How Much Protein Women Need and How to Get It Efficiently - The Cost of Deficiency on Skin, Hair, and Muscle

A Protein Shortfall Eats Away at Both Looks and Condition

Your skin has lost its firmness, your hair has become thinner, you tire more easily. It is surprisingly little known that a protein shortfall can lie at the root of these complaints. Protein is the raw material not only for muscle but for every component of the body, including the collagen in skin, the keratin in hair, nails, hormones, immune antibodies, and enzymes.

In the Dietary Reference Intakes for Japanese (2020 edition) from the Ministry of Health, Labour and Welfare, the recommended protein intake for women aged 18 and over is 50g a day. That level itself is often reached if you eat three proper meals. The recommended amount, however, is a guide for avoiding deficiency, not an amount calculated to keep the quality of your skin and hair or to maintain muscle mass. To serve both beauty and health, the guide is 1.0 to 1.2g per kg of body weight, which for a woman of 55kg works out to 55 to 66g a day. People who exercise regularly need more, and 1.2 to 1.6g is recommended.

What Protein Does for Skin, Hair, and Muscle

Skin - the Raw Material of Collagen

Converted to dry weight, about 70% of the dermis is made up of collagen. Collagen is a type of protein, and synthesizing it in the body requires amino acids (glycine, proline, and hydroxyproline in particular) along with vitamin C. When protein intake falls short, the rate of collagen synthesis drops below the rate of breakdown, and the skin loses firmness and elasticity. Before reaching for an expensive collagen supplement, check first whether your everyday meals are supplying enough protein.

Hair - the Raw Material of Keratin

About 80 to 90% of a strand of hair is made of the protein keratin. Keratin holds a large share of sulfur-containing amino acids, so the essential amino acid methionine, and the cystine the body makes from it, matter especially for its synthesis. When a protein shortfall continues, hair becomes thinner, loses its shine, and breakage and shedding increase. When protein is scarce, the body gives priority to supplying the organs needed to stay alive and leaves hair and nails until later. A change in your hair can be read as an early sign of a protein shortfall.

Muscle - Maintaining Basal Metabolism

Muscle is a metabolically active tissue that consumes energy even at rest. When muscle mass drops, basal metabolism falls and you gain weight more easily on the same amount of food. Past your thirties, muscle mass declines little by little each year if you do nothing. When that decline advances far enough to reduce your strength and everyday movement, the condition is called sarcopenia. Stopping the decline calls for the combination of adequate protein intake and resistance training.

Protein Needs by Stage of Life

Your Twenties - Building the Foundation

Your twenties are when bone density reaches its peak, and protein takes part in bone formation alongside calcium. Aim for 1.0 to 1.2g per kg of body weight, taken evenly across three meals. If your habit is a sweet roll and coffee for breakfast, simply adding an egg or yogurt makes a large improvement.

Your Thirties and Forties - Holding On to Muscle Mass

In this period, when the loss of muscle mass begins, treat 1.2g per kg of body weight as the floor, and raise it as far as 1.6g if you exercise. Work and childcare make meals irregular, but protein synthesis is more efficient when protein is spread across three meals rather than concentrated in one. Use 20 to 30g per meal as your guide.

From Your Fifties - When the Synthetic Response Dulls

What declines with age is less digestion and absorption themselves than the capacity to respond to the protein you have eaten by building muscle protein (this is known as anabolic resistance). Eating the same amount is less likely to translate into muscle than it was when you were younger. In this period, aim for 1.2 to 1.5g per kg of body weight and take it in easily digested forms such as simmered fish, tofu, and egg dishes. Foods rich in leucine (dairy products, chicken, fish) are especially good at switching on muscle protein synthesis.

Amino Acid Score and the Quality of Foods

Not only the quantity of protein but its quality matters. The amino acid score is an index that rates the balance of essential amino acids in a food out of 100. Eggs, milk, chicken, and fish have an amino acid score of 100 and contain essential amino acids in good balance. Grains such as rice and wheat score lower, and plant foods tend to fall short of particular amino acids such as lysine.

Even so, plant foods can complement each other's amino acid scores depending on how you combine them. Rice (low in lysine) paired with soybeans (rich in lysine) as "rice and miso soup" is a traditional Japanese meal that also happens to be an excellent combination for amino acid balance.

Animal Protein Versus Plant Protein

Advantages and Cautions of Animal Protein

Animal protein has a high rate of digestion and absorption (90 to 95%) and a high amino acid score. Chicken breast gives you about 23g of protein per 100g, one egg about 6g, and a fillet of salmon about 20g. Because an excess of red meat leads to too much saturated fat, however, keep the balance centered on fish, chicken, and eggs.

Advantages and Cautions of Plant Protein

Plant protein has the advantage of bringing dietary fiber and polyphenols along with it. Soy products (tofu, natto, soy milk) have a high amino acid score and also contain isoflavones. The rate of digestion and absorption of plant protein is 70 to 85%, lower than that of animal protein, so you need to eat somewhat more of it to obtain the same amount of protein.

How to Choose a Protein Supplement

The Difference Between Whey, Casein, and Soy

Whey protein comes from milk and is absorbed quickly, which makes it ideal for muscle protein synthesis after exercise. Casein protein also comes from milk but is absorbed slowly, which suits taking it before bed. Soy protein comes from soybeans and suits people with a dairy allergy or a preference for plant sources.

Do Not Lean on Supplements Too Heavily

A protein supplement is a supplement, not a replacement for meals. Taking protein from food brings other nutrients such as vitamins, minerals, and dietary fiber at the same time. Use supplements to top up when meals alone do not reach your target, and avoid depending on them for more than half of your daily intake.

Practical Techniques for Getting Protein Efficiently

Add Protein to Breakfast

In Japanese eating patterns, breakfast is overwhelmingly the meal short of protein. Adding two boiled eggs to a breakfast of toast and coffee alone adds about 12g of protein. Greek yogurt (about 10g of protein per 100g) is another easy option.

Replace Snacks with Protein Sources

Instead of sweets, make boiled eggs, cheese, nuts, or a protein bar your snack. Taking protein at the mid-afternoon snack in particular curbs hunger before dinner and helps prevent overeating at dinner.