Intro

You’ve heard the reports that wine – especially red wine – has health properties when used in moderate amounts.  And the amazing nutrition available from many edible seeds is also common knowledge.  It might stand to reason, then, that grape seeds would also harbor beneficial compounds.  (Spoiler alert:  they do, though you’ll have to read on to find out how best to reap the benefits.)

Grapeseed oil (GSO) is made by pressing the grape seeds, which were once simply considered the waste products of wine production.  Interest in the nutritional properties of GSO has grown in conjunction with continued advice to decrease dietary SFA as well as recognition of the phytosterol and antioxidant (including phenolic compounds and vitamin E) content of grape seeds.

How healthful is GSO and how does it compare to other dietary fats and oils?  The first benefit that most readers think of is that GSO is a plant fat rather than an animal fat, and therefore likely to be low in saturated fat.

You’ve likely heard that plant oils lower cholesterol and your risk for cardiovascular disease (CVD) or heart disease, which generally refers to the narrowing or blockage of blood vessels, but can refer to other problems affecting the heart.

Other claims about GSO include everything from wound healing to cancer prevention to immune enhancement.  It’s also used in the cosmetics industry and some people use it by itself as a moisturizer for skin and hair.  Below we’ll look into what the research says about GSO and how it compares to other fats and oils.

What Is Grapeseed Oil?

Dietary oils and fats are comprised of fatty acids (from now on, I’ll use “fats” or “oils” interchangeably to refer to both fats and oils).  Nearly all fats are a mixture of monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and saturated fatty acids (SFA); even butter and lard, which most people likely consider to be highly saturated, are roughly 33% and 45% MUFA, respectively. (1)

In contrast, GSO is mostly PUFA, containing roughly 72% polyunsaturated, 16-21% monounsaturated, and 7-12% saturated fatty acids. (1, 2)   Fats are generally described as belonging to the category (SFA, MUFA, or PUFA) that comprises more than half of their FAs.

One difficulty in discussing the healthfulness of common dietary fats is that most can be both “good” and “bad” for you, depending on how they are used, their FA composition, and how much they appear in your diet compared to other fats, other foods, and other food groups.

For example, the healthiest fat will be detrimental to your health if you eat it after it has gone rancid, while some of the most maligned fats, like butter, are least likely to spoil and subsequently create a situation where you would be exposed to free radicals.

GSO is not different in this regard:  there is research promoting its health benefits and research describing how it doesn’t stack up to other fats in keeping you healthy.  Let’s dive in.

Is There Any Research?

Searching three separate research databases, I found nearly 200 published articles on grapeseed oil.  In contrast, there were nearly 8,000 articles pertaining to grape seeds.  Compared to vegetable oils of similar FA composition to GSO, nearly 9,000 references showed up for “sunflower oil” and more than 20,000 papers showed up for the search words “corn oil.”

Much of the research about GSO compares different testing methods to determine whether olive oil or other oils have been adulterated with GSO, while another category discusses GSO’s cosmetic applications.  Most studies I read appear well conducted, with a notable exception mentioned below.

However, little research exists using human volunteers, so, as is common, findings must be extrapolated – with a hefty grain of salt – from animal to human health, as well as from the laboratory to real life.

Comparing Polyunsaturated Fats: How Does Grapeseed Oil Compare?

GSO has one of the highest concentrations of PUFA of any common edible oil.  Safflower oil and sunflower oil are two others that are very high in PUFA, followed by corn oil, cottonseed oil, and soybean oil.  Olive oil, on the other hand, is primarily MUFA, while canola and peanut oil also contain more MUFA than other FAs, but not in as large a concentration as olive oil.  Coconut oil, meanwhile, is the most highly saturated fat, followed by butter, while palm oil and beef tallow are about half SFA.

Standard dietary recommendations include advice to decrease saturated fatty acids and increase plant oils higher in MUFA and PUFA.  Yet there exists some controversy about these recommendations, mainly that PUFA are less stable than MUFA and SFA and this instability can create a “broken” or oxidized molecule that is detrimental to the body.

The “poly” part of polyunsaturated means that there are multiple places in the fatty acid molecule where double bonds exist.  (“Mono”-unsaturated, then, means just one double bond in the molecule, while saturated fatty acids have no double bonds, as every available bonding spot is saturated with a hydrogen atom.)  These double bonds decrease the stability of the molecule, and increase the chances for the creation of a free radical (an oxidized and unstable compound).

(Researchers sometimes talk about the double bond index (DBI), which describes, essentially, the chances of creating free radicals.  In one study, GSO was reported as having higher DBI than soybean oil, (3) which makes sense given its higher concentration of PUFA than most other oils.  Keep reading:  more on the healthfulness and stability of PUFAs to come.)

In addition, not all individual polyunsaturated fatty acids are created equal.  Not only do we have SFA, MUFA, and PUFA categories, but we have discrete FAs within each category.  For example, much, seemingly well-deserved acclaim has been given to the omega-3 subcategory of PUFA, which include DHA and EPA, among others.

GSO, however, contains mostly omega-6 PUFA, especially an omega 6 called linoleic acid.  Linoleic acid accounts for 66-75% of the FA in GSO.(4) Linoleic acid has been found to have health properties, including decreasing blood cholesterol.  However, recent meta-analyses report conflicting views of linoleic acid, and other research reports that even while lowering cholesterol, linoleic acid has not decreased atherosclerosis. (5)

In fact, there is concern about too much dietary linoleic acid:  linoleic acid can turn into arachidonic acid in the body, a precursor to pro-inflammatory compounds.

In contrast, another common PUFA, linolenic acid (see the “n” in the middle there?), is an omega-3 FA and can convert to other omega-3 FA like DHA and EPA, which have been studied for numerous health benefits.  This illustrates a very distinct example as to why we might care about which PUFA we are consuming:  they react differently in our bodies, with potentially dramatically different health outcomes over time.

More important than which PUFA we eat is how much of which PUFA we eat. Modern diets contain dramatically more omega-6 PUFA than they used to.  While the best sources of omega-3 PUFA are fish and seafood, the best sources of omega-6 PUFA are plant oils.  The 20th century saw a 20-fold increase in the consumption of plant oils,5 significantly altering the ratio of dietary omega-6 to omega-3 FAs in human diets.

Some sources estimate that humans evolved on a 1:1 ratio of omega-6 to omega-3 FA;  We now consume diets averaging 15:1 to 17:1. (6)   This imbalance is considered nearly unequivocally detrimental to health, with connections to increased risk of CVD and cancer, among other diseases and health problems.  Research that corrects this ratio in varying degrees (usually below 7:1) has met with promising outcomes for many health problems.

So, while PUFA are recommended for CVD prevention, don’t throw out all your other oils yet.  Coming up: specific examples of positive and negative health outcomes related to GSO.  Stick around.

Comparing Saturated Fats: How Does Grapeseed Oil Compare?

Saturated fats have long been implicated in increasing the risk of heart disease, and this continues to be the consensus, with the corresponding message being to decrease SFA and increase PUFA and MUFA in the diet. (7)

Indeed, a 2011 review of randomized clinical trials reducing or modifying fat intake did confirm a 14% reduction of cardiovascular events in participants who decreased saturated fat by reducing or modifying dietary fat intake. (8)  Further analysis showed that changing the type of fat rather than the percent of calories from fat for at least two years caused this decrease in cardiac events in men but not women, and did not affect mortality from cardiovascular or any other cause.

  This means that swapping saturated fatty acids for other fats decreased cardiac problems but not deaths.

Importantly, this study didn’t show any benefit to swapping fat calories for carbohydrate calories (in other words, reducing the percent of fat in the diet), nor did it determine a greater benefit between MUFA or PUFA for cardiac health. (8)

In contrast, a study of Native Americans found higher rates of coronary heart disease (CHD) in those who had the highest intake of SFA or MUFA, while those in the lowest intake of either fat had lower CHD rates. (9)  (CHD is a condition where plaque builds up in the arteries of the heart, restricting or blocking blood flow, which can lead to a heart attack.)  In this study, it was the amount of fat, rather than the type that correlated with disease and death.

Exploring the research on saturated fatty acids and its health implications is the work of another day.  However, based on current recommendations to eat less SFA and more MUFA and PUFA, GSO aligns with guidelines for a healthful diet.  As mentioned, GSO is low in SFA, and most of the roughly 10% of SFA it contains are palmitic and stearic acid. (4)  As with PUFA content, GSO is similar to sunflower and safflower oils in its composition of these SFA.

Is Eating Grapeseed Oil Likely To Increase Cholesterol?

GSO is good source of phytosterol. (10) which has been proven to benefit blood cholesterol by inhibiting the body’s production of cholesterol in the liver.  GSO is also very high in PUFA, as we have discussed, and PUFA in general have been recommended as a dietary strategy to help decrease blood cholesterol, with an end goal of decreasing atherosclerosis and subsequent cardiacvascular-related deaths. (11)

Studies using GSO corroborate this beneficial impact on blood cholesterol.  When researchers exposed rats to a pesticide pollutant or the same pollutant plus GSO, they found that GSO protected against the significantly increased triglycerides (TG) and LDL (bad) cholesterol the pollutant-only group experienced. (12)  In another study using rats, GSO resulted in lower triglycerides, lower total cholesterol, and higher HDL (good) cholesterol when compared to coconut oil and corn oil. (10)

Researchers also determined that several beneficial markers of genomic response of the liver were more pronounced in the GSO group.  This suggests that – rather than its antioxidant or phytosterol content – GSO specifically influences how the liver handles FA, which is what exerts its positive influence on cholesterol.

(These authors also describe other studies where GSO performed better than soybean oil and lard in effects on blood lipids, but worse than corn oil, noting that discrepancies between results may be due to study duration and feed composition. (10)

Similarly, compared to a high-SFA diet, a high-PUFA (from corn oil) diet resulted in lower LDL cholesterol and triglycerides in rats. (11)  Notably, however, the PUFA diet also resulted in more oxidative stress to cardiac tissue, as well as a decrease in reserve energy (glycogen) for cardiac cells and greater alteration to cardiac cell membranes.(11)

In contrast, one poorly designed study found a butter/rapeseed oil blend lowered LDL cholesterol in young men while a butter/GSO blend did not. (13) However, the butter/rapeseed ratio was 65:35 while the butter/GSO ratio was 90:10, which dramatically alters the mixture of fatty acids participants were ingesting.  Namely, the butter/GSO blend was higher in SFA.  In addition, only 13 subjects completed the study.

Bottom line

Most studies reviewed show that GSO consumption benefits blood cholesterol.  If you are using other high-PUFA oils, like safflower, sunflower, soybean or corn oil, you could reasonably use GSO instead, while also watching your total PUFA intake from these oils and prepared foods. 

Still, most studies have been performed on animals, not people.  And, as mentioned, linoleic acid, the most prominent FA in GSO, has not been found to reduce atherosclerosis as it lowers blood cholesterol, (5)  so additional action should be employed for optimal heart health.

Is Eating GSO Likely to Promote Weight Gain?

Several studies that compared GSO to other oils or to control diets reported no impact of GSO on the amount of food consumed, meaning that it neither promoted more or less food intake than meals with different fat sources or different amounts of fat. (3, 10, 14, 15) This can be viewed as a benefit or a detriment.

If the studies had equal amounts of fat and animals ate the same amount, it means that the taste of GSO did not alter intake negatively, and GSO can feed these animals adequately. (15)  However, other studies used varying amounts of GSO, and animals ate just as much of the higher-GSO feed as of the non-FA supplemented control diet. (14)

 This could promote weight gain (and it did in this study) as fats are higher in calories than protein and carbohydrate.  (In this study of lambs, that was seen as a benefit, as it likely would be in most instances where animals are being raised for food production.)

Another rodent study examining PUFA versus SFA in cardiac health noted higher weight gain in the group eating the high-PUFA diet, even though the SFA group had a higher calorie intake. (11)  This study used corn oil as its source of PUFA, and, notably, coconut oil as the SFA, which researchers noted may be less apt to contribute to weight gain than SFA from animal sources, due to how coconut oil is metabolized.

Bottom line

No studies examining the effect of GSO on human body weight were found.  Fats have nine calories per gram, while proteins and carbohydrates have four calories per gram.  If you substitute GSO (or other fats) for some of the protein or carbohydrates in your diet for long enough (without increasing your activity level), you will gain weight.

Is Eating GSO Likely To Increase Inflammation?

Inflammation can be caused by injury or in reaction to oxidative stress (free radical damage). (16)  Thus, it would follow that foods with antioxidants should decrease inflammation by attenuating the harmful effects of free radicals.

In fact, “grapeseed oil …is considered as a good and potent antioxidant compound for its contents of polyphenols, flavonoids, unsaturated fatty acids and vitamin E.”(12)  In addition to vitamin E, the phytosterols in GSO also help prevent pro-inflammatory compounds from being created by oxidized cholesterol. (4)

Research demonstrates these anti-inflammatory benefits.  In a study of 44 overweight women randomly assigned to either a GSO-enriched or sunflower oil-enriched diet, inflammatory markers were lower in the GSO group after the study’s eight-week duration. (17)

In one animal study, researchers tested GSO against a topical antibiotic cream and petroleum gel to gauge the effects on wound healing in rats.  The GSO healed wounds more quickly than the antibiotic and petroleum gels, and was effective against two strains of E. coli. (2)

Researchers suspect it is the antioxidant properties of the phenolic compounds, the anthocyanins, and the omega-6 and omega-9 fatty acids in GSO that exert a beneficial effect on the standard inflammatory response of healing.  Another proposed explanation is a combined wound-healing effect of GSO’s antimicrobial, anti-inflammatory, and antioxidant activities.

Similarly, lambs fed a diet containing GSO also had higher total antioxidant activity in their blood compared to lambs eating a control diet, and lower amounts of malondialdehyde, a marker of oxidative stress, in both their serum and their muscle.(14)

Researchers also tested the ability of GSO to protect against toxins and pollutants:  Five groups of rats were used:  a control, a group exposed to the pesticide diazinon (DZN), a group given DZN and GSO, a group given just GSO, and a group given corn oil. (12) DZN significantly and negatively altered several blood and tissue markers, indicating its toxicity.

However, rats who were given GSO and DZN were protected from the detrimental physiological and tissue changes.  Researchers again cited GSO’s antioxidant activity as the likely protective element, supporting its role against inflammatory oxidative stress.

The above study was developed after previous findings indicating success of GSO in protecting the eyes, liver, testes, and DNA of rodents.  However, another rodent study comparing four discrete oils added to the diets of rats found that the GSO-supplemented diet increased oxidative stress (and likely inflammatory markers) in testicular tissue compared to oils higher in SFA or MUFA, which researchers blamed on the instability of PUFA.

In still another rodent study, researchers tested the antioxidant response of GSO, corn oil, and coconut oil.  GSO performed worst of the three against one type of oxygen radical, and better than coconut oil against another.(10)  GSO also had the highest deterioration index, meaning its FA oxidized more readily than corn oil (higher MUFA) and coconut oil (higher SFA).

Another lab animal study found similar results:  female rats were fed one of four oils of varying FA composition.  After four weeks, the rats eating the diet highest in linoleic acid (from sunflower oil, not GSO in this study) had the highest rate of oxidative stress in the liver. (18)

Bottom line

More studies were found that support the protective role of GSO against inflammation, though those that found the opposite can’t be ignored.  GSO can be part of a healthful diet.  See below for recommendations about how to make sure you get benefits when adding this oil to your diet.

Are There Any Other Health Considerations?

GSO can be part of an anti-inflammatory diet if A) you have a low intake of processed foods (usually high in soybean, cottonseed, corn, safflower oils), B)use cold-pressed GSO to replace lesser quality, high-omega-6 vegetable oils (chemically processed, which would most likely be any that don’t say expeller or cold pressed), and C) if you use the GSO for low- and moderate-temperature applications.

First, evaluate other sources of omega-6 PUFA in your diet, keeping in mind that most people are eating far too high a ratio of omega 6s to omega 3s.  As mentioned, the highest omega-6 PUFA are GSO, safflower, sunflower, corn, soybean, and cottonseed oils. In most Westernized diets, main sources of these oils are salad dressings; processed snacks like chips, crackers, donuts, and cookies; and prepared sauces and frozen meals.

In addition, prepared food from deli counters and restaurants are very likely to use these higher-omega-6 PUFA oils. If you rarely eat these foods, and if you have adequate sources of omega-3 PUFA in your diet, you can afford to use more high-PUFA dietary oils like GSO at home.

The bottom line is that most people are eating far too much omega-6 in relation to omega-3 PUFA.  If you do not currently use GSO and would like to, be sure you are lowering your other sources of PUFA, especially processed foods and snacks, and increasing your intake of omega-3-rich foods and oils, like fish and seafood, flaxseed, and walnuts, among others.

Choose GSO that indicates it has been cold pressed or expeller pressed.  These methods avoid the use of chemical solvents, which results in a safer product that is more desirable to consumers.(14) In addition, these methods may retain more of the beneficial compounds available in the seed.

Because of its higher likelihood of deterioration, GSO is best used in cold applications like salad dressings or in moderate-heat cooking, but should not be used for frying.(10)  Because it contains antioxidants, however, it may have a longer shelf life than some other oils. (10)  Store your high-PUFA or MUFA oils in a dark cupboard away from heat sources to enhance shelf life and maintain their antioxidant potential.

Is Eating Grapeseed Oil Safe?

Aside from the potential – and inconsistent – concerns noted above, no warnings about avoiding GSO were found.  GSO is safe as part of a diet that also contains good sources of omega-3 FA, as well as MUFA and SFA.  And if you’re not convinced to add it to your next homemade salad dressing, you can always give it a try as a moisturizer or throw it in your first aid kit as a wound healer.

Conclusion

GSO appears to be just as healthful as other high-omega-6 PUFA oils like safflower, sunflower, soybean or corn oil, (and even more so in a couple of the studies mentioned).  Just don’t swap out your MUFA or high omega-3 oils or foods to increase GSO.  And if you have inflammatory issues or high cholesterol, it would be a reasonable move to use GSO in place of other high-omega-6 PUFA, while also decreasing your use of processed foods containing those same oils.