**Core Concept**
Iron is an essential micronutrient for various bodily functions, including oxygen transport and energy production. The human body has limited iron stores, and it is crucial to obtain sufficient amounts through the diet. A "poor man's iron source" refers to a readily available, inexpensive, and effective means of supplementing iron intake.

**Why the Correct Answer is Right**
The correct answer is **Option D: Prussic acid treated Jaggery**. Prussic acid (hydrogen cyanide) treated jaggery is a traditional method used in India to increase the iron content of jaggery. The prussic acid breaks down the complex iron compounds in the jaggery, making it more bioavailable and easily absorbed by the body. This process allows for the formation of iron cyanohydrin, which is then hydrolyzed to produce free iron ions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not provide any known method of increasing iron content in food.
**Option B:** This option is incorrect as it does not mention any traditional or scientific method of increasing iron content in food.
**Option C:** This option is incorrect as it does not provide any known method of increasing iron content in food.

**Clinical Pearl / High-Yield Fact**
It is essential to note that while prussic acid treated jaggery is a traditional method of increasing iron content, it should be used under the guidance of a healthcare professional due to potential toxicity risks associated with prussic acid.

**Correct Answer: D. Prussic acid treated Jaggery**