Eat Your Veggies and Don’t Fear the Fat

17 May

Eat Your Veggies and Don’t Fear the Fat

By Tim Skwiat, MEd, CSCS, Pn1

Mom Was Right: Eat Your Veggies

It’s no secret that a diet plentiful in vegetables— packed with vitamins, minerals, phytonutrients, and fiber—confers many health benefits. According the United States Department of Agriculture,1 eating a diet rich in vegetables may:

  • Reduce the risk of heart disease, including heart attack and stroke;
  • Protect against certain types of cancers;
  • Reduce the risk of obesity and type 2 diabetes;
  • Lower blood pressure; and
  • Help decrease bone loss.

While consuming a diet high in vegetables is associated with lower risks for numerous chronic diseases, the impact of eating vegetables on weight management has not been as widely researched. However, recent studies indicate that higher consumptions of vegetables during weight loss efforts are correlated to more weight and fat lost.2

What’s more, scientists have found that reduced-calorie diets including five servings of vegetables per day can lead to sustained weight loss, with associated reductions in cardiovascular disease risk factors. Further, consuming a higher proportion of calories as vegetables may support greater weight loss.3

According to the National Center for Chronic Disease Prevention and Health Promotion Division of Nutrition and Physical Activity,4 there are multiple reasons why a diet higher in vegetables may help folks control energy balance and support healthy body weight management:

  • To lose weight, a person must eat fewer calories than what s/he burns (i.e., negative energy balance).
  • People may not limit what they consume based on calories alone. Satiety (i.e., feeling full) is a major reason that people stop eating. Rather than the calorie content of food, short-term studies indicate that the volume of food people eat at a meal is what makes them feel full and stop eating.
  • At the same calorie level, foods with low energy density provide a greater volume of food, which may help people feel full at a meal while consuming fewer calories.
  • Water and fiber increase the volume of foods and reduce energy density. In their natural state, vegetables have high water and fiber content and thus are low in calories and energy density.
  • Vegetables are good substitutes for foods of high energy density.

Unfortunately, the vast majority of Americans don’t consume enough vegetables. In fact, only 1 in 4 adults eats the recommended amount of vegetables each day. Thus, the first take-home point is to listen to what your mother always told you: “Eat your veggies.”

Don’t Fear The Fat

More and more research has demonstrated that in addition to the micronutrients (e.g., vitamins and minerals) packed into vegetables, there are also important phytochemicals (i.e., plant chemicals) that are essential for optimal physiological functioning. For instance, carotenoids, phytochemicals that are responsible for providing the dark colors of various plant foods, are potent antioxidants that combat oxidative stress,5 one of the most important factors mediating the deleterious effects of aging.6,7

Here’s where things get really interesting. Like some of the important micronutrients (e.g., vitamins A, D, E, and K) in vegetables, carotenoids (e.g., alpha- and beta-carotene, lycopeine, lutein, zeaxanthin) are fat-soluble nutrients. In other words, dietary fat is necessary to ensure absorption of these health-promoting nutrients.

In a 2004 study published in the American Journal of Clinical Nutrition, researchers compared the absorption of carotenoids when participants consumed a salad dressed with a fat-free (i.e., 0 grams of fat), reduced-fat, or full-fat salad dressing rich in monounsaturated fats (e.g., olive oil). After consuming the salad with the fat-free dressing, the appearance of carotenoids in the bloodstream was negligible. That’s right, the participants literally absorbed NONE of the free radical-fighting nutrients.8 While there was a relative increase in absorption of carotenoids when participants ate the salad with a reduced-fat dressing, “a substantially greater absorption of carotenoids was observed when salads were consumed with full-fat dressing.”

In a study published in the Journal of Nutrition, researchers from The Ohio State University found similar results when they added avocado or avocado oil to salsa and salads. When avocado or avocado oil, both rich in monounsaturated fats, was added to salsa, the absorption of fat-soluble carotenoids was up to four times higher than when the salsa was avocado-free. If that’s not enough, when avocado was added to salads, the researchers found that absorption of carotenoids was up to 15 times higher than when the salads were consumed avocado-free (i.e., fat-free).9

By now, you’re starting to see the picture, and recent research from Purdue sheds even more light on the types of fats that may be best for salads and veggies. In a 2012 study published in the journal Molecular Nutrition & Food Research, participants were fed salads topped off with saturated (e.g., butter), monounsaturated (e.g., olive oil), and polyunsaturated (e.g., soybean oil) fat-based dressings, and researchers tested their blood for absorption of fat-soluble carotenoids. The researchers found that monounsaturated (e.g., olive-oil) fat-rich dressings led to the greatest carotenoid absorption.10 In all cases, there was a dose-dependent relationship between the amount of fat consumed and the absorption of carotenoids (i.e., the amount of fat has the strongest effect on bioavailability of carotenoids), and soybean oil salad dressing was most dependent on dose.

To make matters worse, soybean oil is rich in omega-6 fatty acids, which promote inflammation, particularly when they are consumed in excess of omega-3 fats (e.g., fish oil).11 In fact, researchers attribute the ubiquity of soybean oil, which is the most common oil used in store-bought salad dressings, in the modern day food supply to the massive imbalance of the average individual’s consumption of omega-6 fatty acids relative to omega-3 fats.12 This omega imbalance is connected to an increase in nearly all inflammatory diseases, including cardiovascular disease, diabetes, obesity, metabolic syndrome, irritable bowel syndrome, inflammatory bowel disease, rheumatoid arthritis, asthma, mood disorders, mental illness, autoimmune disease, and more.13

“If you want to utilize more from your fruits and vegetables, you have to pair them correctly with fat-based dressings,” said Mario Ferruzzi, a Purdue associate professor of food science. “If you have a salad with a fat-free dressing, there may be a reduction in calories, but you lose some of the benefits of the vegetables.”

The take-home point: Don’t fear the fat. Pair your vegetables with healthy, whole food fats, particularly those rich in monounsaturated fats like extra virgin olive oil, olives, avocados, avocado oil, almonds, almond oil, macadamia nuts, and macadamia nut oil.

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References:

  1. United States Department of Agriculture. Why is it important to eat vegetables? http://choosemyplate.gov/food-groups/vegetables-why.html.
  2. Whigham LD, Valentine AR, Johnson LK, Zhang Z, Atkinson RL, Tanumihardjo SA. Increased vegetable and fruit consumption during weight loss effort correlates with increased weight and fat loss. Nutr Diabetes. 2012;2:e48. doi:10.1038/nutd.2012.22.
  3. Tapsell LC, Batterham MJ, Thorne RL, O’Shea JE, Grafenauer SJ, Probst YC. Weight loss effects from vegetable intake: a 12-month randomised controlled trial. Eur J Clin Nutr. 2014;68(7):778-785. doi:10.1038/ejcn.2014.39.
  4. National Center for Chronic Disease Prevention and Health Promotion. Can eating fruits and vegetables help people to manage their weight? Weight Manag Res Pract Ser. 1. http://www.cdc.gov/nccdphp/dnpa/nutrition/pdf/rtp_practitioner_10_07.pdf.
  5. Rao A, Rao L. Carotenoids and human health. Pharmacol Res. 2007;55(3):207-216. doi:10.1016/j.phrs.2007.01.012.
  6. Betteridge DJ. What is oxidative stress? Metabolism. 2000;49(2 Suppl 1):3-8.
  7. Floyd RA. Antioxidants, oxidative stress, and degenerative neurological disorders. Proc Soc Exp Biol Med Soc Exp Biol Med N Y N. 1999;222(3):236-245.
  8. Brown MJ, Ferruzzi MG, Nguyen ML, et al. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. Am J Clin Nutr. 2004;80(2):396-403.
  9. Unlu NZ, Bohn T, Clinton SK, Schwartz SJ. Carotenoid absorption from salad and salsa by humans is enhanced by the addition of avocado or avocado oil. J Nutr. 2005;135(3):431-436.
  10. Goltz SR, Campbell WW, Chitchumroonchokchai C, Failla ML, Ferruzzi MG. Meal triacylglycerol profile modulates postprandial absorption of carotenoids in humans. Mol Nutr Food Res. 2012;56(6):866-877. doi:10.1002/mnfr.201100687.
  11. Bosma-den Boer MM, van Wetten M-L, Pruimboom L. Chronic inflammatory diseases are stimulated by current lifestyle: how diet, stress levels and medication prevent our body from recovering. Nutr Metab. 2012;9(1):32. doi:10.1186/1743-7075-9-32.
  12. Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. Am J Clin Nutr. 2011;93(5):950-962. doi:10.3945/ajcn.110.006643.
  13. Hibbeln JR, Nieminen LRG, Blasbalg TL, Riggs JA, Lands WEM. Healthy intakes of n-3 and n-6 fatty acids: estimations considering worldwide diversity. Am J Clin Nutr. 2006;83(6 Suppl):1483S – 1493S.
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