Health & Nutrition
2. How to sprout
3. Sprout nutrition differences - for nutrition geeks only!
a. Study types and general results
b. Nutrient increases and decreases are inconsistent
c. Energy, dry matter, and phantom increases
d. Protein
1. Lysine and methionine chart
e. Sugar
f. Vitamins and minerals
g. Antinutrients
h. Digestibility
i. Unfavorable changes
j. Animal studies
k. Miscellaneous topics
l. Why the conundrum?
m. Conclusion
4. Case study using standardized data for mung beans and lentils
Benefits of sprouting - myth and reality
Germination and sprouting set off a biochemical reaction in seeds and grains. It is widely reported on the internet that sprouts are a superfood, and that sprouting causes a significant improvement in the quality and quantity of many beneficial nutrients, along with a decrease in the amount of fat. Unfortunately this is a myth; scientific studies indicate that the nutritional content changes but it doesn't change enough to make a noticeable difference, particularly when the seed has only been sprouted out to a short length.
But even though sprouts aren't a superfood, they are beneficial in other ways. Sprouting improves the digestibility of the seed/grain by making it softer and easier to process, and it may improve the bioavailability of some nutrients by removing anti-nutrients like phytate. Our birds would have easy access to living, growing foods in the wild. Sprouting helps us approximate this part of their diet, even though they probably wouldn't eat sprouts in the wild. Variety in the diet adds interest and enrichment to our birds' lives, and the texture of moist sprouts is very different from that of dry seeds and grains. Grocery-store sprouts aren't recommended for birds due to problems with bacteria and mold.
Equipment. You can buy an inexpensive commercial sprouter if you like, but it's easy to make your own sprouter using simple materials. Basically, you need something that will let you rinse and drain the seeds easily without making a mess or having seeds go down the sink.
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A mason (canning) jar with plastic canvas mesh in the lid works very well. The smaller jelly jar size is convenient for small batches. In the US mason jars can often be found in large grocery stores and craft stores. Plastic canvas can be found in the needlework department of craft stores like Michaels. The standard size seems to be #7 (the size indicates the number of holes per inch), which is fine for bigger seeds. But for small seeds like millet it's best to use a finer mesh (#10). This equipment will not retain really tiny seeds like amaranth.
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A strainer that fits comfortably inside a bowl also works well. A 3-in-1 "berry bowl" that comes with its own strainer is very well suited for sprouting. The slots in the strainer are small enough to retain millet seeds, although for really tiny seeds you'd need to put something in the strainer (like a coffee filter) to keep the seeds in.
Grains and Seeds. You can sprout your bird's regular seed (including sunflower), and sprouting is actually an excellent way to test the quality of the seed. If less than half of it sprouts it's old and stale and should be discarded. Human-quality grains (usually found in the bulk food bins at the local natural-foods grocery) are excellent for sprouting. Things like wheat, kamut, spelt, barley, oats, rye, etc - anything that looks like a seed. Quinoa is a great addition, and raw rice can be added to the mix. Avoid using sorghum since it can develop a large amount of cyanide when it's sprouted, but sorghum isn't typically found in grocery stores anyway. Don't go overboard with alfalfa sprouts; they can cause problems in large amounts because of a toxin in alfalfa seed called canavanine, which displaces the amino acid arginine. Lentils, mung beans, garbanzos, and adzuki beans are good, but other beans are best avoided unless you're willing to cook them after they've sprouted, due to natural toxins in the beans that are eliminated by cooking but not by sprouting. Even the acceptable beans need to have the tails sprouted out to a length of 1/4" to 1/2" to neutralize toxins. Grains don't have this issue, and are considered to be at their nutritional peak when the root is just barely starting to stick out of the seed. For bigger birds you can include bigger items like pumpkin seeds and popcorn.
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How to Sprout. The mason jar technique: at night, put the seeds/grains in the jar and put the lid on. Rinse them a few times by pouring in some cool water, swirling it around a little, and draining. Don't drain the water the last time; let the grains soak overnight. A few drops of vinegar can be added to the soaking water to discourage mold and bacteria. You need enough water that the seeds will still be covered with it after they've been soaking for several hours. You also need to allow space for air circulation in the jar, so the jar should not be more than about half full of seeds after they've soaked. There's no problem with having smaller amounts of seed in the jar.
In the morning, rinse and drain. It's recommended that you leave the jar tilted downward at an angle so it can continue draining, but simply laying the jar on its side may work for people in dry climates. In any case, there must be some open space above the seeds so air can flow in through the mesh. Rinse and drain again in the middle of the day (optional) and once again at night (not optional). Success is somewhat dependent on the climate in your house; some people will get better results from keeping the sprout jar in a dark place (like a cupboard) and others won't need to do this.
In the morning rinse it one last time and give it to the birds. Right before feeding you can add supplemental items if you want, such as chopped veggies. Total prep time: about 36 hours. Total time actually spent working on it: about three minutes.
The bowl and strainer technique
is the same as above, except that you put your sprouting seeds in the
strainer, which is then put in the water-filled bowl. When you're ready to rinse
you just lift out the strainer.
Storage and Safety
It's possible to store sprouts in the refrigerator for a few days, although making a new batch is so easy that this will be a better option for many people. You can't just put the sprouts in the fridge and ignore them because it takes some vigilance to avoid problems with bacteria and mold. The technique that is usually recommended is to continue rinsing them daily, drain them well, then store them in the refrigerator in a covered container with a paper towel in the bottom.
To avoid storage problems, you can start a new batch every night. You will have two jars (or bowls) going every night: the one that was just started, and the one that was started the previous night and will be served in the morning.
Vigilance is also needed both before and after serving the sprouts. Like any moist food, they provide a nice environment for mold and bacteria. So you have to make sure they haven't spoiled before you serve them - if they smell sour throw them away. Be sure to take them out of the cage before they go bad. The amount of time that they stay good will vary depending on the humidity and temperature in your house. It could be anywhere from a couple of hours to all day long, and the safe period will fluctuate from day to day and season to season.
The procedure described above will work in most situations, but some people have a lot of problems with the sprouts spoiling during the sprouting process. In those cases, more air circulation might be helpful; use the bowl and strainer approach instead of the mason jar. If all else fails, just soaking the seed overnight is usually safe and effective. The procedure is the same as above except that the process ends immediately after the overnight soak, and you drain, rinse, and serve at that point.
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Sprout nutrition differences - for nutrition geeks only!
Does sprouting improve the nutritional value of seeds and grains? The answer is that there are a lot of changes that look good on paper. But sprouting hasn’t actually been shown to make a difference in anyone's nutritional status, and in most respects the nutritional/chemical content of a soaked or lightly sprouted seed seems to be pretty similar to that of the dry seed. But maybe you can get a real improvement sometimes, if you get exactly the right seed at exactly the right moment in the sprouting process.
Study types and general results. Studies on the nutritional value of sprouts fall into two main types. One is the laboratory-analysis study, where a chemical analysis is performed to determine the nutrient content of sprouts versus the dry seed. The researchers usually find some kind of change that they believe to be beneficial, and they hypothesize earnestly about how sprouting could help prevent malnutrition. But no one actually eats any sprouts to see the effect of these nutritional improvements. These studies are fairly recent, from the “sprouts are wonderful” era, and it looks like the authors expected to find some beneficial changes.
The other type is the animal feed studies, which are pretty much the opposite. There’s little or no nutrient analysis – instead they feed a bunch of sprouted grain to animals to see what effect it has on their growth rate. Most of the time they find that it makes no difference at all, although there were a few studies where sprout consumption was either beneficial or detrimental (Lorenz & D'Appolonia). Many of the animal feed studies were performed before the “sprouts as superfood” era, and they have a very different attitude toward sprouts. Sprouted grain was considered to be damaged – sometimes feed grain accidentally gets wet and starts sprouting. So they wanted to find out if it was OK to feed sprouted grain to animals.
When they do analyze the nutrient content in the feed studies, they generally find a decrease in the potential calories (which is bad in the agriculture world) and an improvement in digestibility (which is good). Apparently these factors and all the other changes balance each other out, because there isn’t a significant difference in the results. The animal studies just look at the gross physical characteristics, like growth rate and size. It’s possible that they might see more differences if they performed bloodwork and did other internal checks. But the consensus seems to be that looking at the end results tells the story well enough, and it’s actually pretty hard to argue with this. Growth is a time of maximum demand for all nutrients. If there was a significant nutritional difference between sprouts and dry, you should see a difference in the growth rate.
The more recent animal studies tend to find more benefits from feeding sprouts. But these are primarily studies on malted sorghum or barley sprouts, which are not what we normally think of when we talk about sprouts. Malt sprouts are a byproduct of malt production for beer making purposes. Feeding them to animals isn’t a “natural” feeding practice, it’s a practical use for industrial waste. The grains are sprouted for a few days to increase their sugar content, because germinated seeds in general convert their complex carbohydrates into a type of sugar called maltose (JPub, University of Hamburg, Tuscany Diet). After the desired sugar level is reached, the sprouts are dried in a heated kiln to stop their growth, then roasted for several hours at high temperatures to improve their color and flavor (Great Western Malting, Ingredients 101). Then the rootlets are removed from the grain, because the brewers only want the main seed. These leftover rootlets are called malted sprouts or malt sprouts. They can be fed to livestock, and apparently it's beneficial. But the grains have been through too much to say whether the benefits are from sprouting or cooking, and it looks to me like this isolated part simply has a higher concentration of some nutrients than a complete sprout does (McNess). Malt sprouts will not be considered further in this article.
Apparently there are no feeding studies on humans, which is surprising. Nutrient analysis studies have been going on since the 70s if not earlier, so it's not like they haven't had time to do it yet. It wouldn't be that hard to get some people to add sprouts to their diet for a month and then check their blood chemistry to see if it made a difference. And it seems like a logical next step for the researchers who did the laboratory analysis studies. But apparently the results of animal feeding trials were discouraging enough to prevent the research community from taking it to the next level.
A paper by Sharif et al is a good source for references on animal feed studies both old and new. The reference list is a massive wall of font that’s basically unreadable, but the “find in this page” function will help you locate specific papers. But the article itself is flawed, so don’t pay too much attention to what the authors say. They don’t seem to realize that there’s a huge difference between the raw sprouts that were used in the older studies and the malt sprouts in the newer ones. The article talks about “grass juice factor” which is pure woo woo, and one of their references is the website of a wheatgrass promoter. At least one of their other references is a masters thesis, which is preferable to a pseudoscience website but still not high on the authoritativeness scale.
The best overviews come from a literature review by Lorenz & D'Appolonia and another by Chavan et al. Both papers are quite long (30+ pages), and go into detail about sprouting procedures and the changes in nutrient content (mostly beneficial-looking) that have been observed. Then at the end of the paper they blow everything that they just said out of the water by revealing that it doesn't seem to make a difference in the real world, even when sprouts are 50-97% of the diet.
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Nutrient increases and decreases are inconsistent. There is considerable variation in the nutrient changes that occur during sprouting, so the results of one study can't be applied to all sprouts. The changes are influenced by factors like soaking time, sprouting period, temperature, humidity, light, and the characteristics of the individual seed. There isn't a consistent, reliable pattern - the results from various studies are all over the place in terms of the magnitude of the changes and the conditions that produced these changes. So when you see a study reporting that something happened with one type of seed, you can’t assume that the same thing will happen with other types of seed. You also can’t assume that you’ll get the same results if you sprout that same type of seed at home. You might or you might not.
Every seed variety has a specific set of conditions that are most favorable to germination (especially temperature). If you're sprouting different types of seeds at the same time, you won't be able to please them all equally.
Energy, dry matter and phantom increases. Many of the "improvements" in nutrient composition are actually a phantom increase. The seed is using some energy (frequently carbohydrates, sometimes fat) as it germinates and sprouts. This changes the base for computing percentages because the amount of dry matter has decreased, so the percentage of everything that remains automatically gets bigger even if the actual quantity doesn't change at all.
The amount of dry matter that is lost varies depending on the type of seed and the temperature. Table 5 of Lorenz & D'Appolonia indicates that wheat loses 3-5% of its dry matter during the first three days of sprouting, and the loss can be as high as 59% after 10 days. Other types of seed may lose more or less than this. The longer the seed has been sprouted, the more dry matter it will lose, and the greater the phantom increase will be. Higher sprouting temperatures also promote faster dry matter loss, because the sprout is growing faster.
The scientific literature generally favors shorter sprouting periods, because the high loss of dry matter with longer sprouting periods is considered to be a major disadvantage. But longer sprouting periods are often required to get higher numbers for other nutrients, whether it is a real increase or a phantom increase.
According to Chavan et al page 408-409, "The loss in dry weight during sprouting needs to be minimized... if a 5% loss in dry matter is regarded as nonsignificant, then most seeds need to be soaked for 8 to 10 h and germinated for not more than 24 to 48 h. In the grain legumes, maximum nutritional benefits were produced when the seeds were soaked for 10 h and sprouted for 24h". 'Grain legumes' are pulses like lentils, mung beans, and soybeans (Crops Review). The citation refers to the CRC Handbook of World Food Legumes which is not available to me, so I don't know what they meant by "maximum nutritional benefits". Ten hours of soaking and 24 hours of germination may not be enough to eliminate the natural toxins in sprouted legumes.
It seems to be generally agreed that carbohydrates are used as the main source of energy during germination and early growth, at least in high-carbohydrate seeds (Ziegler). But the magnitude of the change is variable, and I couldn't find any information on how much the biochemistry of germination varies from one plant species to another. Taraseviciene et al reported an 80% loss of dry matter in broccoli seeds after 5 days of sprouting. Paremeswaran & Sadasivam reported that proso millet lost 4% of dry matter after one day of sprouting, increasing to a 16.5% loss after seven days.
Marton et al report that there's little difference in the fat content of sprouted and unsprouted seed, apparently referring to the relative percentages of saturated and unsaturated fatty acids. But in contrast to other sources who report that carbohydrates are the main energy source during sprouting, Table 1 of the Marton paper makes it look like the energy source used during germination and sprouting might depend to some degree on what type of energy was stored in the seed to begin with. The table shows that the amount of fat in wheat and lentils hadn't changed at all after three days of sprouting, but there was a slight decrease in the amount of fat in sunflower seed after this time period. Wheat and lentils are relatively high in carbohydrates and low in fat, while the reverse is true of sunflower.
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Protein. Many papers talk about an increase in proteins during sprouting, but this is not necessarily meaningful. There are a great many substances in the seed that are classified as proteins but do not qualify as amino acids, let alone essential amino acids. There is a great deal of activity among these proteins during sprouting, but the net change in total protein content is usually nonsignificant. Excessive soaking can actually cause some protein to leach out of the sprout. (Chavan et al page 411)
The amino acids of greatest concern are methionine and lysine, since it's hard to get enough of them. Cystine can substitute for methionine to some extent so it's important too, although many of the studies don't mention it. All the other essential amino acids are expected to be well enough supplied if the bird is getting most of its calories from seeds/grains/nuts/legumes, as most pet birds do.
It seems to be generally agreed that some sprouts can have a real increase in lysine, with no agreement on what sprouting period produces the best results. The increase in lysine seems to be related to the amount of prolamine that was originally in the seed, which varies considerably. Sprouting for birds is usually done for less than 5 days, so the early-phase data is what's relevant to us.
"Germination seems to have little effect on methionine" according to Lorenz & D'Appolonia, and this seems to be the prevailing viewpoint. But that didn't stop some researchers from finding significant increases in methionine (probably a phantom increase caused by the loss of dry matter).
Taverner et al reported that lysine was higher in sprouted wheat but the digestibility was poorer. I was unable to obtain the full paper so I don't know the details.
Sulieman et al studied the changes in three lentil cultivars. The methionine decreased significantly in one of the three samples, increased significantly in another, and had little change in the third. There was little change in the lysine.
Kuo et al evaluated the protein changes in lentils, the seeds of P. vulgaris L var La Granja which evidently means great white beans, and peas. The legumes were sprouted under both light and dark conditions to see if it made a difference, for a period of two to six days. They reported the results for lysine and several other amino acids, but not for methionine. The results are annoyingly presented in bar charts instead of a numerical format, but the reader can get the gist. For beans, lysine peaked at four days of germination when raised in the light and at six days when raised in the dark. For the peas, there was little change in lysine when sprouted in the light, and lysine peaked after six days of germination when sprouted in the dark. For lentils, lysine peaked at six days of germination when sprouted in the light, and at two days of germination when sprouted in the dark. They couldn't detect any lysine in the raw lentils, which is odd because other sources including the USDA agree that there is lysine in raw lentils.
According to Peer & Leeson, the only amino acids that really increase during the sprouting of barley are aspartic acid and alanine, which are non-essential and of no real relevance. Several amino acids decreased, including glutamic acid, proline, arginine, methionine, and cystine. There were phantom increases in some of the other amino acids including lysine, due to the loss of dry matter.
Lysine and methionine chart. Here's a chart showing the changes in lysine and methionine reported by various researchers for various seeds. Not all researchers used the same units, and I didn't convert them, so look at the percentage changes not the absolute amounts. Notice how some researchers report huge fluctuations while others see hardly any change at all.
| LYSINE | ||||||||||||
| Seed type | Source | Day 0 |
Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Day 8 |
Day 9 |
Day 10 |
| Barley Proctor A | Smith | 4.42 | 4.20 | 5.30 | 5.99 | 6.05 | 6.22 | |||||
| Barley Proctor B | Smith | 3.86 | 3.81 | 4.49 | 5.07 | 5.69 | 5.86 | 6.19 | ||||
| Barley | Peer | 3.98 | 4.02 | 4.19 | 4.00 | 4.23 | 4.00 | 4.02 | 4.53 | |||
| Corn Ganga-5 | Gupta | 1.81 | 2.31 | 2.70 | 3.57 | 4.09 | 4.13 | |||||
| Corn SO/SN | Gupta | 2.30 | 2.54 | 3.41 | 3.96 | 4.58 | 4.81 | |||||
| Corn at 25C | Chavan | 22.5 | 36.0 | 45.0 | 80.0 | 52.5 | ||||||
| Corn at 30C | Chavan | 22.5 | 26.3 | 48.8 | 33.8 | 33.8 | ||||||
| Corn at 35C | Chavan | 22.5 | 36.0 | 37.5 | 45.0 | |||||||
| Corn W64A | Tsai | 0.38 | 0.43 | 0.48 | 0.60 | 0.64 | 0.71 | |||||
| Flaxseed | Wanasundara | 0.20 | 1.14 | 1.19 | 1.69 | 1.95 | ||||||
| Lentil Selaim | Sulieman | 15.13 | 15.69 | 15.17 | ||||||||
| Lentil Rutabab | Sulieman | 17.15 | 16.92 | 16.28 | ||||||||
| Lentil Nadi | Sulieman | 14.62 | 15.24 | 13.38 | ||||||||
| Millet, proso | Parameswaran | 1.64 | 1.80 | 1.80 | 2.35 | 3.20 | 3.50 | 4.20 | 4.40 | |||
| Seed type | Source | Day 0 |
Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Day 8 |
Day 9 |
Day 10 |
| Sorghum | Chavan | 2.20 | 2.30 | 2.50 | 2.70 | 3.10 | ||||||
| Sorghum at 25C | Chavan | 13.5 | 24.0 | 33.0 | 45.0 | 28.0 | ||||||
| Sorghum at 30C | Chavan | 13.5 | 15.0 | 21.0 | 33.0 | 33.0 | ||||||
| Sorghum at 35C | Chavan | 13.5 | 30.0 | 26.3 | 24.0 | |||||||
| Wheat hard red winter | Miller | 0.30 | 0.31 | 0.38 | ||||||||
| Wheat hard red summer | Miller | 0.39 | 0.39 | 0.45 | ||||||||
| Wheat "Sage" at 20C | Nielsen | 2.80 | 2.70 | 2.60 | 2.90 | 3.10 | 3.65 | |||||
| Wheat "Sage" at 30C | Nielsen | 2.60 | 2.60 | 2.70 | 2.90 | 3.70 | 4.20 | |||||
| Wheat "Lakota" at 30C | Nielsen | 2.40 | 2.30 | 2.30 | 2.80 | 2.70 | 3.60 | |||||
| Seed type | Source | Day 0 |
Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Day 8 |
Day 9 |
Day 10 |
| Kuo et al presented bar graphs rather than numbers. I estimated the numbers below based on their bar graph. | ||||||||||||
| Beans grown in light | Kuo | .10 | .20 | .60 | .50 | |||||||
| Beans grown in dark | Kuo | .10 | .20 | .30 | .40 | |||||||
| Lentils grown in light | Kuo | .00 | .55 | .45 | 1.00 | |||||||
| Lentils grown in dark | Kuo | .00 | .30 | .20 | .15 | |||||||
| Peas grown in light | Kuo | .10 | .15 | .30 | .25 | |||||||
| Peas grown in dark | Kuo | .10 | .41 | .40 | .75 | |||||||
| METHIONINE | ||||||||||||
| Seed type | Source | Day 0 |
Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Day 8 |
Day 9 |
Day 10 |
| Barley Proctor A | Smith | 1.91 | 1.83 | 1.90 | 1.89 | 1.74 | 1.90 | |||||
| Barley Proctor B | Smith | 1.71 | 1.80 | 2.02 | 1.86 | 2.07 | 1.95 | 2.17 | ||||
| Barley | Peer | 2.05 | 2.05 | 2.19 | 1.47 | 1.65 | 1.75 | 2.14 | 1.76 | |||
| Corn at 25C | Chavan | 9.0 | 10.8 | 20.4 | 59.0 | 42.0 | ||||||
| Corn at 30C | Chavan | 9.0 | 24.6 | 30.0 | 46.4 | 34.8 | ||||||
| Corn at 35C | Chavan | 9.0 | 17.4 | 24.0 | 22.2 | |||||||
| Flaxseed | Wanasundara | 0.01 | 0.57 | 0.48 | 0.55 | 0.52 | ||||||
| Lentil Selaim | Sulieman | <.553 | <.337 | <.387 | ||||||||
| Lentil Rutabab | Sulieman | <.368 | <.365 | <.362 | ||||||||
| Lentil Nadi | Sulieman | <.231 | <.718 | <.459 | ||||||||
| Millet, proso | Parameswaran | 2.00 | 2.10 | 2.00 | 2.14 | 2.14 | 2.05 | 1.98 | 2.12 | |||
| Seed type | Source | Day 0 |
Day 1 |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 |
Day 8 |
Day 9 |
Day 10 |
| Sorghum | Chavan | 2.60 | 3.80 | 3.60 | 3.60 | 3.60 | ||||||
| Sorghum at 25C | Chavan | 8.5 | 8.4 | 11.5 | 18.6 | 15.3 | ||||||
| Sorghum at 30C | Chavan | 8.5 | 7.2 | 7.5 | 13.8 | 14.3 | ||||||
| Sorghum at 35C | Chavan | 8.5 | 14.0 | 10.2 | 10.0 | |||||||
| Wheat hard red winter | Miller | 0.14 | 0.11 | 0.15 | ||||||||
| Wheat hard red summer | Miller | 0.20 | 0.23 | 0.20 | ||||||||
| Wheat "Sage" at 20C | Nielsen | 1.40 | 1.40 | 1.40 | 1.50 | 1.40 | 1.50 | |||||
| Wheat "Sage" at 30C | Nielsen | 1.30 | 1.30 | 1.30 | 1.40 | 1.30 | 1.30 | |||||
| Wheat "Lakota" at 30C | Nielsen | 1.20 | 1.20 | 1.10 | 1.20 | 1.20 | 1.10 | |||||
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Sugar. The earlier discussion of malt sprouts brought up one fact about sprout nutrition that's not usually mentioned: sprouts have a lot more sugar than the dry seed does. Tsai et al demonstrated this with corn (maize), showing that after 5 days of germination, the total sugars in normal corn rose from 3% to 14% of the weight while the total starch (complex carbohydrates) dropped from 62% to 30%. Lorenz & D'Appolonia report that other researchers have also found considerable increases in the sugar content. They also report that some of the carbohydrates may be transformed into lipids (fat), which may explain why the starch percentage changed much more dramatically than the sugar percentage did. Burning the carbs for energy takes away a substantial amount too.
Paremeswaran & Sadasivam reported that the starch in proso millet dropped from 58% to 15.5% after 7 days of sprouting, while the sugars rose from 0.16% to 11.3% during the same period.
Vitamins and minerals. Lorenz & D'Appolonia report that any claims of superior vitamin and mineral content should be examined carefully. The reported increases are small and likely due to the phantom increase effect. Minerals may actually be lost during sprouting due to leaching into the soaking water. In contrast, Chavan et al states that while some nutrient increases may be a numerical phantom, the increases in the B vitamins are real.
Antinutrients. Sprouting can significantly reduce the amount of antinutrients, particularly phytic acid (Chavan et al page 421). How advantageous is this? It’s hard to say. It seems to be generally agreed that too much phytic acid is bad, but it’s a complex, multi-factor issue. I get the impression that nobody fully understands how it works, but it’s not generally considered to be that big of a deal. See my article on Antinutrients for more information.
Shi et al has did a study on the effect that soaking and cooking have on enzyme inhibitors in a variety of beans and legumes. Table 3 indicates that soaking reduces trypsin inhibitors by roughly 10-25%. A variety of other papers indicate that sprouting causes additional reductions in trypsin, but cooking is significantly more effective at reducing this antinutrient.
Digestibility. A cattle study by Farlin et al found no difference in the results of feeding dry or sprouted wheat, but did report that the dry matter digestibility of dry wheat was 73% and the digestibility of sprouted wheat was 76%.
A pig trial by Peer & Leeson found that that dry matter digestibility was 85% with ground barley, 69% with 4-day sprouted barley, and 32% with whole barley. A second trial that compared ground barley to sprouted (but not to dry) found that the pigs eating sprouted barley gained significantly less weight than the ones eating ground barley, although the feed efficiency was the same. They say that "Results from the above experiments suggest that digestibility decreases as sprouting time increases."
Rule et al reported that for sheep, the dry-matter digestibility of sprouted wheat was 71% and the digestibility of unsprouted wheat was 74%. That is not a typo, the unsprouted wheat was more digestible than the sprouted wheat.
Page 381 of Lorenz & D'Appolonia discusses a study by Müller, who fed sprouted barley to laying hens and found no effect on the digestibility of crude protein. The addition of sprouted barley caused a slight but non-significant increase in egg production. The Müller paper is in German so I haven't attempted to look for it.
Unfavorable changes. The changes caused by sprouting are not always beneficial. For example, it has been shown that sorghum (milo) can produce a large amount of prussic acid (cyanide) when it is sprouted, and currently it's recommended to not sprout it as a food for this reason (Panasiuk & Bills, Ikediobi et al). But this was apparently not noticed in other studies that did a nutritional analysis on sorghum sprouts. I'm not aware of any other sproutable seeds that have been tested for similar issues. Side note: Unripe sorghum seed and mature dry sorghum seed are safe and beneficial, but the sprouts are potentially unsafe, and the green leaves and stems of the plant are also unsafe. Dried-out yellow sorghum stalks and stems are safer than fresh green ones, but are best avoided to be on the safe side.
Being eaten is certainly not in the sprout's best interests, and it would not be surprising if the germinating seed has generated some defensive chemicals to help prevent this from happening. But apart from sorghum, we don't know whether this is actually happening.
In well-fed parts of the world it's good if the body can incur a few less calories while getting other essential nutrients. But other nutrients are sometimes lost during sprouting, so their proportion may be essentially unchanged or even decrease. If too many calories are lost, it becomes a problem to get enough of them.
The scientific literature in general says that sprouts are only taking in water and oxygen, although there was one study that attributed a mineral increase to absorption from the the soaking water. This means that the appearance of anything new requires the disappearance of something that was there before. There are some nutrients that can leach out into the soaking water, including water-soluble protein, and longer soaking periods produce greater losses (Chavan et al page 409).
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This isn't all the animal studies, just the ones that said something more interesting than "no difference was observed". Poultry studies are emphasized.
Falen & Petersen substituted sprouted wheat for 25 to 100 percent of the normal Gaines wheat in the diet of White Leghorn cockerel chicks. There were no differences in their average weight gain and feed efficiency. There was no difference in metabolizable energy between feeding 100% sprouted or 100% dry, but there was an improvement in metabolizable energy when some of each was fed. Metabolizable energy was highest with a 50-50 ratio of sprouted and dry.
Peer & Leeson fed barley that was sprouted or unsprouted to mature White Leghorn cockerels. They reported that barley sprouted for one or two days was superior to unsprouted barley. Barley sprouted for 3 days had the same results as unsprouted, and barley sprouted for longer periods was inferior to unsprouted. However they also report that the sprouts were dried because the birds refused to eat freshly sprouted grain, and they don't say whether heat was used during the drying process. So we don't know whether cooking played a role in the results. The authors report on a few other poultry studies, and hypothesize that the lack of results in most cases might be related to the sprouting time.
The pig trials they conducted in the same study were described earlier. They discuss other pig trials, including some where sprouted grains were detrimental.
Their conclusion is that "results from these trials indicate few positive effects due to sprouting of barley... If field-sprouted grains are necessarily given to animals it seems as though no detrimental effects will occur, other than loss of dry matter and associated nutrients."
Woodham reports that for barley, 12 days of germination had a negative effect on chick growth but 5 days of germination was beneficial. He discusses other poultry studies where no difference was observed. He reports that germination affects barley varieties differently; some are much improved by germination and others are not.
Page 381 of Lorenz & D'Appolonia mentions some additional poultry studies that failed to show a significant difference.
Miscellaneous topics. A paper by Balasaraswathi et al on sunflower sprouts shows an irregular pattern of decreases in dry matter, fats, protein, and carbohydrates over a period of five days. But I'm not quite sure what to make of it all, since this paper only looks at the cotyledon of the seed. Other sources indicate that there are other parts that need to be considered in measuring the total nutrients in the seed.
A paper on fats in sunflower sprouts by Munshi et al tested fast-growing and slow-growing seeds. Apparently all were the same type of seed, and some just sprouted faster than others. The faster-growing seeds had a faster rate of lipid (fat) depletion than the slower-growing seeds did, which makes sense because you'd expect faster growth to use more energy than slower growth. The density of the writing and the amount of detail in the tables are a bit much for me, but it looks like the results are generally the same as the other sources: most of the fat decrease comes sometime after day 3.
The last sentence of the paper indicates that the germination speed of the seed is determined by where in the sunflower head it came from, and the faster-growing seeds are "filled with enhanced amount of lipids and soluble sugars".
Ignore any talk you hear about "living" foods like sprouts being better for you than "dead" foods. This is just romanticized raw-foodist pseudoscience, with no basis in reality. Whether they mention enzymes or not, this claim ultimately traces back to the notion that the enzymes in raw plant foods are beneficial. In reality, they're generally useless - see the Enzymes article for more information. In any case, any "living" food that you eat is going to be thoroughly dead by the time it reaches your small intestine (which is where the absorption of nutrients begins), because the hydrochloric acid in your stomach is very good at killing those "living" enzymes.
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Why the conundrum? So why is there such a big discrepancy between the nutritional analyses and the observed results? Here is my best guess:
The main nutritional improvements reported from sprouting are (1) increased digestibility, (2) reduced phytic acid, (3) more vitamin C, (4) more B vitamins [maybe], and (5) more lysine for better protein quality in some cases. And here's why it might not matter:
(1) Increased digestibility means that you can get more of everything from the food, including more calories. That’s why some of the feeding trials showed that sprouts provided more metabolizable energy (calories) in spite of the fact that some of the stored energy had been burned off. It basically means that you can eat less food to get the same amount of nutrients including calories. Not that you’re getting more nutrients for the number of calories that you eat.
(2) It’s not clear how much of a problem phytic acid really is. Human nutritionists aren’t concerned about it, and reducing it won’t make a difference if you’re already getting enough minerals from the diet.
(3) Most animals make their own vitamin C, so this is irrelevant to just about everybody except humans and other primates.
(4) B vitamins are already well supplied in dry grains. Adding more by sprouting the grains won’t make a difference if you’re already getting enough.
Which leaves #5, more lysine for better protein quality, as the change that’s most likely to have an impact. But the animals in the feeding studies weren’t eating ONLY dry grain or sprouts. They had other foods in the diet too. And if these other foods were already providing a decent amount of lysine, then adding more might not do any good. Extra lysine is only useful until the moment that you run out of methionine, and it’s reported that sprouting doesn’t have much effect on methionine.
So it looks like sprouting might be useful if you have a hard time getting enough food to eat, or if you’re feeding your bird a deficient diet with inadequate protein. If you’re already paying attention to the protein level, it’s unlikely that sprouting will do much for you in the protein department because you’ve already got it covered (see the Protein article for more information). If you’re not paying any attention to the protein level then it's likely that you have a problem, but sprouting may not add enough extra lysine to put the protein in balance.
Conclusion. It comes down to this in the end: the nutritional changes in raw sprouts look good on paper, but haven’t been shown to actually make a difference in the real world. “Animal studies with cattle, pigs, chickens, and rats have failed to show a superior nutritive value of sprouted grains over ungerminated grains” (Lorenz & D'Appolonia) and “The magnitude of the nutritional improvement… is not large enough to account for in feeding experiments with higher animals” (Chavan et al).
It's fine to feed sprouts of course, and I do it every day because my birds like them. Sprouts add variety to the tastes and textures your birds can enjoy. Just don't assume that sprouts will fill any gaps in the diet that the dry seed won't fill, because the available evidence points in a different direction. So make sure that the rest of the diet supplies the nutrients that you don't get from seed. If sprouts actually do have some advantages over dry seed, you’ll get a bonus without even knowing it. And if they don’t have any special benefits, you won’t be impairing your bird’s nutritional status because of internet hype. You will have covered your bases in either case.
To make sure that the point has been thoroughly beaten to death, here are some more comments from the scientific literature:
"On the basis of proximate composition of sprouted grains, it appears that the natural nutritive value of grains may be improved by sprouting. The essential amino acid composition is slightly better and there are slight increases in thiamine and riboflavin concentrations which may be of nutritional importance to persons preferring natural enhancement of nutrients to the enrichment of certain cereal products required by law... Nearly all studies with animals cited in this review have failed to show a superior nutritive value of sprouted grains over ungerminated grains. Studies with humans are not likely to produce more encouraging results. It appears that cereal sprouts do very little to improve the nutritional status of man or beast." Lorenz & D'Appolonia page 383."
The increased contents of protein, fat, fiber, and total ash are only apparent and attributable to the disappearance of starch. However, improvements in amino acid composition, B-group vitamins, sugars, protein and starch digestibilities, and decrease in phytates and protease inhibitors are the metabolic effects of [the] sprouting process. However, the overall nutritional improvement upon sprouting is of smaller magnitude and not often accounted for in animal-feeding experiments. A few reports indicate an improvement in... rat bioassays, while others could find no such improvement with higher animals like cattle, pigs, and chickens for sprouted cereals." Chavan et al page 431"
it can be reasonably accepted that the natural nutritive value of cereal grains is improved by sprouting. However, the experiments with animals having fairly efficient digestion and feed utilization systems fail to account for the smaller increase observed in nutritional and protein quality of cereals upon sprouting." Chavan et al page 426
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Case study using standardized data for mung beans and lentils. Here's an approximation of the nutritional changes that sprouting causes in mung beans and lentils, which had USDA data available for both forms. The discussion uses NutritionData's nutritional analyses for dry mung beans, mung bean sprouts, dry lentils, and lentil sprouts, with some fancy math to get the amount of nutrients in 100 grams of 'dry matter' for each of them. The sprouts are 68-90% water while the dry beans are only 9-10%. The nutrients are a lot more concentrated in the dry beans than they are in the sprouts, so the sprouts look absolutely pathetic if you compare them to the dry beans without adjusting for the difference in water content.
Use some caution with these numbers. As mentioned earlier, there's a numerical wobble caused by the sprout using up some of the dry matter that was in the original bean, which makes the percentage of everything else look better even if it hasn't actually changed at all. This is amplified significantly by the multiplication factors that have to be used to convert the nutrient data to 100 grams of dry matter, especially for the mung beans. The values for the dry mung beans only have to be multiplied by 1.1, while the values for the mung sprouts have to be multiplied by 10.42! So the wobbles and rounding error in the original data will be magnified ten-fold in the dry matter data for the sprouts.
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| Table 1 Comparison of 100 grams of dry matter for dry and sprouted mung beans and lentils |
What about the calories? They show a decrease caused by sprouting of about 18%. Since obesity is a big problem in pet birds, it's not bad to lose some of the calories while keeping everything else more or less the same. Keep in mind though that the actual amount may be less due to the amplified numerical wobble, and also that we're talking about "grocery store" style sprouts, which have been sprouted longer than the typical homegrown sprouts for birds. Barely-sprouted seeds and beans will not have used up as many calories as long sprouts that have been growing for a longer time.
The carbohydrates decrease from 69g to 62, a difference of about 10% which is more or less in the middle of the range reported in the scientific literature. There's no doubt that there's a real decrease in the carbs, and the only question is how big the change really is. But there's also a 46% increase in the fat, from 1.3 to 1.9 grams. Some researchers have reported an increase in fats during sprouting, apparently due to carbohydrates being transformed into lipids (Lorenz & D'Appolonia), which might help explain this. Or else it's one super-large numerical wobble.
The vitamin C changes significantly, from about 5 mg to 138; but it doesn't matter because birds manufacture their own vitamin C and don't need it in the diet. There's also a big increase in vitamin K, from 10 to 344 micrograms. These increases look like they're probably real. The other increases are small enough to very likely be a numerical wobble. If the "phantom increase" effect is strong enough, these statistics could be masking an actual decrease in the total amount of many vitamins and minerals. The beans had to be soaked in water to sprout them, so some loss of water-soluble nutrients is expected.
Notice how the mineral amount generally went up in the sprouts, in amounts ranging from 5% to 375%. The sprout might or might not be able to absorb minerals that were in the soaking water, but this is obviously going to depend on what kind of water was used. If that's the cause of the increase, it isn't something that you can depend on to be true for every batch of sprouts. If the sprout isn't absorbing minerals from the water, it can't create new ones out of thin air. It's expected that some of the mineral increase is due to erratic numerical wobbling. But the amount of calcium and selenium decreased in spite of this mathematical boost. The sprout can leach minerals out into the water as well as absorbing them, or use them in chemical reactions as it grows.
If the sprout does absorb minerals from the soaking water, is that a nutritional improvement? Not really. In a home sprouting situation, you're probably getting the soaking water and the bird's drinking water from the same source. The bird is expected to need about the same amount of water regardless of whether it's getting that water from food or from the water bowl. If the bird is eating a lot of wet food (like sprouts) it will drink less water and vice versa. Either way it's going to be consuming the same water with the same minerals in it.
The nutrient changes with lentils are pretty much the same story as the mung beans. The numerical wobble for the lentil sprouts is expected to be less dramatic than for the mung bean sprouts, since the lentil values only had to be multiplied by 3 instead of by 10 to get the dry matter amount. The values for many items are close enough to probably not be a real change, although with lentils there were more nutrients where the sprouts had less than the dry bean. Interestingly, the lentil sprouts showed a decrease in total protein, but an improvement in the amount of lysine, methionine and threonine. Is this real or a wobble? It's hard to say, since the magnitude of the wobble seems to vary so much from one nutrient to another. As mentioned earlier, a paper by Sulieman et al that studied the amino acid changes in three types of lentil sprouts got variable results, and most of them were not favorable.
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