フォトバイオモジュレーション（光生体調節）は、新しく発展している科学の分野で、光 -特に太陽光 -が私たちの身体や生化学にどのような影響を与えるかを研究しています。研究者たちは、光の波長の違いが細胞の修復、気分、エネルギーなど、さまざまな働きに影響を与えることを発見しています。

この記事は日英バイリンガル解説です。まず日本語で読んで内容をしっかり理解しましょう。その後、英語で読み直して、両方の言語で内容や語彙をつなげていきます。必要であれば印刷して並べて読むのもおすすめです。この方法で読むことで、科学への理解を深めながら、英語力も同時に高めることができます。

多くの人が太陽の光を思い浮かべるとき、頭に浮かぶのは黄金のような温かさ、明るさ、そして長く浴びすぎると日焼けする危険かもしれません。
しかし、太陽光は私たちが目で見える光や紫外線だけではありません。実際には、私たちの目では見えない多くの波長を含んでいます。その中で、可視光の右側（より長い波長の側）に位置するのが「赤外線（infrared light）」です。

赤外線（IR）は、私たちには見えない光です。直接見ることはできませんが、皮膚でその温かさを感じることができます。太陽から地球に届くエネルギーのほぼ半分は赤外線によるものです。近年になってようやく、科学者たちはこの目に見えない光が、私たちの健康維持や体の機能に意外なほど重要な役割を果たしていることを理解し始めました。

赤外線とは何か？

光とは、空間を伝わる電磁放射（でんじほうしゃ）の一種です。
電磁波のスペクトルは、非常に短いガンマ線から始まり、紫外線、可視光線、そしてその先にある長波長の赤外線、マイクロ波、電波へと続きます。
人間の目が見えるのはこのうちごく一部で、私たちが見ている色のすべてはその小さな領域の中に含まれています。

赤外線は「赤」のすぐ外側、つまり人間の目に見えないほど波長が長い領域から始まります。一般的に次の3つのタイプに分類されます。

• 近赤外線（NIR）：およそ700〜1400ナノメートル。可視光の赤に最も近い。
  
• 中赤外線（MIR）：1400〜3000ナノメートル。
  
• 遠赤外線（FIR）：3000ナノメートル〜1ミリメートルまで。
  

それぞれの赤外線は、物質との相互作用の仕方が異なります。
NIRは生体組織に深く浸透し、細胞だけでなく内部のミトコンドリア（エネルギー生産の工場）にまで届きます。
MIRはNIRほど深くは届かないものの、マウス実験などで生理的な効果が報告されています。
FIRは主に皮膚表面で吸収され、熱を発生させて血流に影響を与えます。

フォトバイオモジュレーションという新しい研究分野

赤外線研究の中でも最も注目されている分野のひとつが「フォトバイオモジュレーション（Photobiomodulation）」です。
これは、特定の波長の赤色光や近赤外線を使って生体組織内に有益な変化をもたらす技術を指します。
手術などで使われる高出力レーザーとは異なり、フォトバイオモジュレーションは低出力の光を使用し、組織を損傷させることなく細胞の働きを改善させます。

基本的な仕組みは、光のエネルギーである「光子（photon）」が細胞内に入り、ミトコンドリアの一部に吸収されることです。
この反応により、細胞活動の燃料となるATP（アデノシン三リン酸）の産生が促進され、酸化ストレスのような有害な副産物が減少します。
その結果、細胞の働きがより効率的でバランスの取れたものになります。

臨床研究も急速に進んでいます。
フォトバイオモジュレーションは、皮膚の若返り、創傷治癒、関節や筋肉の痛みの軽減、さらには脳損傷やアルツハイマー病などの神経疾患にまで応用が検討されています。
筋肉、関節、脳、目、心血管系など、さまざまな器官に良い影響を与えるという報告があり、光が私たちの健康や幸福において古代から重要な役割を果たしてきた可能性を示唆しています。

この技術は、今では研究室や病院の外にも広がっています。
小型LEDパネルやハンディタイプの装置、全身用ライトベッドなどが家庭用にも販売されています。
科学はまだ発展段階であり、すべての効果が確実に証明されているわけではありませんが、研究の数は年々増加しています。
多くの科学者が「光」そのものを、生物学的な栄養源として再発見する時代が来たと考えています。

健康における赤外線の重要性

過去数十年の研究により、赤外線は単なる「温かさ」ではなく、体内で実際に生理的な変化を引き起こすことが分かってきました。
主な効果を以下に紹介します。

1. ミトコンドリアの活性化
   ミトコンドリアは、ほぼすべての細胞に存在する微小な構造で、ATPというエネルギー分子を生み出します。
   近赤外線は皮膚を通り抜けてミトコンドリアに届き、シトクロムcオキシダーゼという酵素と反応します。
   その結果、エネルギー産生が向上し、酸化ストレスが減少します。
   より効率的なミトコンドリアは、健康で回復力のある細胞を作ります。
   
2. 血行の改善
   遠赤外線は皮膚表面で吸収され、組織を温めます。
   この穏やかな加熱により血管が拡張し、血流が促進され、酸素や栄養素の供給が改善します。
   研究によると、血圧の低下、運動後の回復促進、創傷治癒の促進などが期待されています。
   
3. 目の健康のサポート
   最近の研究で、赤色光や近赤外線が目のミトコンドリアを活性化し、老化による視力低下を改善する可能性が示されました。
   朝の時間帯に赤や近赤外線を浴びることで、エネルギーを失った網膜細胞を再活性化できると報告されています。
   
4. 痛みと炎症の軽減
   赤外線療法は、関節痛、関節炎、筋肉痛などに対して研究されています。
   血流改善、炎症の抑制、細胞エネルギーの向上によって、痛みを緩和し回復を促します。
   すでに理学療法や家庭用機器にも応用されています。
   
5. 気分と認知機能への影響
   光は概日リズム（体内時計）や脳の化学物質に影響を与えます。
   赤外線は、脳細胞のミトコンドリア機能を改善し、神経炎症を減らすことで、記憶力、集中力、気分の安定、さらには神経変性疾患の予防に役立つ可能性があります。
   

現代生活に潜む「光不足」という問題

ここまで読むと、多くの人が気づくでしょう。
太陽光に豊富に含まれる赤外線を、現代人は十分に浴びていないのです。
私たちは日中の大半を屋内で過ごし、青色成分の多い人工照明の下にいます。
さらに現代の窓ガラスは、室温上昇を防ぐために赤外線を遮断してしまう設計になっています。

都市部では高層ビルや緑地の少なさから、直射日光を浴びる機会も限られています。
過去150年間で、屋外で過ごす時間が劇的に減少したという研究もあります。
特に冬場や通勤・通学時間が短い人は、朝にわずかしか光を浴びないことも多いでしょう。
夜になると、スマートフォンやLEDの青い光を浴び、私たちの光環境は本来の自然のバランスからさらに離れていきます。

人類の祖先は、何百万年もの間、太陽光の全スペクトルを浴びて進化してきました。
私たちの細胞や組織がその波長に依存して健康を保つよう適応しているのは当然のことです。

赤外線をもっと取り入れるための実践方法

では、どうすれば赤外線をもっと生活に取り入れられるでしょうか？
幸いにも、いくつかの簡単で効果的な方法があります。

1. 屋外で過ごす時間を増やす
   最もシンプルな方法は外に出ることです。
   特に朝や夕方の太陽光には、赤外線を多く含む長波長の光が豊富です。
   曇りの日でも、多くの赤外線は雲を通り抜けて地上に届きます。
   
2. 遠赤外線サウナを利用する
   遠赤外線サウナは、リラックス、血行促進、デトックスの目的で人気があります。
   従来のサウナと違い、空気ではなく身体を直接温めるため、より快適な温度で利用できます。
   
3. 赤色光・赤外線デバイスを使用する
   特定の波長を発する赤色光や近赤外線LEDパネルがあり、「フォトバイオモジュレーション」や「赤色光療法」と呼ばれる方法で使われます。
   研究は進行中ですが、多くの人が肌の健康、筋肉回復、エネルギー向上などの効果を感じています。
   
4. 室内照明を見直す
   一般的なLEDや蛍光灯は青色光が強く、赤外線をほとんど含みません。
   最近では、太陽光に近いスペクトルを再現する照明も登場しています。
   長時間屋内で過ごす場合、とくに冬場には有効です。
   
5. 光を浴びるタイミングを工夫する
   赤外線を浴びるのは朝が最も効果的とされています。
   視力や体内時計の調整に役立ちます。
   朝の散歩、窓際でのストレッチ、赤色光デバイスの短時間使用などを日課にすると良いでしょう。
   
6. 日除けを上手に使う
   意外に思うかもしれませんが、服を着込んでも赤外線はほとんど遮られません。
   紫外線は防ぎながら、赤外線は体に届きます。
   したがって、長袖や日傘を使っても赤外線の恩恵を受けることができます。
   また、木陰や植物の下も理想的です。
   植物や木々は赤外線を反射する性質があり、緑地ではこの光が集中的に届きやすくなります。
   

これからの展望

私たちはまだ、光が生物学にどれほど深く関わっているのかを理解し始めたばかりです。
長い間、太陽光は「明るさ」や「暖かさ」として、あるいは「健康へのリスク」として語られてきました。
しかし赤外線の研究は、見えない力がいかに生命にとって重要であるかを教えてくれます。

光は目のための情報であるだけでなく、細胞にとってのエネルギー源でもあります。
食べ物や水が健康に不可欠であるように、適切な光も同様に不可欠なのです。
光環境のバランスを取り戻すことは、視力、筋力、気分、そして老化の遅延にまで関わる可能性があります。

赤外線は「魔法の治療法」ではありませんが、私たちが長い間忘れていた生命の要素のひとつかもしれません。
古代から存在するこの自然の力を再び取り入れることで、私たちはより健康的で調和の取れた生活を取り戻すことができるでしょう。

まとめ

• 赤外線は目に見えないが、太陽エネルギーの約半分を占める。
  
• フォトバイオモジュレーション研究により、赤色光や近赤外線が細胞エネルギーを高め、ストレスを減らすことが確認されている。
  
• 健康効果には、血行改善、痛みや炎症の軽減、視力向上、認知機能のサポートなどがある。
  
• 衣服は赤外線をほとんど遮らないが、建物やガラスは遮断する。緑地は赤外線を反射して私たちに届ける。
  
• 朝の太陽光、赤外線サウナ、赤色光デバイス、照明の見直しなどで取り入れやすい。

The Inner Light: Infrared Light and Our Health

When most of us think about sunlight, we imagine the golden warmth of its rays, the brightness that lets us see, and maybe even the risk of sunburn if we stay out too long. But sunlight is more than just visible light and ultraviolet radiation we have learned to worry about and protect our skin from. It also contains a vast spectrum of wavelengths we cannot see with our eyes. Sitting to the right on visible light are the longer wavelengths known as infrared light.

Infrared, often shortened to IR, is invisible to us. We can’t see it directly, but we can feel it as warmth on our skin. It makes up nearly half of the energy from the sun that reaches Earth. Only in recent years have scientists begun to realize that these invisible rays may play a surprisingly important role in keeping our bodies healthy and functioning at their best.

What Is Infrared Light?

Light is a form of electromagnetic radiation — waves of energy traveling through space. The spectrum runs from very short gamma rays, through ultraviolet and visible light, and then into longer wavelengths like infrared, microwaves, and radio waves. Human eyes only detect a small slice of this spectrum: almost all the colours we see fit into that tiny sliver of the spectrum.

Infrared light begins just beyond red on this rainbow, with wavelengths longer than what our eyes can see. It’s usually divided into three categories:

• Near-infrared (NIR): 700 to about 1400 nanometers. This is closest to visible red light.
  
• Mid-infrared (MIR): 1400 to 3000 nanometers.
  
• Far-infrared (FIR): 3000 nanometers up to 1 millimeter.
  

Each type interacts with matter differently. NIR penetrates more deeply into biological tissue, reaching not just cells but even mitochondria, the energy factories inside them. MIR has shown some effects in mice models despite the fact that it does not penetrate as deep into tissue as NIR. FIR is mostly absorbed at the skin surface, producing heat and influencing blood flow.

The Growing Field of Photobiomodulation

One of the most active areas of research involving infrared light is a field known as photobiomodulation. This term describes the use of specific wavelengths of red and near-infrared light to stimulate beneficial changes inside living tissue. Unlike high-powered lasers used in surgery, photobiomodulation relies on low-level light that does not damage tissue but instead encourages cells to function more effectively.

At its core, the process works by delivering photons — packets of light energy — into cells where they are absorbed by components of the mitochondria. This interaction can boost the production of ATP, the molecule that fuels nearly all cellular activity, while also reducing harmful byproducts like oxidative stress. The result is a more efficient, better-balanced cell.

Clinical studies are expanding rapidly. Photobiomodulation has been investigated for skin rejuvenation, wound healing, reduction of joint and muscle pain, and even neurological conditions such as traumatic brain injury and Alzheimer’s disease. What’s striking is the range of systems that seem to benefit: from muscles and joints to the brain, eyes, and cardiovascular system. It suggests that light has played and continues to do so an essential role in our health and wellbeing for millenia.

The technology has also begun to move beyond laboratories and hospitals. Compact LED panels, handheld devices, and even full-body light beds are now available for use at home. Although the science is still developing and not every claim is supported by strong evidence yet, the body of evidence is growing. Interest in photobiomodulation is growing fast, and the research base is expanding year by year.

Many scientists see it as part of a broader re-discovery — that light itself, long overlooked as a biological resource, is an essential input for human health.

Why Infrared Matters for Health

Research over the past few decades has revealed that infrared light is not just passive warmth. It can trigger real changes inside our bodies. Here are some of the most significant ways infrared affects us:

1. Boosting Mitochondria

Mitochondria are tiny structures inside almost every cell. Their main job is to produce ATP, the molecule that powers nearly all cellular processes. Near-infrared light can penetrate the skin and reach mitochondria, where it interacts with enzymes like cytochrome c oxidase. This improves energy production and reduces harmful byproducts like oxidative stress. More efficient mitochondria mean healthier, more resilient cells.

2. Improving Circulation

Far-infrared light is absorbed at the skin’s surface and warms tissue. This gentle heating dilates blood vessels, increases circulation, and helps deliver oxygen and nutrients to tissues. Studies suggest this can lower blood pressure, improve recovery after exercise, and even help with wound healing.

3. Supporting Eye Health

A relatively new discovery is that longer wavelengths of light can boost the mitochondria rich tissues in the eye. Recent research shows that morning exposure to red and near-infrared light can improve vision in older adults by recharging retinal cells that lose energy with age. 

4. Reducing Pain and Inflammation

Infrared therapy has been studied for joint pain, arthritis, and muscle soreness. The combination of improved blood flow, reduced inflammation, and better cellular energy appears to ease discomfort and promote recovery. It’s already being used in physical therapy clinics and some home devices.

5. Influencing Mood and Cognition

Light exposure is known to affect our circadian rhythm and brain chemistry. Infrared light may support mental health by improving mitochondrial function in brain cells and reducing neuroinflammation. Early studies suggest benefits for memory, attention, and even protection against neurodegenerative conditions.

The Hidden Problem: Modern Life and Missing Light

At this point in time you are probably thinking the obvious; while infrared light is abundant in natural sunlight, many of us don’t get nearly enough of it. Modern lifestyles keep us indoors for most of the day, under artificial lighting that is rich in blue wavelengths but often poor in red and infrared. To make things worse modern types of glass often filter out wavelengths in and above the infrared range to prevent indoor overheating.

Even when we do get outside, it can be difficult to expose ourselves to direct sunlight especially when we live in cities with tall buildings and little green space. Studies show that we have, especially over the last 150 years, spent less and less time outdoors in direct contact with sunlight. We are often forced to be inside and away from sunlight for much of our time during the day and in the winter months we may only get a little exposure in the morning, if any.

 At night, we are flooded with artificial blue light from screens and LEDs, further shifting our light environment away from the balance our biology evolved under.

Our ancestors spent millions of years exposed to the full spectrum of sunlight. It makes sense that our cells and tissues adapted to rely on those wavelengths, including infrared, to maintain health.

So what can be done about it? The most essential step is simply being aware of this fact but there are also some very practical things you can do do expose yourself to more of this essential light.

Practical Ways to Get More Infrared Light

If you’re convinced by now that infrared is important, the next question is: how do we bring more of it back into our lives? Fortunately, there are several strategies — some simple, some more technical.

1. Spend Time Outdoors

The most straightforward solution is to step outside. Sunlight in the early morning and late afternoon is especially rich in longer wavelengths, including near-infrared. Even on cloudy days, a surprising amount of infrared makes it through.

2. Use Infrared Saunas

Far-infrared saunas have gained popularity for relaxation, circulation, and detoxification. Unlike traditional saunas that heat the air, these use infrared panels to warm the body directly, often at lower and more comfortable temperatures.

3. Red and Infrared Light Devices

Specialized lamps and LED panels deliver specific wavelengths of red and near-infrared light. These are used in a practice known as photobiomodulation or red light therapy. While research is ongoing, many people report benefits for skin health, muscle recovery, and general energy.

4. Consider Your Indoor Lighting

Standard LED and fluorescent lights are heavy on blue light and lack infrared. Some newer lighting systems are designed to mimic sunlight more closely, including red and infrared components. If you spend long hours indoors, especially in winter, this can make a difference.

5. Healthy Timing

Infrared exposure in the morning appears to have the strongest biological effects, particularly for vision and circadian rhythm. Building a routine around morning walks, stretches by a sunny window, or a short session with a red-light device can set your body up for the day.

6. Wrap up and seek the right kind of shade

You may think it counterintuitive for me to extol the virtues of getting more light on your body to then turn around and suggest that you wrap up and seek shade. It turns out that clothing, even multiple layers of clothing do not stop infrared light, though they can stop the more photoaging and damaging forms of UV light. So going outside fully covered up and even under a parasol should allow you to still be exposed to infrared light whilst blocking the more damaging light.

Seeking the right kind of shade can also do wonders. It turns out that green plants, trees etc actually reflect infrared light! So trees and green spaces act as lenses and focus all of these beneficial wavelengths directly. 

Looking Ahead

We are still only beginning to grasp how deeply light shapes our biology. For centuries, we thought of sunlight mainly as warmth and brightness and more recently we have come to even view it as a hazard to our health. But the story of infrared reminds us that invisible forces can be just as vital as the ones we see.

The science is pointing in an exciting direction: light is not only information for our eyes but also energy for our cells. Just as food and water are essential to health, so too are the right kinds of light. Restoring balance to our light environment could help with everything from sharper vision to more resilient muscles, calmer moods, and healthier aging.

Infrared light is not a magic cure, but increasingly we are discovering it may be a missing piece — one that has been with us since before people were even people, a fundamental requirement of our biology. By rediscovering it and bringing it back into our modern routines, we may unlock a simple yet profound way to support our health.

Key Takeaways

• Infrared light is invisible but makes up nearly half of the sun’s energy reaching Earth.
  
• Photobiomodulation research shows red and near-infrared light can boost cellular energy and reduce stress.
  
• Health effects include better circulation, reduced pain and inflammation, improved vision, and possible cognitive benefits.
  
• Clothes do not black infrared but buildings and modern glass do. Green spaces help focus this light by reflecting the light on to us.
• Practical steps include morning sunlight, infrared saunas, red-light devices, and better indoor lighting choices.

無料体験レッスンを試してみませんか？
科学や健康の話題に興味がありますか？自分の興味に合った英語を学びたい方へ。
ナチュラルイングリッシュでは、あなたの目的や関心に合わせた無料体験レッスンを行っています。
下のフォームからお申し込みいただければ、あなただけのレッスンをご用意します。

English Word/Phrase	日本語の意味	Simple English Definition	Example Sentence
absorb	吸収する	To take in energy or a substance	Skin absorbs far-infrared heat.
adaptive biology	適応的生物学	The study of how life adjusts to environments	Adaptive biology shows why light affects us.
antioxidant	抗酸化物質	Substance that protects cells from damage	Light may increase antioxidant activity.
artificial blue light	人工の青色光	Blue light from screens or LEDs	Too much blue light at night disturbs sleep.
artificial light	人工光	Light made by humans, not from the sun	Artificial light changes our body rhythms.
arthritis	関節炎	A condition that causes joint pain	People with arthritis often try infrared therapy.
ATP (adenosine triphosphate)	ATP（アデノシン三リン酸）	The main energy molecule in cells	Muscles use ATP for movement.
balance	バランス	A stable, healthy state	Light helps the body maintain balance.
balance restoration	バランスの回復	Returning to a healthy state	Light exposure helps balance restoration.
biological adaptation	生物的適応	How organisms adjust to their environment	Humans adapted to sunlight over millions of years.
biological resource	生物学的資源	Natural factor essential to life	Light is a biological resource for health.
biological tissue	生体組織	Living material that makes up an organism	NIR penetrates deep into biological tissue.
blood flow	血流	The movement of blood through the body	Heat increases blood flow to muscles.
blood pressure	血圧	The force of blood on artery walls	Infrared exposure may lower blood pressure.
blood vessel	血管	A tube that carries blood	Infrared heat opens blood vessels.
byproduct	副産物	Something produced in addition to the main product	Heat is a byproduct of muscle movement.
cell	細胞	The basic unit of all living things	Each cell in your body needs energy.
cellular activity	細胞活動	Processes that happen inside cells	ATP fuels cellular activity.
circadian rhythm	概日リズム	The body’s natural 24-hour clock	Morning light helps reset your circadian rhythm.
clinical evidence	臨床的証拠	Proof from studies on patients	Clinical evidence for PBM is growing.
clinical study	臨床研究	Research done on humans to test treatments	Clinical studies test whether therapies are safe.
cognitive function	認知機能	Mental abilities like memory and attention	Better light exposure may improve cognitive function.
circulation	血行	The movement of blood in the body	Better circulation brings more oxygen to tissues.
circadian rhythm	概日リズム	The body’s 24-hour cycle controlling sleep and hormones	Morning light helps regulate circadian rhythm.
clinical study	臨床研究	Research involving people	Clinical studies confirm safety and effect.
cognitive function	認知機能	Mental processes like memory and attention	Good light helps cognitive function.
cytochrome c oxidase	シトクロムcオキシダーゼ	An enzyme in mitochondria that reacts to light	NIR light helps cytochrome c oxidase work better.
detoxification	解毒	Removing harmful substances from the body	Infrared saunas are used for detoxification.
device	装置	A piece of equipment	This device emits near-infrared light.
dilate	拡張する	To make wider or larger	The blood vessels dilated with heat.
electromagnetic radiation	電磁放射	Energy that travels as waves, like light or radio	Light is one type of electromagnetic radiation.
energy production	エネルギー産生	The process of making energy in the body	Healthy mitochondria increase energy production.
enzyme	酵素	A protein that speeds up chemical reactions	Enzymes help break down food and produce energy.
evolution	進化	The process by which species change over time	Humans evolved under natural sunlight.
exposure	曝露	Contact with something (like light)	Daily light exposure supports health.
fatigue	疲労	Extreme tiredness	Better circulation reduces fatigue.
far-infrared (FIR)	遠赤外線	The longest infrared wavelengths, mostly absorbed at the skin	FIR saunas use this light to warm the body.
green space	緑地	Area with plants and trees	Spending time in green spaces helps our health.
heat	熱	Warmth or high temperature	The light turned into heat on the skin.
health maintenance	健康維持	Keeping the body in good condition	Sunlight is essential for health maintenance.
home device	家庭用装置	Machine used at home	Some home devices emit near-infrared light.
indoor lighting	室内照明	Artificial lights inside buildings	Most indoor lighting lacks infrared light.
infrared light	赤外線	Light with longer wavelengths than visible red light	Infrared light cannot be seen but can be felt as warmth.
laser	レーザー	A strong, focused beam of light	Surgical lasers can cut tissue, but PBM uses gentle light.
metabolism	代謝	The body’s chemical processes	Light may help improve metabolism.
metabolism boost	代謝促進	Increase in body’s energy use	Infrared therapy can cause a metabolism boost.
mid-infrared (MIR)	中赤外線	Infrared light between near and far infrared	MIR is less deep but still useful for body warming.
mitochondria	ミトコンドリア	Cell structures that make energy (ATP)	Mitochondria are called the powerhouses of the cell.
mitochondria-rich tissue	ミトコンドリアが多い組織	Body parts full of mitochondria	The eye’s retina is mitochondria-rich tissue.
molecule	分子	A group of atoms joined together	Water is a molecule made of hydrogen and oxygen.
nanometer (nm)	ナノメートル	Unit of length for light wavelengths	NIR light ranges from 700 to 1400 nm.
near-infrared (NIR)	近赤外線	The part of infrared light closest to visible red light	NIR can go deeper into the skin than other light.
neurodegenerative disease	神経変性疾患	Brain disease that worsens over time	Infrared may help protect against neurodegenerative disease.
neuroinflammation	神経炎症	Swelling or irritation in the brain	Reducing neuroinflammation may protect the brain.
nutrient	栄養素	Substance needed for growth and health	Vitamins are important nutrients.
oxidative stress	酸化ストレス	Damage from too many free radicals in cells	Red light can lower oxidative stress.
parasol	日傘	A small umbrella for sun protection	You can still get infrared light under a parasol.
penetrate	浸透する	To go through or into something	Near-infrared light can penetrate the skin.
photobiomodulation	フォトバイオモジュレーション（光生体調節）	The use of red and NIR light to improve cell function	Photobiomodulation may help with wound healing.
photoreceptor	光受容体	A cell that reacts to light	The retina has photoreceptors for vision.
photon	光子	A single particle of light	Each photon carries energy.
recovery	回復	The process of getting better after injury	Heat can support muscle recovery.
reflection	反射	When light bounces off a surface	Trees reflect infrared light.
rejuvenation	若返り	Making something young again	Red light can help skin rejuvenation.
resilience	回復力	Ability to recover quickly	Healthy mitochondria increase cellular resilience.
retina	網膜	The part of the eye that senses light	The retina sends signals to the brain to form vision.
sauna	サウナ	Room or device for sweating and heat therapy	Many people use infrared saunas to relax.
scientific discovery	科学的発見	Finding new knowledge by research	The role of infrared light is a recent scientific discovery.
screen time	画面を見る時間	Time spent looking at electronic screens	Long screen time reduces natural light exposure.
session	セッション・施術時間	A single period of treatment or activity	A short morning session of red light is effective.
spectrum	スペクトル	Range of wavelengths of light	The sun gives a broad light spectrum.
sunlight	太陽光	Natural light from the sun	Sunlight includes visible, UV, and infrared light.
sunlight deprivation	日光不足	Lack of sunlight	Modern lifestyles cause sunlight deprivation.
sunlight spectrum	太陽光スペクトル	All the wavelengths in sunlight	Our biology depends on the full sunlight spectrum.
tissue	組織	A group of similar cells in the body	Light can affect tissues like skin or muscle.
ultraviolet (UV)	紫外線	Invisible light with shorter wavelengths than violet	UV light can damage the skin.
vision	視力	Ability to see	Morning red light can improve vision.
visible light	可視光線	The light humans can see	The rainbow shows all the colors of visible light.
wavelength	波長	The distance between two peaks of a wave	Longer wavelengths mean lower energy.
wavelength penetration	波長の浸透	How deep light goes into tissue	NIR has the best wavelength penetration.
wound healing	創傷治癒	The process of repairing damaged skin	Red light can help wound healing.