You get much more out of your vegetables by adding a spoonful of oil. Recent research shows that adding soybean oil to a salad increases the absorption of 8 different micronutrients.
Micronutrients in Vegetables
When we consider a diet, we primarily focus on the ‘macros’ – the macronutrients carbohydrates, fats, and proteins. This isn’t surprising; relatively, they constitute a larger part of our needs. As a source of energy and building blocks for muscle mass, they are the major players in determining your health and physique. However, the micronutrients in food, such as vitamins and minerals, are essential for numerous chemical processes in the body and for maintaining normal bodily functions.
I recently wrote an article titled “Not all calories are created equal,” explaining the difference between the calories you intake from food versus the amount of calories the food contains. A similar distinction can be made for micronutrients. You don’t necessarily have to intake all the micronutrients present in consumed food. Yes, you do get them, but some may leave your body without being utilized. So, we’re talking about the absorption of these nutrients. The good news is that you can improve this absorption. At least when eating a salad.
Wendy White, associate professor of food science and human nutrition, has demonstrated with her team that eight different micronutrients in a salad are better absorbed when one tablespoon of fat in the form of soybean oil is added to it. Conversely, the likelihood of absorbing these micronutrients decreases when this oil is not added. The results of the study were recently published in the American Journal of Clinical Nutrition [1].
Strictly speaking, it’s about seven micronutrients in the salad itself. Four carotenoids (alpha-carotene, beta-carotene, lutein, and lycopene), two forms of vitamin E, and vitamin K. The eighth micronutrient, vitamin A, is synthesized in the intestines from alpha-carotene and beta-carotene. According to White, this improved absorption provides various health benefits, including cancer prevention and maintaining eyesight.
For the study, the researchers had 12 young women consume five salads with different amounts of soybean oil (0, 2, 4, 8, or 32 g). Why soybean oil? Because it is a commonly used type of oil in many dressings (although olive oil and peanut oil are also often used). Blood tests were then used to determine the level of absorption. On the days when the different salads were consumed, the participants had to avoid certain foods rich in these micronutrients (otherwise, it wouldn’t be clear whether they were absorbed from the salad or an earlier meal).
The salads themselves consisted of 48 g spinach, 48 g romaine lettuce, 66 g shredded carrots, and 85 g cherry tomatoes.
More Oil, Better Absorption of Micronutrients
The research revealed that the amount of added oil was directly proportional to the increased absorption. So, the more oil, the better the absorption. However, this doesn’t mean you should start dumping a bowl of dressing on your salad. In the study, a maximum of 32 grams (slightly more than two tablespoons) was added. White therefore recommends adhering to the (American) guidelines of approximately two tablespoons per day.
However, White points out that the effect of oil on absorption varied among participants. For some, the effect was negligible. However, overall, the effect was statistically significant.
So, if you’re forced to eat a salad, perhaps due to a diet, you don’t have to feel guilty about adding some dressing immediately. If you’re already restricted in what you can eat, you might as well get as much out of it as possible. As long as it fits into your macros, of course.
Moreover, not all dressings are the same. This research was funded by Unilever, which reportedly didn’t have any substantive role in the study. For example, the first dressing I find online from Unilever (“Hellmann’s Naturel Dressing”) is based on vinegar and contains no fats (but sugars!). You can, of course, create your own dressing.
Reference
- Wendy S White, Yang Zhou, Agatha Crane, Philip Dixon, Frits Quadt, Leonard M Flendrig. Modeling the dose effects of soybean oil in salad dressing on carotenoid and fat-soluble vitamin bioavailability in salad vegetables. The American Journal of Clinical Nutrition, 2017; 106 (4): 1041 DOI: 10.3945/%u200Bajcn.117.153635
