Intermittent Fasting Diet Plan Example

Whole Wheat Orzo and Grilled Vegetable Salad with Feta, Olives, and Herbs

Now, here are a few more things I've been thinking about . . .

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Photo of Christmas Balls from All Things Christmas.

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Spring has sprung, and I'm rushing the season and thinking about Garlic Scape and Chard Pesto.

Now on to a few more things I'm thinking about . . .

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Todd and Diane's huge collection of cutting boards, captured by iPhone!

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For years I've loved this Summer Tomato Salad with Goat Cheese, Basil Vinaigrette, and Fresh Herbs.

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We are what we eat! Acknowledged, but does this also go for your hormones and different in protein intakes? Lets have another look at the contemporarily available research to figure that out.

In recent study in the International Journal of Sport Nutrition and Exercise Metabolism a group of researchers from the Faculty of Physical Education and Recreation at the University of Alberta reports: "Supplementing a typical daily food intake consisting of 0.8 g of protein·kg-1·d-1 with a whey protein isolate (an additional 0.8 or 1.6 g·kg-1·d-1) [...] had no effect on glucose, insulin, testosterone, cortisol, or growth hormone following the final meal" (Forbes. 2013).

I know, anything else would have been a real shocker. What it wouldnt be, though, is a total surprise. If you dig through the available literature you can easily find data that would support the scientists assumption that doing an experiment "to investigate the effects of a controlled typical one day diet supplemented with two different doses of whey protein isolate on blood amino acid profiles and hormonal concentrations following the final meal" (Forbes. 2013) would be a good idea.

True or false? Certainly TRUE!

No, I am not kidding you! We do have plenty of evidence of direct interactions between chronic high vs. low protein intake and the production and metabolism of hormones, like testosterone, cortisol, their corresponding binding proteins, SHGB and CBP, and a whole host of other molecules that act like hormones, although we often dont call them "hormones". Examples? Well, here you go:

• Low protein = low SHBG (Longcope. 2000) - At least in the 1552 men in their "best age" (40-70 years) who participated in a study by scientsts from the University of Massachusetts Medical School the consumption of a diet that had less than the average 80g/day of protein in it lead to decreases in SHBG and corresponding increases in free (~bioavailable) testosterone. Age, dietary fiber, and smoking, on the other hand were positively correlated with SHBG.
• Chronically high protein intakes (40% of total energy) lower testosterone / cortisol ratio (Oi. 2001) - The highly significant increase in cortisol and corresponding decrease in the testosterone to cortisol ratio, Oi et al. report in a 2001 paper have luckily (a) been observed in rodents, only, and thats actually the main finding of the study (b) could be countered by the administration of garlic extract.
  
  

  Figure 1: In rodents, a high protein intake (40% of total energy from casein) will increase cortisol at stable T-levels and thus decrease the testosterone : cortisol ratio (Oi. 2001)

  I can only speculate whether and to which degree the endocrine effects of high protein diets differ between rats and men (the Anderson study discussed below suggests they dont) - and you know I love facts and hate speculations and unsupported hypothesis. So I stick to an assumption I could support, i.e. the supposition that the improvements in testosterone, the researchers observed, when they fed their rodents garlic was mediated  by its glutathione (GSH) boosting effects. These effects - and you as a regular SuppVersity reader know that are not "garlic exclusive". Whey protein, for example will also increase GSH (Bounous. 1989). Obviously whey doesnt increase your testosterone, but a "protein overload" from a glutathione boosting protein source may not have to be countered by GSH boosters in the first place.
• A high protein : carb ratio decreases total testosterone levels in man (Anderson. 1987) - Some people live by the principle that things that mustnt be. As a SuppVersity reader you obviously dont belong to this group of people and will thus be willing to accept that Anderson et al. were able to show that...

  "[...] the testosterone concentrations in seven normal men were consistently higher after ten days on a high carbohydrate diet (468 ± 34 ng/dl, mean ± S.E.) than during a high protein diet (371 ± 23 ng/d1, p<0.05) and were accompanied by parallel changes in sex hormone binding globulin (32.5 ± 2.8 nmol/1 vs. 23.4 ± 1.6 nmol/1 respectively, p<0.01)." (Anderson. 1987)

  As a SuppVersity reader you are yet also smart enough to know that this data is irrelevant, without adequately measured free testosterone levels: If we do the math and calculate the latter (obviously not 100% accurately), i.e. free testosterone on normal protein diet: 9.4 ng/dL  =  2.01 % vs. free testosterone on high protein + low carb diet: 9.02 ng/dL  =  2.43 %, the difference does no longer look so bad, anyway - does it?
  
  

  Figure 2: Total (TT in ng/dL) and free testosterone (FT in ng/dL), SHBG (µg/L) and testosterone : cotisol ratio after one months on high protein + low carb vs. control (Anderson. 1987)

  This would not change the fact that youd suffered a -42% decrease of the testosterone : cortisol ratio from 60.5 to 35 which occurred in the Anderson study, when the participants were put on a meat, fish, poultry, egg white, and protein supplement based 44% protein, 35% carbohydrates, 21% fat diet.
• A high protein very low calorie diet can increase testosterone levels, but it will do so only if it is used to produce significant weight loss in obese adolescents, whose abundant body fat stores are gnawing away their androgens. In a corresponding study by Brown et al., the eight 11-15-year-old boys and girls where put on liquid (starvation) diets with a protein / carb / fat ratio of 67% / 28% / 5% that containing a total of 492-709 kcal per day.

  Figure 3: Total testosterone levels (ng/dl; left axis) and insulin levels (in µU/ml) in 14 (subj. 3 & 7) and 18 year-old male adolescents before and after 5 weeks on low calorie high protein liquid diets (Brown. 1983)

  As you can see in Figure 3 the significant reduction in body weight (13.5 kg total, 70-75% fat) went hand in hand with improvements in insulin sensitivity and the previously mentioned increase in total testosterone levels in the 14 year-old subjects 3 & 7 and the 18 year-old male adolescents (subject 6) - the only subjects for whom a complete testosterone panel was available.
• High protein diets are driving forces of GH induced skeletal muscle IGF-1 expression (Sanchez-Gomez. 1999) - With IGF-1 being equally important to men and women, it does not matter that the "subjects" in the study at hand were female growing rats that received either a high- or a low-protein diet with crude protein contents of 222 and 83 g/kg respectively.
  
  After 14 days on which the rodents were concamittantly injected with saline control, or growth hormone (rhGH) or recombinant human IGF-I (rhIGF-I) at dosages of 350 and 500µg/day, respectively, Sanchez-Gomes et al. observed that
  

  • Learn more about IGF-1.

    ...the low-protein diet alone reduced IGF-I concentrations in serum and in tissue taken from the gastrocnemius muscle as well as IGF-I mRNA from the same muscle, significantly.
  • ...the high protein diet amplified the retention of injected rhIGF-I in the muscle tissues and was associated with significant improvements of the nitrogen balance
  Based on these results, Myriam Sanchez-Gomez conclude that "the level of dietary protein ingested regulates not only the effect of IGF-I on whole-body N economy but also the regulation of IGF-I gene expression in muscles" (Myriam Sanchez-Gomez. 1999). 
• Increased f 2-hydroxylation of endogenous estrogen with high protein diets could have cancer protective effects (Anderson. 1984) - Certainly far fetched but not impossible is the connection between the increased 2-hydroxylation of endogenous estrogen in response to high protein diets Anderson et al. observed in a 1984 study in male study participants and the significant association between lower ratios an the risk of breast cancer (Liehr. 1996).
  
  

  Table 1: Cox regression of energy-adjusted dietary predictors of breast cancer recurrence and death (Saxe. 1999)

  It goes without saying that this is nothing but a hypothesis - a hypothesis that would yet be supported by a 1999 paper on "dietary predictors of breast cancer recurrence and death" by Saxe et al. which is based on one of the few papers that did not control for "meat" intake (you know that Pizza Salami qualifies as "meat", right?) in which each 5% increase in protein intake was associated with risk reductions of 18% for breast cancer recurrence and 44% for death in premenopausal women (Saxe 1999).
  
  And whats more, the fact that the associations were less pronounced in the post-menopausal study participants (the "low estrogen counterpart", if you will; see Table 1) only support the notion that the protective effects of protein may (at least in part) be mediated by its effects on estrogen metabolism.

References:

• Anderson, K. E., Kappas, A., Conney, A. H., Bradlow, H. L., & Fishman, J. (1984). The influence of dietary protein and carbohydrate on the principal oxidative biotransformations of estradiol in normal subjects. Journal of Clinical Endocrinology & Metabolism, 59(1), 103-107.
• Anderson, K. E., Rosner, W., Khan, M. S., New, M. I., Pang, S., Wissel, P. S., & Kappas, A. (1987). Diet-hormone interactions: protein/carbohydrate ratio alters reciprocally the plasma levels of testosterone and cortisol and their respective binding globulins in man. Life Sciences, 40(18), 1761-1768.
• Bounous, G., Gervais, F., Amer, V., Batist, G., & Gold, P. (1989). The influence of dietary whey protein on tissue glutathione and the diseases of aging. Clin Invest Med, 12(6), 343-9. 
• Brown, M. R., Klish, W. J., Hollander, J., Campbell, M. A., & Forbes, G. B. (1983). A high protein, low calorie liquid diet in the treatment of very obese adolescents: long-term effect on lean body mass. The American Journal of Clinical Nutrition, 38(1), 20-31. 
• Forbes, S. C., McCargar, L., Jelen, P., & Bell, G. J. (2013). Dose Response of Whey Protein Isolate in Addition to a Typical Mixed Meal on Blood Amino Acids and Hormonal Concentrations. International journal of sport nutrition and exercise metabolism. 
• Liehr, J. G., & Ricci, M. J. (1996). 4-Hydroxylation of estrogens as marker of human mammary tumors. Proceedings of the National Academy of Sciences, 93(8), 3294-3296.
• Longcope, C., Feldman, H. A., McKinlay, J. B., & Araujo, A. B. (2000). Diet and sex hormone-binding globulin. Journal of Clinical Endocrinology & Metabolism, 85(1), 293-296. 
• Sanchez-Gomez, M., Malmlöf, K., Mejia, W., Bermudez, A., Ochoa, M. T., Carrasco-Rodriguez, S., & Skottner, A. (1999). Insulin-like growth factor-I, but not growth hormone, is dependent on a high protein intake to increase nitrogen balance in the rat. British Journal of Nutrition, 81(02), 145-152.
• Saxe, G. A., Rock, C. L., Wicha, M. S., & Schottenfeld, D. (1999). Diet and risk for breast cancer recurrence and survival. Breast cancer research and treatment, 53(3), 241-253.

Caffeine wont do the "last rep" for ya.

Time for a brief review of the latest exercise and supplementation science in the SuppVersity Short News. You can see an overview of all previous articles in an RSS feed here.

This time you can take a look at the surprisingly lasting pro-anabolic effects of HIIT as measured by skeletal muscle protein synthesis in the elderly and the similarly surprising finding that caffeine - even if its consumed in significant doses before a workout - will not have you curl an extra pound on either barbell or dumbbell curls.

• 27% increase in protein synthesis even 24h after HIIT exercise in the elderly - Resistance exercise (RE) and aerobic exercise are recommended for older adults for fitness and strength. High-intensity interval exercise (HIIT) is an understudied but potent potential alternative to aerobic exercise. A recent study from the McMaster University aimed to determine how each mode of exercise affected the integrated day-to-day response of muscle protein synthesis.
  
  To do so, they recruited 22 sedentary men (mean age = 22; 67±4 years; body mass index: 27.0±2.6 kg m- 2 [mean ± SEM]) who were randomly assigned to perform resistance training, aerobic exercise, or HIIT. The participants consumed a stable isotope tracer (D2O) for 9 days. Daily saliva samples were taken to measure tracer incorporation in body water. Muscle biopsies were obtained on Days 5-8 of D2O consumption to measure tracer incorporation into muscle at rest, 24 hours, and 48 hours following each exercise bout: RE (3 × 10 repetitions: leg extensor and press, 95% 10RM), HIIT (10 × 1 minute, 95% maximal heart rate [HRmax]), or aerobic exercise (30 minutes, 55%-60% HRmax).
  

  Figure 1: Myofirillar (left) and sarcoplasmic (right) protein fractional synthesis rate (FSR) at baseline and postexercise. Data are means ± SEM. Bars bearing different letters are signifiantly different within each exercise group | AE = aerobic exercise; HIIT = high-intensity interval exercise; RE = resistance exercise (Bell. 2015).

  What the scientists found is quite surprising: While resistance training showed, as it was expected, the greatest increase in fractional protein synthesis immediately, post workout, only the HIIT protocol lead do significant increases in sarcoplasmic protein fractional synthetic rate 24-hour postexercise (2.30±0.34% d- 1 vs 1.83±0.21% d- 1).
  
  That does not mean that HIIT is the better muscle builder, though. Specifically in view of the fact that its the myofibrilar, not the sarcoplasmic protein synthesis rate that bunks with aging (Balagopal. 1997), the higher myofibrilar post-workout protein synthesis after the relatively low volume resistance training session is more important than the long-lasting elevation of the protein influx into the sarcoplasma, a muscle protein fraction that is involved in the anaerobic ATP production, intracellular transport, and several other enzyme functions. 
• Stronger biceps with caffeine? No, ... at least during insometric contractions the administration of 5 mg/kg and 10 mg/kg caffeine does not have ergogenic effects on the elbow flexors.
  Thats at least what the latest study from the University of Kansas shows. In their 13 recreationally trained male subjects, the ingestion of the aforementioned amounts of caffeine in form of of a caffeineated drink did not lead to significant increases in any of the relevant performance markers.
  

  Figure 2: Caffeine did not have significant ergogenic effects; at least the rate of torque development did increase, though (Trevino. 2015).

  In contrast to previous research which has indicated that under certain conditions, caffeine may increase muscle force production during anaerobic activities (3,6,15,17). The results of our study revealed that caffeine did not significantly affect peak torque during the maximal isometric contractions. As Trevino et al. point out, this finding may result from a variety of factors:

  Figure 3: In contrast to the study at hand a study by Beck et al. found significant increases in bench press performance in slightly better trained subjects (Beck. 2006).

  "Past equivocal findings with caffeine ingestion and anaerobic performance may have resulted from the type of muscle action and exercise performed, caffeine dose used, muscle group tested, or training status of the subjects. Our protocol used a single-joint isometric exercise to test the effects of caffeine doses of 5 and 10 mg/kg of body mass on maximal strength of the elbow flexors in resistance trained males (participating in at least 2 training sessions per week). Beck et al. (2006) reported that a 201 mg dose of caffeine significantly increased bench press 1RM in resistance trained males (participating in at least 4 training sessions/week). 

  Because significant results were found with a caffeine dose less than ours (average absolute doses in the current study were 426.7 and 853.4 mg for the 0 and 5 mg/ kg body mass conditions, respectively), it seems that the exercise test and training status may have led to different findings between the studies" (Trevino. 2015).

  Next to the training status and the lack of familiarity with performing maximal muscle contrations (the subjects in Beck et al. (2006) trained 4 times per week, the ones in the study at hand only two times), the exercise may play a role as well. The bench press is after all a multi-joint exercise requiring dynamic involvement of the pectoralis major, deltoid, and triceps. The biceps curl, on the other hand is the classic single-joint exercise, where the CNS activating effect of caffeine may simply offer less benefits than on bench presses, squats and other multi-joint exercises. The same may be true for comparisons of large and small muscle groups and could explain why Astorino et al. (2010), Jacobson, et al. (1992) and Kalmar et al. (1999) found beneficial effect of caffeine on the leg extension performance of their subjects, while Trevino et al. were not able to detect ergogenic effects for the small elbow flexors.

References

• Astorino, Todd A., et al. "Effect of two doses of caffeine on muscular function during isokinetic exercise." Medicine and science in sports and exercise 42.12 (2010): 2205-2210.
• Balagopal, P., et al. "Effects of aging on in vivo synthesis of skeletal muscle myosin heavy-chain and sarcoplasmic protein in humans." American Journal of Physiology-Endocrinology And Metabolism 273.4 (1997): E790-E800.
• Beck, Travis W., et al. "The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities." The Journal of Strength & Conditioning Research 20.3 (2006): 506-510.
• Bell et al. "Day-to-Day Changes in Muscle Protein Synthesis in Recovery From Resistance, Aerobic, and High-Intensity Interval Exercise in Older Men." J Gerontol A Biol Sci Med Sci (2015). 
• Jacobson, B. H., et al. "Effect of caffeine on maximal strength and power in élite male athletes." British journal of sports medicine 26.4 (1992): 276-280.
• Kalmar, J. M., and E. Cafarelli. "Effects of caffeine on neuromuscular function." Journal of Applied Physiology 87.2 (1999): 801-808.
• Trevino, Michael A., et al. "Acute Effects of Caffeine on Strength and Muscle Activation of the Elbow Flexors." The Journal of Strength & Conditioning Research 29.2 (2015): 513-520.

Forbidden fruit or not: You got to love your daily apples ;-)

An apple a day keeps the doctor away. I’m sure you’ve heard this before. And while there are many ways in which we could keep the doctor at bay with an apple (target practice anyone?), our wellbeing demands we eat the luscious fruit. Truthfully, the old adage could not be truer for a variety of reasons. So to keep things organized I am going to worm through the benefits of apples categorically. Also remember we are dealing with the apple fruit, not the apple fritter or apple flavored candy or the iPhone.

I suppose the best starting point is the apple’s nutritional worth. As you can see in the nutritional label to the right, a single medium apple is less than 100 Calories and provides over 10% of the RDA for fiber. Apples also contain every vitamin needed by the body with the exception of Vitamin B12, which is only found in animal products, and Vitamin D, which you can produce by eating your apple under the sun. The same applies to minerals, with apples providing a little of everything except selenium.

A hearty bite for a healthy heart

If you have ever looked at an apple you may have noticed it resembles the humble heart, and for good reason. A comprehensive review of nine human studies conducted by researchers at the British Nutrition Foundation in London examined the effects of apples on cardiovascular disease risk factors and found that apple polyphenols, a type of antioxidant, have a positive influence on blood lipids and blood pressure in human beings (Weichselbaum, Wyness and Stanner 2010). Furthermore, don’t think that apple juice has you covered, since these compounds are most concentrated in the peel of the apple (Wolfe, Wu and Liu 2003). In fact, whole apples have an average of 57 times more polyphenols than commercial apple juice (Hyson 2011; cf. Figure 1).
Okay, so heart health is from the antioxidants in apples and I can get those in any fruit or vegetable. Well, not quite. In one study of nonsmoking healthy middle-age adults who ate apples less than twice a month, simply eating one apple per day lowered blood levels of oxidized LDL – a substance linked to hardening of the arteries – by 40% (Ohio State University 2012). And it’s not just because of the polyphenols either, since a group in this study that took a polyphenol supplement instead of eating the apple had similar but not as pronounced effects. Even dried apples show promise, with a separate study concluding that daily dried apple consumption “can significantly lower atherogenic cholesterol levels” (Chai, et al. 2012). The only caveat is that you need to eat the equivalent of two apples per day if dried rather than fresh.

Apples can help with weight management and protect against cancer

In a very recent study, researchers from the University of Navarra in Spain sought to determine the mechanisms through which the beneficial effects of apple polyphenols act on diet-induced obesity (Boqué, et al. 2013). Overall, they found that apple polyphenols exerted potent anti-obesity and anti-diabetic effects through prevention of fat cell growth, decreased intestinal glucose uptake, and increased fat breakdown. These effects were observed at both the surface and genetic level. The researchers even conclude their study with the acknowledgement that apple polyphenols can act “as a promising functional food ingredient for the management of obesity and its metabolic complications”.

Figure 2: Vitamin & Mineral content of one large apple relative to RDA. Data based on USDA food database for 09003, Apples, raw, with skin (USDA. 2013) - left;  Nutritional label of one raw apple with skin - right (skipthepie.org. 2013)

A review summarizing the current knowledge on potential cancer preventive effects of apples conducted by a lone researcher at the German Cancer Research Center in Germany found that apples influence multiple mechanisms relevant for cancer prevention on the genetic level, and regular consumption of one (or more) apple per day has been shown to prevent skin, breast, and colon cancer (Gerhauser 2008). And it all comes back to the whole fruit, with some of the most potent anti-cancer compounds residing in the peel (Cornell University 2007).

Apples can do even more!

The antioxidants in apples have been shown to extend the average lifespan of fruit flies by 10% (American Chemical Society 2011). Granted the relevance to humans is debatable, but it’s interesting nonetheless. Apple polyphenols may even provide protection against some autoimmune diseases such as ulcerative colitis and Crohn’s disease (Federation of American Societies for Experimental Biology 2011). Another unique compound found in apple peels, ursolic acid, prevents muscle loss during illness and aging, and “animals given ursolic acid also became leaner and had lower blood levels of glucose, cholesterol and triglycerides” (Cell Press 2011).

And it doesn’t end there. In a review and analysis of apples and related compounds, Dianne Hyson (Hyson 2011) from the Department of Family and Consumer Sciences, California State University concluded that, There are current data suggesting that [apple polyphenols] might be linked to reduced risk of several forms of cancer, cardiovascular disease, and asthma. [Apple polyphenols] may also have beneficial effects on outcomes related to Alzheimer’s disease, cognitive decline of normal aging, diabetes, weight management, bone health, and gastrointestinal protection from drug injury.
Oh, and before I forget. Apples are harvested in the fall, which makes local organic difficult to find during other times of the year. Usually, a bunch of apples will be picked and stored through the winter until the next harvest. Fret not, since “long-term storage, both at refrigerator temperature and under controlled atmosphere conditions, was found not to influence flavonoid concentration or antioxidant activity” (van der Sluis, et al. 2001) of the apple.

Emotional Eating

Have your head in the clouds from choosing to eat that apple with lunch? I’m not surprised, given that recent research has shown that eating fruit and vegetables may promote emotional wellbeing (White, Horwath and Conner 2013). More specifically, “on days when people ate more fruits and vegetables, they reported feeling calmer, happier and more energetic than they normally did" (IANS 2013). Even just eating apples in everyday life has been shown to reduce hunger and elevate mood (Macht and Dettmer 2006). Eating more apples isn’t challenging either. Actually, it’s as simple as buying a new fruit bowl. People are more likely to eat apples when they are visible and easily accessible (Privitera and Creary 2012). So keep your fruits close, and your apples closer. Especially during stressful times, as you may find yourself a little less anxious (Hyson 2011).
References:

• American Chemical Society. Eating apples extends lifespan of test animals by 10 percent. March 8, 2011. http://www.sciencedaily.com/releases/2011/03/110302121702.htm (accessed May 13, 2013). 
• —. Red Delicious, Northern Spy Apples Have Most Antioxidants, Chemists Find. May 23, 2005. http://www.sciencedaily.com/releases/2005/05/050523234141.htm (accessed May 16, 2013). 
• Boqué, Noemi, et al. "Prevention of diet-induced obesity by apple polyphenols in Wistar rats through regulation of adipocyte gene expression and DNA methylation patterns." Molecular Nutrition & Food Research, 2013: [ePub ahead of print].
• Cell Press. Apple Ingredient Keeps Muscles Strong: Component of Apple Peels Found to Help Prevent Muscle Weakening in Mice. June 7, 2011. http://www.sciencedaily.com/releases/2011/06/110607131718.htm (accessed May 13, 2013).
• Chai, S C, S Hooshmand, R L Saadat, M E Payton, K Brummel-Smith, and B H Arjmandi. "Daily apple versus dried plum: impact on cardiovascular disease risk factors in postmenopausal women." J Acad Nutr Diet 112, no. 8 (2012): 1158-1168.
• Cornell University. An Apple Peel A Day Might Keep Cancer At Bay. June 3, 2007. http://www.sciencedaily.com/releases/2007/06/070601181005.htm (accessed May 13, 2013).
  Federation of American Societies for Experimental Biology. Scientists discover anti-inflammatory polyphenols in apple peels. December 15, 2011. http://www.sciencedaily.com/releases/2011/11/111130100455.htm (accessed May 13, 2013).
• Gerhauser, Clarissa. "Cancer Chemopreventive Potential of Apples, Apple Juice, and Apple Components." Planta Medica 74, no. 13 (2008): 1608-1624.
• Hyson, Dianne A. "A Comprehensive Review of Apples and Apple Components and Their Relationship to Human Health." Advances in Nutrition 2, no. 5 (2011): 408-420.
  IANS. Eating fruits, vegetables linked to emotional well being. January 30, 2013. http://cooks.ndtv.com/article/show/eating-fruits-vegetables-linked-to-emotional-well-being-321793 (accessed May 16, 2013).
• Macht, M, and D Dettmer. "Everyday mood and emotions after eating a chocolate bar or an apple." Appetite 46, no. 3 (2006): 332-336. 
• Markowski, J., W. Plocharski, and M. Mieszczakowska. "Effect of cultivar and processing on phenolics and antioxidant activity of apple products." I International Symposium on Human Health Effects of Fruits and Vegetables 744. 2005.
• Muraki, Isao, et al. "Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies." BMJ: British Medical Journal 347 (2013).
• Nutritional Info: Raw Apple with skin. 2013. http://skipthepie.org/fruits-and-fruit-juices/apples-raw-with-skin/?weight=182 (accessed May 2, 2013). 
• Ohio State University. An apple a day lowers level of blood chemical linked to hardening of the arteries, research suggests. October 2, 2012. http://www.sciencedaily.com/releases/2012/10/121002143220.htm (accessed May 13, 2013).
• Privitera, G J, and H E Creary. "Proximity and Visibility of Fruits and Vegetables Influence Intake in a Kitchen Setting Among College Students." Environment and Behavior, 2012.
  Stracke, B A, C E Rüfer, F P Weibel, A Bub, and B Watzl. "Three-year comparison of the polyphenol contents and antioxidant capacities in organically and conventionally produced apples ( Malus domestica Bork. Cultivar Golden Delicious)." J Agric Food Chem 57, no. 11 (2009): 4598-4605.
• U.S. Department of Agriculture. "USDA National Nutrient Database for Standard Reference, Release 26." 2013.
• van der Sluis, A A, M Dekker, A de Jager, and W M Jongen. "Activity and concentration of polyphenolic antioxidants in apple: effect of cultivar, harvest year, and storage conditions." J Agric Food Chem 49, no. 8 (2001): 3606-3613. 
• Weichselbaum, E, L Wyness, and S Stanner. "Apple polyphenols and cardiovascular disease – a review of the evidence." Nutrition Bulletin 35, no. 2 (2010): 92-101.
• White, Bonnie A, Caroline C Horwath, and Tamlin S Conner. "Many apples a day keep the blues away – Daily experiences of negative and positive affect and food consumption in young adults." British Journal of Health Psychology, January 2013.
• Wolfe, Kelly, Xianzhong Wu, and Rui Hai Liu. "Antioxidant Activity of Apple Peels." J. Agric. Food Chem 51, no. 3 (2003): 609-614.