Q. What else influences plasma palmitoleic acid levels?
The current study lends support to the idea that palmitoleic acid concentration in the plasma is more reliant on carbohydrate intake than fat intake. However, the study was conducted under hypocaloric conditions, and previous research has suggested that dietary intake of palmitoleic acid (which is rich in a few select foods such as macadamia nuts) does significantly influence plasma concentrations during weight maintenance. Alcohol has also been suggested to reduce palmitoleic acid concentrations, with one study reporting significantly lower levels in people consuming more than 100mL of ethanol consumption per week (seven regular 12-ounce beers) compared to people consuming less. This study also found palmitoleic acid concentrations to be independent of smoking status.
Q. How do various biomarkers of fatty acids in the body differ?
Biomarkers of fatty acid composition differ from dietary intake, in that biomarkers reflect both the intake and the utilization of the fatty acids. Because not everyone is similar in how we absorb, transport, and metabolize nutrients, biomarkers allow us to look beyond simple dietary intake and focus on the physiological consequences of consuming certain substances. Moreover, biomarkers can provide a long-term picture of dietary intake.
Due to the essential nature of fatty acids in cell structure, assessment can involve numerous body tissues in addition to blood and urine (e.g. hair, nails, skin, breath, saliva, feces). However, measuring blood plasma is the most common method. Serum triglycerides reflect dietary intakes over the past hours to days, whereas cholesterol esters and phospholipids reflect daily intakes. Only body fat stores (adipose tissue) tend to reflect long-term dietary fat consumption (e.g. years), and even this measure can be inaccurate in people who have experienced cycles of fat loss and gain.
Q. How strongly is palmitoleic acid associated with heart disease, when compared to other biomarkers?
Although statistically significant, the strength of the relationships between palmitoleic acid and health parameters is low to moderate. For instance, in one study of over 3200 Chinese adults, palmitoleic acid concentrations could only explain about 37% of the variance in triglyceride levels and 14% of the variance in HDL-cholesterol levels.
It should also be kept in mind that fatty acid levels in any biomarker represent a proportion and not an absolute measure. Thus, greater integration of certain fatty acids into the biomarker can reduce the percentage of other fatty acids without their absolute amount changing. All of the aforementioned studies demonstrating associations between fatty acids and health outcomes were based on percentages, making it difficult to draw conclusions as these are not quantifiable values. One person could have double the amount of palmitoleic acid in serum as another person and still have similar percentages if they also have double the amount of blood lipid.
There is also evidence of seasonal variations in fatty acid profiles. One early study showed greater proportions of saturated fatty acids in the adipose tissue of the legs and arms during summer compared to winter. This difference was attributable to a reduction of palmitoleic and oleic acid levels, with a simultaneous increase in palmitic, myristic, and stearic acid levels.
Although these changes were in adipose tissue and not serum biomarkers, it raises the question of whether the current study could have been influenced by seasonal changes as its six month duration, by necessity, spanned more than one season. Since subtle changes in plasma fatty acid levels were tracked over increments of time, it would be difficult to differentiate what changes were at least partly a result of the season.
Q. What dietary sources have a lot of palmitoleic acid in them?
According to the USDA nutrient database, roasted chicken skin from the leg and thigh contains the greatest amount of palmitoleic acid with 2.8 grams per 100 grams of food. Beef fat follows with about 1.9 grams, then turkey skin with 1.34-1.5 grams, and finally butter at 0.96 grams. Poultry skins contain the most palmitoleic acid on average, followed by beef fat and butter. Macadamia oil is a rich source, containing 19% palmitoleic acid.
Keep in mind that palmitoleic acid is different than trans-palmitoleic acid. The latter comes from very limited sources, mostly red meat and dairy from grass-fed cows, and is not synthesized by the body. Trans-palmitoleic acid in plasma lipids and adipose tissue has been repeatedly associated with better metabolic outcomes, as shown in this paper by Study Deep Dives reviewer Stephan Guyenet, PhD.
Q. Are there benefits to palmitoleic acid from diet? In plasma? Elsewhere?
A very recent study published in December of 2014 found that feeding mice 300 milligrams of pure palmitoleic acid per kilogram of bodyweight daily, in addition to their normal diets for ten days significantly increased glucose uptake in fat tissue through increased expression of glucose-uptake transporter 4 (GLUT4; necessary for insulin-stimulated glucose uptake into tissues). This was despite no changes in plasma fatty acid levels.
Earlier studies have also found palmitoleic acid to enhance glucose uptake and insulin sensitivity of skeletal muscle, and reduce liver fat buildup. The authors of this study suggest that palmitoleic acid may act as a major signaling lipid produced from fat tissue for communication with distant organs. In obese sheep, infusion of palmitoleic acid twice daily for 28 days preserved insulin sensitivity before beginning an obesogenic diet, possibly through a reduction of intramuscular fat.
It appears that the benefits of palmitoleic acid revolve around insulin-mediated glucose disposal into both muscle and fat tissue. This raises an interesting contradiction, with the studies demonstrating associations between palmitoleic fatty acid levels in the blood and some adverse health outcomes such as diabetes. Like certain cholesterol markers, palmitoleic acid may be more of an indicator that something might be physiologically wrong rather than a cause. DNL is one possible cause of increased palmitoleic acid levels, and very high levels may be a marker that something is increasing DNL to dangerous amounts (such as prolonged overeating of carbohydrate, or worsening glucose tolerance from uncontrolled diabetes, both of which can screw with carbohydrate metabolism). Suggesting that palmitoleic acid is 100% detrimental does not seem accurate given the complexity of evidence on the topic.