Rapid degradation of beta-carotene in the rice during storage and cooking means it's not a solution to vitamin A deficiency in the developing world. Report: Claire Robinson
The vitamin A precursor beta-carotene is only present at low levels in GM golden rice, when compared to carrots and green leafy vegetables. But it rapidly degrades to even lower levels when the rice is stored after harvest, a new study by Indian scientists has found. After just 6 months of storage in the presence of air, even at the low refrigerated temperature of 4 degrees C, the beta-carotene degraded by around 68–79%.
The lowest degradation rate was seen in paddy rice (unprocessed rice complete with the hull), the middle rate in brown rice (with the hull removed), and the highest in polished rice (with the hull removed and the bran mostly polished off). Polishing is the standard treatment given to rice throughout Asia. Brown rice is hardly ever eaten and paddy rice is never eaten.
At a more normal Asian temperature of 25 degrees C, degradation was higher – around 80–84%. Cooking also degraded the beta-carotene, by about 17-24%.
The scientists concluded that the best way to preserve the beta-carotene content of the GM golden rice was to vacuum pack it as paddy (though no one eats paddy). Under these conditions, at 25 degrees C, just over half (54%) of the beta-carotene was retained, versus only around 20% under non-vacuum packaging (air packaging) at the same temperature.
So in order for the poor and hungry to be "helped" by this product, someone (who?) will have to vacuum pack the rice first as paddy.
Having to adopt any storage method beyond putting the rice in a bag and keeping it in a dry place would rule out the utility of this technology in the developing world. The local farmers simply will not have access to vacuum packing facilities. Vacuum packaging is a rarity in Asia, especially in rural areas, and will push up the price of the packaged rice. Normal rice, on the other hand, has at least a three-year shelf life.
“Let them eat butter”
Beta-carotene is only a vitamin A precursor. Beta-carotene is converted to vitamin A, predominantly in the intestines. But in order for beta-carotene to be effectively absorbed and be converted, fat (e.g. butter or vegetable oil) must be present in the meal.
The people who are the claimed targets for GM golden rice are considered to be too poor to buy any food apart from rice. How they are expected to find the money to buy rice that has been vacuum packed at some expense, as well as butter or vegetable oil to eat with it, has never been explained by advocates of this product.
Low beta-carotene levels at the start
The study found that beta-carotene levels in GM golden rice were low to begin with, at 7.13 to 22.81 µg/g. The highest level, 22.81 µg/g, translates to 2281 micrograms of beta-carotene per 100g rice. That's roughly equivalent to the lowest level of beta-carotene found in leafy green vegetables (2199 μg/100g) in an analysis of commonly eaten vegetables and fruits in India.
Most of the leafy green vegetables analyzed have far more beta-carotene – there's 7753 μg/100g in edible amaranth. Carrots have about 8300 μg/100g. Some fruits can have higher levels: Alphonso mango has up to 11789 μg/100g.
How the sums add up
The US Food and Drug Administration’s recommended daily allowance of vitamin A for an adult woman is 700 μg (micrograms). This vitamin A could be obtained completely by conversion of beta-carotene ingested from vegetables.
However, the conversion rate of beta-carotene to vitamin A is not very efficient. It varies greatly between 3.6–28:1 by weight of beta-carotene to vitamin A – meaning you’d have to eat between 3.6 and 28 units of beta-carotene to produce 1 unit of vitamin A. Bearing this in mind, in a best case scenario, 700 μg of vitamin A could be obtained from consuming 110g of the best golden rice variety identified in the new study, at an optimum conversion rate of 3.6:1 and with sufficient amounts of fat or oil in the meal to allow maximum absorption of the beta-carotene.
However, since this study found that up to 24% of the beta-carotene in the golden rice is destroyed during cooking, the minimum amount of the best golden rice variety required to provide 700 μg of vitamin A increases to 136g (prior to cooking).
The situation is worse for men, whose recommended daily intake is 900 μg of vitamin A. They would need to eat about 175g of the best golden rice.
The problem is that in the developing world, where vitamin A deficiency is prevalent and where the target populations for golden rice live, circumstances will be far removed from this best case scenario. Not everyone will have access to the best golden rice variety. The fat or oil that is required to be part of the meal in order that the eater can absorb the beta-carotene and convert it to vitamin A will be hard to afford.
More importantly, as the target population will be generally malnourished and not just deficient in vitamin A, their digestive system will not be in the best condition and thus their ability to digest and absorb nutrients from the little food they eat, including the beta-carotene in the golden rice, is likely to be poor.
Truckload of GM golden rice per day
This all adds up to a situation closer to a worst case scenario, in which the best golden rice is unavailable to many and in which consumers have far lower beta-carotene to vitamin A conversion rates. So an individual will need to eat far more rice to obtain their recommended daily allowance of vitamin A. With a worst case conversion rate of 28:1 and taking into account beta-carotene losses during cooking, a woman would need to eat 1084g golden rice per day to obtain her recommended daily intake of vitamin A – and that’s only if the rice has not degraded through storage.
For men, who require more vitamin A per day, the amount of the best golden rice required rises to a staggering 1393g per day. Thus the relatively efficient uptake and conversion of beta-carotene previously reported in a feeding trial on healthy adults in the USA, on the basis of which golden rice is being promoted, has no bearing on what can be expected in the developing world.
In short, you’d have to eat a truckload of GM golden rice each day to get sufficient daily beta-carotene to meet your daily requirement of vitamin A, and that’s when the golden rice is freshly harvested, before the beta-carotene has had time to degrade. In contrast, 100g of spinach can typically contain 5600 μg of beta-carotene and would cook down to a normal sized portion. Provided it’s eaten with fat or oil and assuming a modest conversion factor of 8:1, it would give the recommended daily intake of vitamin A for an adult woman.
Levels of beta-carotene in GM golden rice varied
The new study found that the levels of beta-carotene in GM golden rice varied, depending on the background genetics of the rice that the "golden" trait was engineered into and the position in the genome where the GM genes (transgenes) inserted. The genetic engineers who generated the different golden rice lines could not control where the GM genes inserted in the rice plant DNA and so this varied between different GM rice lines.
This is one of the many uncontrollable factors in the genetic engineering process that can lead to unintended effects in terms of GM gene function, GM crop performance and GM crop composition. Other undesirable effects include potential toxicity and allergenicity, which has not been tested for in the case of GM golden rice.
In conclusion, GM golden rice is not a practical way of getting your daily vitamin A and is completely out of reach for the poor and hungry. Leafy greens have much higher nutrient density (micrograms of nutrient per calorie) compared to golden rice.
Toxic degradation products
Beta-carotene degrades by oxidation through exposure to air, as reported in the paper by the Indian scientists. But the result isn't only low nutrient levels. What the paper doesn’t mention is that this process results in products that are toxic. They include substances that can cause oxidative stress in the body of the consumer, which can lead to cancer. This syndrome has been seen in people taking vitamin A supplements.
The upside of the dismal levels of beta-carotene in GM golden rice is that they will likely be too low to result in toxic effects from degradation products.
How the Green Revolution impoverished diets
Beta-carotene-rich leafy green vegetables were abundant in in rice-growing areas of the developing world before the so-called Green Revolution.
Typically the leafy green veg were grown in backyards but also in rice (paddy) fields on the banks between the flooded ditches in which the rice grew. The ditches also contained fish, which ate pests. People thus had access to rice, green leafy veg, and fish – a balanced diet that gave them a healthy mix of nutrients, including plenty of beta-carotene.
However, the Green Revolution saw the rice fields change, to the detriment of local people's health. Indigenous crops and farming systems were replaced by monocultures dependent on chemical inputs. The green leafy veg were killed off with pesticides, artificial fertilizers were introduced, and the fish could not live in the resulting chemically contaminated water. Decreased access to land meant that many people no longer had backyards containing leafy green veg.
People only had access to an impoverished diet of rice alone, laying the foundation for the supposed GMO "solution" of enriching rice to contain beta-carotene.
Thus the "second Green Revolution" – GM – is being presented as a solution to a problem that was caused by the “first Green Revolution".
FDA confirms GM golden rice nutritionally useless
In 2018 the US Food and Drug Administration (FDA) concluded its consultation process on GM golden rice by informing its current developers, the International Rice Research Institute (IRRI), that golden rice does not meet the nutritional requirements to make a health claim, as the concentration of beta-carotene is too low.
There are so many factors that influence the uptake of beta-carotene and its conversion to vitamin A that it seems irresponsible to gamble with the health and lives of malnourished people by selling them one risky and experimental foodstuff.
Stunted and deformed GM rice plants
Previous research by the same group of Indian scientists found that the golden rice trait engineered into the elite Indian variety Swarna (also one of the rice varieties studied for the new publication on beta-carotene levels) produced deformed, stunted, and abnormal rice plants, due to disruption of the genome caused by the transgene insertion.
Molecular geneticist Dr Michael Antoniou commented on the findings by blaming the developers of GM golden rice: “If [they] had conducted a proper molecular characterization of this GM event at the time it was generated, they would have identified the host gene disruption that led to the stunted and deformed growth of the rice plants. Then they could potentially have avoided this negative outcome at such a late stage in the development and release of golden rice. Now it’s back to square one, with years of research work and millions of dollars wasted.”
The researchers’ latest study showing low and unstable beta-carotene content in GM golden rice represents a new blow to GMO advocates who use this crop as a “poster child” to get the technology accepted in developing and affluent countries alike.
Simpler approaches have proven effective
Developing and promoting golden rice has swallowed up millions of dollars and over two decades' worth of research time and brain power. The saddest aspect of this waste of money and resources is that simpler, safer, and cheaper measures have proven effective in reducing vitamin A deficiency – in the Philippines, for instance. If these measures had benefited from the level of support given to the GM golden rice project, they would likely have solved the problem by now.
Ensuring that all people have access to a varied and nourishing diet remains the best solution to hunger. Even if GM golden rice was successful in providing the daily recommended intake of vitamin A, it would still fail to solve the problem of general malnutrition because hungry people are not just deficient in one nutrient, but in many.
Kinetics of β-carotene degradation under different storage conditions in transgenic Golden Rice® lines
Bollinedi, H., Dhakane-Lad, J., Krishnan, S. G., Bhowmick, P. K., Prabhu, K. V., Singh, N. K., & Singh, A. K. (2019).
Food Chemistry 278, 773-779.
Genetic constitution of the rice variety and transgene position influenced β-carotene accumulation. Vacuum packaging enhances the storage stability of β-carotene in Golden Rice®. The β-carotene deterioration was faster when rice was stored after polishing. Oxidative deterioration of β-carotene is higher followed by thermal deterioration.
The effect of vacuum packing and ambient storage conditions on the stability of the β-carotene in the transgenic Golden Rice® lines was studied. The β-carotene was quantified using RP-HPLC at bimonthly intervals for a period of six months. The β-carotene concentration in the genotypes analyzed ranged from 7.13 to 22.81 µg/g of endosperm. The transgene being the same in all the genotypes, variation in the β-carotene concentration reflects on the genetic background of the rice variety and the transgene position that governed the differential accumulation of β-carotene. It was observed that in the absence of light, oxidative degradation is higher followed by thermal degradation. Weibull model with higher R2 best explained the degradation kinetics of β-carotene in Golden Rice® lines across all the storage conditions. The knowledge generated through this study can be utilized in devising an effective delivery system for Golden Rice® to the consumer.