Nutritional Deficiencies

What connects these conditions

A deficiency is rarely about not eating enough of something. Far more often it is about absorption — the nutrient was on the plate and your body did not take it up.

That distinction changes what you do. Eating more spinach will not fix iron deficiency if you drink tea with every meal, because the tannins block absorption at the point of uptake.

The absorption rules worth knowing

• Vitamin C multiplies plant iron absorption. Lemon on dal, tomato in the curry, guava after the meal. This is the single most useful habit for anyone eating a mostly plant-based diet.
• Tea and coffee block iron. Leave an hour either side of an iron-rich meal.
• Calcium and iron compete. Do not take them together.
• Vitamin D controls calcium absorption. Calcium without adequate vitamin D is largely wasted.
• Fat-soluble vitamins need fat. A, D, E and K are barely absorbed from a fat-free meal. Oil on your salad is doing real work.
• Oxalates bind minerals. Spinach looks rich in calcium and delivers almost none, because oxalates hold onto it. Low-oxalate greens like bok choy and kale are far more efficient.

Get tested rather than guessing

Deficiency symptoms overlap almost completely. Fatigue, poor concentration and hair loss fit iron, B12, vitamin D and thyroid problems equally well — and several other things besides.

Supplementing on a guess is a genuinely bad idea. Iron in particular accumulates and is harmful in excess, and taking it when you are not deficient can mask something else. A blood test costs little and settles it.