitamin E (mostly in the form of γ-tocopherol) and plant sterols11 that may also contribute to its cardioprotective properties. 

By far the most important area of evidence supporting the cardioprotective properties of soybean oil from a regulatory perspective was its ability to lower the concentration of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) when used as a replacement for dietary saturated fat without adversely affecting high-density lipoprotein cholesterol (HDL-C) or triglycerides (TG). The petitioner submitted 10 publications12-21 that described 14 dietary interventions in which soybean oil was substituted for a diet higher in saturated fat. All but one of these studies14 (which included two interventions) were classified as high or medium quality according to criteria published by FDA in its 2009 document entitled, “Guidance for Industry:  Evidence-Based Review System for the Scientific Evaluation of Health Claims – Final.” Nine of the 12 interventions from the high and medium quality studies reported that a soybean oil-containing diet resulted in significantly lower concentrations of both TC and LDL-C compared to a higher saturated fat control diet.

However, FDA’s rigorous review of these studies disqualified four of them due to what it deemed inappropriate statistical analysis,12 inadequate control group,14 insufficient fatty acid intake data,15 and data derived from a subset of a previously published study.18 Therefore, the final evaluation of the proposed claim was based on eight interventions described in the six remaining publications.13,16,17,19-21  Six of the eight comparisons in these studies reported that soybean oil statistically significantly lowered both TC and LDL-C compared to a control diet higher in saturated fatty acids.

The petitioner also submitted a large Costa Rican case-control study to substantiate the proposed claim.22 This study reported that palm oil users were more likely to have a myocardial infarction (MI) than users of soybean oil (adjusted odds ratio = 1.33; 95% confidence interval: 1.08-1.63) based on 2,111 case-control pairs (mean age = 58 years) who were survivors of a first acute MI.

The FDA considered all of this evidence and decided to authorize claim language that is stronger than any of the other oils that currently have a QHC. This decision was prompted by the consistency of results from the controlled intervention studies as well as alignment with the available observational data.

Specifically, FDA agreed with the qualifying language proposed by the petitioner – “Supportive, but not conclusive scientific evidence suggests...” This phrase is less restrictive than the qualifying language already stipulated for olive oil and canola oils (i.e., “Limited and not conclusive scientific evidence suggests…”) and much less restrictive than that for corn oil (i.e., “Very limited and preliminary scientific evidence suggests…”).

Qualified vs. unqualified health claims

The perception by some that QHCs should not be taken seriously because they are based on less scientific evidence than unqualified health claims is an oversimplification. The regulatory standard for an unqualified claim is “Significant Scientific Agreement” (SSA) among experts qualified by scientific training and experience to evaluate such claims (21 CFR §101.14(c)). The FDA requires a high degree of consistency among a large number of high quality studies conducted among many participants before it agrees that the SSA standard has been met. In fact, only five such claims have been approved since the enactment of the Nutrition Labeling and Education Act of 1990: Folic acid and neural tube defects; noncariogenic sweeteners and dental caries; soluble fiber and risk of CHD; plant sterol/stanol esters and risk of CHD; and soy protein and risk of CHD. The latter claim is currently being re-evaluated by the FDA as discussed in another article in this issue.

On the other hand, 23 QHCs have been authorized based on varying degrees of scientific evidence. The scientific veracity of these claims can be determined from the qualifying language that has been stipulated. For example, claims with less restrictive language such as that for nuts and reduced risk of CHD – “Scientific evidence suggests but does not prove…” or for omega-3 fatty acids and reduced risk of CHD – “Supportive but not conclusive research shows…” are based on a considerable amount of science (as is the new claim for soybean oil.)  However, QHCs with severe qualifying language are based on considerably less scientific evidence. Examples of such claims include, “FDA concludes, however, that the existence of such a relationship between chromium picolinate and either insulin resistance or type 2 diabetes is highly uncertain,” or “Green tea may reduce the risk of breast or prostate cancer. FDA has concluded that there is very little scientific evidence for this claim.” Health professionals have an opportunity to use qualifying language to help consumers understand the relevance of such claims.

Conclusions

The new QHC for soybean oil is among the strongest of such claims approved by the FDA to date. This outcome reflects the strength of the scientific evidence attesting to the cardioprotective protective properties of this commonly used oil, and is consistent with recommendations in the 2015-2020 Dietary Guidelines for Americans and those from other public health authorities. The availability of this claim allows soybean oil and certain soybean oil-containing foods to use heart-shaped vignettes in labeling and promotional materials, and offers incentives for the food industry and other stakeholders to educate consumers about the benefits of this heart-healthy oil.

References

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