13 12 2012
Hydroxypropyl Distarch Phosphate (HDP), the Fat-burning Carb
Hydroxypropyl distarch phosphate or HDP is the prototypical chemically modified (RS4) resistant starch. Research shows that it can increase liver, and possibly muscle, fatty acid oxidation, and lower the glucose, insulin and incretin responses to a meal. It seemingly offers intriguing opportunities for health, weight loss, weight management and endurance performance.
What does it do and what studies support this?
Dietary resistant starches are aching to insoluble dietary fibers in their properties, in that they are highly resistant to digestion. Instead they pass through the small intestine and are partially or completely fermented by the gut microbiota in the large intestine. The intestinal microflora thrive on this and produce short chain fatty acids (SCFA), a portion of which they themselves consume. The result is that less glucose is produced during digestion leading to a lower glucose and insulin response. Insulin is an anabolic hormone and the primary stimulus for muscle, liver and adipose tissue to store glucose and fatty acids as glycogen and triglycerides. It drastically reduces the use of fatty acids as a primary fuel source. Because less glucose is sensed by the intestinal K-cells, less glucose-dependent insulinogenic peptide (GIP) is released in response to the meal as well. GIP is an incretin hormone that not only stimulates a fast insulin response after a meal, but also seems to directly negatively affect fat utilization in the body by lowering adiponectin. Because not all the RS is fermented and a portion of it is used by the gut microbiota, a meal of the same composition containing resistant starch instead of digestible carbohydrates is less calorically dense. And because the remaining energy is taken up as SCFA in the large intestine instead of glucose in the small intestine, fatty acid oxidation in the liver is maintained and glycogen stores are spared. The net result is that replacing a portion of digestible carbohydrates by resistant starches can lead to increased insulin sensitivity, fatty acid oxidation and resting energy expenditure.
Of particular note was the study of Shimotoyodome et al. (2010) however, which compared the effect of chemically modified RS4 starches to their unmodified (digestible) counterparts and an RS2 type starch. The study clearly demonstrated that the RS4 versions outperformed their unmodified counterparts (not surprisingly given the previous data and the reduced in vivo availability), but also outperformed the RS2 type resistant starch. The authors had determined the in vitro and in vivo availability of the RS4 and RS2 type starches to be identical, so that the increase in fatty acid oxidation and resting energy expenditure and reduced GIP response could not be due to the aforementioned reasons that impart the benefits of resistant starch versus digestible starches and soluble fiber. On top of that, it appeared that RS4 type starches were able to attenuate the incretin response to other macronutrients in a mixed meal (in short it implies it’s not only better as a substitute for other macronutrients, but also ameliorates the impact of nutrients ingested with it). Although the exact mechanisms remain to be elucidated, the authors of the study postulated that “RS4 lowers nutrient transport from the lumen to the intestinal epithelium, and thereby stimulates lower GIP secretion from K cells located in the intestinal epithelium.” RS4 starches have been shown to block the uptake of various micronutrients, and according to this hypothesis, may slow or limit the availability of macronutrients in a mixed meal as well. Particularly dietary fat absorption would be attenuated by reduced chylomicron (lipoprotein particles that transport fats and cholesterol from the intestines to the liver) formation , and combined with the reduced chylomicron unloading in the liver as a result of lower Lipoprotein lipase (LPL) activity due to reduced insulin and incretin response. So the fats in a mixed meal would be absorbed slower and possibly end up contributing to the SCFA pool in the large intestine.
General health: A plethora of studies already demonstrated that increased resistant starch in the diet can contribute to lower total cholesterol, blood triglyceride content and insulin resistant. On top of that they heavily contribute to colon health by acting as prebiotics and preventing colon cancer.
Weight loss and weight maintenance: The increased or maintained fatty acid oxidation and increased resting energy expenditure associated with resistant starch intake, as well as the reduction in caloric intake compared to other macronutrients, and the reduction in postprandial responses to other macronutrients co-ingested, make HDP an attractive modality in preventing obesity, weight maintenance and even weight loss. Although appetite reduction does not seem to be a major factor in the benefits of natural resistant starches, I personally can attest that HDP is quite satiating as well.
Increases endurance performance: For sustained efforts, fatty acids form a far more economical fuel source than carbohydrates. While carbohydrates have always been a principle factor in the diet of endurance athletes, their importance in the bigger picture may have been overstated, especially when ingested close to the exercising. In fact, whether glycogen synthase was increased or decreased, did not seem to affect endurance performance at all. In contrast, carbohydrate ingestion leads to an insulin peak which reduces fatty acid oxidation, making it hard for endurance athletes to consume necessary calories close to a contest or training without it affecting initial performance. Many a study has demonstrated the beneficial effect on endurance performance of increasing fatty acid oxidation by way of supplementation. Because HDP has a lower glucose and insulin response and decreases said responses to other macronutrients ingested along with it, it manages to sustain fatty acid oxidation in liver and muscle. But contrary to other supplements HDP will also contribute to the amount of available energy in the form of SCFA produced in the large intestine, thereby promoting, instead of blunting, the use of fatty acids as a substrate.
Is it safe?
HDP is not just safe, it is recognized as a food additive in the US, Australia, the European Union (E1442) and several other countries, used to increase the physical properties of various food items, even baby-food. It is primarily used as a thickening agent or to add shine. Its use comes with a few caveats however. It has already been demonstrated that HDP will inhibit the uptake of certain micronutrients like zinc and iron, so it is wise to make sure you eat ample zinc and iron rich meals when not consuming HDP, and if you happen to take supplemental micronutrients or other supplements, given the properties of HDP, you would probably do wise to take them at a different time, preferably on an empty stomach 15-30 minutes prior to HDP ingestion. HDP, as most fibers and resistant starches, seems to increase faecal volume as well (meaning you may need to use the bathroom more often depending on how much you use). Resistant starches can both cause and resolve constipation. Which it does seems to depend largely on fluid intake. So it is prudent to make sure you consume adequate fluids throughout the day.
What are effective doses?
Although studies on natural resistant starches seem to suggest 8-16% of the total diet is needed to produce many of the benefits short term, and the Shimotoyodome study seems to suggest at least 5-10% is needed to see significant increases in fatty acid oxidation and resting energy expenditure (equating to 100-200 of your calories on a 2000 calorie diet being replaced with HDP) the effects seem to be largely dose dependent and of that nature that any amount of substitution should already be beneficial. The study testing the endurance increase used 0.2% of bodyweight, which is 200 g for a 100 kg (220 lbs) individual. Because HDP is quite versatile and easy in use, it not at all unfeasible to consume that amount on a daily basis depending on price. I recently acquired a 25 kg bag at wholesale price, at about 3 euros per kg. But obtaining wholesale products isn’t attainable for everyone, nor is a quantity of 25 kg desirable for all (although a very good investment). No doubt it’s quite possible to produce a cost-effective commercial form of HDP, but if of course you have to buy it from companies like this one, at a whopping 1000% mark-up for some hype and shiny packaging, then it can be rather daunting and economically unsound to take in such quantities.
How is it best used?
Now we get to my favorite part. The recommendation to increase dietary resistant starch for health benefits isn’t a new one. However, it is a rather unappetizing notion for many, especially those who find them in a predicament of overweight or insulin insensitivity as a result of poor diet choices, to consume more of the typical sources like vegetables. Let alone such a significant quantity. But HDP is a white, odorless flour-like powder that is quite bland in taste, and it can easily be used in any type of application where you would normally use flour, as well as in many recipes where you would use alternative carbohydrate sources like oatmeal. I have tried it in a wide variety of preparations, from successfully using it when making meat loaf or roux for sauces, and less successful attempts at making brownies and cookies (it is quite possible, but such recipes will still require quite a bit of sugar to be successful, my attempts at health versions were rather chewy and tasteless). But by far my favorite way of consuming this stuff is making pancakes. In their human trial, Shimotoyodome et al. actually did make pancakes as the means of feeding their subjects. They made them in a quite classic way with a significant amount of sugars and digestible carbohydrates, and they still noticed significant differences in incretin response and resting energy expenditure. One can only assume the effect would be even more pronounced if the recipe contained no sugar and high protein. After comparing the recipe in the study with various recipes for classic and protein-rich pancakes, I came up with an amazingly simple and easy recipe for delicious HDP/protein pancakes that are quite tasty to be consumed as is, but can also easily be combined with jam without added sugars, additional stevia, or any other healthy topping of your choice.
125g Vanilla protein powder
10g of stevia
4g of cinnamon
Add milk to desired consistency
Note: The amount of milk will differ with the type of protein. With whey protein you’ll find 300-500ml of fluid adequate, depending on desired consistency, with casein protein you’ll need a lot more (700-1000ml). In the interest of limiting calories from carbs for certain purposes, like my own brand of dieting (food for a future article in the nutrition section, I’ll add the link here when it’s up), I’ll usually use casein, but only add 400 ml of milk and instead add water until it reaches the desired consistency. This does not seem to affect taste and the extra fluid makes the pancakes fluffier.
Nutritional facts: (per pancake)
Carbs: 17.8g (of which 15.5g HDP)
Making 100g pancakes I have to say I’m quite full after just 2 or 3 yielding 30-50g of protein and HDP each.
The stuff is alas not incredibly soluble, although solubility can be increased somewhat by gelatinization. Increased solubility decreases the effect somewhat, but it is believed the increased viscosity can make up for that. You can obtain your HDP pre-gelatinized, but you can also gelatinize it yourself. It’s typically done by autoclaving at 120°C the stuff in 15x the volume of water for 15 minutes, a process easily simulated in your average pressure cooker. The remaining blob after drying is still not exactly soluble, but can yield a creamy substance after mixing that can be drank. In such a fashion you could easily add it to a protein shake as well or use it in cold preparations.
If any of you have some suggestions for possible recipes using HDP, feel free to leave a comment in the section below or send an email to firstname.lastname@example.org, and if we can successfully recreate your recipes and eat them, we will add them here. Most recipes involving flour will usually lend themselves well to using HDP instead.
Is all HDP the same?
There are various sources of HDP, the most notable ones being potato, corn, tapioca and waxy corn starch. All of them outperformed their unmodified counterparts and RS2 starches by a margin, so really any HDP will do, but the effect of tapioca and waxy corn starch seemed to be somewhat more pronounced than that of regular corn starch (potato starch wasn’t included in the test – but I would avoid potato if you want to gelatinize since it retrogrades more easily, one of the reasons why letting your potatoes cool before consumption is a great way of increasing dietary resistant starch). In short the difference is minimal, and any verified HDP will yield the ascribed benefits comparative to RS2 starches, unmodified starches and certainly higher GI carbohydrates (since degree of resistance is inversely correlated with glycemic index for obvious reasons).
When is it best used?
Well contrary to the way it is currently marketed by at least one company, HDP is probably not a good bet for your peri-workout nutrition. Its proposed effect of lowering nutrient transport from the lumen to the intestinal epithelium would likely affect the rate of appearance of amino acids and possibly dampen the much needed amino acid spike. Its effect on increasing fatty acid oxidation is also linearly opposed to the maximal glycogen depletion needed to induce metabolic stress on the muscle and initiate hypertrophy, as well as to the requirement of rapid repletion of glycogen and amino acid stores after resistance training which synergistically enhances protein synthesis.
For people on a diet pretty much any other time will do. For those individuals who like the concepts of carb-backloading and intermittent fasting but find it hard to refrain from eating carbohydrates or getting satiated sufficiently in the morning, a high-HDP, high protein meal is also perfect, since the reduced glucose and insulin response and sustained fatty acid oxidation will help maintain a semi-fasted status to keep you in fat-burning mode during your most insulin-sensitive moments. The ideal time to take it of course is 30-60 minutes prior to a cardio workout (or a training or meet if you are in fact an endurance athlete) since studies not only reveal that HDP will increase fat utilization and boost performance during endurance exercise, other studies also demonstrate the importance of consuming a light meal prior to cardiovascular exercise for maximal fat-burning benefits. This works out well, since if at all possible, it’s best to put the greatest amount of time possible between cardio and resistance workouts because of the concurrent training effect (which states that either will blunt the adaptation to the other because of the negative influence mTOR and AMPK have on each other)
For people attempting to gain maximal amounts of weight, just about the only time I can see this benefiting you most is in your last meal before bed, because it will deliver additional energy and calories, but without affecting resting energy expenditure or fatty acid oxidation much, allowing you to maximally benefit from your overnight fast while still keeping calories somewhat higher. Speaking of which, the combination with a long acting casein-type protein is probably a winning one. Casein is known to spare more protein than fast-acting proteins, while maintaining elevated amino acid levels for a much longer timespan. This is beneficial both when dieting when you may wish to reduce the number of meals, because you can’t dilute calories anymore, or for your pre-bedtime meal since it will keep amino acids elevated for a longer stretch of time overnight to maintain anabolism.
HDP is an absolute must-have in the arsenal of an endurance athlete as it increases performance and substrate utilization while providing at least some actual calories. On top of that it is likely a valuable weapon in the arsenal of the fitness athlete or bodybuilder, especially during phases of calorie-restriction, for its ability to maintain fatty acid oxidation after feeding, lower fat deposition and blunting the incretin and insulin response from other foods ingested with it. It can be exceptionally useful to fuel sessions of cardiovascular work.
For people dealing with overweight and insulin-insensitivity HDP is a low-threshold way to dilute energy of meals, lower cholesterol and triglyceride levels, burn more fat and improve insulin responsiveness. It provides an easy and often tastier way of including more dietary resistant starch in the diet, which in turn improves the rate of compliance with a healthier diet that is often so elusive for many.
In the end it is a very economical (if obtained at the right price) and easy to use form of resistant starch, lending many of the benefits of dietary fiber on health, appearance and well-being.
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