## 2 Cost
### Example 2: Vegetables Grown in Own Garden or Purchased from Local Markets  
In developing countries, particularly in rural areas, the supply of perishable foods, such as leafy vegetables, tends to be more local; vegetables are grown in the consumer's  
\begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{**Food**} & **Average Nitrate Content** & **Quantity Required to** & **Cost per 100 g of Each** & **Cost per 400 mg** \\  & **per 100 g of Each** & **Consume 400 mg** & **Vegetable \({}^{\text{c}}\)** & **Nitrate \({}^{\text{c}}\)** \\  & **Vegetable \({}^{\text{a}}\)** & **Nitrate \({}^{\text{b}}\)** & **Vegetable \({}^{\text{c}}\)** & **Nitrate \({}^{\text{c}}\)** \\ \hline Spinach & 193 mg & 208 g & GBP 0.43 (USD 0.53) & GBP 0.89 (USD 1.11) \\ Beetroot & 158 mg & 253 g & GBP 0.20 (USD 0.25) & GBP 0.51 (USD 0.63) \\ Iceberg lettuce & 94 mg & 424 g & GBP 0.22 (USD 0.27) & GBP 0.93 (USD 1.16) \\ Rhubarb & 110 mg & 364 g & GBP 0.75 (USD 0.93) & GBP 2.73 (USD 3.39) \\ Watercress & 232 mg & 172 g & GBP 1.45 (USD 1.80) & GBP 2.49 (USD 3.09) \\ Radish & 166 mg & 240 g & GBP 0.23 (USD 0.29) & GBP 0.55 (USD 0.68) \\ Arquula (Rocket) & 348 mg & 115 g & GBP 1.64 (USD 2.04) & GBP 1.89 (USD 2.35) \\ Celery & 187 mg & 214 g & GBP 0.32 (USD 0.40) & GBP 0.69 (USD 0.86) \\ Pak choi & 249 mg & 161 g & GBP 0.56 (USD 0.70) & GBP 0.90 (USD 1.12) \\ Kale & 175 mg & 229 g & GBP 0.42 (USD 0.52) & GBP 0.96 (USD 1.19) \\ Romaine Lettuce & 129 mg & 310 g & GBP 0.38 (USD 0.47) & GBP 1.18 (USD 1.46) \\ Swiss chard & 208 mg & 192 g & GBP 0.84 (USD 1.04) & GBP 1.61 (USD 2.00) \\ Turnip & 171 mg & 234 g & GBP 0.21 (USD 0.26) & GBP 0.49 (USD 0.61) \\ Fennel & 131 mg & 305 g & GBP 0.50 (USD 0.62) & GBP 1.52 (USD 1.89) \\ \hline \hline \end{tabular}  
* Nitrate content per 100 g of each vegetable adapted from [41]. \({}^{\text{b}}\) Aggregate cost represents cost in 3 UK supermarkets (Sainsburys, Tesco, and Asda) per 100 g as of May 2023. Data rounded to three significant figures. \({}^{\text{c}}\) US dollar equivalent presented in parentheses and based on the available exchange rate in May 2023.  
\end{table}
Table 1: Quantity and cost of consuming a standardised nitrate dose (400 mg, equivalent to one beetroot juice ‘shot’) via nitrate-containing vegetables widely available in the UK.  
family garden or peri-urban vegetable farms, and harvested on the day they will be used, or dried in the sun for use in soups and stews [44]. While drying drastically reduces vitamin C content, it probably does not affect the nitrate content (per leaf). The cost is difficult to quantify, but is likely to be much lower than purchasing an imported product, such as beetroot juice.  
In Table 2, we provide an outline of the nitrate content of some common vegetables grown or collected and available in markets in tropical and subtropical regions. It should be noted that many other vegetables sources of nitrate are likely to exist in these settings. However, for some of the most widely consumed leaf vegetables, such as sweet potato leaves, cassava leaves, Indian pennywort, and baobab leaves, few, if any, values on nitrate content have been published. Therefore, as discussed later, more research is needed to understand key vegetable sources of nitrate in different settings.