Chlorella
Encyclopedia
Chlorella is a genus
of single-celled
green algae
, belonging to the phylum Chlorophyta
. It is spherical in shape, about 2 to 10 μm
in diameter, and is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll
-a and -b in its chloroplast
. Through photosynthesis
it multiplies rapidly requiring only carbon dioxide
, water
, sunlight
, and a small amount of mineral
s to reproduce.
The name Chlorella is taken from the Greek
word chloros which means "green" and the Latin
diminutive suffix ella meaning "small". German
biochemist
and cell physiologist Otto Heinrich Warburg
, awarded with the Nobel Prize in Physiology or Medicine
for his research on cell respiration in 1931, also studied photosynthesis in Chlorella. In 1961 Melvin Calvin
of the University of California
received the Nobel Prize in Chemistry
for his research on the pathways of carbon dioxide assimilation in plant
s using Chlorella. In recent years, researchers have made less use of Chlorella as an experimental organism
because it lacks a sexual cycle
and, therefore, the research advantages of genetics
are unavailable .
Many people believed Chlorella could serve as a potential source of food and energy because its photosynthetic efficiency
can, in theory, reach 8%, comparable with other highly efficient crops such as sugar cane.
and other essential nutrients; when dried, it is about 45% protein
, 20% fat
, 20% carbohydrate
, 5% fibre, and 10% minerals and vitamin
s. Mass-production methods are now being used to cultivate it in large artificial circular ponds. Chlorella is a complete protein
source. It is also packed with calories, fat, and vitamins.
Initially, Chlorella was suggested as a "dirt-cheap" protein supplement to the human diet. Advocates sometimes focus on other supposed health benefits of the algae, such as claims of weight control, cancer prevention, and immune system support.
Under certain growing conditions, Chlorella yields oils high in polyunsaturated fat
s—Chlorella minutissima has yielded EPA
at 39.9% of total lipids.
Several studies suggest Chlorella supplementation has a positive effect on the reduction of dioxin
levels in breast milk and it may also have beneficial effects on nursing infants by increasing the IgA
levels in breast milk.
Many institutions began to research the algae, including the Carnegie Institution, the Rockefeller Foundation
, the NIH
, UC Berkeley
, the Atomic Energy Commission
, and Stanford University
. Following WWII, many Europeans were starving and many Malthusians
attributed this not only to the war but to the inability of the world to produce enough food to support the currently-increasing population. According to a 1946 FAO report, the world would need to produce 25 to 35 percent more food in 1960 than in 1939 to keep up with the increasing population, while health improvements would require a 90 to 100 percent increase. Because meat was costly and energy-intensive to produce, protein shortages were also an issue. Increasing cultivated area alone would go only so far in providing adequate nutrition to the population. The USDA
calculated to feed the U.S. population by 1975, it would have to add 200 million acres (800,000 km²) of land, but only 45 million were available. One way to combat national food shortages was to increase the land available for farmers, yet the American frontier and farm land had long since been extinguished in trade for expansion and urban life. Hopes rested solely on new agricultural techniques and technologies. Because of these circumstances, an alternative solution was needed.
To cope with the upcoming post-war population boom in the United States and elsewhere, researchers decided to tap into the unexploited sea resources. Initial testing by the Stanford Research Institute
showed Chlorella (when growing in warm, sunny, shallow conditions) could convert 20 percent of solar energy into a plant which when dried, contained 50 percent protein. In addition, Chlorella contained fat and vitamins. The plant's photosynthetic efficiency allowed it to yield more protein per unit area than any other plant—one scientist predicted 10,000 tons of protein a year could be produced with just 20 workers staffing a one thousand-acre (4 km²) Chlorella farm. The pilot research performed at Stanford and elsewhere led to immense press from journalists and newspapers, yet did not lead to large-scale algae production. Chlorella was a seemingly-viable option because of the technological advances in agriculture at the time and the widespread acclaim it got from experts and scientists who studied it. Algae researchers had even hoped to add a neutralized Chlorella powder to conventional food products, as a way to fortify them with vitamins and minerals.
When the preliminary laboratory results were published the reaction of scientific literature backed the possibilities of the supposed superfood. Science News Letter praised the optimistic results in an article entitled "Algae to Feed the Starving." John Burlew, the reported editor of Carnegie Institute stated, "the algae culture may fill a very real need," which Science News Letter turned into "future populations of the world will be kept from starving by the production of improved or educated algae related to the green scum on ponds." The cover of the magazine also featured Arthur D. Little's Cambridge laboratory, which was a supposed future food factory. A few years later, the magazine published an article entitled "Tomorrow's Dinner", which stated, "There is no doubt in the mind of scientists that the farms of the future will actually be factories." Science Digest also reported, "common pond scum would soon become the world's most important agricultural crop." At least in the decades that followed, algae was not cultivated on nearly that scale, however.
," Chlorella has not seen the kind of public and scientific interest that it had in the 1940s. Chlorella can still be found today from companies promoting its "super food" effects.
cell walls would have to be pulverized. The plant could reach its nutritional potential only in highly-modified artificial situations. Another problem was developing sufficiently tasty foods from Chlorella,
Although the production of Chlorella looked promising and involved creative technology, it has not to date been cultivated on the scale some had predicted. It has not been sold on the scale of Spirulina
, soybean products, or whole-grains. Costs have remained high and Chlorella has for the most part been sold as a health food, for cosmetics, or animal feed. After a decade of experimentation, studies showed that following exposure to sunlight, Chlorella captured just 2.5 percent — not much better than conventional crops. Chlorella, too, was found by scientists in the 1960s to be impossible for humans and other animals to digest in its natural state due to the tough cell walls encapsulating the nutrients, which presented further problems for its use in American food production. Since then, multiple methods have been developed to break down this cell wall to make the nutrients available for digestion.
, clinical studies on Chlorella suggest effects including polychlorinated dibenzodioxins detoxification in humans and other animals, healing from radiation exposure in animals and the ability to reduce high blood pressure, lower serum cholesterol levels, accelerate wound healing, and enhance immune functions in humans.
Chlorella has been found to have anti-tumor properties when fed to mice.
Another study found enhanced vascular function in hypertensive rats given oral doses of chlorella. However, the use of Chlorella for healing effects has received criticism.
. Chlorella can grow due to high nitrate
and phosphate
levels or direct sunlight. Decreasing phosphate and nitrate by partial water change and moving the aquarium to shade can help alleviate the problem.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of single-celled
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
green algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
, belonging to the phylum Chlorophyta
Chlorophyta
Chlorophyta is a division of green algae, informally called chlorophytes. The name is used in two very different senses so that care is needed to determine the use by a particular author...
. It is spherical in shape, about 2 to 10 μm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
in diameter, and is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
-a and -b in its chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
. Through photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
it multiplies rapidly requiring only carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
, and a small amount of mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s to reproduce.
The name Chlorella is taken from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word chloros which means "green" and the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
diminutive suffix ella meaning "small". German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
biochemist
Biochemist
Biochemists are scientists who are trained in biochemistry. Typical biochemists study chemical processes and chemical transformations in living organisms. The prefix of "bio" in "biochemist" can be understood as a fusion of "biological chemist."-Role:...
and cell physiologist Otto Heinrich Warburg
Otto Heinrich Warburg
Otto Heinrich Warburg , son of physicist Emil Warburg, was a German physiologist, medical doctor and Nobel laureate. He served as an officer in the elite Uhlan during the First World War and won the Iron Cross for bravery. Warburg was one of the twentieth century's leading biochemists...
, awarded with the Nobel Prize in Physiology or Medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...
for his research on cell respiration in 1931, also studied photosynthesis in Chlorella. In 1961 Melvin Calvin
Melvin Calvin
Melvin Ellis Calvin was an American chemist most famed for discovering the Calvin cycle along with Andrew Benson and James Bassham, for which he was awarded the 1961 Nobel Prize in Chemistry. He spent most of his five-decade career at the University of California, Berkeley.- Life :Calvin was born...
of the University of California
University of California
The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...
received the Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
for his research on the pathways of carbon dioxide assimilation in plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s using Chlorella. In recent years, researchers have made less use of Chlorella as an experimental organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
because it lacks a sexual cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
and, therefore, the research advantages of genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
are unavailable .
Many people believed Chlorella could serve as a potential source of food and energy because its photosynthetic efficiency
Photosynthetic efficiency
The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in plants and algae. Photosynthesis can be described by the simplified chemical reactionwhere CH2O represents carbohydrates such as sugars, cellulose, and lignin.The value of the...
can, in theory, reach 8%, comparable with other highly efficient crops such as sugar cane.
Chlorella as a food source
It is an attractive potential food source because it is high in proteinProtein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
and other essential nutrients; when dried, it is about 45% protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, 20% fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
, 20% carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
, 5% fibre, and 10% minerals and vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s. Mass-production methods are now being used to cultivate it in large artificial circular ponds. Chlorella is a complete protein
Complete protein
A complete protein is a source of protein that contains an adequate proportion of all nine of the essential amino acids necessary for the dietary needs of humans or other animals...
source. It is also packed with calories, fat, and vitamins.
Initially, Chlorella was suggested as a "dirt-cheap" protein supplement to the human diet. Advocates sometimes focus on other supposed health benefits of the algae, such as claims of weight control, cancer prevention, and immune system support.
Under certain growing conditions, Chlorella yields oils high in polyunsaturated fat
Polyunsaturated fat
In nutrition, polyunsaturated fat, or polyunsaturated fatty acid, are fatty acids in which more than one carbon–carbon double bond exists within the representative molecule. That is, the molecule has two or more points on its structure capable of supporting hydrogen atoms not currently part of the...
s—Chlorella minutissima has yielded EPA
Eicosapentaenoic acid
Eicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5. It also has the trivial name timnodonic acid...
at 39.9% of total lipids.
Several studies suggest Chlorella supplementation has a positive effect on the reduction of dioxin
Dioxins and dioxin-like compounds
Dioxins and dioxin-like compounds are by-products of various industrial processes, and are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants . They include:...
levels in breast milk and it may also have beneficial effects on nursing infants by increasing the IgA
IGA
Iga or IGA may stand for:-Given name:* a female given name of Polish origin. The name originates from the female given name Jadwiga and stands for gia,or gina in the USA....
levels in breast milk.
History
Following global fears of an uncontrollable population boom, during the late 1940s and the early 1950s Chlorella was seen as a new and promising primary food source and as a possible solution to the then current world hunger crisis. Many people during this time thought hunger would be an overwhelming problem and saw Chlorella as a way to end this crisis by providing large amounts of high quality food for a relatively low cost.Many institutions began to research the algae, including the Carnegie Institution, the Rockefeller Foundation
Rockefeller Foundation
The Rockefeller Foundation is a prominent philanthropic organization and private foundation based at 420 Fifth Avenue, New York City. The preeminent institution established by the six-generation Rockefeller family, it was founded by John D. Rockefeller , along with his son John D. Rockefeller, Jr...
, the NIH
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...
, UC Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
, the Atomic Energy Commission
United States Atomic Energy Commission
The United States Atomic Energy Commission was an agency of the United States government established after World War II by Congress to foster and control the peace time development of atomic science and technology. President Harry S...
, and Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
. Following WWII, many Europeans were starving and many Malthusians
Malthusianism
Malthusianism refers primarily to ideas derived from the political/economic thought of Reverend Thomas Robert Malthus, as laid out initially in his 1798 writings, An Essay on the Principle of Population, which describes how unchecked population growth is exponential while the growth of the food...
attributed this not only to the war but to the inability of the world to produce enough food to support the currently-increasing population. According to a 1946 FAO report, the world would need to produce 25 to 35 percent more food in 1960 than in 1939 to keep up with the increasing population, while health improvements would require a 90 to 100 percent increase. Because meat was costly and energy-intensive to produce, protein shortages were also an issue. Increasing cultivated area alone would go only so far in providing adequate nutrition to the population. The USDA
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
calculated to feed the U.S. population by 1975, it would have to add 200 million acres (800,000 km²) of land, but only 45 million were available. One way to combat national food shortages was to increase the land available for farmers, yet the American frontier and farm land had long since been extinguished in trade for expansion and urban life. Hopes rested solely on new agricultural techniques and technologies. Because of these circumstances, an alternative solution was needed.
To cope with the upcoming post-war population boom in the United States and elsewhere, researchers decided to tap into the unexploited sea resources. Initial testing by the Stanford Research Institute
SRI International
SRI International , founded as Stanford Research Institute, is one of the world's largest contract research institutes. Based in Menlo Park, California, the trustees of Stanford University established it in 1946 as a center of innovation to support economic development in the region. It was later...
showed Chlorella (when growing in warm, sunny, shallow conditions) could convert 20 percent of solar energy into a plant which when dried, contained 50 percent protein. In addition, Chlorella contained fat and vitamins. The plant's photosynthetic efficiency allowed it to yield more protein per unit area than any other plant—one scientist predicted 10,000 tons of protein a year could be produced with just 20 workers staffing a one thousand-acre (4 km²) Chlorella farm. The pilot research performed at Stanford and elsewhere led to immense press from journalists and newspapers, yet did not lead to large-scale algae production. Chlorella was a seemingly-viable option because of the technological advances in agriculture at the time and the widespread acclaim it got from experts and scientists who studied it. Algae researchers had even hoped to add a neutralized Chlorella powder to conventional food products, as a way to fortify them with vitamins and minerals.
When the preliminary laboratory results were published the reaction of scientific literature backed the possibilities of the supposed superfood. Science News Letter praised the optimistic results in an article entitled "Algae to Feed the Starving." John Burlew, the reported editor of Carnegie Institute stated, "the algae culture may fill a very real need," which Science News Letter turned into "future populations of the world will be kept from starving by the production of improved or educated algae related to the green scum on ponds." The cover of the magazine also featured Arthur D. Little's Cambridge laboratory, which was a supposed future food factory. A few years later, the magazine published an article entitled "Tomorrow's Dinner", which stated, "There is no doubt in the mind of scientists that the farms of the future will actually be factories." Science Digest also reported, "common pond scum would soon become the world's most important agricultural crop." At least in the decades that followed, algae was not cultivated on nearly that scale, however.
Current status
Since the growing world food problem of the 1940s was solved by better crop efficiency and not from a "super foodSuperfood
Superfood is a term used by various people in a wide variety of manners and contexts. For example, it is sometimes used to describe food with high phytonutrient content that may confer health benefits as a result...
," Chlorella has not seen the kind of public and scientific interest that it had in the 1940s. Chlorella can still be found today from companies promoting its "super food" effects.
Production difficulties
In the end, scientists discovered Chlorella would be much more difficult to produce than previously thought. The experimental research was carried out in laboratories, not in the field. In order to be practical, the entire batch of algae grown would have to be placed either in artificial light or in shade to produce at its maximum photosynthetic efficiency. Also, for the Chlorella to be as productive as the world would require, it would have to be grown in carbonated water, which would have added millions to the production cost. A sophisticated process, and additional cost, was required to harvest the crop, and for Chlorella to be a viable food source, its celluloseCellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
cell walls would have to be pulverized. The plant could reach its nutritional potential only in highly-modified artificial situations. Another problem was developing sufficiently tasty foods from Chlorella,
Although the production of Chlorella looked promising and involved creative technology, it has not to date been cultivated on the scale some had predicted. It has not been sold on the scale of Spirulina
Spirulina
Spirulina may refer to:* Spirulina , a health-food supplement* Spirulina , a cyanobacterium group* Ochthephila spirulina, species of gastropod in the Hygromiidae family...
, soybean products, or whole-grains. Costs have remained high and Chlorella has for the most part been sold as a health food, for cosmetics, or animal feed. After a decade of experimentation, studies showed that following exposure to sunlight, Chlorella captured just 2.5 percent — not much better than conventional crops. Chlorella, too, was found by scientists in the 1960s to be impossible for humans and other animals to digest in its natural state due to the tough cell walls encapsulating the nutrients, which presented further problems for its use in American food production. Since then, multiple methods have been developed to break down this cell wall to make the nutrients available for digestion.
Claims of health and healing effects
Like blue green algaeAphanizomenon flos-aquae
Aphanizomenon flos-aquae is a freshwater species of cyanobacteria. Cyanobacteria are an ancient clade of bacterial microphyte, part of the cyanobacteria phylum.AFA as a species has both toxic and nontoxic forms...
, clinical studies on Chlorella suggest effects including polychlorinated dibenzodioxins detoxification in humans and other animals, healing from radiation exposure in animals and the ability to reduce high blood pressure, lower serum cholesterol levels, accelerate wound healing, and enhance immune functions in humans.
Chlorella has been found to have anti-tumor properties when fed to mice.
Another study found enhanced vascular function in hypertensive rats given oral doses of chlorella. However, the use of Chlorella for healing effects has received criticism.
Aquarium
Chlorella can create green and opaque water problems in aquariaAquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
. Chlorella can grow due to high nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
and phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
levels or direct sunlight. Decreasing phosphate and nitrate by partial water change and moving the aquarium to shade can help alleviate the problem.