Antioxidant and Vitamin D Supplements for Athletes: Sense or Nonsense? – Research Review

Powers S et. al. Antioxidant and Vitamin D supplements for athletes: Sense or nonsense? J Sports Sci. 2011  Aug 11. [Epub ahead of print]

The idea that dietary supplements can improve athletic performance is popular among athletes. The use of antioxidant supplements is widespread among endurance athletes because of evidence that free radicals contribute to muscle fatigue during prolonged exercise. Furthermore, interest in vitamin D supplementation is increasing in response to studies indicating that vitamin D deficiency exists in athletic populations. This review explores the rationale for supplementation with both antioxidants and vitamin D and discusses the evidence to support and deny the benefits of these dietary supplements. The issue of whether athletes should use antioxidant supplements remains highly controversial. Nonetheless, at present there is limited scientific evidence to recommend antioxidant supplements to athletes or other physically active individuals. Therefore, athletes should consult with their health care professional and/or nutritionist when considering antioxidant supplementation. The issue of whether athletes should supplement with vitamin D is also controversial. While arguments for and against vitamin D supplementation exist, additional research is required to determine whether vitamin D supplementation is beneficial to athletes. Nevertheless, based upon the growing evidence that many athletic populations are vitamin D deficient or insufficient, it is recommended that athletes monitor their serum vitamin D concentration and consult with their health care professional and/or nutritionist to determine if they would derive health benefits from vitamin D supplementation.


Supplements for athletic performance have been a part of the landscape for decades and athletes are always looking for an edge in terms of either promoting adaptations to training, recovery, or outright performance.    And while many in the field tend to think of me as anti-supplement, this really sort of misses my issue with supplements.  Because I’m not anti-supplement; rather I’m simply anti-bs.


Casein Hydrolysate and Anabolic Hormones and Growth – Research Review

I want to try something a little bit different for today’s research review.  Rather than looking at a single study in the kind of obsessive detail that only I and three readers really care about, I want to look at multiple studies but in lesser detail.  Not only will this hopefully make the article a bit more relevant and readable, it will let me address more than a single topic at once.

With the sheer volume of research appearing on a weekly basis, this will at least help me to look at data in a more timely fashion.  I’d mention that, for anyone who wants an even better look at a lot of studies, you’d be well served to consider Alan Aragon’s monthly Research Review which I reviewed in the confusingly titled Alan Aragon Research Review – Product Review.

In any case, today I want to look at two recent studies which are:

  1. Deglaire et al. Hydrolyzed dietary casein as compared with the intact protein reduces postprandial peripheral, but not whole-body, uptake of nitrogen in humans. Am J Clin Nutr. (2009) 90(4):1011-22.
  2. West et. al. Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. J Appl Physiol. 2009 Nov 12.

For each study I’ll give a brief background to the topic, look at what was done and then jump straight to the conclusions with some final summing up.  As noted above, some of the detail will be left out but I figure that anyone who is that interested in the details of methodology and such will simply get ahold of the full paper and read it themselves.


Coffee Diabetes and Weight Control – Research Review

Title and Abstract

Greenberg JA et. al. Coffee, diabetes, and weight control. Am J Clin Nutr. (2006) 84(4):682-93.

Several prospective epidemiologic studies over the past 4 y concluded that ingestion of caffeinated and decaffeinated coffee can reduce the risk of diabetes. This finding is at odds with the results of trials in humans showing that glucose tolerance is reduced shortly after ingestion of caffeine or caffeinated coffee and suggesting that coffee consumption could increase the risk of diabetes. This review discusses epidemiologic and laboratory studies of the effects of coffee and its constituents, with a focus on diabetes risk. Weight loss may be an explanatory factor, because one prospective epidemiologic study found that consumption of coffee was followed by lower diabetes risk but only in participants who had lost weight. A second such study found that both caffeine and coffee intakes were modestly and inversely associated with weight gain. It is possible that caffeine and other constituents of coffee, such as chlorogenic acid and quinides, are involved in causing weight loss. Caffeine and caffeinated coffee have been shown to acutely increase blood pressure and thereby to pose a health threat to persons with cardiovascular disease risk. One short-term study found that ground decaffeinated coffee did not increase blood pressure. Decaffeinated coffee, therefore, may be the type of coffee that can safely help persons decrease diabetes risk. However, the ability of decaffeinated coffee to achieve these effects is based on a limited number of studies, and the underlying biological mechanisms have yet to be elucidated.


My Comments

Caffeine is another one of those compounds about which there is endless argument and debate.  Some feel that it is evil, too much causes all manners of problems, and should be eliminated completely. Others like me feel that the only problem with caffeine is when there isn’t enough of it.


Effects of (-)-hydroxycitrate on Net Fat Synthesis as De Novo Lipogenesis

Kovacs EM and MS Westerterp-Plantenga Effects of (-)-hydroxycitrate on net fat synthesis as de novo lipogenesis. Physiol Behav. (2006) May 23; [Epub ahead of print]

(-)-Hydroxycitrate (HCA) might promote weight maintenance by limiting the capacity for de novo lipogenesis (DNL). It was investigated whether HCA may reduce DNL in humans during a persistent excess of energy intake as carbohydrate. In a double-blind, placebo-controlled, randomized and cross-over design, 10 sedentary lean male subjects (mean+/-S.D., age: 24+/-5 years, BMI: 21.8+/-2.1 kg/m(2)) performed a glycogen depletion exercise test followed by a 3-day high-fat diet (F/CHO/P, 60/25/15% energy; 100% of energy expenditure (EE)) and a 7-day high-CHO diet (F/CHO/P, <5/>85/10% energy; 130-175% of EE; overfeeding). During overfeeding, they ingested 3×500 mg/day HCA or placebo (PLA). Each intervention ended with a 60-h stay in the respiration chamber (days 9 and 10). Body weight increased during overfeeding (mean+/-S.E., HCA: 2.9+/-0.2 kg, PLA: 2.8+/-0.2 kg). Respiratory quotient (RQ) was >1.00 in all subjects indicating that DNL was present. On day 9, 24-h EE was lower with HCA compared to PLA (P<0.05). On day 10, resting metabolic rate and RQ during night were lower (P<0.01 and P<0.05, respectively). Non-protein RQ, fat balance and net fat synthesis as DNL tended to be lower (P<0.1) with HCA compared to PLA indicating lower DNL; activity-induced EE was higher with HCA (P<0.05) indicating the urge to eliminate the excess of energy ingested. We conclude that an experimental condition resulting in DNL in humans was created and that treatment with HCA during overfeeding with carbohydrates may reduce DNL.

My comments: I choose this week’s study for two reasons as it addresses two separate issues, that of de novo lipogenesis (DNL, the synthesis of fat from carbohydrates) as well as the supplement hydroxycitric acid (HCA) which has been touted as a ‘fat-burner’ (for use on a fat loss diet) for quite some time.

DNL has been the subject of much debate for years and many readers have probably seen it claimed that ‘carbs in excess of needs simply get converted to fat and stored’. This is true if you’re looking at rats, mice and hamsters. One study (Acheson et. al., 1982) in humans gave the subjects 500 grams of carbohydrates (2000 calories) all at once; conversion of carbs to fat was insignificant. The majority of research in humans has not found DNL to contribute significantly to fat gain except under a few very extreme conditions. They are

  1. An artificially low-fat diet: less than 10% of total calories which well-meaning but otherwise misguided athletes and bodybuilders sometimes try to achieve.
  2. Chronic massive carbohydrate overfeeding: one study (Acheson et. al., 1988) gave 700-900 grams of carbohydrates for 3 straight days following glycogen depletion. In the first 24 hours, as glycogen was refilled, there was no net DNL. Over the next 2 days, as carb intake remained massive and sustained, DNL increased and a significant amount of fat was synthesized. This is part of why diets like Bodyopus and my Ultimate Diet 2.0 taper carbohydrates down as the carb-load continues.

This study created a situation similar to both, for the first 3 days, the subjects followed a low-carbohydrate diet with glycogen depletion (sound familiar). Then they were overfed for the next 7 days on 85% carbohydrates(5% fat and 10% protein) with caloric intake at 130-170% over maintenance. Massive carbohydrate overfeeding accompanied by a very low fat intake, and DNL increased significantly as indicated by a respiratory quotient (RQ) greater than 1.0.

Along with this, the researchers gave the subjects HCA to see if it blunted DNL during the overfeeding, which it did. Back in my first book The Ketogenic Diet, I mentioned that HCA might have some use during CKD style carb-loads for this very reason: empirically, some people found that HCA would limit bloating and puffiness during their carb-load.

But what relevance does this study have to normal conditions? Essentially none. Unless you’re deliberately overfeeding carbs for many days in a row (along with an extremely low-fat intake), DNL generally contributes minimally, if at all to fat gain (for review, see Hellerstein, 1999). As well, HCA only has an impact in humans during massive carbohydrate overfeeding, although one study (Westerterp-Plantenga, 2002) suggested it might help reduce food intake. Its use as a fat-burner on a diet (by definiton you can’t be overfeeding carbs, except during refeeds or CKD style carb-loads) was misguided anyhow, since that’s not how it works.

Summing up: except under the most extreme of dietary conditions, DNL contributes almost insignificantly to fat gain in humans. Which isn’t to say that carbs don’t contribute to fat gain, it’s simply generally not through direct conversion to fat. And while HCA might have some use during those types of extreme dietary conditions, in general it’s fairly useless as a supplement; especially as any kind of fat burner on a diet.