Touted as a superfood, quinoa is a darling of the health-conscious community. It’s credited with everything from preventing heart disease to curing world hunger, but how much of the hype is backed up by research? Take a closer look at the science of quinoa to find out.
What is Quinoa?
Quinoa (Chenopodium quinoa) has been cultivated for thousands of years in the Andes Mountains of South America, where it is a food staple for indigenous cultures. It’s only in recent years that is has attracted global attention [R].
Climate change and increasing global food demand have created a need for crops that thrive in suboptimal growing conditions and provide quality nutrition. Quinoa, a stress-tolerant crop with a better nutritional profile than many kinds of cereal like rice and corn, has attracted attention for this reason. It’s now grown in more than 70 countries [R, R].
Its potential to improve the health of undernourished people is supported by research. When 10 undernourished boys from poor Ecuadorian families between the ages of 4 and 5.5 years were fed a quinoa-based infant food twice a day for 15 days, growth hormone (somatomedin C) production increased compared to a control group [R].
Although it’s often referred to as a cereal, quinoa is actually a pseudocereal. Cereal grains like wheat, rice, and corn are grasses, and their nutritional value comes from the grass fruit. Quinoa is more closely related to spinach and chard and its nutritional value comes from the plant’s seed [R].
Although there are more than a hundred varieties of quinoa, only 3 are commonly available in grocery stores around the world: red, black, and white. It’s prepared like rice, but before boiling, all quinoa must first be soaked to remove the outer coating (pericarp), which contains bitter compounds (saponins) [R].
Quinoa is rich in many important macronutrients, micronutrients, and other molecules (secondary metabolites) that can affect human health [R].
Although quinoa is more nutritious than most grains, it shows a lot of variability in its nutritional composition. The strain of quinoa and where it’s grown impact its nutritional profile. That means nutrients in the quinoa you eat may vary from the values reported here and elsewhere [R, R].
Relative to most grains, quinoa has a high protein content (12.9 to 16.5% protein). It has more protein than rice, corn, oats, and barley, and about the same amount as wheat (14.3 to 15.4% protein) [R].
Unlike wheat, quinoa is a complete protein. It contains all 10 essential amino acids, including twice the amount of lysine found in corn or wheat. Quinoa is gluten-free, has an amino acid profile similar to whole dried milk, and can provide over 180% of the recommended daily intake of essential amino acids [R, R].
Lysine is an essential amino acid that is not produced by the human body. As a result, lysine must be obtained through food consumption. Adults (>18 yrs) require 30 mg of lysine per kilogram of body weight every day [R].
Quinoa is a rich source of lysine (4.6 to 6.6 grams per 100 grams). This makes it a good source of lysine for vegans, vegetarians, and undernourished populations [R].
Approximately 58 to 64% of the quinoa seed (by weight) is starch (D-xylose, amylose, and maltose). It also has a low glycemic index, making it suitable for diabetics [R].
The fiber comprises around 10% of quinoa seeds. Roughly 78% of that is insoluble fiber, which isn’t broken down in the intestines, and the other 22% is soluble. This gives quinoa a fiber profile similar to vegetables, legumes, and fruits [R].
On average, quinoa seeds are comprised of 5 to 7% fats. This can vary depending on the strain. The fats in quinoa seeds are mostly unsaturated (90%) and they have an omega-6 to the omega-3 ratio of 6/1, giving quinoa a better ratio than most plant-derived oils [R].
Quinoa (3.4%) has a total mineral content higher than rice (0.5%), wheat (1.8%), and other cereals [R].
It is also low in phytic acid. This compound, common in many grains and vegetables, binds to the minerals in food and prevents them from being absorbed by the body. Since quinoa is low in phytic, it is a good source of easily absorbed minerals [R].
Quinoa is also a rich source of beneficial phytonutrients. These are chemicals produced by plants that have specific effects on human health. For example, they can be anti-inflammatory, anti-microbial, neuroprotective, anti-aging, and much more [R].
The most common phytosterols in quinoa include β-sitosterol (63.7 mg/100 g), campesterol (15.6 mg/100 g), and stigmasterol (3.2 mg/100 g). 20-hydroxyecdysone accounts for 62 to 90% of phytoecdysteroids, and quercetin and kaempferol are the most abundant flavonoids.
Saponins are bitter-tasting chemical compounds found in the outer layer of quinoa seeds. The number of saponins varies depending on the strain. ‘Sweet’ strains contain less than 0.11% saponin by dry weight and ‘bitter’ strains can contain as much as 7.5% [R, R].
Quinoa is soaked before cooking to remove some of the saponins, helping get rid of the bitter flavor (although some saponins remain) [R].
Health Benefits of Quinoa
1) Quinoa Is Usually Gluten Free
Quinoa is a safe alternative to gluten-containing cereals for people with celiac disease or non-celiac gluten intolerance. A biochemical analysis of quinoa proteins found that they did not behave like the wheat proteins that are toxic to celiacs (gliadins) [R].
Another study found that 19 celiac patients had normal intestinal and blood test results after eating quinoa every day for 6 weeks [R].
Although quinoa varieties commercially available outside of South America are gluten-free, some traditional varieties are not. When 15 different strains were tested, 2 of them (Ayacuchana and Pasankalla) had the same effect as wheat proteins on celiac intestinal cells [R].
2) Quinoa Lowers Cholesterol and May Prevent Heart Disease
In a study (DB-RCT) of 35 overweight women, participants who ate quinoa flakes every day for 4 weeks had reduced total cholesterol (191 to 181 mg/dl) and LDL, or ‘bad’ cholesterol (129 to 121 mg/dl), compared to those who ate cornflakes. Both groups had reduced triglycerides (112 to 108 mg/dl in the quinoa group) [R].
The women in the study who ate quinoa flakes also had increased glutathione levels (1.78 to 1.91 µmol/l) compared to those who ate cornflakes. Low levels of GSH have been associated with heart disease, cancer, AIDS, Parkinson’s disease, Alzheimer’s disease, alcoholism, and autism [R].
In a study of celiac patients, those who ate quinoa every day for 6 weeks also saw a small reduction in triglycerides (from 0.8 to 0.79 mmol/l) and total cholesterol (4.6 to 4.3 mmol/l) [R].
In another study of 22 students aged 18 to 45 years, triglycerides, total cholesterol, and bad cholesterol were reduced after eating a quinoa cereal bar every day [R].
Animal feeding studies have also shown that saponins prevent high cholesterol in rats [R].
Quinoa is relatively high in fiber and a pooled analysis of 10 prospective cohort studies found that diets high in fiber decrease the risk of coronary heart disease [R].
Saponins may also help to lower cholesterol. Although there are no human clinical trials on the subject, when saponins were added to the diet of rats with high cholesterol, it reduced their total and LDL cholesterol [R].
3) Quinoa May Lower Blood Sugar and Improve Diabetes
Although there haven’t been any human clinical trials examining the effects of quinoa consumption on diabetes, a study on sugar-fed rats found quinoa reduced blood glucose levels and oxidative stress [R].
Although quinoa reduced blood glucose levels by 3.4% (at 90 minutes after eating), eating amaranth caused a much better 15% improvement. While quinoa is a healthy choice for diabetics, it is one of many possible healthy choices. [R].
In sugar-fed rats, quinoa reduced the number of free radicals (via reduced lipid peroxidation), which cause damage to cells. Additionally, it improved antioxidant capabilities in the rats’ blood, heart, lungs, kidneys, pancreas, and testes. This indicates that quinoa reduces the negative effects of sugar on the body by protecting it from oxidative stress [R].
20-hydroxyecdysone also has multiple anti-diabetic effects. Consumption lowered blood glucose levels and increased insulin in diabetic rats [R].
In another study of diabetic rats, consuming 20-hydroxyecdysone reduced blood glucose levels, total cholesterol, LDL, triglycerides, and free fatty acids. It also increased HDL, or ‘good’ cholesterol [R].
Memory defects caused by diabetes were also alleviated by consuming 20-hydroxyecdysone. It may achieve this by increasing antioxidant capability in the brain [R].
4) Quinoa Is Rich in Antioxidants
Antioxidants are molecules that neutralize free radicals, reducing cellular damage in the body. Oxidative damage has been linked to heart disease, Alzheimer’s disease, Parkinson’s disease, cancer, a variety of inflammatory diseases, and other negative health effects [R, R, R, R].
In a longitudinal study of 23,595 people over 30, eating a diet rich in antioxidants were linked to a lower risk of death from all causes [R].
- Vitamin E (tocopherols)
- Vitamin A (carotenoids)
- Fatty acids
In a study of how different cooking techniques affect antioxidants in quinoa, the most antioxidants were preserved when quinoa was washed, then cooked in a pressure cooker, while the most antioxidants were lost when it was toasted [R].
5) Quinoa Is an Anti-Inflammatory Food
The antioxidants found in quinoa help break the cycle by reacting with free radicals, preventing further cellular damage [R].
Obesity is a common cause of inflammation. As mentioned, a diet rich in fiber is linked with a lower risk of obesity. This also results in a reduction of inflammatory markers (C-reactive protein) in the blood [R, R, R].
Quinoa is rich in phytonutrients such as quercetin. A meta-analysis of 7 RCTs associated a significant reduction of C-reactive protein in the blood with quercetin supplementation [R].
6) Quinoa Can Aid Weight Loss
In a study (RCT) of 30 prediabetic patients, the group that ate quinoa for 28 days felt full and satisfied and lost weight, compared to a control group who didn’t eat quinoa [R].
The relatively high protein content of quinoa may play a part in its ability to prevent weight gain and aid weight loss. High protein diets increase satiety, causing people to eat less.. High-protein diets also burn more calories (through increased metabolism and thermogenesis) [R, R].
However, this may not be the only mechanism involved. Quinoa contains 20-hydroxyecdysone, a steroid hormone. In a mouse study, it interfered with several genes responsible for fat storage, inflammation, and insulin resistance [R].
In cell studies, saponin prevented the formation of fat cells, indicating it may also play a role [R].
Limitations and Caveats
When considering the benefits associated with saponins, it’s important to remember that there are no human clinical trials assessing their impact on human health.
Likewise, human research on how quinoa affects weight loss is limited to a single randomized controlled trial of 30 women. More research studies on this finding are necessary.
While quinoa has positive effects on cholesterol and blood glucose levels, no single food is curative in the treatment of disease. The health benefits of eating quinoa are the same benefits that are received from eating a healthy, whole-food diet rich in fruits and vegetables.
Diabetics who include quinoa in their diet report that it doesn’t spike their blood sugar like rice or bread. Most also agree it has a pleasant, nutty flavor, though some claim it smells terrible and tastes like animal feed.
Quinoa is also popular with bodybuilders who use it in place of brown rice to increase their intake of complete proteins. However, some lifters feel it’s too calorie dense and prefer to eat more of other foods to get the same amount of nutrients.
While quinoa is a heart-healthy food, plenty of people who eat quinoa regularly report struggling with high cholesterol.
Some users of quinoa report bloating, gas, and diarrhea. Quinoa is high in fiber, so these symptoms are likely a result of increasing fiber intake.