二十二碳六烯酸（DHA）是大脑发育和维持的关键和关键
Docosahexaenoic acid (DHA) is Essential and Critical for Brain Development and Maintenance
二十二碳六烯酸（DHA）在进化中
Docosahexaenoic acid (DHA) in Evolution
地球上生命起源后的第一个25亿年的生命形式是厌氧的单细胞系统。寒武纪化石记录代表了此前25亿年来化石记录的突然变化。
大约5亿至6亿年前，呼吸式生命形式在热力学上变得可能，并且在以前的生命形式中看不到的细胞内细节开始出现。事实上，在坎布里亚记录中也证明了32门，这也称为寒武纪爆发。
寒武纪爆炸的图像结果
来自Cambria爆炸的化石记录显示出与之前的25亿年相比的变化，细胞膜由脂质（脂肪酸）构成的细胞膜区域化出现。这些脂质形成细胞膜，其容纳转运蛋白，离子通道，信号传导和细胞识别系统。
因此，脂质使细胞内特化成为可能，并且已经成为专业化和多细胞进化的组成部分。在坎布里亚爆炸之前，脂质在生命的进化中没有发挥作用。
特别是海洋脂类是寒武纪爆发的驱动因素。
图像结果为寒武纪爆炸海洋脂质
从什么引发寒武纪爆炸的艺术？ - 科学美国人
一种称为二十二碳六烯酸（DHA）的海洋脂质在人类进化，特别是大脑发育中起着关键和重要的作用。 DHA为新光感受器的出现提供了膜骨架，将光子转化为电能，为其他信号系统，神经系统和大脑的进化奠定了基础。
二十二碳六烯酸（DHA）
二十二碳六烯酸（DHA）是一种ω-3脂肪酸，是人脑，大脑皮层，皮肤和视网膜的主要结构成分。它可以由α-亚麻酸合成或直接从母乳（母乳），鱼油或藻油中获得。
分子生物学也有明确的证据表明DHA是神经元迁移，神经发生和参与大脑生长和功能的几种基因表达的决定因素。同样的过程对于人类进化的最终大脑扩张至关重要。 1
DHA提供了新的光感受器的基本膜骨架，其将光子转换成电。这就是专家声称DHA必须在人类大脑的进化中发挥作用的原因。生物科学支持这样的观点，即脑扩张的强大进化优势将来自常规的，富含食物的DHA和相关微量元素来源。 2
现代人类已经在饮食中使用预先形成的二十二碳六烯酸（DHA）的主要来源进化。人类进化的一个重要转折点是从沿海海产品和内陆淡水资源中发现高质量，易消化的养分。 3
二十二碳六烯酸（DHA）作为必需脑营养素
DHA在以下方面最为丰富：
脑
眼睛
心
它是不可或缺的：
学习和记忆能力
大脑和智力发展
视力
预防和管理心血管疾病
DHA的好处的图像结果
（资源）
DHA是大脑和视网膜中含量最丰富的ω-3脂肪酸。 DHA包括：
大脑中40％的多不饱和脂肪酸（PUFA）
视网膜中60％的PUFA
神经元质膜的50％重量由DHA组成。 4
多项研究表明，脑组织中含有最高浓度的DHA。事实上，60％的大脑由结构性脂肪（灰质）组成，其中近一半由DHA组成。由于这一事实，它是早期大脑发育的重要组成部分，也是维持生命各阶段健康大脑功能的关键结构元素。
DHA对大脑及其发育和功能的影响最大。它有助于确定大脑结构并保护脑组织免受损伤。 DHA在三个主要方面保护大脑：
保护脑组织免受炎症损害
DHA促进抗炎分子的发展，同时抑制脑细胞膜中的促炎分子。 6
DHA保护学习和记忆
DHA浓度最高的区域与记忆密切相关。人们常常认识到那些表现出认知缺陷和痴呆症和阿尔茨海默病风险增加的人患有DHA缺乏症。 7
由于DHA是细胞膜中的主要脂质，因此它维持神经元的流动性，这是正常功能记忆所需的。它还促进突触间的快速信号转导。
DHA还促进了形成新记忆的神经突的生长。它也集中在突触膜上。
DHA促进受损脑组织的愈合
如果脑组织受损，脑细胞膜会大量释放DHA，转化为称为保护素的化合物。 9
持续膳食DHA对脑健康的需求
DHA在大脑中周转非常快，特别是在大脑的海马区域。在老化的大脑中尤其如此，其中DHA通常很快下降。
由于DHA是一种脂肪，不是储存在脂肪细胞中，而是仅存在于细胞膜中，因此需要连续补充。持续补充DHA的需要是由于细胞膜经历持续降解和更新。
因此，必须持续饮食供应DHA，以避免耗尽和损伤大脑细胞。
消费鱼油作为膳食DHA是最好的生物可利用形式
人们普遍认为，获得膳食DHA的最佳方法是食用海洋动物和/或补充富含EPA / DHA的鱼油或藻油。消耗基于植物的ω-3脂肪酸将提供有限量的DHA。
Omega-3脂肪酸是多不饱和脂肪酸，包括：
α-亚麻酸（ALA）
二十碳五烯酸（EPA）
二十二碳六烯酸（DHA）
它是ω-3脂肪酸，动物和植物来源的两个主要来源。鱼类和磷虾等海洋动物提供二十碳五烯酸（EPA）和二十二碳六烯酸（DHA）。植物性食物，如亚麻籽和奇异子提供α-亚麻酸（ALA）。当食用基于植物的ω-3脂肪酸时，身体必须将ALA转化为EPA和DHA，这种转化可能是有限的。
Docosahexaenoic acid (DHA) is Essential and Critical for Brain Development and Maintenance
Docosahexaenoic acid (DHA) in Evolution
The life forms of the first 2.5 billion years after the origin of life on Earth were anaerobic, single celled systems. The Cambrian fossil record represents an abrupt change in the fossil record from the previous 2.5 billion years.
About 500 to 600 million years ago, air-breathing life forms became thermodynamically possible and intracellular detail not seen in previous life forms began to appear. In fact, 32 phyla appeared at this time as evidenced in the Cambria record, also known as the Cambrian explosion.
Image result for cambrian explosion
The fossil records from the Cambria explosion has shown changes from the previous 2.5 billion years with the appearance of intracellular compartmentalization provided by cell membranes which constitute of lipids (fatty acids). These lipids formed the membranes of cells that housed the transporters, ion channels, signaling, and cell recognition systems.
As such, lipids made intracellular specialization possible, and have been integral to specialization and multicellular evolution. Prior to the Cambria explosion, lipids did not play a role in the evolution of life.
In particular, it was marine lipids that were the drivers in the Cambrian explosion.
Image result for cambrian explosion marine lipids
Art from What Sparked the Cambrian Explosion? – Scientific American
A certain marine lipid called Docosahexaenoic acid (DHA) played a key and significant role in human evolution and specifically the development of the brain. DHA provided the membrane backbone for the emergence of new photoreceptors that converted photons into electricity, laying the foundation for the evolution of other signalling systems, the nervous system and the brain.
Docosahexaenoic acid (DHA)
Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. It can be synthesized from alpha-linolenic acid or obtained directly from maternal milk (breast milk), fish oil, or algae oil.
There is also clear evidence from molecular biology that DHA is a determinant of neuronal migration, neurogenesis and the expression of several genes involved in brain growth and function. That same process was essential to the ultimate cerebral expansion in human evolution. 1
DHA provided the basic membrane backbone of new photoreceptors that converted photons into electricity. This is why experts state that DHA must have played a role in the evolution of the human brain. The biological science supports the view that a powerful evolutionary advantage for cerebral expansion would have come from a regular, food-rich source of DHA and associated trace elements. 2
Modern humans have evolved with a staple source of preformed docosahexaenoic acid (DHA) in the diet. An important turning point in human evolution was the discovery of high-quality, easily digested nutrients from coastal seafood and inland freshwater sources. 3
Docosahexaenoic acid (DHA) as an Essential Brain Nutrient
DHA is most abundant in the:
brain
eyes
heart
It is integral in:
learning and memory ability
brain and mental development
visual acuity
prevention and management of cardiovascular disease
Image result for benefits of dha
(Source)
DHA is the most abundant omega-3 fatty acid in the brain and retina. DHA comprises:
40% of the polyunsaturated fatty acids (PUFAs) in the brain
60% of the PUFAs in the retina
Fifty percent of the weight of a neuron’s plasma membrane is composed of DHA. 4
Multiple studies indicate that brain tissue contains the highest concentration of DHA in the body. 5 In fact, 60 percent of the brain is composed of structural fat (the gray matter), of which nearly half is composed of DHA. Due to this fact, it is an essential building block for early brain development, as well as a key structural element in maintaining healthy brain functioning through all stages of life.
Image result for development of the brain and DHA
(Source)
DHA has the most influence on the brain and how it develops and functions. It assists in the determination of brain structure and protects brain tissue from damage. DHA protects the brain in three major areas:
Protects brain tissue from inflammatory damage
DHA promotes the development of anti-inflammatory molecules while suppressing pro-inflammatory molecules in brain cell membranes. 6
DHA protects learning and memory
The regions with the greatest concentrations of DHA are closely related to memory. It is often recognized that those people that show cognitive deficiencies and an increased risk for dementia and Alzheimer’s disease have a DHA deficiency. 7
Since DHA is a major lipid in the cell membrane, it maintains the fluidity of the neuron which is required for a properly functioning memory. It also promotes rapid signal transduction across synapses.
DHA also promotes the outgrowth of neurites which is involved in forming new memories. 8 It also concentrates in the synaptic membranes.
DHA promotes the healing of damaged brain tissue
If brain tissue is damaged, brain cell membranes release DHA in massive amounts for conversion into compounds called protectins. 9
The Need for Continuous Dietary DHA for Brain Health
DHA turns over very fast in the brain, especially in the hippocampus region of the brain. This is especially true in the aging brain where DHA normally drops off quite quickly.
Since DHA is a fat that is not stored in fat cells but instead resides exclusively in cell membranes, it needs to be replenished on a continuous basis. The need for constant supplementation of DHA is due to the cell membrane undergoing continuous degradation and renewal.
It is therefore necessary to have a constant dietary supply of DHA to avoid depletion and injury to the cells of the brain.
Consuming Fish Oil as Dietary DHA is the Best Bioavialable Form
It is widely accepted that the best way to obtain dietary DHA is to consume marine animals and/or to supplement with EPA/DHA rich fish oil or algae oil. Consuming plant based omega-3 fatty acids will provide a limited amount of DHA.
Omega-3 fatty acids are polyunsaturated fatty acids and consist of:
alpha-linolenic acid (ALA)
eicosapentaenoic acid (EPA)
docosahexaenoic acid (DHA)
The are two primary sources of omega-3 fatty acids, animal and plant sources. Marine animals such as fish and krill provide eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Plant foods, such as flaxseed and chia seed provide alpha-linolenic acid (ALA). When consuming plant-based omega-3 fatty acids, the body has to convert the ALA into EPA and DHA, which can be limited.
Plant and Animal Based Omega-3 Fatty Acids
Plant Based Omega-3 Fatty Acid
Flaxseed/oil
Hemp seed/oil
Canola oil
Mustard oil
Algae oil
Chia seed
Chicken egg
Broccoli
Walnuts
Soybeans
Microalgae (oil) (Crypthecodinium cohnii, Schizochytrium, brown algae and Nannochloropsis)
Perilla (Perilla frutescens)
Edible seaweeds (e.g., Wakame, Hijiki, Kombu)
Camelina
Lingon Berry (Vaccinium vitis-idaea)
Purslane (Portulaca oleracea)
Kiwifruit seed oil (Actinidia deliciosa)
Animal Based Omega-3 Fatty Acids
Fish (oily fish)
Fish oil
Krill oil
Cod Liver oil
Greenshell/lipped mussels
Fish roe (eggs) (Both red and black caviar)
Turkey (limited)
Grass fed lean red meat (The omega-6:omega-3 ratio of grass-fed beef is about 2:1, making it a more useful source of omega-3 than grain-fed beef, which usually has a ratio of 4:1.)
ALA is converted into EPA and DHA in your body through desaturations (addition of a double bond) and elongation (addition of two carbon atoms) enzymes. However, this process results in a very low ratio of EPA and DHA.
This means that even when consuming large quantities of ALA (e.g., flaxseeds/oil or chia seeds), the body can only convert a relatively small amount into EPA and DHA, and only when there are sufficient enzymes.
Linoleic Acid (LA), (which is also called omega-6 fatty acid) and ALA compete for the same elongase and desaturase enzymes in the synthesis of longer polyunsaturated fatty acids, such as Arachidonic acid (AA) and EPA.
Figure 3. Desaturation and Elongation of Essential Fatty Acids. Humans can synthesize longer omega-6 and omega-3 fatty acids from the essential fatty acids LA and ALA through a series of desaturation (addition of a double bond) and elongation (addition of two carbon atoms) reactions. Delta-6 desaturase (FADS2) is considered the rate-limiting enzyme in this metabolic pathway. Retroconversion of DHA to EPA in peroxisomes occurs at low basal rates and following DHA supplementation.
Desaturation and Elongation of Essential Fatty Acids (Source)
In addition to the fact that LA and ALA compete for the same elongase and desaturase enzymes in the synthesis of longer polyunsaturated fatty acids, namely AA and EPA, there are two other factors that influence the ability to generate long-chain polyunsaturated fatty acids (LC-PUFA). These two factors include:
Gender
Genetic variability
The capacity to generate DHA from ALA differs based on gender. The capacity is higher in women than men:
Women 10
21% of ALA converted to EPA
9% of ALA converted to DHA
Men 11
8% of ALA converted to EPA
0-4% of ALA converted to DHA
Estrogens cause higher DHA concentrations in women than in men, probably by upregulating synthesis of DHA from vegetable precursors. 12
The two key enzymes in fatty acid metabolism include:
delta-6 desaturase (FADS2)
delta-5 desaturase (FADS1)
The single nucleotide polymorphisms (SNPs) in the FADS gene differ dramatically in their ability to generate Long Chain Polyunsaturated Fatty Acids (LC-PUFA), which include AA, EPA and DHA. With these FADS polymorphisms there may be up to 30% of the variability in blood levels of omega-3 and omega-6 fatty acids among individuals.
The FADS2 gene converts the omega-3 fatty acid ALA to EPA and downstream to DHA. FADS2 is responsible for elongating ALA and converting it into eicosapentenoic acid (EPA).
The minor “G” allele in the FADS2 gene is associated with a lower rate of ALA conversion to EPA and a decrease in the conversion of EPA to DHA. As a result, only a small percentage of ALA can be changed via the enzymes produced by FADS1 and FADS2 genes into eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
The U.S. Office of Disease Prevention and Health Promotion published Nutrition and Your Health: Dietary Guidelines for Americans which provides a list of EPA and DHA content of Fish Species.
The Table below provides the data from this list from the U.S. Office of Disease Prevention and Health Promotion. (Source)
Tag: DAH - BioFoundations https://biofoundations.org/tag/dah/?print=print-search
